Android 5.1 兼容性定义

使用集合让一切井井有条 根据您的偏好保存内容并对其进行分类。
目录

一、简介

本文档列举了设备与 Android 5.1 兼容必须满足的要求。

根据 IETF,“必须”、“不得”、“要求”、“应”、“不应”、“应该”、“不应”、“推荐”、“可以”和“可选”的使用RFC2119 [资源,1 ]中定义的标准。

如本文档中所用,“设备实施者”或“实施者”是指开发运行 Android 5.1 的硬件/软件解决方案的个人或组织。 “设备实现”或“实现”是这样开发的硬件/软件解决方案。

要被视为与 Android 5.1 兼容,设备实现必须满足本兼容性定义中提出的要求,包括通过引用并入的任何文档。

如果此定义或第 10 节中描述的软件测试是沉默的、模棱两可的或不完整的,则设备实现者有责任确保与现有实现的兼容性。

出于这个原因,Android 开源项目 [资源,2 ] 既是 Android 的参考,也是首选的实现。强烈建议设备实现者尽可能将其实现基于 Android 开源项目提供的“上游”源代码。虽然假设某些组件可以替换为替代实现,但强烈建议不要这样做,因为通过软件测试将变得更加困难。实施者有责任确保与标准 Android 实施的行为完全兼容,包括和超越兼容性测试套件。最后,请注意,本文档明确禁止某些组件替换和修改。

第 14 节中列出的许多资源直接或间接源自 Android SDK,并且在功能上与该 SDK 文档中的信息相同。对于本兼容性定义或兼容性测试套件与 SDK 文档不一致的任何情况,SDK 文档被视为具有权威性。包含在第 14 节中的参考资料中提供的任何技术细节都被认为是本兼容性定义的一部分。

2.设备类型

虽然 Android 开源项目已用于实现各种设备类型和外形尺寸,但架构和兼容性要求的许多方面都针对手持设备进行了优化。从 Android 5.0 开始,Android 开源项目旨在涵盖更广泛的设备类型,如本节所述。

Android 手持设备是指通常通过手持使用的 Android 设备实现,例如 mp3 播放器、手机和平板电脑。 Android 手持设备实现:

  • 必须在设备中嵌入触摸屏。
  • 必须具有提供移动性的电源,例如电池。

Android 电视设备是指一种 Android 设备实现,它是一种娱乐界面,可供坐在大约 10 英尺外的用户使用数字媒体、电影、游戏、应用程序和/或直播电视(“向后倾斜”或“10 英尺用户界面”) ”)。 Android 电视设备:

  • 必须具有嵌入式屏幕或包括视频输出端口,例如 VGA、HDMI 或用于显示的无线端口。
  • 必须声明功能 android.software.leanback 和 android.hardware.type.television [资源,3 ]。

Android Watch 设备是指旨在佩戴在身体上(可能戴在手腕上)的 Android 设备实现,并且:

  • 必须有一个物理对角线长度在 1.1 到 2.5 英寸范围内的屏幕。
  • 必须声明功能 android.hardware.type.watch。
  • 必须支持 uiMode = UI_MODE_TYPE_WATCH [资源,4 ]。

Android Automotive 实施是指运行 Android 作为操作系统的车辆主机单元,用于部分或全部系统和/或信息娱乐功能。 Android Automotive 实现必须支持 uiMode = UI_MODE_TYPE_CAR [ Resources, 111 ]。

不适合上述任何设备类型的所有 Android 设备实现仍必须满足本文档中与 Android 5.1 兼容的所有要求,除非明确说明该要求仅适用于上述特定 Android 设备类型。

2.1 设备配置

这是对不同设备类型的硬件配置主要差异的总结。 (空单元格表示“可能”)。此表并未涵盖所有配置;有关详细信息,请参阅相关硬件部分。

类别特征部分手持式电视手表汽车其他
输入方向键7.2.2.非触摸式导航必须
触摸屏7.2.4.触摸屏输入必须必须应该
麦克风7.8.1.麦克风必须应该必须必须应该
传感器加速度计7.3.1 加速度计应该应该应该
全球定位系统7.3.3.全球定位系统应该应该
连接性无线上网7.4.2. IEEE 802.11应该必须应该应该
无线直连7.4.2.1。无线直连应该应该应该
蓝牙7.4.3.蓝牙应该必须必须必须应该
低功耗蓝牙7.4.3.蓝牙应该必须应该应该应该
USB 外设/主机模式7.7. USB应该应该应该
输出扬声器和/或音频输出端口7.8.2.音频输出必须必须必须必须

3. 软件

3.1。托管 API 兼容性

托管的 Dalvik 字节码执行环境是 Android 应用程序的主要工具。 Android 应用程序编程接口 (API) 是向在托管运行时环境中运行的应用程序公开的一组 Android 平台接口。设备实现必须提供完整的实现,包括所有记录在案的行为,由 Android SDK [资源,5 ] 或上游 Android 源代码中装饰有“@SystemApi”标记的任何 API 公开的任何记录在案的 API。

设备实现不得省略任何托管 API、更改 API 接口或签名、偏离记录的行为或包含无操作,除非此兼容性定义特别允许。

此兼容性定义允许设备实现忽略 Android 包含 API 的某些类型的硬件。在这种情况下,API 必须仍然存在并以合理的方式运行。有关此方案的具体要求,请参见第 7 节

3.2.软 API 兼容性

除了第 3.1 节中的托管 API 之外,Android 还包括一个重要的仅运行时“软”API,其形式为 Android 应用程序的意图、权限和类似方面,这些内容无法在应用程序编译时强制执行。

3.2.1。权限

设备实现者必须支持并强制执行权限参考页 [资源,6]中记录的所有权限常量。请注意,第 9 节列出了与 Android 安全模型相关的其他要求。

3.2.2.构建参数

Android API 在 android.os.Build 类 [ Resources, 7 ] 上包含许多常量,用于描述当前设备。为了在设备实现中提供一致、有意义的值,下表包含了对设备实现必须遵守的这些值的格式的额外限制。

范围细节
版本.发布当前执行的 Android 系统的版本,采用人类可读的格式。该字段必须具有 [ Resources, 8]中定义的字符串值之一。
版本.SDK当前执行的 Android 系统的版本,采用第三方应用程序代码可访问的格式。对于 Android 5.1,此字段必须具有整数值 22。
VERSION.SDK_INT当前执行的 Android 系统的版本,采用第三方应用程序代码可访问的格式。对于 Android 5.1,此字段必须具有整数值 22。
版本.增量设备实现者选择的值,以人类可读的格式指定当前执行的 Android 系统的特定构建。此值不得用于最终用户可用的不同构建。此字段的典型用途是指示使用哪个构建号或源代码控制更改标识符来生成构建。该字段的具体格式没有要求,但不能为空或空字符串(“”)。
木板设备实现者选择的一个值,用于标识设备使用的特定内部硬件,采用人类可读的格式。该字段的一个可能用途是指示为设备供电的电路板的特定版本。此字段的值必须可编码为 7 位 ASCII 并匹配正则表达式“^[a-zA-Z0-9_-]+$”。
反映与最终用户所知的设备关联的品牌名称的值。必须采用人类可读的格式,并且应该代表设备的制造商或销售该设备的公司品牌。此字段的值必须可编码为 7 位 ASCII 并匹配正则表达式“^[a-zA-Z0-9_-]+$”。
支持_ABIS本机代码的指令集名称(CPU 类型 + ABI 约定)。请参阅第 3.3 节。本机 API 兼容性
SUPPORTED_32_BIT_ABIS本机代码的指令集名称(CPU 类型 + ABI 约定)。请参阅第 3.3 节。本机 API 兼容性
SUPPORTED_64_BIT_ABIS本机代码的第二个指令集(CPU 类型 + ABI 约定)的名称。请参阅第 3.3 节。本机 API 兼容性
CPU_ABI本机代码的指令集名称(CPU 类型 + ABI 约定)。请参阅第 3.3 节。本机 API 兼容性
CPU_ABI2本机代码的第二个指令集(CPU 类型 + ABI 约定)的名称。请参阅第 3.3 节。本机 API 兼容性
设备由设备实现者选择的一个值,包含标识硬件功能配置和设备工业设计的开发名称或代号。此字段的值必须可编码为 7 位 ASCII 并匹配正则表达式“^[a-zA-Z0-9_-]+$”。
指纹唯一标识此构建的字符串。它应该是合理的人类可读的。它必须遵循这个模板:

$(BRAND)/$(PRODUCT)/$(DEVICE):$(VERSION.RELEASE)/$(ID)/$(VERSION.INCREMENTAL):$(TYPE)/$(TAGS)

例如:acme/myproduct/mydevice:5.1/LMYXX/3359:userdebug/test-keys

指纹不得包含空格字符。如果上面模板中包含的其他字段包含空格字符,则必须在构建指纹中将它们替换为另一个字符,例如下划线(“_”)字符。该字段的值必须可编码为 7 位 ASCII。

硬件硬件的名称(来自内核命令行或 /proc)。它应该是合理的人类可读的。此字段的值必须可编码为 7 位 ASCII 并匹配正则表达式“^[a-zA-Z0-9_-]+$”。
主持人一个字符串,以人类可读的格式唯一标识构建所基于的主机。该字段的具体格式没有要求,但不能为空或空字符串(“”)。
ID设备实现者选择的一个标识符,用于引用特定版本,采用人类可读的格式。此字段可以与 android.os.Build.VERSION.INCREMENTAL 相同,但应该是一个足以让最终用户区分软件构建的值。此字段的值必须可编码为 7 位 ASCII 并匹配正则表达式“^[a-zA-Z0-9._-]+$”。
制造商产品的原始设备制造商 (OEM) 的商品名称。该字段的具体格式没有要求,但不能为空或空字符串(“”)。
模型由设备实现者选择的一个值,其中包含最终用户已知的设备名称。这应该与设备销售和销售给最终用户的名称相同。该字段的具体格式没有要求,但不能为空或空字符串(“”)。
产品设备实施者选择的一个值,其中包含特定产品 (SKU) 的开发名称或代码名称,在同一品牌中必须是唯一的。必须是人类可读的,但不一定供最终用户查看。此字段的值必须可编码为 7 位 ASCII 并匹配正则表达式“^[a-zA-Z0-9_-]+$”。
串行硬件序列号,必须可用。此字段的值必须可编码为 7 位 ASCII 并匹配正则表达式“^([a-zA-Z0-9]{6,20})$”。
标签由设备实现者选择的以逗号分隔的标签列表,用于进一步区分构建。此字段必须具有对应于三种典型 Android 平台签名配置的值之一:release-keys、dev-keys、test-keys。
时间表示构建发生时间的时间戳的值。
类型设备实现者选择的值,指定构建的运行时配置。此字段必须具有对应于三种典型 Android 运行时配置的值之一:user、userdebug 或 eng。
用户生成构建的用户(或自动用户)的名称或用户 ID。该字段的具体格式没有要求,但不能为空或空字符串(“”)。

3.2.3。意图兼容性

设备实现必须遵循 Android 的松散耦合 Intent 系统,如下节所述。 “尊敬”意味着设备实现者必须提供一个 Android 活动或服务,该活动或服务指定一个匹配的意图过滤器,该过滤器绑定到每个指定的意图模式并实现正确的行为。

3.2.3.1。核心应用意图

Android Intent 允许应用程序组件向其他 Android 组件请求功能。 Android 上游项目包括一系列被视为核心 Android 应用程序的应用程序,这些应用程序实现了几种意图模式来执行常见操作。核心Android应用程序是:

  • 台钟
  • 浏览器
  • 日历
  • 联系人
  • 画廊
  • 全球搜索
  • 启动器
  • 音乐
  • 设置

设备实现应酌情包括核心 Android 应用程序,但必须包括一个组件,该组件实现由这些核心 Android 应用程序的所有“公共”活动或服务组件定义的相同意图模式。请注意,当属性 android:exported 不存在或值为 true 时,Activity 或 Service 组件被视为“公共”。

3.2.3.2。意图覆盖

由于 Android 是一个可扩展的平台,设备实现必须允许第 3.2.3.1 节中引用的每个意图模式被第三方应用程序覆盖。上游 Android 开源实现默认允许这样做;设备实现者不得为系统应用程序对这些意图模式的使用附加特殊权限,或阻止第三方应用程序绑定并控制这些模式。该禁止具体包括但不限于禁用“Chooser”用户界面,该用户界面允许用户在所有处理相同意图模式的多个应用程序之间进行选择。

但是,如果默认活动为数据 URI 提供更具体的过滤器,则设备实现可以为特定 URI 模式(例如 http://play.google.com)提供默认活动。例如,指定数据 URI“http://www.android.com”的意图过滤器比“http://”的浏览器过滤器更具体。设备实现必须为用户提供一个用户界面来修改意图的默认活动。

3.2.3.3。意图命名空间

设备实现不得包含任何使用 android.* 或 com.android.* 命名空间中的 ACTION、CATEGORY 或其他键字符串遵守任何新意图或广播意图模式的 Android 组件。设备实施者不得在属于另一个组织的包空间中包含任何支持任何新意图或广播意图模式的 Android 组件,这些组件使用 ACTION、CATEGORY 或其他键字符串。设备实施者不得更改或扩展第 3.2.3.1 节中列出的核心应用程序使用的任何意图模式。设备实现可能包括使用名称空间的意图模式,这些意图模式与他们自己的组织清楚且明显地相关联。此禁止类似于第 3.6 节中为 Java 语言类指定的禁止。

3.2.3.4。广播意图

第三方应用程序依靠平台广播某些意图,以通知他们硬件或软件环境的变化。 Android 兼容设备必须广播公共广播意图以响应适当的系统事件。 SDK 文档中描述了广播意图。

3.2.3.5。默认应用设置

Android 包含的设置为用户提供了一种选择默认应用程序的简单方法,例如主屏幕或 SMS。在有意义的情况下,设备实现必须提供类似的设置菜单,并与以下 SDK 文档中描述的意图过滤器模式和 API 方法兼容。

设备实现:

  • 如果设备实现报告 android.software.home_screen [资源,10] ,则必须遵守 android.settings.HOME_SETTINGS 意图以显示主屏幕的默认应用设置菜单
  • 如果设备实现报告 android.hardware.telephony [资源,9 ],必须提供一个设置菜单,该菜单将调用 android.provider.Telephony.ACTION_CHANGE_DEFAULT Intent 以显示一个对话框以更改默认 SMS 应用程序
  • 如果设备实现报告 android.hardware.nfc.hce [资源,10] ,则必须遵守 android.settings.NFC_PAYMENT_SETTINGS Intent 以显示 Tap and Pay 的默认应用设置菜单

3.3.原生 API 兼容性

3.3.1。应用程序二进制接口

托管 Dalvik 字节码可以调用应用程序 .apk 文件中提供的本机代码,作为为适当的设备硬件架构编译的 ELF .so 文件。由于原生代码高度依赖底层处理器技术,Android 在 Android NDK 中定义了许多应用程序二进制接口 (ABI)。设备实现必须与一个或多个定义的 ABI 兼容,并且必须实现与 Android NDK 的兼容性,如下所示。

如果设备实现包括对 Android ABI 的支持,它:

  • 必须包括对在托管环境中运行的代码的支持,以调用本机代码,使用标准 Java 本机接口 (JNI) 语义
  • 必须与以下列表中的每个所需库兼容源代码(即标头兼容)和二进制兼容(对于 ABI)
  • 如果支持任何 64 位 ABI,则必须支持等效的 32 位 ABI
  • 必须通过 android.os.Build.SUPPORTED_ABIS、android.os.Build.SUPPORTED_32_BIT_ABIS 和 android.os.Build.SUPPORTED_64_BIT_ABIS 参数准确报告设备支持的本机应用程序二进制接口 (ABI),每个参数都是逗号分隔的列表ABI 从最喜欢到最不喜欢的顺序排列
  • 必须通过上述参数报告最新版本的 Android NDK 中记录的 ABI,“NDK 程序员指南 | ABI 管理”在 docs/ 目录中
  • 应该使用上游 Android 开源项目中可用的源代码和头文件构建

以下本机代码 API 必须可用于包含本机代码的应用程序:

  • libc(C 库)
  • libm(数学库)
  • 对 C++ 的最低支持
  • JNI接口
  • liblog(Android 日志记录)
  • libz(Zlib 压缩)
  • libdl(动态链接器)
  • libGLESv1_CM.so (OpenGL ES 1.x)
  • libGLESv2.so (OpenGL ES 2.0)
  • libGLESv3.so (OpenGL ES 3.x)
  • libEGL.so(原生 OpenGL 表面管理)
  • libjnigraphics.so
  • libOpenSLES.so(OpenSL ES 1.0.1 音频支持)
  • libOpenMAXAL.so(OpenMAX AL 1.0.1 支持)
  • libandroid.so(原生 Android 活动支持)
  • libmediandk.so(原生媒体 API 支持)
  • 支持 OpenGL,如下所述

请注意,Android NDK 的未来版本可能会引入对其他 ABI 的支持。如果设备实现与现有的预定义 ABI 不兼容,则它根本不得报告对任何 ABI 的支持。

请注意,设备实现必须包含 libGLESv3.so,并且必须符号链接(符号链接)到 libGLESv2.so。反过来,必须导出 NDK 版本 android-21 中定义的所有 OpenGL ES 3.1 和 Android 扩展包 [ Resources, 11 ] 函数符号。尽管所有符号都必须存在,但只有设备实际支持的 OpenGL ES 版本和扩展的相应功能必须完全实现。

本机代码兼容性具有挑战性。出于这个原因,强烈建议设备实现者使用来自上游 Android 开源项目的上述库的实现。

3.3.2. 32 位 ARM 本机代码兼容性

ARMv8 架构弃用了一些 CPU 操作,包括现有本机代码中使用的一些操作。在 64 位 ARM 设备上,以下已弃用的操作必须通过本机 CPU 支持或通过软件仿真对 32 位本机 ARM 代码保持可用:

  • SWP 和 SWPB 指令
  • SETEND 指令
  • CP15ISB、CP15DSB 和 CP15DMB 屏障操作

旧版 Android NDK 使用 /proc/cpuinfo 从 32 位 ARM 本机代码中发现 CPU 功能。为了与使用此 NDK 构建的应用程序兼容,当 32 位 ARM 应用程序读取 /proc/cpuinfo 时,设备必须在 /proc/cpuinfo 中包含以下行:

  • “功能:”,后跟设备支持的任何可选 ARMv7 CPU 功能的列表
  • “CPU 架构:”,后跟一个整数,描述设备支持的最高 ARM 架构(例如,“8”代表 ARMv8 设备)

这些要求仅在 32 位 ARM 应用程序读取 /proc/cpuinfo 时适用。当被 64 位 ARM 或非 ARM 应用程序读取时,设备不应更改 /proc/cpuinfo。

3.4.网络兼容性

3.4.1。 Web 视图兼容性

Android Watch 设备可以,但所有其他设备实现必须提供 android.webkit.Webview API 的完整实现。

平台功能 android.software.webview 必须在提供完整实现 android.webkit.WebView API 的任何设备上报告,并且不得在没有完整实现 API 的设备上报告。 Android 开源实现使用来自 Chromium 项目的代码来实现 android.webkit.WebView [参考资料,12 ]。因为为 Web 渲染系统开发全面的测试套件是不可行的,所以设备实现者必须在 WebView 实现中使用 Chromium 的特定上游构建。具体来说:

  • 设备 android.webkit.WebView 实现必须基于来自上游 Android 5.1 开源项目的 Chromium 构建。此版本包括一组特定的 WebView 功能和安全修复 [参考资料,13 ]。
  • WebView 报告的用户代理字符串必须采用以下格式:

    Mozilla/5.0 (Linux; Android $(VERSION); $(MODEL) Build/$(BUILD)$(WEBVIEW)) AppleWebKit/537.36 (KHTML, like Gecko) Version/4.0 $(CHROMIUM_VER) Mobile Safari/537.36

    • $(VERSION) 字符串的值必须与 android.os.Build.VERSION.RELEASE 的值相同。
    • $(WEBVIEW) 字符串可以省略,但如果包含必须是 "; wv" 以说明这是一个 webview
    • $(MODEL) 字符串的值必须与 android.os.Build.MODEL 的值相同。
    • $(BUILD) 字符串的值必须与 android.os.Build.ID 的值相同。
    • $(CHROMIUM_VER) 字符串的值必须是上游 Android 开源项目中 Chromium 的版本。
    • 设备实现可以在用户代理字符串中省略 Mobile。

WebView 组件应该包含对尽可能多的 HTML5 特性的支持,并且如果它支持该特性应该符合 HTML5 规范 [参考资料,14 ]。

3.4.2.浏览器兼容性

Android TV、Watch 和 Android Automotive 实现可以省略浏览器应用程序,但必须支持第 3.2.3.1 节中描述的公共意图模式。所有其他类型的设备实现必须包括用于一般用户 Web 浏览的独立浏览器应用程序。

独立浏览器可能基于 WebKit 以外的浏览器技术。但是,即使使用备用浏览器应用程序,提供给第三方应用程序的 android.webkit.WebView 组件也必须基于 WebKit,如第 3.4.1 节所述。

实现可以在独立的浏览器应用程序中提供自定义用户代理字符串。

独立的浏览器应用程序(无论是基于上游 WebKit 浏览器应用程序还是第三方替代品)应该尽可能多地支持 HTML5 [参考资料,14 ]。最低限度,设备实现必须支持与 HTML5 相关的这些 API:

此外,设备实现必须支持 HTML5/W3C webstorage API [资源,18 ],并且应该支持 HTML5/W3C IndexedDB API [资源,19 ]。请注意,随着 Web 开发标准机构正在转变为偏爱 IndexedDB 而不是 webstorage,IndexedDB 有望成为未来版本 Android 的必需组件。

3.5. API 行为兼容性

每种 API 类型(托管、软、原生和 Web)的行为必须与上游 Android 开源项目 [资源,2 ] 的首选实现一致。一些特定的兼容性领域是:

  • 设备不得更改标准意图的行为或语义。
  • 设备不得更改特定类型的系统组件(如服务、活动、内容提供者等)的生命周期或生命周期语义。
  • 设备不得更改标准权限的语义。

上面的列表并不全面。兼容性测试套件 (CTS) 测试平台的重要部分的行为兼容性,但不是全部。实施者有责任确保与 Android 开源项目的行为兼容性。出于这个原因,设备实现者应该尽可能使用通过 Android 开源项目提供的源代码,而不是重新实现系统的重要部分。

3.6. API 命名空间

Android 遵循 Java 编程语言定义的包和类命名空间约定。为确保与第三方应用程序的兼容性,设备实施者不得对这些包命名空间进行任何禁止的修改(见下文):

  • 爪哇。*
  • javax.*
  • 太阳。*
  • 安卓。*
  • com.android.*

禁止的修改包括

  • 设备实现不得通过更改任何方法或类签名或删除类或类字段来修改 Android 平台上公开的 API。
  • 设备实现者可以修改 API 的底层实现,但此类修改不得影响任何公开公开的 API 的声明行为和 Java 语言签名。
  • 设备实现者不得将任何公开暴露的元素(例如类或接口,或现有类或接口的字段或方法)添加到上述 API。

“公开暴露的元素”是任何未使用上游 Android 源代码中使用的“@hide”标记修饰的构造。换句话说,设备实现者不得公开新的 API 或更改上述命名空间中的现有 API。设备实施者可以进行仅限内部的修改,但不得向开发人员宣传或以其他方式公开这些修改。

设备实现者可以添加自定义 API,但任何此类 API 不得位于其他组织拥有或引用的命名空间中。例如,设备实现者不得将 API 添加到 com.google.* 或类似名称空间:只有 Google 可以这样做。同样,Google 不得将 API 添加到其他公司的命名空间。 Additionally, if a device implementation includes custom APIs outside the standard Android namespace, those APIs MUST be packaged in an Android shared library so that only apps that explicitly use them (via the <uses-library> mechanism) are affected by the increased memory usage of such APIs.

If a device implementer proposes to improve one of the package namespaces above (such as by adding useful new functionality to an existing API, or adding a new API), the implementer SHOULD visit source.android.com and begin the process for contributing changes and code, according to the information on that site.

Note that the restrictions above correspond to standard conventions for naming APIs in the Java programming language; this section simply aims to reinforce those conventions and make them binding through inclusion in this Compatibility Definition.

3.7. Runtime Compatibility

Device implementations MUST support the full Dalvik Executable (DEX) format and Dalvik bytecode specification and semantics [ Resources, 20 ]. Device implementers SHOULD use ART, the reference upstream implementation of the Dalvik Executable Format, and the reference implementation's package management system.

Device implementations MUST configure Dalvik runtimes to allocate memory in accordance with the upstream Android platform, and as specified by the following table. (See section 7.1.1 for screen size and screen density definitions.)

Note that memory values specified below are considered minimum values and device implementations MAY allocate more memory per application.

Screen Layout Screen Density Minimum Application Memory
small/normal 120 dpi (ldpi) 32MB
160 dpi (mdpi)
213 dpi (tvdpi) 48MB
240 dpi (hdpi)
280 dpi (280dpi)
320 dpi (xhdpi) 80MB
400 dpi (400dpi) 96MB
480 dpi (xxhdpi) 128MB
560 dpi (560dpi) 192MB
640 dpi (xxxhdpi) 256MB
large 120 dpi (ldpi) 32MB
160 dpi (mdpi) 48MB
213 dpi (tvdpi) 80MB
240 dpi (hdpi)
280 dpi (280dpi) 96MB
320 dpi (xhdpi) 128MB
400 dpi (400dpi) 192MB
480 dpi (xxhdpi) 256MB
560 dpi (560dpi) 384MB
640 dpi (xxxhdpi) 512MB
xlarge 120 dpi (ldpi) 48MB
160 dpi (mdpi) 80MB
213 dpi (tvdpi) 96MB
240 dpi (hdpi)
280 dpi (280dpi) 144MB
320 dpi (xhdpi) 192MB
400 dpi (400dpi) 288MB
480 dpi (xxhdpi) 384MB
560 dpi (560dpi) 576MB
640 dpi (xxxhdpi) 768MB

3.8. User Interface Compatibility

3.8.1. Launcher (Home Screen)

Android includes a launcher application (home screen) and support for third-party applications to replace the device launcher (home screen). Device implementations that allow third-party applications to replace the device home screen MUST declare the platform feature android.software.home_screen.

3.8.2. Widgets

Widgets are optional for all Android device implementations, but SHOULD be supported on Android Handheld devices.

Android defines a component type and corresponding API and lifecycle that allows applications to expose an “AppWidget” to the end user [ Resources, 21 ] a feature that is strongly RECOMMENDED to be supported on Handheld Device implementations. Device implementations that support embedding widgets on the home screen MUST meet the following requirements and declare support for platform feature android.software.app_widgets.

  • Device launchers MUST include built-in support for AppWidgets, and expose user interface affordances to add, configure, view, and remove AppWidgets directly within the Launcher.
  • Device implementations MUST be capable of rendering widgets that are 4 x 4 in the standard grid size. See the App Widget Design Guidelines in the Android SDK documentation [ Resources, 21 ] for details.
  • Device implementations that include support for lock screen MAY support application widgets on the lock screen.

3.8.3. Notifications

Android includes APIs that allow developers to notify users of notable events [ Resources, 22 ], using hardware and software features of the device.

Some APIs allow applications to perform notifications or attract attention using hardware—specifically sound, vibration, and light. Device implementations MUST support notifications that use hardware features, as described in the SDK documentation, and to the extent possible with the device implementation hardware. For instance, if a device implementation includes a vibrator, it MUST correctly implement the vibration APIs. If a device implementation lacks hardware, the corresponding APIs MUST be implemented as no-ops. This behavior is further detailed in section 7 .

Additionally, the implementation MUST correctly render all resources (icons, animation files etc.) provided for in the APIs [ Resources, 23 ], or in the Status/System Bar icon style guide [ Resources, 24 ], which in the case of an Android Television device includes the possibility to not display the notifications. Device implementers MAY provide an alternative user experience for notifications than that provided by the reference Android Open Source implementation; however, such alternative notification systems MUST support existing notification resources, as above.

Android includes support for various notifications, such as:

  • Rich notifications . Interactive Views for ongoing notifications.
  • Heads-up notifications . Interactive Views users can act on or dismiss without leaving the current app.
  • Lockscreen notifications . Notifications shown over a lock screen with granular control on visibility.

Android device implementations, when such notifications are made visible, MUST properly execute Rich and Heads-up notifications and include the title/name, icon, text as documented in the Android APIs [Resources, 25] .

Android includes Notification Listener Service APIs that allow apps (once explicitly enabled by the user) to receive a copy of all notifications as they are posted or updated. Device implementations MUST correctly and promptly send notifications in their entirety to all such installed and user-enabled listener services, including any and all metadata attached to the Notification object.

Android includes APIs [ Resources, 26 ] that allow developers to incorporate search into their applications, and expose their application's data into the global system search. Generally speaking, this functionality consists of a single, system-wide user interface that allows users to enter queries, displays suggestions as users type, and displays results. The Android APIs allow developers to reuse this interface to provide search within their own apps, and allow developers to supply results to the common global search user interface.

Android device implementations SHOULD include global search, a single, shared, system-wide search user interface capable of real-time suggestions in response to user input. Device implementations SHOULD implement the APIs that allow developers to reuse this user interface to provide search within their own applications. Device implementations that implement the global search interface MUST implement the APIs that allow third-party applications to add suggestions to the search box when it is run in global search mode. If no third-party applications are installed that make use of this functionality, the default behavior SHOULD be to display web search engine results and suggestions.

3.8.5. Toasts

Applications can use the “Toast” API to display short non-modal strings to the end user, that disappear after a brief period of time [ Resources, 27 ]. Device implementations MUST display Toasts from applications to end users in some high-visibility manner.

3.8.6. Themes

Android provides “themes” as a mechanism for applications to apply styles across an entire Activity or application.

Android includes a “Holo” theme family as a set of defined styles for application developers to use if they want to match the Holo theme look and feel as defined by the Android SDK [ Resources, 28 ]. Device implementations MUST NOT alter any of the Holo theme attributes exposed to applications [ Resources, 29 ].

Android includes a “Material” theme family as a set of defined styles for application developers to use if they want to match the design theme's look and feel across the wide variety of different Android device types. Device implementations MUST support the “Material” theme family and MUST NOT alter any of the Material theme attributes or their assets exposed to applications [ Resources, 30 ].

Android also includes a “Device Default” theme family as a set of defined styles for application developers to use if they want to match the look and feel of the device theme as defined by the device implementer. Device implementations MAY modify the Device Default theme attributes exposed to applications [ Resources, 29 ].

Android supports a new variant theme with translucent system bars, which allows application developers to fill the area behind the status and navigation bar with their app content. To enable a consistent developer experience in this configuration, it is important the status bar icon style is maintained across different device implementations. Therefore, Android device implementations MUST use white for system status icons (such as signal strength and battery level) and notifications issued by the system, unless the icon is indicating a problematic status [ Resources, 29 ].

3.8.7. Live Wallpapers

Android defines a component type and corresponding API and lifecycle that allows applications to expose one or more “Live Wallpapers” to the end user [ Resources, 31 ]. Live wallpapers are animations, patterns, or similar images with limited input capabilities that display as a wallpaper, behind other applications.

Hardware is considered capable of reliably running live wallpapers if it can run all live wallpapers, with no limitations on functionality, at a reasonable frame rate with no adverse effects on other applications. If limitations in the hardware cause wallpapers and/or applications to crash, malfunction, consume excessive CPU or battery power, or run at unacceptably low frame rates, the hardware is considered incapable of running live wallpaper. As an example, some live wallpapers may use an OpenGL 2.0 or 3.x context to render their content. Live wallpaper will not run reliably on hardware that does not support multiple OpenGL contexts because the live wallpaper use of an OpenGL context may conflict with other applications that also use an OpenGL context.

Device implementations capable of running live wallpapers reliably as described above SHOULD implement live wallpapers, and when implemented MUST report the platform feature flag android.software.live_wallpaper.

3.8.8. Activity Switching

As the Recent function navigation key is OPTIONAL, the requirements to implement the overview screen is OPTIONAL for Android Television devices and Android Watch devices.

The upstream Android source code includes the overview screen [ Resources, 32 ], a system-level user interface for task switching and displaying recently accessed activities and tasks using a thumbnail image of the application's graphical state at the moment the user last left the application. Device implementations including the recents function navigation key as detailed in section 7.2.3 , MAY alter the interface but MUST meet the following requirements:

  • MUST display affiliated recents as a group that moves together.
  • MUST support at least up to 20 displayed activities.
  • SHOULD at least display the title of 4 activities at a time.
  • SHOULD display highlight color, icon, screen title in recents.
  • MUST implement the screen pinning behavior [ Resources, 33 ] and provide the user with a settings menu to toggle the feature.
  • SHOULD display a closing affordance ("x") but MAY delay this until user interacts with screens.

Device implementations are STRONGLY ENCOURAGED to use the upstream Android user interface (or a similar thumbnail-based interface) for the overview screen.

3.8.9. Input Management

Android includes support for Input Management and support for third-party input method editors [ Resources, 34 ]. Device implementations that allow users to use third-party input methods on the device MUST declare the platform feature android.software.input_methods and support IME APIs as defined in the Android SDK documentation.

Device implementations that declare the android.software.input_methods feature MUST provide a user-accessible mechanism to add and configure third-party input methods. Device implementations MUST display the settings interface in response to the android.settings.INPUT_METHOD_SETTINGS intent.

3.8.10. Lock Screen Media Control

The Remote Control Client API is deprecated from Android 5.0 in favor of the Media Notification Template that allows media applications to integrate with playback controls that are displayed on the lock screen [ Resources, 35 ]. Device implementations that support a lock screen, unless an Android Automotive or Watch implementation, MUST display the Lockscreen Notifications including the Media Notification Template.

3.8.11. Dreams

Android includes support for interactive screensavers called Dreams [ Resources, 36 ]. Dreams allows users to interact with applications when a device connected to a power source is idle or docked in a desk dock. Android Watch devices MAY implement Dreams, but other types of device implementations SHOULD include support for Dreams and provide a settings option for users to configure Dreams in response to the android.settings.DREAM_SETTINGS intent.

3.8.12.地点

When a device has a hardware sensor (eg GPS) that is capable of providing the location coordinates, location modes MUST be displayed in the Location menu within Settings [ Resources, 37 ].

3.8.13. Unicode and Font

Android includes support for color emoji characters. When Android device implementations include an IME, devices SHOULD provide an input method to the user for the Emoji characters defined in Unicode 6.1 [ Resources, 38 ]. All devices MUST be capable of rendering these emoji characters in color glyph.

Android includes support for Roboto 2 font with different weights—sans-serif-thin, sans-serif-light, sans-serif-medium, sans-serif-black, sans-serif-condensed, sans-serif-condensed-light—which MUST all be included for the languages available on the device and full Unicode 7.0 coverage of Latin, Greek, and Cyrillic, including the Latin Extended A, B, C, and D ranges, and all glyphs in the currency symbols block of Unicode 7.0.

3.9. Device Administration

Android includes features that allow security-aware applications to perform device administration functions at the system level, such as enforcing password policies or performing remote wipe, through the Android Device Administration API [ Resources, 39 ]. Device implementations MUST provide an implementation of the DevicePolicyManager class [ Resources, 40 ]. Device implementations that include support for PIN (numeric) or PASSWORD (alphanumeric) based lock screens MUST support the full range of device administration policies defined in the Android SDK documentation [ Resources, 39 ] and report the platform feature android.software.device_admin.

Device implementations MAY have a preinstalled application performing device administration functions but this application MUST NOT be set out-of-the box as the default Device Owner app [ Resources, 41 ].

3.10. Accessibility

Android provides an accessibility layer that helps users with disabilities to navigate their devices more easily. In addition, Android provides platform APIs that enable accessibility service implementations to receive callbacks for user and system events and generate alternate feedback mechanisms, such as text-to-speech, haptic feedback, and trackball/d-pad navigation [ Resources, 42 ].

Device implementations include the following requirements:

  • Android Automotive implementations SHOULD provide an implementation of the Android accessibility framework consistent with the default Android implementation.
  • Device implementations (Android Automotive excluded) MUST provide an implementation of the Android accessibility framework consistent with the default Android implementation.
  • Device implementations (Android Automotive excluded) MUST support third-party accessibility service implementations through the android.accessibilityservice APIs [ Resources, 43 ]
  • Device implementations (Android Automotive excluded) MUST generate AccessibilityEvents and deliver these events to all registered AccessibilityService implementations in a manner consistent with the default Android implementation
  • Device implementations (Android Automotive and Android Watch devices with no audio output excluded), MUST provide a user-accessible mechanism to enable and disable accessibility services, and MUST display this interface in response to the android.provider.Settings.ACTION_ACCESSIBILITY_SETTINGS intent.

Additionally, device implementations SHOULD provide an implementation of an accessibility service on the device, and SHOULD provide a mechanism for users to enable the accessibility service during device setup. An open source implementation of an accessibility service is available from the Eyes Free project [ Resources, 44 ].

3.11. Text-to-Speech

Android includes APIs that allow applications to make use of text-to-speech (TTS) services and allows service providers to provide implementations of TTS services [ Resources, 45 ]. Device implementations reporting the feature android.hardware.audio.output MUST meet these requirements related to the Android TTS framework.

Android Automotive implementations:

  • MUST support the Android TTS framework APIs.
  • MAY support installation of third-party TTS engines. If supported, partners MUST provide a user-accessible interface that allows the user to select a TTS engine for use at system level.

All other device implementations:

  • MUST support the Android TTS framework APIs and SHOULD include a TTS engine supporting the languages available on the device. Note that the upstream Android open source software includes a full-featured TTS engine implementation.
  • MUST support installation of third-party TTS engines
  • MUST provide a user-accessible interface that allows users to select a TTS engine for use at the system level

3.12. TV Input Framework

The Android Television Input Framework (TIF) simplifies the delivery of live content to Android Television devices. TIF provides a standard API to create input modules that control Android Television devices. Android Television device implementations MUST support Television Input Framework [ Resources, 46 ].

Device implementations that support TIF MUST declare the platform feature android.software.live_tv.

4. Application Packaging Compatibility

Device implementations MUST install and run Android “.apk” files as generated by the “aapt” tool included in the official Android SDK [ Resources, 47 ].

Devices implementations MUST NOT extend either the .apk [ Resources, 48 ], Android Manifest [ Resources, 49 ], Dalvik bytecode [ Resources, 20 ], or RenderScript bytecode formats in such a way that would prevent those files from installing and running correctly on other compatible devices.

5. Multimedia Compatibility

5.1. Media Codecs

Device implementations MUST support the core media formats specified in the Android SDK documentation [ Resources, 50 ] except where explicitly permitted in this document. Specifically, device implementations MUST support the media formats, encoders, decoders, file types, and container formats defined in the tables below and reported via MediaCodecList [ Resources,112 ]. Device implementations MUST also be able to decode all profiles reported in its CamcorderProfile [ Resources, 113 ]. All of these codecs are provided as software implementations in the preferred Android implementation from the Android Open Source Project.

Please note that neither Google nor the Open Handset Alliance make any representation that these codecs are free from third-party patents. Those intending to use this source code in hardware or software products are advised that implementations of this code, including in open source software or shareware, may require patent licenses from the relevant patent holders.

5.1.1. Audio Codecs

Format/Codec Encoder Decoder Details Supported File Types/Container Formats
MPEG-4 AAC Profile

(AAC LC)

REQUIRED 1 REQUIRED Support for mono/stereo/5.0/5.1 2 content with standard sampling rates from 8 to 48 kHz.
  • 3GPP (.3gp)
  • MPEG-4 (.mp4, .m4a)
  • ADTS raw AAC (.aac, decode in Android 3.1+, encode in Android 4.0+, ADIF not supported)
  • MPEG-TS (.ts, not seekable, Android 3.0+)
MPEG-4 HE AAC Profile (AAC+) REQUIRED 1
(Android 4.1+)
REQUIRED Support for mono/stereo/5.0/5.1 2 content with standard sampling rates from 16 to 48 kHz.
MPEG-4 HE AACv2

Profile (enhanced AAC+)

REQUIRED Support for mono/stereo/5.0/5.1 2 content with standard sampling rates from 16 to 48 kHz.
AAC ELD (enhanced low delay AAC) REQUIRED 1

(Android 4.1+)

REQUIRED

(Android 4.1+)

Support for mono/stereo content with standard sampling rates from 16 to 48 kHz.
AMR-NB REQUIRED 3 REQUIRED 3 4.75 to 12.2 kbps sampled @ 8kHz 3GPP (.3gp)
AMR-WB REQUIRED 3 REQUIRED 3 9 rates from 6.60 kbit/s to 23.85 kbit/s sampled @ 16kHz
FLAC REQUIRED
(Android 3.1+)
Mono/Stereo (no multichannel). Sample rates up to 48 kHz (but up to 44.1 kHz is recommended on devices with 44.1 kHz output, as the 48 to 44.1 kHz downsampler does not include a low-pass filter). 16-bit recommended; no dither applied for 24-bit. FLAC (.flac) only
MP3 REQUIRED Mono/Stereo 8-320Kbps constant (CBR) or variable bitrate (VBR) MP3 (.mp3)
MIDI REQUIRED MIDI Type 0 and 1. DLS Version 1 and 2. XMF and Mobile XMF. Support for ringtone formats RTTTL/RTX, OTA, and iMelody
  • Type 0 and 1 (.mid, .xmf, .mxmf)
  • RTTTL/RTX (.rtttl, .rtx)
  • OTA (.ota)
  • iMelody (.imy)
Vorbis REQUIRED
  • Ogg (.ogg)
  • Matroska (.mkv, Android 4.0+)
PCM/WAVE REQUIRED 4
(Android 4.1+)
REQUIRED 16-bit linear PCM (rates up to limit of hardware). Devices MUST support sampling rates for raw PCM recording at 8000, 11025, 16000, and 44100 Hz frequencies. WAVE (.wav)
Opus REQUIRED
(Android 5.0+)
Matroska (.mkv)

1 Required for device implementations that define android.hardware.microphone but optional for Android Watch device implementations.

2 Only downmix of 5.0/5.1 content is required; recording or rendering more than 2 channels is optional.

3 Required for Android Handheld device implementations.

4 Required for device implementations that define android.hardware.microphone, including Android Watch device implementations.

5.1.2. Image Codecs

Format/Codec Encoder Decoder Details Supported File Types/Container Formats
JPEG REQUIRED REQUIRED Base+progressive JPEG (.jpg)
GIF REQUIRED GIF (.gif)
PNG REQUIRED REQUIRED PNG (.png)
BMP REQUIRED BMP (.bmp)
WebP REQUIRED REQUIRED WebP (.webp)

5.1.3. Video Codecs

Video codecs are optional for Android Watch device implementations.

Format/Codec Encoder Decoder Details Supported File Types/
Container Formats
H.263 REQUIRED 1 REQUIRED 2
  • 3GPP (.3gp)
  • MPEG-4 (.mp4)
H.264 AVC REQUIRED 2 REQUIRED 2 See section 5.2 and 5.3 for details
  • 3GPP (.3gp)
  • MPEG-4 (.mp4)
  • MPEG-TS (.ts, AAC audio only, not seekable, Android 3.0+)
H.265 HEVC REQUIRED 5 See section 5.3 for details MPEG-4 (.mp4)
MPEG-4 SP REQUIRED 2 3GPP (.3gp)
VP8 3 REQUIRED 2

(Android 4.3+)

REQUIRED 2

(Android 2.3.3+)

See section 5.2 and 5.3 for details
VP9 REQUIRED 2
(Android 4.4+)
See section 5.3 for details

1 Required for device implementations that include camera hardware and define android.hardware.camera or android.hardware.camera.front.

2 Required for device implementations except Android Watch devices.

3 For acceptable quality of web video streaming and video-conference services, device implementations SHOULD use a hardware VP8 codec that meets the requirements in [ Resources, 51 ].

4 Device implementations SHOULD support writing Matroska WebM files.

5 Strongly recommended for Android Automotive, optional for Android Watch, and required for all other device types.

5.2. Video Encoding

Video codecs are optional for Android Watch device implementations.

Android device implementations with H.264 codec support, MUST support Baseline Profile Level 3 and the following SD (Standard Definition) video encoding profiles and SHOULD support Main Profile Level 4 and the following HD (High Definition) video encoding profiles. Android Television devices are STRONGLY RECOMMENDED to encode HD 1080p video at 30 fps.

SD (Low quality) SD (High quality) HD 720p1 HD 1080p1
Video resolution 320 x 240 px 720 x 480 px 1280 x 720 px 1920 x 1080 px
Video frame rate 20 fps 30 fps 30 fps 30 fps
Video bitrate 384 Kbps 2 Mbps 4 Mbps 10 Mbps

1 When supported by hardware, but STRONGLY RECOMMENDED for Android Television devices.

Android device implementations with VP8 codec support MUST support the SD video encoding profiles and SHOULD support the following HD (High Definition) video encoding profiles.

SD (Low quality) SD (High quality) HD 720p1 HD 1080p1
Video resolution 320 x 180 px 640 x 360 px 1280 x 720 px 1920 x 1080 px
Video frame rate 30 fps 30 fps 30 fps 30 fps
Video bitrate 800 Kbps 2 Mbps 4 Mbps 10 Mbps

1 When supported by hardware.

5.3. Video Decoding

Video codecs are optional for Android Watch device implementations.

Device implementations MUST support dynamic video resolution switching within the same stream for all VP8, VP9, H.264, and H.265 codecs exposed to developers through the standard Android APIs.

Android device implementations with H.264 decoders, MUST support Baseline Profile Level 3 and the following SD video decoding profiles and SHOULD support the HD decoding profiles. Android Television devices MUST support High Profile Level 4.2 and the HD 1080p decoding profile.

SD (Low quality) SD (High quality) HD 720p1 HD 1080p1
Video resolution 320 x 240 px 720 x 480 px 1280 x 720 px 1920 x 1080 px
Video frame rate 30 fps 30 fps 30 fps / 60 fps2 30 fps / 60 fps2
Video bitrate 800 Kbps 2 Mbps 8 Mbps 20 Mbps

1 Required for Android Television device implementations, but for other device types only when supported by hardware.

2 Required for Android Television device implementations.

Android device implementations when supporting VP8 codec as described in section 5.1.3 , MUST support the following SD decoding profiles and SHOULD support the HD decoding profiles. Android Television devices MUST support the HD 1080p decoding profile.

SD (Low quality) SD (High quality) HD 720p1 HD 1080p1
Video resolution 320 x 180 px 640 x 360 px 1280 x 720 px 1920 x 1080 px
Video frame rate 30 fps 30 fps 30 fps / 60 fps2 30 / 60 fps2
Video bitrate 800 Kbps 2 Mbps 8 Mbps 20 Mbps

1 Required for Android Television device implementations, but for other type of devices only when supported by hardware.

2 Required for Android Television device implementations.

Android device implementations, when supporting VP9 codec as described in section 5.1.3 , MUST support the following SD video decoding profiles and SHOULD support the HD decoding profiles. Android Television devices are STRONGLY RECOMMENDED to support the HD 1080p decoding profile and SHOULD support the UHD decoding profile. When the UHD video decoding profile is supported, it MUST support 8 bit color depth.

SD (Low quality) SD (High quality) HD 720p 1 HD 1080p 2 UHD 2
Video resolution 320 x 180 px 640 x 360 px 1280 x 720 px 1920 x 1080 px 3840 x 2160 px
Video frame rate 30 fps 30 fps 30 fps 30 fps 30 fps
Video bitrate 600 Kbps 1.6 Mbps 4 Mbps 10 Mbps 20 Mbps

1 Required for Android Television device implementations, but for other type of devices only when supported by hardware.

2 STRONGLY RECOMMENDED for Android Television device implementations when supported by hardware.

Android device implementations, when supporting H.265 codec as described in section 5.1.3 , MUST support the Main Profile Level 3 Main tier and the following SD video decoding profiles and SHOULD support the HD decoding profiles. Android Television devices SHOULD support Main10 Level 5 Main Tier profile and the UHD decoding profile. Android Television devices are STRONGLY RECOMMENDED to support the HD 1080p decoding profile. If the HD 1080p decoding profile is supported, it MUST support the Main Profile Level 4.1 Main tier

SD (Low quality) SD (High quality) HD 720p 1 HD 1080p 2 UHD 2
Video resolution 352 x 288 px 640 x 360 px 1280 x 720 px 1920 x 1080 px 3840 x 2160 px
Video frame rate 30 fps 30 fps 30 fps 30 fps 30 fps
Video bitrate 600 Kbps 1.6 Mbps 4 Mbps 10 Mbps 20 Mbps

1 Required for Android Television device implementation, but for other type of devices only when supported by hardware.

2 STRONGLY RECOMMENDED for Android Television device implementations when supported by hardware.

5.4. Audio Recording

While some of the requirements outlined in this section are stated as SHOULD since Android 4.3, the Compatibility Definition for a future version is planned to change these to MUST. Existing and new Android devices are STRONGLY RECOMMENDED to meet these requirements that are stated as SHOULD, or they will not be able to attain Android compatibility when upgraded to the future version.

5.4.1. Raw Audio Capture

Device implementations that declare android.hardware.microphone MUST allow capture of raw audio content with the following characteristics:

  • Format : Linear PCM, 16-bit
  • Sampling rates : 8000, 11025, 16000, 44100
  • Channels : Mono

Device implementations that declare android.hardware.microphone SHOULD allow capture of raw audio content with the following characteristics:

  • Format : Linear PCM, 16-bit
  • Sampling rates : 22050, 48000
  • Channels : Stereo

5.4.2. Capture for Voice Recognition

In addition to the above recording specifications, when an application has started recording an audio stream using the android.media.MediaRecorder.AudioSource.VOICE_RECOGNITION audio source:

  • The device SHOULD exhibit approximately flat amplitude versus frequency characteristics: specifically, ±3 dB, from 100 Hz to 4000 Hz.
  • Audio input sensitivity SHOULD be set such that a 90 dB sound power level (SPL) source at 1000 Hz yields RMS of 2500 for 16-bit samples.
  • PCM amplitude levels SHOULD linearly track input SPL changes over at least a 30 dB range from -18 dB to +12 dB re 90 dB SPL at the microphone.
  • Total harmonic distortion SHOULD be less than 1% for 1Khz at 90 dB SPL input level at the microphone.
  • Noise reduction processing, if present, MUST be disabled.
  • Automatic gain control, if present, MUST be disabled

If the platform supports noise suppression technologies tuned for speech recognition, the effect MUST be controllable from the android.media.audiofx.NoiseSuppressor API. Moreover, the UUID field for the noise suppressor's effect descriptor MUST uniquely identify each implementation of the noise suppression technology.

5.4.3. Capture for Rerouting of Playback

The android.media.MediaRecorder.AudioSource class includes the REMOTE_SUBMIX audio source. Devices that declare android.hardware.audio.output MUST properly implement the REMOTE_SUBMIX audio source so that when an application uses the android.media.AudioRecord API to record from this audio source, it can capture a mix of all audio streams except for the following:

  • STREAM_RING
  • STREAM_ALARM
  • STREAM_NOTIFICATION

5.5. Audio Playback

Device implementations that declare android.hardware.audio.output MUST conform to the requirements in this section.

5.5.1. Raw Audio Playback

The device MUST allow playback of raw audio content with the following characteristics:

  • Format : Linear PCM, 16-bit
  • Sampling rates : 8000, 11025, 16000, 22050, 32000, 44100
  • Channels : Mono, Stereo

The device SHOULD allow playback of raw audio content with the following characteristics:

  • Sampling rates : 24000, 48000

5.5.2. Audio Effects

Android provides an API for audio effects for device implementations [ Resources, 52 ]. Device implementations that declare the feature android.hardware.audio.output:

  • MUST support the EFFECT_TYPE_EQUALIZER and EFFECT_TYPE_LOUDNESS_ENHANCER implementations controllable through the AudioEffect subclasses Equalizer, LoudnessEnhancer.
  • MUST support the visualizer API implementation, controllable through the Visualizer class.
  • SHOULD support the EFFECT_TYPE_BASS_BOOST, EFFECT_TYPE_ENV_REVERB, EFFECT_TYPE_PRESET_REVERB, and EFFECT_TYPE_VIRTUALIZER implementations controllable through the AudioEffect sub-classes BassBoost, EnvironmentalReverb, PresetReverb, and Virtualizer.

5.5.3. Audio Output Volume

Android Television device implementations MUST include support for system Master Volume and digital audio output volume attenuation on supported outputs, except for compressed audio passthrough output (where no audio decoding is done on the device).

5.6. Audio Latency

Audio latency is the time delay as an audio signal passes through a system. Many classes of applications rely on short latencies, to achieve real-time sound effects.

For the purposes of this section, use the following definitions:

  • output latency . The interval between when an application writes a frame of PCM-coded data and when the corresponding sound can be heard by an external listener or observed by a transducer.
  • cold output latency . The output latency for the first frame, when the audio output system has been idle and powered down prior to the request.
  • continuous output latency . The output latency for subsequent frames, after the device is playing audio.
  • input latency . The interval between when an external sound is presented to the device and when an application reads the corresponding frame of PCM-coded data.
  • cold input latency . The sum of lost input time and the input latency for the first frame, when the audio input system has been idle and powered down prior to the request.
  • continuous input latency . The input latency for subsequent frames, while the device is capturing audio.
  • cold output jitter . The variance among separate measurements of cold output latency values.
  • cold input jitter . The variance among separate measurements of cold input latency values.
  • continuous round-trip latency . The sum of continuous input latency plus continuous output latency plus 5 milliseconds.
  • OpenSL ES PCM buffer queue API . The set of PCM-related OpenSL ES APIs within Android NDK; see NDK_root/docs/opensles/index.html.

Device implementations that declare android.hardware.audio.output SHOULD meet or exceed these audio output requirements:

  • cold output latency of 100 milliseconds or less
  • continuous output latency of 45 milliseconds or less
  • minimize the cold output jitter

If a device implementation meets the requirements of this section after any initial calibration when using the OpenSL ES PCM buffer queue API, for continuous output latency and cold output latency over at least one supported audio output device, it MAY report support for low-latency audio, by reporting the feature android.hardware.audio.low_latency via the android.content.pm.PackageManager class [ Resources, 53 ]. Conversely, if the device implementation does not meet these requirements it MUST NOT report support for low-latency audio.

Device implementations that include android.hardware.microphone SHOULD meet these input audio requirements:

  • cold input latency of 100 milliseconds or less
  • continuous input latency of 30 milliseconds or less
  • continuous round-trip latency of 50 milliseconds or less
  • minimize the cold input jitter

5.7. Network Protocols

Devices MUST support the media network protocols for audio and video playback as specified in the Android SDK documentation [ Resources, 50 ]. Specifically, devices MUST support the following media network protocols:

  • RTSP (RTP, SDP)
  • HTTP(S) progressive streaming
  • HTTP(S) Live Streaming draft protocol, Version 3 [ Resources, 54 ]

5.8. Secure Media

Device implementations that support secure video output and are capable of supporting secure surfaces MUST declare support for Display.FLAG_SECURE. Device implementations that declare support for Display.FLAG_SECURE, if they support a wireless display protocol, MUST secure the link with a cryptographically strong mechanism such as HDCP 2.x or higher for Miracast wireless displays. Similarly if they support a wired external display, the device implementations MUST support HDCP 1.2 or higher. Android Television device implementations MUST support HDCP 2.2 for devices supporting 4K resolution and HDCP 1.4 or above for lower resolutions. The upstream Android open source implementation includes support for wireless (Miracast) and wired (HDMI) displays that satisfies this requirement.

6. Developer Tools and Options Compatibility

6.1. Developer Tools

Device implementations MUST support the Android Developer Tools provided in the Android SDK. Android compatible devices MUST be compatible with:

Device implementations MUST support all adb functions as documented in the Android SDK including dumpsys [ Resources, 56 ]. The device-side adb daemon MUST be inactive by default and there MUST be a user-accessible mechanism to turn on the Android Debug Bridge. If a device implementation omits USB peripheral mode, it MUST implement the Android Debug Bridge via local-area network (such as Ethernet or 802.11).

Android includes support for secure adb. Secure adb enables adb on known authenticated hosts. Device implementations MUST support secure adb.

Device implementations MUST support all ddms features as documented in the Android SDK. As ddms uses adb, support for ddms SHOULD be inactive by default, but MUST be supported whenever the user has activated the Android Debug Bridge, as above.

Device implementations MUST include the Monkey framework, and make it available for applications to use.

Device implementations MUST support systrace tool as documented in the Android SDK. Systrace must be inactive by default, and there MUST be a user-accessible mechanism to turn on Systrace.

Most Linux-based systems and Apple Macintosh systems recognize Android devices using the standard Android SDK tools, without additional support; however Microsoft Windows systems typically require a driver for new Android devices. (For instance, new vendor IDs and sometimes new device IDs require custom USB drivers for Windows systems.) If a device implementation is unrecognized by the adb tool as provided in the standard Android SDK, device implementers MUST provide Windows drivers allowing developers to connect to the device using the adb protocol. These drivers MUST be provided for Windows XP, Windows Vista, Windows 7, Windows 8, and Windows 9 in both 32-bit and 64-bit versions.

6.2. Developer Options

Android includes support for developers to configure application development-related settings. Device implementations MUST honor the android.settings.APPLICATION_DEVELOPMENT_SETTINGS intent to show application development-related settings [ Resources, 60 ]. The upstream Android implementation hides the Developer Options menu by default and enables users to launch Developer Options after pressing seven (7) times on the Settings > About Device > Build Number menu item. Device implementations MUST provide a consistent experience for Developer Options. Specifically, device implementations MUST hide Developer Options by default and MUST provide a mechanism to enable Developer Options that is consistent with the upstream Android implementation.

7. Hardware Compatibility

If a device includes a particular hardware component that has a corresponding API for third-party developers, the device implementation MUST implement that API as described in the Android SDK documentation. If an API in the SDK interacts with a hardware component that is stated to be optional and the device implementation does not possess that component:

  • Complete class definitions (as documented by the SDK) for the component APIs MUST still be presented.
  • The API's behaviors MUST be implemented as no-ops in some reasonable fashion.
  • API methods MUST return null values where permitted by the SDK documentation.
  • API methods MUST return no-op implementations of classes where null values are not permitted by the SDK documentation.
  • API methods MUST NOT throw exceptions not documented by the SDK documentation.

A typical example of a scenario where these requirements apply is the telephony API: even on non-phone devices, these APIs must be implemented as reasonable no-ops.

Device implementations MUST consistently report accurate hardware configuration information via the getSystemAvailableFeatures() and hasSystemFeature(String) methods on the android.content.pm.PackageManager class for the same build fingerprint. [ Resources, 53]

7.1. Display and Graphics

Android includes facilities that automatically adjust application assets and UI layouts appropriately for the device, to ensure that third-party applications run well on a variety of hardware configurations [ Resources, 61 ]. Devices MUST properly implement these APIs and behaviors, as detailed in this section.

The units referenced by the requirements in this section are defined as follows:

  • physical diagonal size . The distance in inches between two opposing corners of the illuminated portion of the display.
  • dots per inch (dpi) . The number of pixels encompassed by a linear horizontal or vertical span of 1”. Where dpi values are listed, both horizontal and vertical dpi must fall within the range.
  • aspect ratio . The ratio of the pixels of the longer dimension to the shorter dimension of the screen. For example, a display of 480x854 pixels would be 854/480 = 1.779, or roughly “16:9”.
  • density-independent pixel (dp) The virtual pixel unit normalized to a 160 dpi screen, calculated as: pixels = dps * (density/160).

7.1.1. Screen Configuration

7.1.1.1. Screen Size

Android Watch devices (detailed in section 2 ) MAY have smaller screen sizes as described in this section.

The Android UI framework supports a variety of different screen sizes, and allows applications to query the device screen size (aka “screen layout") via android.content.res.Configuration.screenLayout with the SCREENLAYOUT_SIZE_MASK. Device implementations MUST report the correct screen size as defined in the Android SDK documentation [ Resources, 61 ] and determined by the upstream Android platform. Specifically, device implementations MUST report the correct screen size according to the following logical density-independent pixel (dp) screen dimensions.

  • Devices MUST have screen sizes of at least 426 dp x 320 dp ('small'), unless it is an Android Watch device.
  • Devices that report screen size 'normal' MUST have screen sizes of at least 480 dp x 320 dp.
  • Devices that report screen size 'large' MUST have screen sizes of at least 640 dp x 480 dp.
  • Devices that report screen size 'xlarge' MUST have screen sizes of at least 960 dp x 720 dp.

In addition,

  • Android Watch devices MUST have a screen with the physical diagonal size in the range from 1.1 to 2.5 inches.
  • Other types of Android device implementations, with a physically integrated screen, MUST have a screen at least 2.5 inches in physical diagonal size.

Devices MUST NOT change their reported screen size at any time.

Applications optionally indicate which screen sizes they support via the <supports-screens> attribute in the AndroidManifest.xml file. Device implementations MUST correctly honor applications' stated support for small, normal, large, and xlarge screens, as described in the Android SDK documentation.

7.1.1.2. Screen Aspect Ratio

Android Watch devices MAY have an aspect ratio of 1.0 (1:1).

The screen aspect ratio MUST be a value from 1.3333 (4:3) to 1.86 (roughly 16:9), but Android Watch devices MAY have an aspect ratio of 1.0 (1:1) because such a device implementation will use a UI_MODE_TYPE_WATCH as the android.content.res.Configuration.uiMode.

7.1.1.3. Screen Density

The Android UI framework defines a set of standard logical densities to help application developers target application resources. Device implementations MUST report only one of the following logical Android framework densities through the android.util.DisplayMetrics APIs, and MUST execute applications at this standard density and MUST NOT change the value at at any time for the default display.

  • 120 dpi (ldpi)
  • 160 dpi (mdpi)
  • 213 dpi (tvdpi)
  • 240 dpi (hdpi)
  • 280 dpi (280dpi)
  • 320 dpi (xhdpi)
  • 400 dpi (400dpi)
  • 480 dpi (xxhdpi)
  • 560 dpi (560dpi)
  • 640 dpi (xxxhdpi)

Device implementations SHOULD define the standard Android framework density that is numerically closest to the physical density of the screen, unless that logical density pushes the reported screen size below the minimum supported. If the standard Android framework density that is numerically closest to the physical density results in a screen size that is smaller than the smallest supported compatible screen size (320 dp width), device implementations SHOULD report the next lowest standard Android framework density.

7.1.2. Display Metrics

Device implementations MUST report correct values for all display metrics defined in android.util.DisplayMetrics [ Resources, 62 ] and MUST report the same values regardless of whether the embedded or external screen is used as the default display.

7.1.3. Screen Orientation

Devices MUST report which screen orientations they support (android.hardware.screen.portrait and/or android.hardware.screen.landscape) and MUST report at least one supported orientation. For example, a device with a fixed orientation landscape screen, such as a television or laptop, SHOULD only report android.hardware.screen.landscape.

Devices that report both screen orientations MUST support dynamic orientation by applications to either portrait or landscape screen orientation. That is, the device must respect the application's request for a specific screen orientation. Device implementations MAY select either portrait or landscape orientation as the default.

Devices MUST report the correct value for the device's current orientation, whenever queried via the android.content.res.Configuration.orientation, android.view.Display.getOrientation(), or other APIs.

Devices MUST NOT change the reported screen size or density when changing orientation.

7.1.4. 2D and 3D Graphics Acceleration

Device implementations MUST support both OpenGL ES 1.0 and 2.0, as embodied and detailed in the Android SDK documentations. Device implementations SHOULD support OpenGL ES 3.0 or 3.1 on devices capable of supporting it. Device implementations MUST also support Android RenderScript, as detailed in the Android SDK documentation [ Resources, 63 ].

Device implementations MUST also correctly identify themselves as supporting OpenGL ES 1.0, OpenGL ES 2.0, OpenGL ES 3.0 or OpenGL 3.1. That is:

  • The managed APIs (such as via the GLES10.getString() method) MUST report support for OpenGL ES 1.0 and OpenGL ES 2.0.
  • The native C/C++ OpenGL APIs (APIs available to apps via libGLES_v1CM.so, libGLES_v2.so, or libEGL.so) MUST report support for OpenGL ES 1.0 and OpenGL ES 2.0.
  • Device implementations that declare support for OpenGL ES 3.0 or 3.1 MUST support the corresponding managed APIs and include support for native C/C++ APIs. On device implementations that declare support for OpenGL ES 3.0 or 3.1, libGLESv2.so MUST export the corresponding function symbols in addition to the OpenGL ES 2.0 function symbols.

In addition to OpenGL ES 3.1, Android provides an extension pack with Java interfaces [ Resources, 64 ] and native support for advanced graphics functionality such as tessellation and the ASTC texture compression format. Android device implementations MAY support this extension pack, and—only if fully implemented—MUST identify the support through the android.hardware.opengles.aep feature flag.

Also, device implementations MAY implement any desired OpenGL ES extensions. However, device implementations MUST report via the OpenGL ES managed and native APIs all extension strings that they do support, and conversely MUST NOT report extension strings that they do not support.

Note that Android includes support for applications to optionally specify that they require specific OpenGL texture compression formats. These formats are typically vendor-specific. Device implementations are not required by Android to implement any specific texture compression format. However, they SHOULD accurately report any texture compression formats that they do support, via the getString() method in the OpenGL API.

Android includes a mechanism for applications to declare that they want to enable hardware acceleration for 2D graphics at the Application, Activity, Window, or View level through the use of a manifest tag android:hardwareAccelerated or direct API calls [ Resources, 65 ].

Device implementations MUST enable hardware acceleration by default, and MUST disable hardware acceleration if the developer so requests by setting android:hardwareAccelerated="false” or disabling hardware acceleration directly through the Android View APIs.

In addition, device implementations MUST exhibit behavior consistent with the Android SDK documentation on hardware acceleration [ Resources, 65 ].

Android includes a TextureView object that lets developers directly integrate hardware-accelerated OpenGL ES textures as rendering targets in a UI hierarchy. Device implementations MUST support the TextureView API, and MUST exhibit consistent behavior with the upstream Android implementation.

Android includes support for EGL_ANDROID_RECORDABLE, an EGLConfig attribute that indicates whether the EGLConfig supports rendering to an ANativeWindow that records images to a video. Device implementations MUST support EGL_ANDROID_RECORDABLE extension [ Resources, 66 ].

7.1.5. Legacy Application Compatibility Mode

Android specifies a “compatibility mode” in which the framework operates in a 'normal' screen size equivalent (320dp width) mode for the benefit of legacy applications not developed for old versions of Android that pre-date screen-size independence.

  • Android Automotive does not support legacy compatibility mode.
  • All other device implementations MUST include support for legacy application compatibility mode as implemented by the upstream Android open source code. That is, device implementations MUST NOT alter the triggers or thresholds at which compatibility mode is activated, and MUST NOT alter the behavior of the compatibility mode itself.

7.1.6. Screen Technology

The Android platform includes APIs that allow applications to render rich graphics to the display. Devices MUST support all of these APIs as defined by the Android SDK unless specifically allowed in this document.

  • Devices MUST support displays capable of rendering 16-bit color graphics and SHOULD support displays capable of 24-bit color graphics.
  • Devices MUST support displays capable of rendering animations.
  • The display technology used MUST have a pixel aspect ratio (PAR) between 0.9 and 1.15. That is, the pixel aspect ratio MUST be near square (1.0) with a 10 ~ 15% tolerance.

7.1.7. Secondary Displays

Android includes support for secondary display to enable media sharing capabilities and developer APIs for accessing external displays. If a device supports an external display either via a wired, wireless, or an embedded additional display connection then the device implementation MUST implement the display manager API as described in the Android SDK documentation [ Resources, 67 ].

7.2. Input Devices

Devices MUST support a touchscreen or meet the requirements listed in 7.2.2 for non-touch navigation.

7.2.1. Keyboard

Android Watch and Android Automotive implementations MAY implement a soft keyboard. All other device implementations MUST implement a soft keyboard and:

Device implementations:

  • MUST include support for the Input Management Framework (which allows third-party developers to create Input Method Editors—ie soft keyboard) as detailed at http://developer.android.com .
  • MUST provide at least one soft keyboard implementation (regardless of whether a hard keyboard is present) except for Android Watch devices where the screen size makes it less reasonable to have a soft keyboard.
  • MAY include additional soft keyboard implementations.
  • MAY include a hardware keyboard.
  • MUST NOT include a hardware keyboard that does not match one of the formats specified in android.content.res.Configuration.keyboard [ Resources, 68 ] (QWERTY or 12-key).

7.2.2. Non-touch Navigation

Android Television devices MUST support D-pad.

Device implementations:

  • MAY omit a non-touch navigation option (trackball, d-pad, or wheel) if the device implementation is not an Android Television device.
  • MUST report the correct value for android.content.res.Configuration.navigation [ Resources, 68 ].
  • MUST provide a reasonable alternative user interface mechanism for the selection and editing of text, compatible with Input Management Engines. The upstream Android open source implementation includes a selection mechanism suitable for use with devices that lack non-touch navigation inputs.

7.2.3. Navigation Keys

The availability and visibility requirement of the Home, Recents, and Back functions differ between device types as described in this section.

The Home, Recents, and Back functions (mapped to the key events KEYCODE_HOME, KEYCODE_APP_SWITCH, KEYCODE_BACK, respectively) are essential to the Android navigation paradigm and therefore:

  • Android Handheld device implementations MUST provide the Home, Recents, and Back functions.
  • Android Television device implementations MUST provide the Home and Back functions.
  • Android Watch device implementations MUST have the Home function available to the user, and the Back function except for when it is in UI_MODE_TYPE_WATCH.
  • Android Automotive implementations MUST provide the Home function and MAY provide Back and Recent functions.
  • All other types of device implementations MUST provide the Home and Back functions.

These functions MAY be implemented via dedicated physical buttons (such as mechanical or capacitive touch buttons), or MAY be implemented using dedicated software keys on a distinct portion of the screen, gestures, touch panel, etc. Android supports both implementations. All of these functions MUST be accessible with a single action (eg tap, double-click or gesture) when visible.

Recents function, if provided, MUST have a visible button or icon unless hidden together with other navigation functions in full-screen mode. This does not apply to devices upgrading from earlier Android versions that have physical buttons for navigation and no recents key.

The Home and Back functions, if provided, MUST each have a visible button or icon unless hidden together with other navigation functions in full-screen mode or when the uiMode UI_MODE_TYPE_MASK is set to UI_MODE_TYPE_WATCH.

The Menu function is deprecated in favor of action bar since Android 4.0. Therefore the new device implementations shipping with Android 5.0 and later MUST NOT implement a dedicated physical button for the Menu function. Older device implementations SHOULD NOT implement a dedicated physical button for the Menu function, but if the physical Menu button is implemented and the device is running applications with targetSdkVersion > 10, the device implementation:

  • MUST display the action overflow button on the action bar when it is visible and the resulting action overflow menu popup is not empty. For a device implementation launched before Android 4.4 but upgrading to Android 5.1, this is RECOMMENDED.
  • MUST NOT modify the position of the action overflow popup displayed by selecting the overflow button in the action bar.
  • MAY render the action overflow popup at a modified position on the screen when it is displayed by selecting the physical menu button.

For backwards compatibility, device implementations MUST make the Menu function available to applications when targetSdkVersion is less than 10, either by a physical button, a software key, or gestures. This Menu function should be presented unless hidden together with other navigation functions.

Android supports Assist action [ Resources, 69 ]. Android device implementations except for Android Watch devices MUST make the Assist action available to the user at all times when running applications. The Assist action SHOULD be implemented as a long-press on the Home button or a swipe-up gesture on the software Home key. This function MAY be implemented via another physical button, software key, or gesture, but MUST be accessible with a single action (eg tap, double-click, or gesture) when other navigation keys are visible.

Device implementations MAY use a distinct portion of the screen to display the navigation keys, but if so, MUST meet these requirements:

  • Device implementation navigation keys MUST use a distinct portion of the screen, not available to applications, and MUST NOT obscure or otherwise interfere with the portion of the screen available to applications.
  • Device implementations MUST make available a portion of the display to applications that meets the requirements defined in section 7.1.1 .
  • Device implementations MUST display the navigation keys when applications do not specify a system UI mode, or specify SYSTEM_UI_FLAG_VISIBLE.
  • Device implementations MUST present the navigation keys in an unobtrusive “low profile” (eg. dimmed) mode when applications specify SYSTEM_UI_FLAG_LOW_PROFILE.
  • Device implementations MUST hide the navigation keys when applications specify SYSTEM_UI_FLAG_HIDE_NAVIGATION.

7.2.4. Touchscreen Input

Android Handhelds and Watch Devices MUST support touchscreen input.

Device implementations SHOULD have a pointer input system of some kind (either mouse-like or touch). However, if a device implementation does not support a pointer input system, it MUST NOT report the android.hardware.touchscreen or android.hardware.faketouch feature constant. Device implementations that do include a pointer input system:

  • SHOULD support fully independently tracked pointers, if the device input system supports multiple pointers.
  • MUST report the value of android.content.res.Configuration.touchscreen [ Resources, 68 ] corresponding to the type of the specific touchscreen on the device.

Android includes support for a variety of touchscreens, touch pads, and fake touch input devices. Touchscreen based device implementations are associated with a display [ Resources, 70 ] such that the user has the impression of directly manipulating items on screen. Since the user is directly touching the screen, the system does not require any additional affordances to indicate the objects being manipulated. In contrast, a fake touch interface provides a user input system that approximates a subset of touchscreen capabilities. For example, a mouse or remote control that drives an on-screen cursor approximates touch, but requires the user to first point or focus then click. Numerous input devices like the mouse, trackpad, gyro-based air mouse, gyro-pointer, joystick, and multi-touch trackpad can support fake touch interactions. Android includes the feature constant android.hardware.faketouch, which corresponds to a high-fidelity non-touch (pointer-based) input device such as a mouse or trackpad that can adequately emulate touch-based input (including basic gesture support), and indicates that the device supports an emulated subset of touchscreen functionality. Device implementations that declare the fake touch feature MUST meet the fake touch requirements in section 7.2.5 .

Device implementations MUST report the correct feature corresponding to the type of input used. Device implementations that include a touchscreen (single-touch or better) MUST report the platform feature constant android.hardware.touchscreen. Device implementations that report the platform feature constant android.hardware.touchscreen MUST also report the platform feature constant android.hardware.faketouch. Device implementations that do not include a touchscreen (and rely on a pointer device only) MUST NOT report any touchscreen feature, and MUST report only android.hardware.faketouch if they meet the fake touch requirements in section 7.2.5 .

7.2.5. Fake Touch Input

Device implementations that declare support for android.hardware.faketouch:

  • MUST report the absolute X and Y screen positions of the pointer location and display a visual pointer on the screen [ Resources, 71 ].
  • MUST report touch event with the action code that specifies the state change that occurs on the pointer going down or up on the screen [ Resources, 71 ].
  • MUST support pointer down and up on an object on the screen, which allows users to emulate tap on an object on the screen.
  • MUST support pointer down, pointer up, pointer down then pointer up in the same place on an object on the screen within a time threshold, which allows users to emulate double tap on an object on the screen [ Resources, 71 ].
  • MUST support pointer down on an arbitrary point on the screen, pointer move to any other arbitrary point on the screen, followed by a pointer up, which allows users to emulate a touch drag.
  • MUST support pointer down then allow users to quickly move the object to a different position on the screen and then pointer up on the screen, which allows users to fling an object on the screen.

Devices that declare support for android.hardware.faketouch.multitouch.distinct MUST meet the requirements for faketouch above, and MUST also support distinct tracking of two or more independent pointer inputs.

7.2.6. Game Controller Support

Android Television device implementations MUST support button mappings for game controllers as listed below. The upstream Android implementation includes implementation for game controllers that satisfies this requirement.

7.2.6.1. Button Mappings

Android Television device implementations MUST support the following key mappings:

Button HID Usage 2 Android Button
A 1 0x09 0x0001 KEYCODE_BUTTON_A (96)
B 1 0x09 0x0002 KEYCODE_BUTTON_B (97)
X 1 0x09 0x0004 KEYCODE_BUTTON_X (99)
Y 1 0x09 0x0005 KEYCODE_BUTTON_Y (100)
D-pad up 1

D-pad down 1

0x01 0x0039 3 AXIS_HAT_Y 4
D-pad left 1

D-pad right 1

0x01 0x0039 3 AXIS_HAT_X 4
Left shoulder button 1 0x09 0x0007 KEYCODE_BUTTON_L1 (102)
Right shoulder button 1 0x09 0x0008 KEYCODE_BUTTON_R1 (103)
Left stick click 1 0x09 0x000E KEYCODE_BUTTON_THUMBL (106)
Right stick click 1 0x09 0x000F KEYCODE_BUTTON_THUMBR (107)
Home 1 0x0c 0x0223 KEYCODE_HOME (3)
Back 1 0x0c 0x0224 KEYCODE_BACK (4)

1 [ Resources, 72 ]

2 The above HID usages must be declared within a Game pad CA (0x01 0x0005).

3 This usage must have a Logical Minimum of 0, a Logical Maximum of 7, a Physical Minimum of 0, a Physical Maximum of 315, Units in Degrees, and a Report Size of 4. The logical value is defined to be the clockwise rotation away from the vertical axis; for example, a logical value of 0 represents no rotation and the up button being pressed, while a logical value of 1 represents a rotation of 45 degrees and both the up and left keys being pressed.

4 [ Resources, 71 ]

Analog Controls 1 HID Usage Android Button
Left Trigger 0x02 0x00C5 AXIS_LTRIGGER
Right Trigger 0x02 0x00C4 AXIS_RTRIGGER
Left Joystick 0x01 0x0030

0x01 0x0031

AXIS_X

AXIS_Y

Right Joystick 0x01 0x0032

0x01 0x0035

AXIS_Z

AXIS_RZ

1 [ Resources, 71 ]

7.2.7. Remote Control

Android Television device implementations SHOULD provide a remote control to allow users to access the TV interface. The remote control MAY be a physical remote or can be a software-based remote that is accessible from a mobile phone or tablet. The remote control MUST meet the requirements defined below.

  • Search affordance . Device implementations MUST fire KEYCODE_SEARCH when the user invokes voice search either on the physical or software-based remote.
  • Navigation . All Android Television remotes MUST include Back, Home, and Select buttons and support for D-pad events [ Resources, 72 ].

7.3. Sensors

Android includes APIs for accessing a variety of sensor types. Devices implementations generally MAY omit these sensors, as provided for in the following subsections. If a device includes a particular sensor type that has a corresponding API for third-party developers, the device implementation MUST implement that API as described in the Android SDK documentation and the Android Open Source documentation on sensors [ Resources, 73 ]. For example, device implementations:

  • MUST accurately report the presence or absence of sensors per the android.content.pm.PackageManager class [ Resources, 53] .
  • MUST return an accurate list of supported sensors via the SensorManager.getSensorList() and similar methods.
  • MUST behave reasonably for all other sensor APIs (for example, by returning true or false as appropriate when applications attempt to register listeners, not calling sensor listeners when the corresponding sensors are not present; etc.).
  • MUST report all sensor measurements using the relevant International System of Units (metric) values for each sensor type as defined in the Android SDK documentation [ Resources, 74 ].
  • SHOULD report the event time in nanoseconds as defined in the Android SDK documentation, representing the time the event happened and synchronized with the SystemClock.elapsedRealtimeNano() clock. Existing and new Android devices are very strongly encouraged to meet these requirement so they will be able to upgrade to the future platform releases where this might become a REQUIRED component. The synchronization error SHOULD be below 100 milliseconds [ Resources, 75 ].

The list above is not comprehensive; the documented behavior of the Android SDK and the Android Open Source Documentations on Sensors [ Resources, 73 ] is to be considered authoritative.

Some sensor types are composite, meaning they can be derived from data provided by one or more other sensors. (Examples include the orientation sensor, and the linear acceleration sensor.) Device implementations SHOULD implement these sensor types, when they include the prerequisite physical sensors as described in [ Resources, 76 ]. If a device implementation includes a composite sensor it MUST implement the sensor as described in the Android Open Source documentation on composite sensors [ Resources, 76 ].

Some Android sensors support a “continuous” trigger mode, which returns data continuously [ Resources, 77 ]. For any API indicated by the Android SDK documentation to be a continuous sensor, device implementations MUST continuously provide periodic data samples that SHOULD have a jitter below 3%, where jitter is defined as the standard deviation of the difference of the reported timestamp values between consecutive events.

Note that the device implementations MUST ensure that the sensor event stream MUST NOT prevent the device CPU from entering a suspend state or waking up from a suspend state.

Finally, when several sensors are activated, the power consumption SHOULD NOT exceed the sum of the individual sensor's reported power consumption.

7.3.1. Accelerometer

Device implementations SHOULD include a 3-axis accelerometer. Android Handheld devices and Android Watch devices are strongly encouraged to include this sensor. If a device implementation does include a 3-axis accelerometer, it:

  • MUST implement and report TYPE_ACCELEROMETER sensor [ Resources, 78 ].
  • MUST be able to report events up to a frequency of at least 50 Hz for Android Watch devices as such devices have a stricter power constraint and 100 Hz for all other device types.
  • SHOULD report events up to at least 200 Hz.
  • MUST comply with the Android sensor coordinate system as detailed in the Android APIs [ Resources, 74 ].
  • MUST be capable of measuring from freefall up to four times the gravity (4g) or more on any axis.
  • MUST have a resolution of at least 8-bits and SHOULD have a resolution of at least 16-bits.
  • SHOULD be calibrated while in use if the characteristics changes over the life cycle and compensated, and preserve the compensation parameters between device reboots.
  • SHOULD be temperature compensated.
  • MUST have a standard deviation no greater than 0.05 m/s^, where the standard deviation should be calculated on a per axis basis on samples collected over a period of at least 3 seconds at the fastest sampling rate.
  • SHOULD implement the TYPE_SIGNIFICANT_MOTION, TYPE_TILT_DETECTOR, TYPE_STEP_DETECTOR, TYPE_STEP_COUNTER composite sensors as described in the Android SDK document. Existing and new Android devices are very strongly encouraged to implement the TYPE_SIGNIFICANT_MOTION composite sensor. If any of these sensors are implemented, the sum of their power consumption MUST always be less than 4 mW and SHOULD each be below 2 mW and 0.5 mW for when the device is in a dynamic or static condition.
  • If a gyroscope sensor is included, MUST implement the TYPE_GRAVITY and TYPE_LINEAR_ACCELERATION composite sensors and SHOULD implement the TYPE_GAME_ROTATION_VECTOR composite sensor. Existing and new Android devices are strongly encouraged to implement the TYPE_GAME_ROTATION_VECTOR sensor.
  • SHOULD implement a TYPE_ROTATION_VECTOR composite sensor, if a gyroscope sensor and a magnetometer sensor is also included.

7.3.2. Magnetometer

Device implementations SHOULD include a 3-axis magnetometer (compass). If a device does include a 3-axis magnetometer, it:

  • MUST implement the TYPE_MAGNETIC_FIELD sensor and SHOULD also implement TYPE_MAGNETIC_FIELD_UNCALIBRATED sensor. Existing and new Android devices are strongly encouraged to implement the TYPE_MAGNETIC_FIELD_UNCALIBRATED sensor.
  • MUST be able to report events up to a frequency of at least 10 Hz and SHOULD report events up to at least 50 Hz.
  • MUST comply with the Android sensor coordinate system as detailed in the Android APIs [ Resources, 74 ].
  • MUST be capable of measuring between -900 µT and +900 µT on each axis before saturating.
  • MUST have a hard iron offset value less than 700 µT and SHOULD have a value below 200 µT, by placing the magnetometer far from dynamic (current-induced) and static (magnet-induced) magnetic fields.
  • MUST have a resolution equal or denser than 0.6 µT and SHOULD have a resolution equal or denser than 0.2 µ.
  • SHOULD be temperature compensated.
  • MUST support online calibration and compensation of the hard iron bias, and preserve the compensation parameters between device reboots.
  • MUST have the soft iron compensation applied—the calibration can be done either while in use or during the production of the device.
  • SHOULD have a standard deviation, calculated on a per axis basis on samples collected over a period of at least 3 seconds at the fastest sampling rate, no greater than 0.5 µT.
  • SHOULD implement a TYPE_ROTATION_VECTOR composite sensor, if an accelerometer sensor and a gyroscope sensor is also included.
  • MAY implement the TYPE_GEOMAGNETIC_ROTATION_VECTOR sensor if an accelerometer sensor is also implemented. However if implemented, it MUST consume less than 10 mW and SHOULD consume less than 3 mW when the sensor is registered for batch mode at 10 Hz.

7.3.3. GPS

Device implementations SHOULD include a GPS receiver. If a device implementation does include a GPS receiver, it SHOULD include some form of“assisted GPS” technique to minimize GPS lock-on time.

7.3.4. Gyroscope

Device implementations SHOULD include a gyroscope (angular change sensor). Devices SHOULD NOT include a gyroscope sensor unless a 3-axis accelerometer is also included. If a device implementation includes a gyroscope, it:

  • MUST implement the TYPE_GYROSCOPE sensor and SHOULD also implement TYPE_GYROSCOPE_UNCALIBRATED sensor. Existing and new Android devices are strongly encouraged to implement the SENSOR_TYPE_GYROSCOPE_UNCALIBRATED sensor.
  • MUST be capable of measuring orientation changes up to 1,000 degrees per second.
  • MUST be able to report events up to a frequency of at least 50 Hz for Android Watch devices as such devices have a stricter power constraint and 100 Hz for all other device types.
  • SHOULD report events up to at least 200 Hz.
  • MUST have a resolution of 12-bits or more and SHOULD have a resolution of 16-bits or more.
  • MUST be temperature compensated.
  • MUST be calibrated and compensated while in use, and preserve the compensation parameters between device reboots.
  • MUST have a variance no greater than 1e-7 rad^2 / s^2 per Hz (variance per Hz, or rad^2 / s). The variance is allowed to vary with the sampling rate, but must be constrained by this value. In other words, if you measure the variance of the gyro at 1 Hz sampling rate it should be no greater than 1e-7 rad^2/s^2.
  • SHOULD implement a TYPE_ROTATION_VECTOR composite sensor, if an accelerometer sensor and a magnetometer sensor is also included.
  • If an accelerometer sensor is included, MUST implement the TYPE_GRAVITY and TYPE_LINEAR_ACCELERATION composite sensors and SHOULD implement the TYPE_GAME_ROTATION_VECTOR composite sensor. Existing and new Android devices are strongly encouraged to implement the TYPE_GAME_ROTATION_VECTOR sensor.

7.3.5. Barometer

Device implementations SHOULD include a barometer (ambient air pressure sensor). If a device implementation includes a barometer, it:

  • MUST implement and report TYPE_PRESSURE sensor.
  • MUST be able to deliver events at 5 Hz or greater.
  • MUST have adequate precision to enable estimating altitude.
  • MUST be temperature compensated.

7.3.6. Thermometer

Device implementations MAY include an ambient thermometer (temperature sensor). If present, it MUST be defined as SENSOR_TYPE_AMBIENT_TEMPERATURE and it MUST measure the ambient (room) temperature in degrees Celsius.

Device implementations MAY but SHOULD NOT include a CPU temperature sensor. If present, it MUST be defined as SENSOR_TYPE_TEMPERATURE, it MUST measure the temperature of the device CPU, and it MUST NOT measure any other temperature. Note the SENSOR_TYPE_TEMPERATURE sensor type was deprecated in Android 4.0.

7.3.7. Photometer

Device implementations MAY include a photometer (ambient light sensor).

7.3.8. Proximity Sensor

Device implementations MAY include a proximity sensor. Devices that can make a voice call and indicate any value other than PHONE_TYPE_NONE in getPhoneType SHOULD include a proximity sensor. If a device implementation does include a proximity sensor, it:

  • MUST measure the proximity of an object in the same direction as the screen. That is, the proximity sensor MUST be oriented to detect objects close to the screen, as the primary intent of this sensor type is to detect a phone in use by the user. If a device implementation includes a proximity sensor with any other orientation, it MUST NOT be accessible through this API.
  • MUST have 1-bit of accuracy or more.

7.4. Data Connectivity

7.4.1. Telephony

“Telephony” as used by the Android APIs and this document refers specifically to hardware related to placing voice calls and sending SMS messages via a GSM or CDMA network. While these voice calls may or may not be packet-switched, they are for the purposes of Android considered independent of any data connectivity that may be implemented using the same network. In other words, the Android “telephony” functionality and APIs refer specifically to voice calls and SMS. For instance, device implementations that cannot place calls or send/receive SMS messages MUST NOT report the android.hardware.telephony feature or any subfeatures, regardless of whether they use a cellular network for data connectivity.

Android MAY be used on devices that do not include telephony hardware. That is, Android is compatible with devices that are not phones. However, if a device implementation does include GSM or CDMA telephony, it MUST implement full support for the API for that technology. Device implementations that do not include telephony hardware MUST implement the full APIs as no-ops.

7.4.2. IEEE 802.11 (Wi-Fi)

Android Television device implementations MUST include Wi-Fi support.

Android Television device implementations MUST include support for one or more forms of 802.11 (b/g/a/n, etc.) and other types of Android device implementation SHOULD include support for one or more forms of 802.11. If a device implementation does include support for 802.11 and exposes the functionality to a third-party application, it MUST implement the corresponding Android API and:

  • MUST report the hardware feature flag android.hardware.wifi.
  • MUST implement the multicast API as described in the SDK documentation [ Resources, 79 ].
  • MUST support multicast DNS (mDNS) and MUST NOT filter mDNS packets (224.0.0.251) at any time of operation including when the screen is not in an active state.

7.4.2.1. Wi-Fi Direct

Device implementations SHOULD include support for Wi-Fi Direct (Wi-Fi peer-to-peer). If a device implementation does include support for Wi-Fi Direct, it MUST implement the corresponding Android API as described in the SDK documentation [ Resources, 80 ]. If a device implementation includes support for Wi-Fi Direct, then it:

  • MUST report the hardware feature android.hardware.wifi.direct.
  • MUST support regular Wi-Fi operation.
  • SHOULD support concurrent Wi-Fi and Wi-Fi Direct operation.

Android Television device implementations MUST include support for Wi-Fi Tunneled Direct Link Setup (TDLS).

Android Television device implementations MUST include support for Wi-Fi Tunneled Direct Link Setup (TDLS) and other types of Android device implementations SHOULD include support for Wi-Fi TDLS as described in the Android SDK Documentation [ Resources, 81 ]. If a device implementation does include support for TDLS and TDLS is enabled by the WiFiManager API, the device:

  • SHOULD use TDLS only when it is possible AND beneficial.
  • SHOULD have some heuristic and NOT use TDLS when its performance might be worse than going through the Wi-Fi access point.

7.4.3.蓝牙

Android Watch and Automotive implementations MUST support Bluetooth. Android Television implementations MUST support Bluetooth and Bluetooth LE.

Android includes support for Bluetooth and Bluetooth Low Energy [ Resources, 82 ]. Device implementations that include support for Bluetooth and Bluetooth Low Energy MUST declare the relevant platform features (android.hardware.bluetooth and android.hardware.bluetooth_le respectively) and implement the platform APIs. Device implementations SHOULD implement relevant Bluetooth profiles such as A2DP, AVCP, OBEX, etc. as appropriate for the device. Android Television device implementations MUST support Bluetooth and Bluetooth LE.

Device implementations including support for Bluetooth Low Energy:

  • MUST declare the hardware feature android.hardware.bluetooth_le.
  • MUST enable the GATT (generic attribute profile) based Bluetooth APIs as described in the SDK documentation and [ Resources, 82 ].
  • SHOULD support offloading of the filtering logic to the bluetooth chipset when implementing the ScanFilter API [ Resources, 83 ], and MUST report the correct value of where the filtering logic is implemented whenever queried via the android.bluetooth.BluetoothAdapter.isOffloadedFilteringSupported() method.
  • SHOULD support offloading of the batched scanning to the bluetooth chipset, but if not supported, MUST report 'false' whenever queried via the android.bluetooth.BluetoothAdapater.isOffloadedScanBatchingSupported() method.
  • SHOULD support multi advertisement with at least 4 slots, but if not supported, MUST report 'false' whenever queried via the android.bluetooth.BluetoothAdapter.isMultipleAdvertisementSupported() method.

7.4.4. Near-Field Communications

Device implementations SHOULD include a transceiver and related hardware for Near-Field Communications (NFC). If a device implementation does include NFC hardware and plans to make it available to third-party apps, then it:

  • MUST report the android.hardware.nfc feature from the android.content.pm.PackageManager.hasSystemFeature() method [ Resources, 53 ].
  • MUST be capable of reading and writing NDEF messages via the following NFC standards:
    • MUST be capable of acting as an NFC Forum reader/writer (as defined by the NFC Forum technical specification NFCForum-TS-DigitalProtocol-1.0) via the following NFC standards:
      • NfcA (ISO14443-3A)
      • NfcB (ISO14443-3B)
      • NfcF (JIS 6319-4)
      • IsoDep (ISO 14443-4)
      • NFC Forum Tag Types 1, 2, 3, 4 (defined by the NFC Forum)
    • SHOULD be capable of reading and writing NDEF messages via the following NFC standards. Note that while the NFC standards below are stated as SHOULD, the Compatibility Definition for a future version is planned to change these to MUST. These standards are optional in this version but will be required in future versions. Existing and new devices that run this version of Android are very strongly encouraged to meet these requirements now so they will be able to upgrade to the future platform releases.
      • NfcV (ISO 15693)
    • MUST be capable of transmitting and receiving data via the following peer-to-peer standards and protocols:
      • ISO 18092
      • LLCP 1.0 (defined by the NFC Forum)
      • SDP 1.0 (defined by the NFC Forum)
      • NDEF Push Protocol [ Resources, 84 ]
      • SNEP 1.0 (defined by the NFC Forum)
    • MUST include support for Android Beam [ Resources, 85 ]:
      • MUST implement the SNEP default server. Valid NDEF messages received by the default SNEP server MUST be dispatched to applications using the android.nfc.ACTION_NDEF_DISCOVERED intent. Disabling Android Beam in settings MUST NOT disable dispatch of incoming NDEF message.
      • MUST honor the android.settings.NFCSHARING_SETTINGS intent to show NFC sharing settings [ Resources, 86 ].
      • MUST implement the NPP server. Messages received by the NPP server MUST be processed the same way as the SNEP default server.
      • MUST implement a SNEP client and attempt to send outbound P2P NDEF to the default SNEP server when Android Beam is enabled. If no default SNEP server is found then the client MUST attempt to send to an NPP server.
      • MUST allow foreground activities to set the outbound P2P NDEF message using android.nfc.NfcAdapter.setNdefPushMessage, and android.nfc.NfcAdapter.setNdefPushMessageCallback, and android.nfc.NfcAdapter.enableForegroundNdefPush.
      • SHOULD use a gesture or on-screen confirmation, such as 'Touch to Beam', before sending outbound P2P NDEF messages.
      • SHOULD enable Android Beam by default and MUST be able to send and receive using Android Beam, even when another proprietary NFC P2p mode is turned on.
      • MUST support NFC Connection handover to Bluetooth when the device supports Bluetooth Object Push Profile. Device implementations MUST support connection handover to Bluetooth when using android.nfc.NfcAdapter.setBeamPushUris, by implementing the “Connection Handover version 1.2” [ Resources, 87 ] and “Bluetooth Secure Simple Pairing Using NFC version 1.0” [ Resources, 88 ] specs from the NFC Forum. Such an implementation MUST implement the handover LLCP service with service name “urn:nfc:sn:handover” for exchanging the handover request/select records over NFC, and it MUST use the Bluetooth Object Push Profile for the actual Bluetooth data transfer. For legacy reasons (to remain compatible with Android 4.1 devices), the implementation SHOULD still accept SNEP GET requests for exchanging the handover request/select records over NFC. However an implementation itself SHOULD NOT send SNEP GET requests for performing connection handover.
    • MUST poll for all supported technologies while in NFC discovery mode.
    • SHOULD be in NFC discovery mode while the device is awake with the screen active and the lock-screen unlocked.

(Note that publicly available links are not available for the JIS, ISO, and NFC Forum specifications cited above.)

Android includes support for NFC Host Card Emulation (HCE) mode. If a device implementation does include an NFC controller chipset capable of HCE and Application ID (AID) routing, then it:

  • MUST report the android.hardware.nfc.hce feature constant.
  • MUST support NFC HCE APIs as defined in the Android SDK [ Resources, 10 ].

Additionally, device implementations MAY include reader/writer support for the following MIFARE technologies.

  • MIFARE Classic
  • MIFARE Ultralight
  • NDEF on MIFARE Classic

Note that Android includes APIs for these MIFARE types. If a device implementation supports MIFARE in the reader/writer role, it:

  • MUST implement the corresponding Android APIs as documented by the Android SDK.
  • MUST report the feature com.nxp.mifare from the android.content.pm.PackageManager.hasSystemFeature() meth od [Resources, 53] . Note that this is not a standard Android feature and as such does not appear as a constant on the PackageManager class.
  • MUST NOT implement the corresponding Android APIs nor report the com.nxp.mifare feature unless it also implements general NFC support as described in this section.

If a device implementation does not include NFC hardware, it MUST NOT declare the android.hardware.nfc feature from the android.content.pm.PackageManager.hasSystemFeature() method [ Resources, 53] , and MUST implement the Android NFC API as a no-op.

As the classes android.nfc.NdefMessage and android.nfc.NdefRecord represent a protocol-independent data representation format, device implementations MUST implement these APIs even if they do not include support for NFC or declare the android.hardware.nfc feature.

7.4.5. Minimum Network Capability

Device implementations MUST include support for one or more forms of data networking. Specifically, device implementations MUST include support for at least one data standard capable of 200Kbit/sec or greater. Examples of technologies that satisfy this requirement include EDGE, HSPA, EV-DO, 802.11g, Ethernet, Bluetooth PAN, etc.

Device implementations where a physical networking standard (such as Ethernet) is the primary data connection SHOULD also include support for at least one common wireless data standard, such as 802.11 (Wi-Fi).

Devices MAY implement more than one form of data connectivity.

7.4.6. Sync Settings

Device implementations MUST have the master auto-sync setting on by default so that the method getMasterSyncAutomatically() returns “true” [ Resources, 89 ].

7.5. Cameras

Device implementations SHOULD include a rear-facing camera and MAY include a front-facing camera. A rear-facing camera is a camera located on the side of the device opposite the display; that is, it images scenes on the far side of the device, like a traditional camera. A front-facing camera is a camera located on the same side of the device as the display; that is, a camera typically used to image the user, such as for video conferencing and similar applications.

If a device implementation includes at least one camera, it SHOULD be possible for an application to simultaneously allocate 3 bitmaps equal to the size of the images produced by the largest-resolution camera sensor on the device.

7.5.1. Rear-Facing Camera

Device implementations SHOULD include a rear-facing camera. If a device implementation includes at least one rear-facing camera, it:

  • MUST report the feature flag android.hardware.camera and android.hardware.camera.any.
  • MUST have a resolution of at least 2 megapixels.
  • SHOULD have either hardware auto-focus or software auto-focus implemented in the camera driver (transparent to application software).
  • MAY have fixed-focus or EDOF (extended depth of field) hardware.
  • MAY include a flash. If the Camera includes a flash, the flash lamp MUST NOT be lit while an android.hardware.Camera.PreviewCallback instance has been registered on a Camera preview surface, unless the application has explicitly enabled the flash by enabling the FLASH_MODE_AUTO or FLASH_MODE_ON attributes of a Camera.Parameters object. Note that this constraint does not apply to the device's built-in system camera application, but only to third-party applications using Camera.PreviewCallback.

7.5.2. Front-Facing Camera

Device implementations MAY include a front-facing camera. If a device implementation includes at least one front-facing camera, it:

  • MUST report the feature flag android.hardware.camera.any and android.hardware.camera.front.
  • MUST have a resolution of at least VGA (640x480 pixels).
  • MUST NOT use a front-facing camera as the default for the Camera API. The camera API in Android has specific support for front-facing cameras and device implementations MUST NOT configure the API to to treat a front-facing camera as the default rear-facing camera, even if it is the only camera on the device.
  • MAY include features (such as auto-focus, flash, etc.) available to rear-facing cameras as described in section 7.5.1 .
  • MUST horizontally reflect (ie mirror) the stream displayed by an app in a CameraPreview, as follows:
    • If the device implementation is capable of being rotated by user (such as automatically via an accelerometer or manually via user input), the camera preview MUST be mirrored horizontally relative to the device's current orientation.
    • If the current application has explicitly requested that the Camera display be rotated via a call to the android.hardware.Camera.setDisplayOrientation()[ Resources, 90 ] method, the camera preview MUST be mirrored horizontally relative to the orientation specified by the application.
    • Otherwise, the preview MUST be mirrored along the device's default horizontal axis.
  • MUST mirror the image displayed by the postview in the same manner as the camera preview image stream. If the device implementation does not support postview, this requirement obviously does not apply.
  • MUST NOT mirror the final captured still image or video streams returned to application callbacks or committed to media storage.

7.5.3. External Camera

Device implementations with USB host mode MAY include support for an external camera that connects to the USB port. If a device includes support for an external camera, it:

  • MUST declare the platform feature android.hardware.camera.external and android.hardware camera.any.
  • MUST support USB Video Class (UVC 1.0 or higher).
  • MAY support multiple cameras.

Video compression (such as MJPEG) support is RECOMMENDED to enable transfer of high-quality unencoded streams (ie raw or independently compressed picture streams). Camera-based video encoding MAY be supported. If so, a simultaneous unencoded/ MJPEG stream (QVGA or greater resolution) MUST be accessible to the device implementation.

7.5.4. Camera API Behavior

Android includes two API packages to access the camera, the newer android.hardware.camera2 API expose lower-level camera control to the app, including efficient zero-copy burst/streaming flows and per-frame controls of exposure, gain, white balance gains, color conversion, denoising, sharpening, and more.

The older API package, android.hardware.Camera, is marked as deprecated in Android 5.0 but as it should still be available for apps to use Android device implementations MUST ensure the continued support of the API as described in this section and in the Android SDK.

Device implementations MUST implement the following behaviors for the camera-related APIs, for all available cameras:

  • If an application has never called android.hardware.Camera.Parameters.setPreviewFormat(int), then the device MUST use android.hardware.PixelFormat.YCbCr_420_SP for preview data provided to application callbacks.
  • If an application registers an android.hardware.Camera.PreviewCallback instance and the system calls the onPreviewFrame() method when the preview format is YCbCr_420_SP, the data in the byte[] passed into onPreviewFrame() must further be in the NV21 encoding format. That is, NV21 MUST be the default.
  • For android.hardware.Camera, device implementations MUST support the YV12 format (as denoted by the android.graphics.ImageFormat.YV12 constant) for camera previews for both front- and rear-facing cameras. (The hardware video encoder and camera may use any native pixel format, but the device implementation MUST support conversion to YV12.)
  • For android.hardware.camera2, device implementations must support the android.hardware.ImageFormat.YUV_420_888 and android.hardware.ImageFormat.JPEG formats as outputs through the android.media.ImageReader API.

Device implementations MUST still implement the full Camera API included in the Android SDK documentation [ Resources, 91 ], regardless of whether the device includes hardware autofocus or other capabilities. For instance, cameras that lack autofocus MUST still call any registered android.hardware.Camera.AutoFocusCallback instances (even though this has no relevance to a non-autofocus camera.) Note that this does apply to front-facing cameras; for instance, even though most front-facing cameras do not support autofocus, the API callbacks must still be “faked” as described.

Device implementations MUST recognize and honor each parameter name defined as a constant on the android.hardware.Camera.Parameters class, if the underlying hardware supports the feature. If the device hardware does not support a feature, the API must behave as documented. Conversely, device implementations MUST NOT honor or recognize string constants passed to the android.hardware.Camera.setParameters() method other than those documented as constants on the android.hardware.Camera.Parameters. That is, device implementations MUST support all standard Camera parameters if the hardware allows, and MUST NOT support custom Camera parameter types. For instance, device implementations that support image capture using high dynamic range (HDR) imaging techniques MUST support camera parameter Camera.SCENE_MODE_HDR [ Resources, 92 ].

Because not all device implementations can fully support all the features of the android.hardware.camera2 API, device implementations MUST report the proper level of support with the android.info.supportedHardwareLevel property as described in the Android SDK [ Resources, 93] and report the appropriate framework feature flags [ Resources, 94] .

Device implementations MUST also declare its Individual camera capabilities of android.hardware.camera2 via the android.request.availableCapabilities property and declare the appropriate feature flags [ Resources, 94] ; a device must define the feature flag if any of its attached camera devices supports the feature.

Device implementations MUST broadcast the Camera.ACTION_NEW_PICTURE intent whenever a new picture is taken by the camera and the entry of the picture has been added to the media store.

Device implementations MUST broadcast the Camera.ACTION_NEW_VIDEO intent whenever a new video is recorded by the camera and the entry of the picture has been added to the media store.

7.5.5. Camera Orientation

Both front- and rear-facing cameras, if present, MUST be oriented so that the long dimension of the camera aligns with the screen's long dimension. That is, when the device is held in the landscape orientation, cameras MUST capture images in the landscape orientation. This applies regardless of the device's natural orientation; that is, it applies to landscape-primary devices as well as portrait-primary devices.

7.6. Memory and Storage

7.6.1. Minimum Memory and Storage

Android Television devices MUST have at least 5GB of non-volatile storage available for application private data.

The memory available to the kernel and userspace on device implementations MUST be at least equal or larger than the minimum values specified by the following table. (See section 7.1.1 for screen size and density definitions.)

Density and screen size 32-bit device 64-bit device
Android Watch devices (due to smaller screens) 416MB Not applicable
  • 280dpi or lower on small/normal screens
  • mdpi or lower on large screens
  • ldpi or lower on extra large screens
424MB 704MB
  • xhdpi or higher on small/normal screens
  • hdpi or higher on large screens
  • mdpi or higher on extra large screens
512MB 832MB
  • 400dpi or higher on small/normal screens
  • xhdpi or higher on large screens
  • tvdpi or higher on extra large screens
896MB 1280MB
  • 560dpi or higher on small/normal screens
  • 400dpi or higher on large screens
  • xhdpi or higher on extra large screens
1344MB 1824MB

The minimum memory values MUST be in addition to any memory space already dedicated to hardware components such as radio, video, and so on that is not under the kernel's control.

Device implementations with less than 512MB of memory available to the kernel and userspace, unless an Android Watch, MUST return the value "true" for ActivityManager.isLowRamDevice().

Android Television devices MUST have at least 5GB and other device implementations MUST have at least 1.5GB of non-volatile storage available for application private data. That is, the /data partition MUST be at least 5GB for Android Television devices and at least 1.5GB for other device implementations. Device implementations that run Android are very strongly encouraged to have at least 3GB of non-volatile storage for application private data so they will be able to upgrade to the future platform releases.

The Android APIs include a Download Manager that applications MAY use to download data files [ Resources, 95 ]. The device implementation of the Download Manager MUST be capable of downloading individual files of at least 100MB in size to the default “cache" location.

7.6.2. Application Shared Storage

Device implementations MUST offer shared storage for applications also often referred as “shared external storage”.

Device implementations MUST be configured with shared storage mounted by default, “out of the box”. If the shared storage is not mounted on the Linux path /sdcard, then the device MUST include a Linux symbolic link from /sdcard to the actual mount point.

Device implementations MAY have hardware for user-accessible removable storage, such as a Secure Digital (SD) card slot. If this slot is used to satisfy the shared storage requirement, the device implementation:

  • MUST implement a toast or pop-up user interface warning the user when there is no SD card.
  • MUST include a FAT-formatted SD card 1GB in size or larger OR show on the box and other material available at time of purchase that the SD card has to be separately purchased.
  • MUST mount the SD card by default.

Alternatively, device implementations MAY allocate internal (non-removable) storage as shared storage for apps as included in the upstream Android Open Source Project; device implementations SHOULD use this configuration and software implementation. If a device implementation uses internal (non-removable) storage to satisfy the shared storage requirement, while that storage MAY share space with the application private data, it MUST be at least 1GB in size and mounted on /sdcard (or /sdcard MUST be a symbolic link to the physical location if it is mounted elsewhere).

Device implementations MUST enforce as documented the android.permission.WRITE_EXTERNAL_STORAGE permission on this shared storage. Shared storage MUST otherwise be writable by any application that obtains that permission.

Device implementations that include multiple shared storage paths (such as both an SD card slot and shared internal storage) MUST allow only pre-installed and privileged Android applications with the WRITE_EXTERNAL_STORAGE permission to write to the secondary external storage, except when writing to their package-specific directories or within the URI returned by firing the ACTION_OPEN_DOCUMENT_TREE intent.

However, device implementations SHOULD expose content from both storage paths transparently through Android's media scanner service and android.provider.MediaStore.

Regardless of the form of shared storage used, if the device implementation has a USB port with USB peripheral mode support, it MUST provide some mechanism to access the contents of shared storage from a host computer. Device implementations MAY use USB mass storage, but SHOULD use Media Transfer Protocol to satisfy this requirement. If the device implementation supports Media Transfer Protocol, it:

  • SHOULD be compatible with the reference Android MTP host, Android File Transfer [ Resources, 96 ].
  • SHOULD report a USB device class of 0x00.
  • SHOULD report a USB interface name of 'MTP'.

7.7. USB

Device implementations SHOULD support USB peripheral mode and SHOULD support USB host mode.

If a device implementation includes a USB port supporting peripheral mode:

  • The port MUST be connectable to a USB host that has a standard type-A or type -C USB port.
  • The port SHOULD use micro-B, micro-AB or Type-C USB form factor. Existing and new Android devices are STRONGLY RECOMMENDED to meet these requirements so they will be able to upgrade to future platform releases.
  • The port SHOULD either be located on the bottom of the device (according to natural orientation) or enable software screen rotation for all apps (including home screen), so that the display draws correctly when the device is oriented with the port at bottom. Existing and new Android devices are STRONGLY RECOMMENDED to meet these requirements so they will be able to upgrade to future platform releases.
  • It SHOULD implement the Android Open Accessory (AOA) API and specification as documented in the Android SDK documentation, and if it is an Android Handheld device it MUST implement the AOA API. Device implementations implementing the AOA specification:
    • MUST declare support for the hardware feature android.hardware.usb.accessory [ Resources, 97 ].
    • MUST implement the USB audio class as documented in the Android SDK documentation [ Resources, 98 ].
  • It SHOULD implement support to draw 1.5 A current during HS chirp and traffic as specified in the USB Battery Charging Specification, Revision 1.2 [ Resources, 99 ]. Existing and new Android devices are STRONGLY RECOMMENDED to meet these requirements so they will be able to upgrade to the future platform releases.
  • The value of iSerialNumber in USB standard device descriptor MUST be equal to the value of android.os.Build.SERIAL.

If a device implementation includes a USB port supporting host mode, it:

  • SHOULD use a type-C USB port, if the device implementation supports USB 3.1.
  • MAY use a non-standard port form factor, but if so MUST ship with a cable or cables adapting the port to a standard type-A or type-C USB port.
  • MAY use a micro-AB USB port, but if so SHOULD ship with a cable or cables adapting the port to a standard type-A or type-C USB port.
  • is very strongly RECOMMENDED to implement the USB audio class as documented in the Android SDK documentation [ Resources, 98 ].
  • MUST implement the Android USB host API as documented in the Android SDK, and MUST declare support for the hardware feature android.hardware.usb.host [ Resources, 100 ].
  • SHOULD support the Charging Downstream Port output current range of 1.5 A ~ 5 A as specified in the USB Battery Charging Specification, Revision 1.2 [ Resources, 99 ].

7.8. Audio

7.8.1. Microphone

Android Handheld, Watch, and Automotive implementations MUST include a microphone.

Device implementations MAY omit a microphone. However, if a device implementation omits a microphone, it MUST NOT report the android.hardware.microphone feature constant, and MUST implement the audio recording API at least as no-ops, per section 7 . Conversely, device implementations that do possess a microphone:

  • MUST report the android.hardware.microphone feature constant
  • MUST meet the audio recording requirements in section 5.4
  • MUST meet the audio latency requirements in section 5.6

7.8.2. Audio Output

Android Watch devices MAY include an audio output.

Device implementations including a speaker or with an audio/multimedia output port for an audio output peripheral as a headset or an external speaker:

  • MUST report the android.hardware.audio.output feature constant.
  • MUST meet the audio playback requirements in section 5.5 .
  • MUST meet the audio latency requirements in section 5.6 .

Conversely, if a device implementation does not include a speaker or audio output port, it MUST NOT report the android.hardware.audio output feature, and MUST implement the Audio Output related APIs as no-ops at least.

Android Watch device implementation MAY but SHOULD NOT have audio output, but other types of Android device implementations MUST have an audio output and declare android.hardware.audio.output.

7.8.2.1. Analog Audio Ports

In order to be compatible with the headsets and other audio accessories using the 3.5mm audio plug across the Android ecosystem [ Resources, 101 ], if a device implementation includes one or more analog audio ports, at least one of the audio port(s) SHOULD be a 4 conductor 3.5mm audio jack. If a device implementation has a 4 conductor 3.5mm audio jack, it:

  • MUST support audio playback to stereo headphones and stereo headsets with a microphone, and SHOULD support audio recording from stereo headsets with a microphone.
  • MUST support TRRS audio plugs with the CTIA pin-out order, and SHOULD support audio plugs with the OMTP pin-out order.
  • MUST support the detection of microphone on the plugged in audio accessory, if the device implementation supports a microphone, and broadcast the android.intent.action.HEADSET_PLUG with the extra value microphone set as 1.
  • SHOULD support the detection and mapping to the keycodes for the following 3 ranges of equivalent impedance between the microphone and ground conductors on the audio plug:
    • 70 ohm or less : KEYCODE_HEADSETHOOK
    • 210-290 Ohm : KEYCODE_VOLUME_UP
    • 360-680 Ohm : KEYCODE_VOLUME_DOWN
  • SHOULD support the detection and mapping to the keycode for the following range of equivalent impedance between the microphone and ground conductors on the audio plug:
    • 110-180 Ohm: KEYCODE_VOICE_ASSIST
  • MUST trigger ACTION_HEADSET_PLUG upon a plug insert, but only after all contacts on plug are touching their relevant segments on the jack.
  • MUST be capable of driving at least 150mV +/- 10% of output voltage on a 32 Ohm speaker impedance.
  • MUST have a microphone bias voltage between 1.8V ~ 2.9V.

8. Performance Compatibility

Some minimum performance criterias are critical to the user experience and impacts the baseline assumptions developers would have when developing an app. Android Watch devices SHOULD and other type of device implementations MUST meet the following criteria:

8.1. User Experience Consistency

Device implementations MUST provide a smooth user interface by ensuring a consistent frame rate and response times for applications and games. Device implementations MUST meet the following requirements:

  • Consistent frame latency . Inconsistent frame latency or a delay to render frames MUST NOT happen more often than 5 frames in a second, and SHOULD be below 1 frames in a second.
  • User interface latency . Device implementations MUST ensure low latency user experience by scrolling a list of 10K list entries as defined by the Android Compatibility Test Suite (CTS) in less than 36 secs.
  • Task switching . When multiple applications have been launched, re-launching an already-running application after it has been launched MUST take less than 1 second.

8.2. File I/O Access Performance

Device implementations MUST ensure internal storage file access performance consistency for read and write operations.

  • Sequential write . Device implementations MUST ensure a sequential write performance of at least 5MB/s for a 256MB file using 10MB write buffer.
  • Random write . Device implementations MUST ensure a random write performance of at least 0.5MB/s for a 256MB file using 4KB write buffer.
  • Sequential read . Device implementations MUST ensure a sequential read performance of at least 15MB/s for a 256MB file using 10MB write buffer.
  • Random read . Device implementations MUST ensure a random read performance of at least 3.5MB/s for a 256MB file using 4KB write buffer.

9. Security Model Compatibility

Device implementations MUST implement a security model consistent with the Android platform security model as defined in Security and Permissions reference document in the APIs [ Resources, 102 ] in the Android developer documentation. Device implementations MUST support installation of self-signed applications without requiring any additional permissions/certificates from any third parties/authorities. Specifically, compatible devices MUST support the security mechanisms described in the follow subsections.

9.1. Permissions

Device implementations MUST support the Android permissions model as defined in the Android developer documentation [ Resources, 102 ]. Specifically, implementations MUST enforce each permission defined as described in the SDK documentation; no permissions may be omitted, altered, or ignored. Implementations MAY add additional permissions, provided the new permission ID strings are not in the android.* namespace.

9.2. UID and Process Isolation

Device implementations MUST support the Android application sandbox model, in which each application runs as a unique Unixstyle UID and in a separate process. Device implementations MUST support running multiple applications as the same Linux user ID, provided that the applications are properly signed and constructed, as defined in the Security and Permissions reference [ Resources, 102 ].

9.3. Filesystem Permissions

Device implementations MUST support the Android file access permissions model as defined in the Security and Permissions reference [ Resources, 102 ].

9.4. Alternate Execution Environments

Device implementations MAY include runtime environments that execute applications using some other software or technology than the Dalvik Executable Format or native code. However, such alternate execution environments MUST NOT compromise the Android security model or the security of installed Android applications, as described in this section.

Alternate runtimes MUST themselves be Android applications, and abide by the standard Android security model, as described elsewhere in section 9 .

Alternate runtimes MUST NOT be granted access to resources protected by permissions not requested in the runtime's AndroidManifest.xml file via the <uses-permission> mechanism.

Alternate runtimes MUST NOT permit applications to make use of features protected by Android permissions restricted to system applications.

Alternate runtimes MUST abide by the Android sandbox model. Specifically, alternate runtimes:

  • SHOULD install apps via the PackageManager into separate Android sandboxes ( Linux user IDs, etc.).
  • MAY provide a single Android sandbox shared by all applications using the alternate runtime.
  • and installed applications using an alternate runtime, MUST NOT reuse the sandbox of any other app installed on the device, except through the standard Android mechanisms of shared user ID and signing certificate.
  • MUST NOT launch with, grant, or be granted access to the sandboxes corresponding to other Android applications.
  • MUST NOT be launched with, be granted, or grant to other applications any privileges of the superuser (root), or of any other user ID.

The .apk files of alternate runtimes MAY be included in the system image of a device implementation, but MUST be signed with a key distinct from the key used to sign other applications included with the device implementation.

When installing applications, alternate runtimes MUST obtain user consent for the Android permissions used by the application. If an application needs to make use of a device resource for which there is a corresponding Android permission (such as Camera, GPS, etc.), the alternate runtime MUST inform the user that the application will be able to access that resource. If the runtime environment does not record application capabilities in this manner, the runtime environment MUST list all permissions held by the runtime itself when installing any application using that runtime.

9.5. Multi-User Support

This feature is optional for all device types.

Android includes support for multiple users and provides support for full user isolation [ Resources, 103] . Device implementations MAY enable multiple users, but when enabled MUST meet the following requirements related to multi-user support [ Resources, 104 ]:

  • Device implementations that do not declare the android.hardware.telephony feature flag MUST support restricted profiles, a feature that allows device owners to manage additional users and their capabilities on the device. With restricted profiles, device owners can quickly set up separate environments for additional users to work in, with the ability to manage finer-grained restrictions in the apps that are available in those environments.
  • Conversely device implementations that declare the android.hardware.telephony feature flag MUST NOT support restricted profiles but MUST align with the AOSP implementation of controls to enable /disable other users from accessing the voice calls and SMS.
  • Device implementations MUST, for each user, implement a security model consistent with the Android platform security model as defined in Security and Permissions reference document in the APIs [ Resources, 102 ].
  • Device implementations MAY support creating users and managed profiles via the android.app.admin.DevicePolicyManager APIs, and if supported, MUST declare the platform feature flag android.software.managed_users.
  • Device implementations that declare the feature flag android.software.managed_users MUST use the upstream AOSP icon badge to represent the managed applications and other badge UI elements like Recents & Notifications.
  • Each user instance on an Android device MUST have separate and isolated external storage directories. Device implementations MAY store multiple users' data on the same volume or filesystem. However, the device implementation MUST ensure that applications owned by and running on behalf a given user cannot list, read, or write to data owned by any other user. Note that removable media, such as SD card slots, can allow one user to access another's data by means of a host PC. For this reason, device implementations that use removable media for the primary external storage APIs MUST encrypt the contents of the SD card if multiuser is enabled using a key stored only on non-removable media accessible only to the system. As this will make the media unreadable by a host PC, device implementations will be required to switch to MTP or a similar system to provide host PCs with access to the current user's data. Accordingly, device implementations MAY but SHOULD NOT enable multi-user if they use removable media [ Resources, 105 ] for primary external storage.

9.6. Premium SMS Warning

Android includes support for warning users of any outgoing premium SMS message [ Resources, 106 ] . Premium SMS messages are text messages sent to a service registered with a carrier that may incur a charge to the user. Device implementations that declare support for android.hardware.telephony MUST warn users before sending a SMS message to numbers identified by regular expressions defined in /data/misc/sms/codes.xml file in the device. The upstream Android Open Source Project provides an implementation that satisfies this requirement.

9.7. Kernel Security Features

The Android Sandbox includes features that can use the Security-Enhanced Linux (SELinux) mandatory access control (MAC) system and other security features in the Linux kernel. SELinux or any other security features, if implemented below the Android framework:

  • MUST maintain compatibility with existing applications.
  • MUST NOT have a visible user interface when a security violation is detected and successfully blocked, but MAY have a visible user interface when an unblocked security violation occurs resulting in a successful exploit.
  • SHOULD NOT be user or developer configurable.

If any API for configuration of policy is exposed to an application that can affect another application (such as a Device Administration API), the API MUST NOT allow configurations that break compatibility.

Devices MUST implement SELinux or an equivalent mandatory access control system if using a kernel other than Linux and meet the following requirements, which are satisfied by the reference implementation in the upstream Android Open Source Project.

Device implementations:

  • MUST support a SELinux policy that allows the SELinux mode to be set on a per-domain basis, and MUST configure all domains in enforcing mode. No permissive mode domains are allowed, including domains specific to a device/vendor.
  • SHOULD load policy from /sepolicy file on the device.
  • MUST NOT modify, omit, or replace the neverallow rules present within the sepolicy file provided in the upstream Android Open Source Project (AOSP) and the policy MUST compile with all neverallow present, for both AOSP SELinux domains as well as device/vendor specific domains.
  • MUST support dynamic updates of the SELinux policy file without requiring a system image update.

Device implementations SHOULD retain the default SELinux policy provided in the upstream Android Open Source Project, until they have first audited their additions to the SELinux policy. Device implementations MUST be compatible with the upstream Android Open Source Project.

9.8. Privacy

If the device implements functionality in the system that captures the contents displayed on the screen and/or records the audio stream played on the device, it MUST continuously notify the user whenever this functionality is enabled and actively capturing/recording.

If a device implementation has a mechanism that routes network data traffic through a proxy server or VPN gateway by default (for example, preloading a VPN service with android.permission.CONTROL_VPN granted), the device implementation MUST ask for the user's consent before enabling that mechanism.

9.9. Full-Disk Encryption

Optional for Android device implementations without a lock screen.

If the device implementation supports a lock screen with PIN (numeric) or PASSWORD (alphanumeric), the device MUST support full-disk encryption of the application private data (/data partition), as well as the SD card partition if it is a permanent, non-removable part of the device [ Resources, 107 ]. For devices supporting full-disk encryption, the full-disk encryption SHOULD be enabled all the time after the user has completed the out-of-box experience. While this requirement is stated as SHOULD for this version of the Android platform, it is very strongly RECOMMENDED as we expect this to change to MUST in the future versions of Android. Encryption MUST use AES with a key of 128-bits (or greater) and a mode designed for storage (for example, AES-XTS, AES-CBC-ESSIV). The encryption key MUST NOT be written to storage at any time without being encrypted. Other than when in active use, the encryption key SHOULD be AES encrypted with the lockscreen passcode stretched using a slow stretching algorithm (eg PBKDF2 or scrypt). If the user has not specified a lockscreen passcode or has disabled use of the passcode for encryption, the system SHOULD use a default passcode to wrap the encryption key. If the device provides a hardware-backed keystore, the password stretching algorithm MUST be cryptographically bound to that keystore. The encryption key MUST NOT be sent off the device (even when wrapped with the user passcode and/or hardware bound key). The upstream Android Open Source project provides a preferred implementation of this feature based on the linux kernel feature dm-crypt.

9.10. Verified Boot

Verified boot is a feature that guarantees the integrity of the device software. If a device implementation supports the feature, it MUST:

  • Declare the platform feature flag android.software.verified_boot
  • Perform verification on every boot sequence
  • Start verification from a hardware key that is the root of trust, and go all the way up to the system partition
  • Implement each stage of verification to check the integrity and authenticity of all the bytes in the next stage before executing the code in the next stage
  • Use verification algorithms as strong as current recommendations from NIST for hashing algorithms (SHA-256) and public key sizes (RSA-2048)

Device implementations SHOULD support verified boot for device integrity. While this requirement is SHOULD for this version of the Android platform, it is strongly RECOMMENDED as we expect this to change to MUST in future versions of Android. The upstream Android Open Source Project provides a preferred implementation of this feature based on the linux kernel feature dm-verity.

10. Software Compatibility Testing

Device implementations MUST pass all tests described in this section.

However, note that no software test package is fully comprehensive. For this reason, device implementers are very strongly encouraged to make the minimum number of changes as possible to the reference and preferred implementation of Android available from the Android Open Source Project. This will minimize the risk of introducing bugs that create incompatibilities requiring rework and potential device updates.

10.1. Compatibility Test Suite

Device implementations MUST pass the Android Compatibility Test Suite (CTS) [ Resources, 108 ] available from the Android Open Source Project, using the final shipping software on the device. Additionally, device implementers SHOULD use the reference implementation in the Android Open Source tree as much as possible, and MUST ensure compatibility in cases of ambiguity in CTS and for any reimplementations of parts of the reference source code.

The CTS is designed to be run on an actual device. Like any software, the CTS may itself contain bugs. The CTS will be versioned independently of this Compatibility Definition, and multiple revisions of the CTS may be released for Android 5.1. Device implementations MUST pass the latest CTS version available at the time the device software is completed.

10.2. CTS Verifier

Device implementations MUST correctly execute all applicable cases in the CTS Verifier. The CTS Verifier is included with the Compatibility Test Suite, and is intended to be run by a human operator to test functionality that cannot be tested by an automated system, such as correct functioning of a camera and sensors.

The CTS Verifier has tests for many kinds of hardware, including some hardware that is optional. Device implementations MUST pass all tests for hardware that they possess; for instance, if a device possesses an accelerometer, it MUST correctly execute the Accelerometer test case in the CTS Verifier. Test cases for features noted as optional by this Compatibility Definition Document MAY be skipped or omitted.

Every device and every build MUST correctly run the CTS Verifier, as noted above. However, since many builds are very similar, device implementers are not expected to explicitly run the CTS Verifier on builds that differ only in trivial ways. Specifically, device implementations that differ from an implementation that has passed the CTS Verifier only by the set of included locales, branding, etc. MAY omit the CTS Verifier test.

11. Updatable Software

Device implementations MUST include a mechanism to replace the entirety of the system software. The mechanism need not perform “live” upgrades—that is, a device restart MAY be required.

Any method can be used, provided that it can replace the entirety of the software preinstalled on the device. For instance, any of the following approaches will satisfy this requirement:

  • “Over-the-air (OTA)” downloads with offline update via reboot
  • “Tethered” updates over USB from a host PC
  • “Offline” updates via a reboot and update from a file on removable storage

However, if the device implementation includes support for an unmetered data connection such as 802.11 or Bluetooth PAN (Personal Area Network) profile:

  • Android Automotive implementations SHOULD support OTA downloads with offline update via reboot.
  • All other device implementations MUST support OTA downloads with offline update via reboot.

The update mechanism used MUST support updates without wiping user data. That is, the update mechanism MUST preserve application private data and application shared data. Note that the upstream Android software includes an update mechanism that satisfies this requirement.

For device implementations that are launching with Android 5.1 and later, the update mechanism SHOULD support verifying that the system image is binary identical to expected result following an OTA. The block-based OTA implementation in the upstream Android Open Source Project, added since Android 5.1, satisfies this requirement.

If an error is found in a device implementation after it has been released but within its reasonable product lifetime that is determined in consultation with the Android Compatibility Team to affect the compatibility of third-party applications, the device implementer MUST correct the error via a software update available that can be applied per the mechanism just described.

12. Document Changelog

The following table contains a summary of the changes to the Compatibility Definition in this release.

Section Summary of change
2. Device Types Added definition for Android automotive implementation.
2.1 Device Configurations Added column for Android automotive implementation.
3.3.2. 32-bit ARM Native Code Compatibility New section added.
3.4.1. WebView Compatibility Updated webview user agent string requirement to accommodate upstream implementation change.
3.4.2. Browser compatibility Added Android automotive implementations as another case that MAY omit a browser application.
3.7. Runtime Compatibility Updated required runtime heap size for smaller screens and added requirement for the new dpi bucket (280dpi).
3.8.3. Notifications Clarified notification requirement for Android Watch, Television and Automotive implementations.
3.8.8. Activity Switching Relax Overview title count requirement.
3.8.10. Lock Screen Media Control Clarified requirement for Android Watch and Automotive implementations.
3.8.13. Unicode and font Relaxed Emoji character input method requirement.
3.9. Device Administration Clarified condition when the full range of device administration policies has to be supported.
3.10. Accessibility Added Android automotive requirements.
3.11. Text-To-Speech Added Android automotive requirements.
5.1. Media Codecs Mandated decoding support for codecs reported by CamcorderProfile.
5.1.3 Video Codecs Added Android automotive requirements.
5.4. Audio Recording Clarified language at the beginning of the section to ensure MUST requirements are read as REQUIRED.
7.1.1.3. Screen Density Added a new screen dpi (280dpi).
7.1.5. Legacy Application Compatibility Mode Added Android automotive requirements.
7.2 Input Devices Added general introduction statement.
7.2.1. Keyboard Added Android Automotive requirements.
7.2.3. Navigation Keys Added Android Automotive requirements.
7.3.1. Accelerometer Relaxed requirement for reporting frequency on Android Watch.
7.3.4. Gyroscope Relaxed requirement for reporting frequency on Android Watch.
7.4.3 Bluetooth Added Android Automotive requirements.
7.4.4. Near-Field Communications Clarified condition for when Host Card Emulation is a requirement.
7.6.1. Minimum Memory and Storage Updated minimum memory requirements for lower resulution screen devices and added hard-limit requirement isLowRamDevice().
7.6.2. Application Shared Storage Updated requirements when support for host machine access is mandatory.
7.7 USB Fixing typos in USB section
7.6.2. Application Shared Storage Updated requirements that pre-installed system apps may write to secondary external storage.
7.6.2. Application Shared Storage Apps can use ACTION_OPEN_DOCUMENT_TREE to write to secondary ext. storage
7.6.2. Application Shared Storage Clarify that /sdcard can share storage with /data
7.7 USB Remove redundant requirement on UMS/MTP from 7.7
7.8.1. Microphone Added Android Automotive requirements.
8.2. File I/O Access Performance Clarified requirements.
9.5. Multi-User Support SD card encryption required for the primary external storage.
9.8. Privacy Added privacy requirement for preloaded VPNs.
9.9. Full-Disk Encryption Clarified condition when Full-Disk encryption support is mandatory.
9.10. Verified Boot Clarified definition of verified boot.
11. Updatable Software Clarified the OTA download requirement is allowed but not mandatory for Android Automotive implementations.

13. Contact Us

You can join the android-compatibility forum [Resources, 109 ] and ask for clarifications or bring up any issues that you think the document does not cover.

14. Resources

1. IETF RFC2119 Requirement Levels: http://www.ietf.org/rfc/rfc2119.txt

2. Android Open Source Project: http://source.android.com/

3. Android Television features: http://developer.android.com/reference/android/content/pm/PackageManager.html#FEATURE_LEANBACK

4. Android Watch feature: http://developer.android.com/reference/android/content/res/Configuration.html#UI_MODE_TYPE_WATCH

5. API definitions and documentation: http://developer.android.com/reference/packages.html

6. Android Permissions reference: http://developer.android.com/reference/android/Manifest.permission.html

7. android.os.Build reference: http://developer.android.com/reference/android/os/Build.html

8. Android 5.1 allowed version strings: http://source.android.com/compatibility/5.1/versions.html

9. Telephony Provider: http://developer.android.com/reference/android/provider/Telephony.html

10. Host-based Card Emulation: http://developer.android.com/guide/topics/connectivity/nfc/hce.html

11. Android Extension Pack: http://developer.android.com/guide/topics/graphics/opengl.html#aep

12. android.webkit.WebView class: http://developer.android.com/reference/android/webkit/WebView.html

13. WebView compatibility: http://www.chromium.org/

14. HTML5: http://html.spec.whatwg.org/multipage/

15. HTML5 offline capabilities: http://dev.w3.org/html5/spec/Overview.html#offline

16. HTML5 video tag: http://dev.w3.org/html5/spec/Overview.html#video

17. HTML5/W3C geolocation API: http://www.w3.org/TR/geolocation-API/

18. HTML5/W3C webstorage API: http://www.w3.org/TR/webstorage/

19. HTML5/W3C IndexedDB API: http://www.w3.org/TR/IndexedDB/

20. Dalvik Executable Format and bytecode specification: available in the Android source code, at dalvik/docs

21. AppWidgets: http://developer.android.com/guide/practices/ui_guidelines/widget_design.html

22. Notifications: http://developer.android.com/guide/topics/ui/notifiers/notifications.html

23. Application Resources: https://developer.android.com/guide/topics/resources/available-resources.html

24. Status Bar icon style guide: http://developer.android.com/design/style/iconography.html

25. Notifications Resources: https://developer.android.com/design/patterns/notifications.html

26. Search Manager: http://developer.android.com/reference/android/app/SearchManager.html

27. Toasts: http://developer.android.com/reference/android/widget/Toast.html

28. Themes: http://developer.android.com/guide/topics/ui/themes.html

29. R.style class: http://developer.android.com/reference/android/R.style.html

30. Material design: http://developer.android.com/reference/android/R.style.html#Theme_Material

31. Live Wallpapers: http://developer.android.com/reference/android/service/wallpaper/WallpaperService.html

32. Overview screen resources: http://developer.android.com/guide/components/recents.html

33. Screen pinning: https://developer.android.com/about/versions/android-5.0.html#ScreenPinning

34. Input methods: http://developer.android.com/guide/topics/text/creating-input-method.html

35. Media Notification: https://developer.android.com/reference/android/app/Notification.MediaStyle.html

36. Dreams: http://developer.android.com/reference/android/service/dreams/DreamService.html

37. Settings.Secure LOCATION_MODE:

http://developer.android.com/reference/android/provider/Settings.Secure.html#LOCATION_MODE

38. Unicode 6.1.0: http://www.unicode.org/versions/Unicode6.1.0/

39. Android Device Administration: http://developer.android.com/guide/topics/admin/device-admin.html

40. DevicePolicyManager reference: http://developer.android.com/reference/android/app/admin/DevicePolicyManager.html

41. Android Device Owner App:

http://developer.android.com/reference/android/app/admin/DevicePolicyManager.html#isDeviceOwnerApp(java.lang.String)

42. Android Accessibility Service APIs: http://developer.android.com/reference/android/accessibilityservice/AccessibilityService.html

43. Android Accessibility APIs: http://developer.android.com/reference/android/view/accessibility/package-summary.html

44. Eyes Free project: http://code.google.com/p/eyes-free

45. Text-To-Speech APIs: http://developer.android.com/reference/android/speech/tts/package-summary.html

46. Television Input Framework: /devices/tv/index.html

47. Reference tool documentation (for adb, aapt, ddms, systrace): http://developer.android.com/tools/help/index.html

48. Android apk file description: http://developer.android.com/guide/components/fundamentals.html

49. Manifest files: http://developer.android.com/guide/topics/manifest/manifest-intro.html

50. Android Media Formats: http://developer.android.com/guide/appendix/media-formats.html

51. RTC Hardware Coding Requirements: http://www.webmproject.org/hardware/rtc-coding-requirements/

52. AudioEffect API: http://developer.android.com/reference/android/media/audiofx/AudioEffect.html

53. Android android.content.pm.PackageManager class and Hardware Features List:

http://developer.android.com/reference/android/content/pm/PackageManager.html

54. HTTP Live Streaming Draft Protocol: http://tools.ietf.org/html/draft-pantos-http-live-streaming-03

55. ADB: http://developer.android.com/tools/help/adb.html

56. Dumpsys: /devices/input/diagnostics.html

57. DDMS: http://developer.android.com/tools/debugging/ddms.html

58. Monkey testing tool: http://developer.android.com/tools/help/monkey.html

59. SysyTrace tool: http://developer.android.com/tools/help/systrace.html

60. Android Application Development-Related Settings:

http://developer.android.com/reference/android/provider/Settings.html#ACTION_APPLICATION_DEVELOPMENT_SETTINGS

61. Supporting Multiple Screens: http://developer.android.com/guide/practices/screens_support.html

62. android.util.DisplayMetrics: http://developer.android.com/reference/android/util/DisplayMetrics.html

63. RenderScript: http://developer.android.com/guide/topics/renderscript/

64. Android extension pack for OpenGL ES: https://developer.android.com/reference/android/opengl/GLES31Ext.html

65. Hardware Acceleration: http://developer.android.com/guide/topics/graphics/hardware-accel.html

66. EGL Extension-EGL_ANDROID_RECORDABLE:

http://www.khronos.org/registry/egl/extensions/ANDROID/EGL_ANDROID_recordable.txt

67. Display Manager: http://developer.android.com/reference/android/hardware/display/DisplayManager.html

68. android.content.res.Configuration: http://developer.android.com/reference/android/content/res/Configuration.html

69. Action Assist: http://developer.android.com/reference/android/content/Intent.html#ACTION_ASSIST

70. Touch Input Configuration: http://source.android.com/devices/tech/input/touch-devices.html

71. Motion Event API: http://developer.android.com/reference/android/view/MotionEvent.html

72. Key Event API: http://developer.android.com/reference/android/view/KeyEvent.html

73. Android Open Source sensors: http://source.android.com/devices/sensors

74. android.hardware.SensorEvent: http://developer.android.com/reference/android/hardware/SensorEvent.html

75. Timestamp sensor event: http://developer.android.com/reference/android/hardware/SensorEvent.html#timestamp

76. Android Open Source composite sensors: /devices/sensors/sensor-types.html#composite_sensor_type_summary

77. Continuous trigger mode: /devices/sensors/report-modes.html#continuous

78. Accelerometer sensor: http://developer.android.com/reference/android/hardware/Sensor.html#TYPE_ACCELEROMETER

79. Wi-Fi Multicast API: http://developer.android.com/reference/android/net/wifi/WifiManager.MulticastLock.html

80. Wi-Fi Direct (Wi-Fi P2P): http://developer.android.com/reference/android/net/wifi/p2p/WifiP2pManager.html

81. WifiManager API: http://developer.android.com/reference/android/net/wifi/WifiManager.html

82. Bluetooth API: http://developer.android.com/reference/android/bluetooth/package-summary.html

83. Bluetooth ScanFilter API: https://developer.android.com/reference/android/bluetooth/le/ScanFilter.html

84. NDEF Push Protocol: http://source.android.com/compatibility/ndef-push-protocol.pdf

85. Android Beam: http://developer.android.com/guide/topics/connectivity/nfc/nfc.html

86. Android NFC Sharing Settings:

http://developer.android.com/reference/android/provider/Settings.html#ACTION_NFCSHARING_SETTINGS

87. NFC Connection Handover: http://members.nfc-forum.org/specs/spec_list/#conn_handover

88. Bluetooth Secure Simple Pairing Using NFC: http://members.nfc-forum.org/apps/group_public/download.php/18688/NFCForum-AD-BTSSP_1_1.pdf

89. Content Resolver: http://developer.android.com/reference/android/content/ContentResolver.html

90. Camera orientation API: http://developer.android.com/reference/android/hardware/Camera.html#setDisplayOrientation(int)

91. Camera: http://developer.android.com/reference/android/hardware/Camera.html

92. Camera: http://developer.android.com/reference/android/hardware/Camera.Parameters.html

93. Camera hardware level: https://developer.android.com/reference/android/hardware/camera2/CameraCharacteristics.html#INFO_SUPPORTED_HARDWARE_LEVEL

94. Camera version support: http://source.android.com/devices/camera/versioning.html

95. Android DownloadManager: http://developer.android.com/reference/android/app/DownloadManager.html

96. Android File Transfer: http://www.android.com/filetransfer

97. Android Open Accessories: http://developer.android.com/guide/topics/connectivity/usb/accessory.html

98. Android USB Audio: http://developer.android.com/reference/android/hardware/usb/UsbConstants.html#USB_CLASS_AUDIO

99. USB Charging Specification: http://www.usb.org/developers/docs/devclass_docs/USB_Battery_Charging_1.2.pdf

100. USB Host API: http://developer.android.com/guide/topics/connectivity/usb/host.html

101. Wired audio headset: http://source.android.com/accessories/headset-spec.html

102. Android Security and Permissions reference: http://developer.android.com/guide/topics/security/permissions.html

103. UserManager reference: http://developer.android.com/reference/android/os/UserManager.html

104. External Storage reference: http://source.android.com/devices/storage

105. External Storage APIs: http://developer.android.com/reference/android/os/Environment.html

106. SMS Short Code: http://en.wikipedia.org/wiki/Short_code

107. Android Open Source Encryption: http://source.android.com/devices/tech/security/encryption/index.html

108. Android Compatibility Program Overview: http://source.android.com/compatibility/index.html

109. Android Compatibility forum: https://groups.google.com/forum/#!forum/android-compatibility

110. WebM project: http://www.webmproject.org/

111. Android UI_MODE_TYPE_CAR API: http://developer.android.com/reference/android/content/res/Configuration.html#UI_MODE_TYPE_CAR

112. Android MediaCodecList API: http://developer.android.com/reference/android/media/MediaCodecList.html

113. Android CamcorderProfile API: http://developer.android.com/reference/android/media/CamcorderProfile.html

Many of these resources are derived directly or indirectly from the Android SDK, and will be functionally identical to the information in that SDK's documentation. In any cases where this Compatibility Definition or the Compatibility Test Suite disagrees with the SDK documentation, the SDK documentation is considered authoritative. Any technical details provided in the references included above are considered by inclusion to be part of this Compatibility Definition.