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Customizing Car UI Preferences

This article describes how to use and customize elements in the com.android.car.ui.preference package, which includes UI elements that can be used to present preferences for apps.

Most elements are subclassing com.androidx.preference classes to which you add CarUi customizations. In most cases, you can use the elements in the com.android.car.ui.preferences package by using com.android.car.PreferenceFragment. PreferenceFragment replaces all androidx.preference elements with their equivalents in car.ui.preferences. To view these functionalities in action, see the car-ui-lib Paintbooth reference app. For example:

Car UI preference layout

Figure 1. Car UI preference layout.

Available Preference Types

PreferenceFragment

PreferenceFragment is a subclass of androidx.preference.PreferenceFragmentCompat and is the base class that clients should use. During a call to setPreferenceScreen, this class automatically replaces the elements from androidx.preference with the available equivalent from car.ui.preference elements.

<style name="PreferenceFragment.CarUi">
        <item name="android:divider">?android:attr/listDivider</item>
        <item name="android:layout">@layout/car_ui_preference_fragment_with_toolbar</item>
</style>

CarUiPreference

This is the CarUi equivalent of the androidx.preference.Preference class that supports the following attributes, which can be customized using a Runtime Resource Overlay (RRO). All other CarUi elements that use a variant of CarUiPreference style also support the following attributes.

<declare-styleable name="CarUiPreference">
      <!-- Toggle for showing chevron -->
      <attr name="showChevron" format="boolean" />
      <!-- Show ripple when disabled preference is clicked -->
      <attr name="showRippleOnDisabledPreference" format="boolean" />
</declare-styleable>

The following is the base style for com.android.car.ui.preference, which extends the androidx.Preference theme. The chevron drawable is defined in car_ui_preference_icon_chevron.xml.

<selector xmlns:android="http://schemas.android.com/apk/res/android">
  <item android:state_enabled="false" android:drawable="@drawable/car_ui_preference_icon_chevron_disabled"/>
  <item android:state_enabled="true" android:drawable="@drawable/car_ui_preference_icon_chevron_enabled"/>
</selector>

The ripple is defined in car_ui_recyclerview_button_ripple_background.

<ripple
    xmlns:android="http://schemas.android.com/apk/res/android"
    android:color="@color/car_ui_ripple_color" />
<style name="Preference.CarUi">
        <item name="allowDividerBelow">false</item>
        <item name="allowDividerAbove">false</item>
        <item name="android:layout">@layout/car_ui_preference</item>
</style>

If the layout in the style above is being overlaid, clients need to make sure the new layout at least provides the ids that are expected by corresponding androidx classes. This also applies to the other elements that use this base style.

CarUiDropDownPreference

This is the CarUi equivalent of the androidx.preference.DropDownPreference class and uses the following style:

<style name="Preference.CarUi.DropDown">
        <item name="android:layout">@layout/car_ui_preference_dropdown</item>
</style>

CarUiRadioButtonPreference

This subclass of androidx.preference.TwoStatePreference inflates car_ui_radio_button_preference_widget layout during initialization. If this layout is being overlaid in an RRO, the new layout must contain an element of type android.widget.RadioButton, with id R.id.radio_button and must also contain other elements and ids required by the base class.

CarUiSwitchPreference

This is the CarUi equivalent of the androidx.preference.SwitchPreference class. The difference is that when this element is not enabled, a toast message is shown. The toast message can be customized by calling the setMessageToShowWhenDisabledPreferenceClicked method in Android 10 and Android 11. This element uses the following style:

<style name="Preference.CarUi.SwitchPreference">
        <item name="android:widgetLayout">@layout/car_ui_preference_widget_switch</item>
        <item name="android:switchTextOn">@string/car_ui_preference_switch_on</item>
        <item name="android:switchTextOff">@string/car_ui_preference_switch_off</item>
</style>

CarUiTwoActionPreference

A subclass of CarUiPreference that enables a secondary action. The of attributes that can be used to customize this element are provided below:

<declare-styleable name="CarUiTwoActionPreference">
        <!-- Determines if the secondary action is initially shown -->
        <attr name="actionShown" format="boolean"/>
</declare-styleable>

This element uses the same style as the base class and requires R.id.action_widget_container, and android.R.id.widget_frame.

CarUiDialogFragment

This class is borrowed as is from androidx.preference.PreferenceDialogFragmentCompat with some additions specific to CarUi. Clients should use subclasses of this class to present themed platform AlertDialog.

PreferenceDialogFragment

A direct subclass of CarUiDialogFragment . Clients should subclass this class to present any themed platform AlertDialog.

CarUiEditTextPreference

This is the CarUi equivalent of the androidx.preference.EditTextPreference class:

<style name="Preference.CarUi.DialogPreference.EditTextPreference">
        <item name="android:dialogLayout">@layout/car_ui_preference_dialog_edittext</item>
</style>

If the layout in the style above is being overlaid, clients need to make sure the new layout provides the ids expected by androidx.preference.EditTextPreference class.

EditTextPreferenceDialogFragment

A direct subclass of PreferenceDialogFragment. Also, the CarUi equivalent of the androidx.preference.PreferenceDialogFragments class. Clients should use this class to present any themed platform AlertDialog.

CarUiSeekBarDialogPreference

An implementation of androidx.preference.DialogPreference class, which provides SeekBar functionality:

<style name="Preference.CarUi.SeekBarPreference">
        <item name="android:layout">@layout/car_ui_preference_widget_seekbar</item>
        <item name="adjustable">true</item>
        <item name="showSeekBarValue">false</item>
</style>

SeekBarPreferenceDialogFragment

A fragment that provides a layout with a SeekBar in a dialog.

CarUiListPreference

CarUi equivalent of androidx.preference.ListPreference class.

ListPreferenceFragment

A fragment that provides a layout with androidx.preference.ListPreference in it.

CarUiMultiSelectListPreference

The CarUi equivalent of the androidx.preference.Preference class.

MultiSelectListPreferenceFragment

A fragment that provides a layout with com.android.car.ui.CarUiMultiSelectListPreference in it.