Configure a transition

Use a transition to define changes between panels. You can define a transition to describe how and when to make a change between two variants of a panel. You can define a list of transitions for each panel.

Use the <Transitions> XML tag as a container for one or more <Transition> definitions in the configuration of a single <TaskPanel> or <DecorPanel>. You can use this tag to define a set of animation rules to govern when and how a panel should change the visual state from one distinct variant to another.

XML attributes

The <Transitions> tag can define default values for these child <Transition> elements:

Attribute Status Description
<defaultDuration> Optional

Specifies a default duration in milliseconds to be applied to all child

<Transition> elements that don't explicitly set a duration attribute.

The system's DEFAULT_DURATION constant, typically 300 milliseconds, is used when this attribute is not specified.
defaultInterpolator Optional

References an Android Interpolator XML resource ID. For example, @android:anim/accelerate_decelerate_interpolator. The interpolator is used as the default for all child <Transition> elements that don't explicitly set an interpolator attribute.

If no default interpolator is specified, the system typically defaults to an AccelerateDecelerateInterpolator.

XML child elements

The child element of <Transitions> is <Transition>, the core element used to define a specific animation path between PanelState variants. Multiple <Transition> elements can be nested within a single <Transitions> block.

Sample code

In this sample, fromVariant is optional. When not defined, the current variant is used. If fromVariant is defined, the transition is used only when all parameters match. Parameters are specified in the Event and fromVariant.

<Transitions defaultDuration="400"
         defaultInterpolator="@android:anim/linear_interpolator">
  <Transition fromVariant="closed_app"
              toVariant="opened_app">
    <Event id="app_opened" panel="application_panel" />
  </Transition>
</Transitions>

Transition

A transition describes how to animate a change in visual state between two variants of a panel. A transition outlines the path from a variant to a variant. To do so, the transition specifies details such as the animation to apply and the event needed to trigger the animation.

For a panel, transitions can define animations for properties such as bounds, visibility, and alpha. If a custom animator is not specified, a default animator is used.

XML attributes

The <Transition> tag uses several attributes to define the characteristics of the animation and the conditions under which it is to occur.

XML child elements

<Event> defines the properties of the event that can trigger the transition.

Unique identifier of the panel associated with this event.
Attribute Status Description
<id> Mandatory Unique identifier of the event to activate the trigger.
<panelId> Optional Unique identifier of the panel associated with the event.
componentName Optional Component name associated with this event.
packageName Optional Package name associated with the event.

Sample code

<Transitions defaultDuration="400"
        defaultInterpolator="@android:anim/accelerate_interpolator">
  <!-- A transition from 'closed_app' to 'opened_app' variant, triggered by 'open_app_event' -->
  <Transition fromVariant="closed_app"
              toVariant="opened_app">
    <Event id="app_opened" panel="application_panel" />
  <Transition>

  <!-- A transition from 'opened_app' to 'closed_app' variant, using a custom animator -->
  <Transition fromVariant="opened_app"
              toVariant="closed_app"
              animator="@animator/close_app">
    <Event id="_System_PanelEmptyEvent"
           panelId="application_panel" />
  <Transition>
</Transitions>
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