Add support for predictive back animations in Views

You can create custom in-app property animations and transitions, custom cross-activity animations, and custom cross-fragment animations with predictive back gestures using Views or Compose. To try the Compose way, see Add support for predictive back animations.

Add custom transitions using the Progress API

With AndroidX Activity 1.8.0-alpha01 or higher, you can use the Predictive Back Progress APIs to develop custom animations for the predictive back gesture in your app. Progress APIs are helpful in animating views but have limitations when animating transitions between fragments. Within OnBackPressedCallback we've introduced the handleOnBackProgressed, handleOnBackCancelled and handleOnBackStarted methods to animate objects while the user swipes back. Use these methods if you need to customize more than the default animations provided by the system, or the Material Component animations.

We expect most apps to use the backward compatible AndroidX APIs, but there are also similar platform APIs within the OnBackAnimationCallback interface available to test in Android 14 and higher.

Use the Progress APIs with AndroidX Transitions

The Progress APIs can be used with AndroidX Transitions 1.5.0-alpha01 or higher on Android 14 and higher to create Predictive Back transitions.

  1. Use TransitionManager#controlDelayedTransition instead of beginDelayedTransition to play transitions as the user swipes back.
  2. Create the transition within handleOnBackStarted.
  3. Play the transition with the back event within handleOnBackProgressed by relating currentFraction to BackEvent.progress which exposes how far the user has swiped back.
  4. Finish the transition after the user has committed the back gesture in handleOnBackPressed.
  5. Finally, reset the state of the transition within handleOnBackCancelled.

The following video, Kotlin code, and XML demonstrate a custom transition between two boxes implemented with OnBackPressedCallback:

    class MyFragment : Fragment() {

    val transitionSet = TransitionSet().apply {
        addTransition(Fade(Fade.MODE_OUT))
        addTransition(ChangeBounds())
        addTransition(Fade(Fade.MODE_IN))
    }
    ...
    override fun onViewCreated(view: View, savedInstanceState: Bundle?) {
        super.onViewCreated(view, savedInstanceState)

        val callback = object : OnBackPressedCallback(enabled = false) {

            var controller: TransitionSeekController? = null

            @RequiresApi(34)
            override fun handleOnBackStarted(backEvent: BackEvent) {
                // Create the transition
                controller = TransitionManager.controlDelayedTransition(
                    binding.card,
                    transitionSet
                )
                changeTextVisibility(ShowText.SHORT)
            }

            @RequiresApi(34)
            override fun handleOnBackProgressed(backEvent: BackEvent) {
                // Play the transition as the user swipes back
                if (controller?.isReady == true) {
                    controller?.currentFraction = backEvent.progress
                }
            }

            override fun handleOnBackPressed() {
                // Finish playing the transition when the user commits back
                controller?.animateToEnd()
                this.isEnabled = false
            }

            @RequiresApi(34)
            override fun handleOnBackCancelled() {
                // If the user cancels the back gesture, reset the state
                transition(ShowText.LONG)
            }
        }

        binding.shortText.setOnClickListener {
            transition(ShowText.LONG)
            callback.isEnabled = true
        }

        this.requireActivity().onBackPressedDispatcher.addCallback(callback)
    }

    private fun transition(showText: ShowText) {
        TransitionManager.beginDelayedTransition(
            binding.card,
            transitionSet
        )
        changeTextVisibility(showText)
    }

    enum class ShowText { SHORT, LONG }
    private fun changeTextVisibility(showText: ShowText) {
        when (showText) {
            ShowText.SHORT -> {
                binding.shortText.isVisible = true
                binding.longText.isVisible = false
            }
            ShowText.LONG -> {
                binding.shortText.isVisible = false
                binding.longText.isVisible = true
            }
        }
    }
}
  
<?xml version="1.0" encoding="utf-8"?>
...
    <androidx.constraintlayout.widget.ConstraintLayout
        android:id="@+id/card"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        ...>

        <TextView
            android:id="@+id/short_text"
            android:layout_width="match_parent"
            android:layout_height="match_parent"
            ... />

        <TextView
            android:id="@+id/long_text"
            android:layout_width="match_parent"
            android:layout_height="match_parent"
            android:visibility="gone"
            .../>

    </androidx.constraintlayout.widget.ConstraintLayout>

When working with Predictive Back transitions, keep the following in mind:

  • Use isSeekingSupported to check if the transition supports Predictive Back.
  • Override isSeekingSupported to return true for your custom transitions.
  • Create one controller per animation.
  • Predictive Back transitions are supported with AndroidX transitions, but not with framework transitions. Migrate away from framework transitions and use Animator and AndroidX transitions instead.
  • Predictive Back transitions are supported on devices running Android 14 and higher and are not backward compatible.
  • Transitions created with XML scenes are also supported. In handleOnBackStarted, set your TransitionSeekController to the result of TransitionManager.createSeekController instead of the result of controlDelayedTransition.

Additional Resources