Make it possible to cancel swipes (1/2) (c5645ba3) · Commits · e / os / android_frameworks_base

packages/SystemUI/compose/scene/src/com/android/compose/animation/scene/SceneGestureHandler.kt

+18 −4

Original line number	Diff line number	Diff line
		@@ -348,6 +348,8 @@ internal class SceneGestureHandler(
		// Compute the destination scene (and therefore offset) to settle in.
		val offset = swipeTransition.dragOffset
		val distance = swipeTransition.distance
		var targetScene: Scene
		var targetOffset: Float
		if (
		shouldCommitSwipe(
		offset,
		@@ -356,12 +358,24 @@ internal class SceneGestureHandler(
		wasCommitted = swipeTransition._currentScene == toScene,
		)
		) {
		// Animate to the next scene
		animateTo(targetScene = toScene, targetOffset = distance)
		targetScene = toScene
		targetOffset = distance
		} else {
		// Animate to the initial scene
		animateTo(targetScene = fromScene, targetOffset = 0f)
		targetScene = fromScene
		targetOffset = 0f
		}

		if (
		targetScene != swipeTransition._currentScene &&
		!layoutState.canChangeScene(targetScene.key)
		) {
		// We wanted to change to a new scene but we are not allowed to, so we animate back
		// to the current scene.
		targetScene = swipeTransition._currentScene
		targetOffset = if (targetScene == fromScene) 0f else distance
		}

		animateTo(targetScene = targetScene, targetOffset = targetOffset)
		} else {
		// We are doing an overscroll animation between scenes. In this case, we can also start
		// from the idle position.

packages/SystemUI/compose/scene/src/com/android/compose/animation/scene/SceneTransitionLayoutImpl.kt

+6 −1

Original line number	Diff line number	Diff line
		@@ -232,7 +232,12 @@ internal class SceneTransitionLayoutImpl(
		scene(state.transitionState.currentScene).userActions[Back]?.let { result ->
		// TODO(b/290184746): Handle predictive back and use result.distance if
		// specified.
		BackHandler { with(state) { coroutineScope.onChangeScene(result.toScene) } }
		BackHandler {
		val targetScene = result.toScene
		if (state.canChangeScene(targetScene)) {
		with(state) { coroutineScope.onChangeScene(targetScene) }
		}
		}
		}

		Box {

packages/SystemUI/compose/scene/src/com/android/compose/animation/scene/SceneTransitionLayoutState.kt

+47 −5

Original line number	Diff line number	Diff line
		@@ -101,13 +101,30 @@ sealed interface MutableSceneTransitionLayoutState : SceneTransitionLayoutState
		): TransitionState.Transition?
		}

		/** Return a [MutableSceneTransitionLayoutState] initially idle at [initialScene]. */
		/**
		* Return a [MutableSceneTransitionLayoutState] initially idle at [initialScene].
		*
		* @param initialScene the initial scene to which this state is initialized.
		* @param transitions the [SceneTransitions] used when this state is transitioning between scenes.
		* @param canChangeScene whether we can transition to the given scene. This is called when the user
		* commits a transition to a new scene because of a [UserAction]. If [canChangeScene] returns
		* `true`, then the gesture will be committed and we will animate to the other scene. Otherwise,
		* the gesture will be cancelled and we will animate back to the current scene.
		* @param stateLinks the [StateLink] connecting this [SceneTransitionLayoutState] to other
		* [SceneTransitionLayoutState]s.
		*/
		fun MutableSceneTransitionLayoutState(
		initialScene: SceneKey,
		transitions: SceneTransitions = SceneTransitions.Empty,
		canChangeScene: (SceneKey) -> Boolean = { true },
		stateLinks: List<StateLink> = emptyList(),
		): MutableSceneTransitionLayoutState {
		return MutableSceneTransitionLayoutStateImpl(initialScene, transitions, stateLinks)
		return MutableSceneTransitionLayoutStateImpl(
		initialScene,
		transitions,
		canChangeScene,
		stateLinks,
		)
		}

		/**
		@@ -120,18 +137,32 @@ fun MutableSceneTransitionLayoutState(
		* This is called when the user commits a transition to a new scene because of a [UserAction], for
		* instance by triggering back navigation or by swiping to a new scene.
		* @param transitions the definition of the transitions used to animate a change of scene.
		* @param canChangeScene whether we can transition to the given scene. This is called when the user
		* commits a transition to a new scene because of a [UserAction]. If [canChangeScene] returns
		* `true`, then [onChangeScene] will be called right afterwards with the same [SceneKey]. If it
		* returns `false`, the user action will be cancelled and we will animate back to the current
		* scene.
		* @param stateLinks the [StateLink] connecting this [SceneTransitionLayoutState] to other
		* [SceneTransitionLayoutState]s.
		*/
		@Composable
		fun updateSceneTransitionLayoutState(
		currentScene: SceneKey,
		onChangeScene: (SceneKey) -> Unit,
		transitions: SceneTransitions = SceneTransitions.Empty,
		canChangeScene: (SceneKey) -> Boolean = { true },
		stateLinks: List<StateLink> = emptyList(),
		): SceneTransitionLayoutState {
		return remember {
		HoistedSceneTransitionLayoutScene(currentScene, transitions, onChangeScene, stateLinks)
		HoistedSceneTransitionLayoutScene(
		currentScene,
		transitions,
		onChangeScene,
		canChangeScene,
		stateLinks,
		)
		}
		.apply { update(currentScene, onChangeScene, transitions, stateLinks) }
		.apply { update(currentScene, onChangeScene, canChangeScene, transitions, stateLinks) }
		}

		@Stable
		@@ -208,6 +239,9 @@ internal abstract class BaseSceneTransitionLayoutState(

		private val activeTransitionLinks = mutableMapOf<StateLink, LinkedTransition>()

		/** Whether we can transition to the given [scene]. */
		internal abstract fun canChangeScene(scene: SceneKey): Boolean

		/**
		* Called when the [current scene][TransitionState.currentScene] should be changed to [scene].
		*
		@@ -334,21 +368,26 @@ internal class HoistedSceneTransitionLayoutScene(
		initialScene: SceneKey,
		override var transitions: SceneTransitions,
		private var changeScene: (SceneKey) -> Unit,
		private var canChangeScene: (SceneKey) -> Boolean,
		stateLinks: List<StateLink> = emptyList(),
		) : BaseSceneTransitionLayoutState(initialScene, stateLinks) {
		private val targetSceneChannel = Channel<SceneKey>(Channel.CONFLATED)

		override fun CoroutineScope.onChangeScene(scene: SceneKey) = changeScene(scene)
		override fun canChangeScene(scene: SceneKey): Boolean = canChangeScene.invoke(scene)

		override fun CoroutineScope.onChangeScene(scene: SceneKey) = changeScene.invoke(scene)

		@Composable
		fun update(
		currentScene: SceneKey,
		onChangeScene: (SceneKey) -> Unit,
		canChangeScene: (SceneKey) -> Boolean,
		transitions: SceneTransitions,
		stateLinks: List<StateLink>,
		) {
		SideEffect {
		this.changeScene = onChangeScene
		this.canChangeScene = canChangeScene
		this.transitions = transitions
		this.stateLinks = stateLinks

		@@ -374,6 +413,7 @@ internal class HoistedSceneTransitionLayoutScene(
		internal class MutableSceneTransitionLayoutStateImpl(
		initialScene: SceneKey,
		override var transitions: SceneTransitions,
		private val canChangeScene: (SceneKey) -> Boolean = { true },
		stateLinks: List<StateLink> = emptyList(),
		) : MutableSceneTransitionLayoutState, BaseSceneTransitionLayoutState(initialScene, stateLinks) {
		override fun setTargetScene(
		@@ -388,6 +428,8 @@ internal class MutableSceneTransitionLayoutStateImpl(
		)
		}

		override fun canChangeScene(scene: SceneKey): Boolean = canChangeScene.invoke(scene)

		override fun CoroutineScope.onChangeScene(scene: SceneKey) {
		setTargetScene(scene, coroutineScope = this)
		}

packages/SystemUI/compose/scene/tests/src/com/android/compose/animation/scene/SceneGestureHandlerTest.kt

+43 −1

Original line number	Diff line number	Diff line
		@@ -51,8 +51,13 @@ class SceneGestureHandlerTest {
		private class TestGestureScope(
		private val testScope: MonotonicClockTestScope,
		) {
		var canChangeScene: (SceneKey) -> Boolean = { true }
		private val layoutState =
		MutableSceneTransitionLayoutStateImpl(SceneA, EmptyTestTransitions)
		MutableSceneTransitionLayoutStateImpl(
		SceneA,
		EmptyTestTransitions,
		canChangeScene = { canChangeScene(it) },
		)

		val mutableUserActionsA = mutableMapOf(Swipe.Up to SceneB, Swipe.Down to SceneC)
		val mutableUserActionsB = mutableMapOf(Swipe.Up to SceneC, Swipe.Down to SceneA)
		@@ -890,4 +895,41 @@ class SceneGestureHandlerTest {
		)
		assertThat(transitionState).isNotSameInstanceAs(firstTransition)
		}

		@Test
		fun blockTransition() = runGestureTest {
		assertIdle(SceneA)

		// Swipe up to scene B.
		onDragStarted(overSlop = up(0.1f))
		assertTransition(currentScene = SceneA, fromScene = SceneA, toScene = SceneB)

		// Block the transition when the user release their finger.
		canChangeScene = { false }
		onDragStopped(velocity = -velocityThreshold)
		advanceUntilIdle()
		assertIdle(SceneA)
		}

		@Test
		fun blockInterceptedTransition() = runGestureTest {
		assertIdle(SceneA)

		// Swipe up to B.
		onDragStarted(overSlop = up(0.1f))
		assertTransition(currentScene = SceneA, fromScene = SceneA, toScene = SceneB)
		onDragStopped(velocity = -velocityThreshold)
		assertTransition(currentScene = SceneB, fromScene = SceneA, toScene = SceneB)

		// Intercept the transition and swipe down back to scene A.
		assertThat(sceneGestureHandler.shouldImmediatelyIntercept(startedPosition = null)).isTrue()
		onDragStartedImmediately()

		// Block the transition when the user release their finger.
		canChangeScene = { false }
		onDragStopped(velocity = velocityThreshold)

		advanceUntilIdle()
		assertIdle(SceneB)
		}
		}