Fixed incorrect predictive back animation playing on hardware back button click with the new animation API

[arkivanov]

Summary by CodeRabbit

• New Features

  • Improved back navigation animations with enhanced state management.
  • New logic ensures animations are triggered predictably during back navigation events.

• Bug Fixes

  • Enhanced tests for predictive back gestures to ensure correct UI behavior during complex interactions.

• Documentation

  • Updated test case names for clarity and better understanding of functionality.

[coderabbitai]

Walkthrough

The changes introduce enhancements to the DefaultStackAnimation class for improved back navigation handling and state management. A new variable, initialBackEvent, is added to manage back events effectively, preventing multiple animations from triggering for the same event. Additionally, the PredictiveBackGestureTest.kt file is updated with clearer test case names and new tests to validate the behavior of predictive back gestures in stack navigation, ensuring accurate UI responses during user interactions.

Changes

File	Change Summary
extensions-compose-experimental/src/commonMain/kotlin/com/arkivanov/decompose/extensions/compose/experimental/stack/animation/DefaultStackAnimation.kt	Introduced initialBackEvent to manage back navigation events, modified onBackStarted, onBackProgressed, onBackCancelled, and onBack methods for better state management and animation control.
extensions-compose-experimental/src/jvmTest/kotlin/com/arkivanov/decompose/extensions/compose/experimental/stack/animation/PredictiveBackGestureTest.kt	Updated test case names for clarity, added new tests for predictive back gestures to ensure proper UI behavior during complex interactions, including checks for child visibility and animation handling.

Possibly related PRs

• Removed unused type parameters from the experimental PredictiveBackParams #777: The changes in the DefaultStackAnimation class regarding the predictiveBackParams parameter are directly related to the modifications made in the PredictiveBackParams class, enhancing type safety and simplifying the code structure.

🐰 In the land of code where rabbits play,
New animations hop in a smooth ballet.
With back events tracked, no more will they clash,
Predictive gestures now dance in a flash!
Tests are clearer, ensuring all's right,
Hopping through changes, oh what a delight! 🌟

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Recent review details

Configuration used: CodeRabbit UI
Review profile: CHILL

Commits

Files that changed from the base of the PR and between 14ffffd and fa095ea.

Files selected for processing (2)

• extensions-compose-experimental/src/commonMain/kotlin/com/arkivanov/decompose/extensions/compose/experimental/stack/animation/DefaultStackAnimation.kt (2 hunks)
• extensions-compose-experimental/src/jvmTest/kotlin/com/arkivanov/decompose/extensions/compose/experimental/stack/animation/PredictiveBackGestureTest.kt (5 hunks)

Additional comments not posted (9)

extensions-compose-experimental/src/commonMain/kotlin/com/arkivanov/decompose/extensions/compose/experimental/stack/animation/DefaultStackAnimation.kt (6)

224-224: LGTM!

The addition of the initialBackEvent variable is a good change as it allows the animation to be initiated only once per back navigation event, ensuring that the animation handler is correctly set up before processing any back progress.

---

227-228: LGTM!

Assigning the incoming backEvent to initialBackEvent in onBackStarted is a good change. This ensures that the initial back event is stored when a back navigation starts, which is part of the new mechanism for handling back navigation events with improved state management.

---

230-236: LGTM!

The changes in onBackProgressed are good:

• Calling startIfNeeded encapsulates the logic for starting the animation handler.
• Launching a coroutine to call animationHandler?.progress(backEvent) ensures that the animation progress is updated asynchronously.

These changes are part of the new mechanism for handling back navigation events with improved state management, where onBackProgressed now checks if initialBackEvent is not null before proceeding to start the animation.

---

Line range hint 238-279: LGTM!

The addition of the startIfNeeded method is a good change as it encapsulates the logic for starting the animation handler. It checks if initialBackEvent is not null before proceeding, ensuring that the animation is initiated only once per back navigation event.

The method correctly creates a new AnimationHandler instance, sets up the animation items using setItems, and launches a coroutine to call animationHandler.start(backEvent) to start the animation asynchronously.

These changes are part of the new mechanism for handling back navigation events with improved state management, where the animation handler is now only invoked if there is a valid initialBackEvent.

---

272-279: LGTM!

The changes in onBackCancelled are good:

• Resetting initialBackEvent to null ensures that the state is clean for subsequent back navigation events.
• Launching a coroutine to cancel the animation handler and set the animation items using setItems(getAnimationItems(newStack = stack)) is the correct way to handle the back cancellation.
• Using the also function to streamline the logic for cancelling the animation handler improves readability and reduces redundancy.

These changes are part of the enhancements to the control flow and state management of back navigation animations, ensuring that animations are handled more predictably and efficiently.

---

284-292: LGTM!

The changes in onBack are good:

• Resetting initialBackEvent to null ensures that the state is clean for subsequent back navigation events.
• Launching a coroutine to finish the animation handler, set the animation items using setItems(getAnimationItems(newStack = stack.dropLast())), and call predictiveBackParams.onBack() is the correct way to handle the back navigation.
• Using the also function to streamline the logic for finishing the animation handler improves readability and reduces redundancy.

These changes are part of the enhancements to the control flow and state management of back navigation animations, ensuring that animations are handled more predictably and efficiently.

extensions-compose-experimental/src/jvmTest/kotlin/com/arkivanov/decompose/extensions/compose/experimental/stack/animation/PredictiveBackGestureTest.kt (3)

Line range hint 54-69: LGTM!

The updated function name better reflects the test case's functionality. The assertions ensure that the UI behaves as expected when a predictive back gesture is started.

---

291-331: LGTM!

The updated function name better reflects the test case's functionality. The test case ensures that unnecessary animations do not occur, which could lead to performance issues or unintended UI behavior.

---

371-408: LGTM!

The new test case reinforces the logic that the animation should only occur under specific conditions, ensuring that the UI behaves as expected during complex interactions.

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