Predictive back transition ends prematurely in Navigation Compose [325998468]

Fixed

Bug

Status Update

No update yet.

Description

ky...@gmail.com

created issue #1

Feb 20, 2024 10:23AM

Component used: Navigation

Version used: 2.8.0-SNAPSHOT

Android versions reproduced on: U

Introduced in https://android-review.googlesource.com/c/platform/frameworks/support/+/2853474

PredictiveBackHandler(currentBackStack.size > 1) { backEvent ->
    inPredictiveBack = true
    progress = 0f
    val currentBackStackEntry = currentBackStack.lastOrNull()
    composeNavigator.prepareForTransition(currentBackStackEntry!!)
    val previousEntry = currentBackStack[currentBackStack.size - 2]
    composeNavigator.prepareForTransition(previousEntry)
    try {
        backEvent.collect {
            progress = it.progress
            logcat("NavHost") { "progress: $progress" }
        }
        inPredictiveBack = false
        composeNavigator.popBackStack(currentBackStackEntry, false)
    } catch (e: CancellationException) {
        inPredictiveBack = false
    }
}

When a regular back is performed, inPredictiveBack will be set to false immediately, causing the AnimatedContent to recompose.

Transition may not complete by the time but will jump to the final state.

Comments

il...@google.com <il...@google.com> #2Feb 22, 2024 12:08AM

I don't think this is enough cause we don't know how it is being produced. If you could create a project that recreates this that would be great, if not please provide us with the steps and we can see if that helps.

ky...@gmail.com <ky...@gmail.com> #3Feb 22, 2024 01:48AM

It looks like we were using a CopyOnWriteArrayList in the Java version of NavController, which was resilient to removing an OnDestinationChangedListener as part of the dispatch i.e.,

addOnDestinationChangedListener(object : OnDestinationChangedListener {
    override fun onDestinationChanged(
        controller: NavController,
        destination: NavDestination,
        arguments: Bundle?
    ) {
        removeOnDestinationChangedListener(this)
    }
})
// Note, you need to have at least one other OnDestinationChangedListener
// that is added after the one that is removed to duplicate this error

We lost that resiliency when we converted over to Kotlin, hence this error. We need to switch back.

ky...@gmail.com <ky...@gmail.com> #4Feb 22, 2024 02:39AM

We get this crash as well. I have a simple sample project where it can't be reproduced so it could be due to our nested graphs.

Kinda tl;dr scenario where it happens Graph 1 > Graph 2 (Graph 2 has bottom hav) - Navigate to dynamic feature module and click back - Navigate with BottomNavigationView.

I've spent some time trying to get a sample project which recreates the crash without success as the request in #2. Is that still needed after #3?

navigation.mp4

1.4 MB

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jb...@google.com <jb...@google.com> Feb 23, 2024 01:00AM

Assigned to jb...@google.com.

ap...@google.com <ap...@google.com> #5Feb 27, 2024 02:23AM

Project: platform/frameworks/support
Branch: androidx-main

commit cb7bd694963278c03e987603f51953f0b89d3f1c
Author: Jeremy Woods <jbwoods@google.com>
Date: Fri May 21 14:03:22 2021

Fix ConcurrentModificationException on the OnDestinationChangedListener

Go back to using the CopyOnWriteArrayList to ensure that
modifying the list of OnDestinationChangedListeners is safe.

RelNote: "You will no longer get a ConcurrentModificationException when
using OnDestinationChangedListeners."
Test: NavControllerTest
Bug: 188860458

Change-Id: Ib17074c773ed9462c6a69ad384c23e28fa8abaf6

M navigation/navigation-runtime/src/androidTest/java/androidx/navigation/NavControllerTest.kt
M navigation/navigation-runtime/src/main/java/androidx/navigation/NavController.kt

https://android-review.googlesource.com/1716168

jb...@google.com <jb...@google.com> #6Feb 28, 2024 04:03AM

Marked as fixed.

This has been fixed internally and will be available in the Navigation 2.4.0-alpha02 release.

ky...@gmail.com <ky...@gmail.com> #7Feb 28, 2024 04:05AM

Will that be tracked in a separate issue?

jb...@google.com <jb...@google.com> #8Feb 28, 2024 04:12AM

You can follow https://issuetracker.google.com/327292110 for that update.

na...@google.com <na...@google.com> #9Mar 6, 2024 07:49PM

The following release(s) address this bug.It is possible this bug has only been partially addressed:

androidx.navigation:navigation-compose:2.8.0-alpha04