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

Do you have a sample project that reproduces your issue?

What do you mean by 'a regular back'?

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

It means back button (in 3-button navigation) or quick gesture (in gesture navigation).

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

It can be reproduced with https://cs.android.com/androidx/platform/frameworks/support/+/androidx-main:navigation/navigation-compose/samples/src/main/java/androidx/navigation/compose/samples/NavigationSamples.kt

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 ba9207cd04a8e832b6bcdd38e39d0084cefba6ec
Author: Jeremy Woods <jbwoods@google.com>
Date: Thu Feb 22 20:56:27 2024

Ensure non-gesture Systemback has transition in Compose

When using system back, the NavHost `inPredictiveBack` flag flips from
false to true, starting a predictive back gesture, then back to false
which cancels the started gesture and pushes it to completion. This
result in the incoming destination immediately appearing on the screen
instead of transitioning.

We can fix the system back case, by waiting to get progress before
changing the `inPredictiveBack` flag.

There is still the "flick" case that will remain as it is. What we would
need for that is a way to seek the transition to completion from the
current state.

RelNote: "Fixed an issue where NavHost in Compose Navigation failed to
properly transition when using System back without a gesture."
Test: tested in sample app
Bug: 325998468

Change-Id: Iceeae260189dd12af8cb3fe690523646a90f57de

M navigation/navigation-compose/src/main/java/androidx/navigation/compose/NavHost.kt

https://android-review.googlesource.com/2974195

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

Marked as fixed.

The basic system back case has been fixed in Navigation 2.8.0-alpha04, the flick case will likely remain for now as we need some further transition support.

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