Flows complete early in navigation-compose 2.4.0-alpha07 on tab reselection [196997433]

Fixed

Bug

Status Update

No update yet.

Description

yu...@gmail.com

created issue #1

Aug 18, 2021 03:11AM

Component used: Navigation Version used: Snapshot #7634339 or 2.4.0-alpha07 Devices/Android versions reproduced on: Pixel 4a

This issue is related to another fixed issue: https://issuetracker.google.com/issues/194925622

2.4.0-alpha05 introduced a bug where tab reselection causes empty screens, unless the current screen is the startDestination of the root graph.

The issue was fixed in Snapshot #7634339, but it introduced another bug:

Flows collected in compose screens via rememberFlowWithLifecycle(flow).collectAsState(initial) complete early on tab reselection, like in the original issue. About rememberFlowWithLifecycle

Attaching the minimal sample that shows the problem and a video.

In sample view model, there is a simple flow that emits text in some interval.

In 2.4.0-alpha04 - Collecting flows directly via collectAsState or via rememberFlowWithLifecycle works as expected (interval Flow doesn't complete until the user leaves the screen)

In 2.4.0-alpha05-06 - Screen becomes empty on tab reselection

In Snapshot #7634339 / 2.4.0-alpha07:

Tab reselection doesn't cause empty screens
Tab reselection doesn't cause early flow completion when collecting interval flow directly via collectAsState
Tab reselection does cause early flow completion when collecting interval flow wrapped in rememberFlowWithLifecycle

Comments

yu...@gmail.com <yu...@gmail.com> #2Aug 18, 2021 03:16AM

Oh I forgot to mention that I thought it might be connected to this issue: https://issuetracker.google.com/issues/243778589. But after trying 2.5.2 I can say that the issue persists.

screen-20210812-232537.mp4

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NavigationComposeBug-Flows.zip

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il...@google.com <il...@google.com> #3Sep 20, 2021 11:52PM

Assigned to jb...@google.com.

Please provide a minimal sample project along with the minimal steps to recreate the issue in the project.

il...@google.com <il...@google.com> #4Sep 28, 2021 09:35PM

Sorry for the delay. I got a working example here: https://github.com/Del-S/issues. The project is set up to crash when navigating to ThirdFragment (nested nav graph) with poping the graph.

I poked into it a little bit and it seems to be connected to SafeArgs gradle plugin. When safe args is used to navigate to ThirdFragment (with nested graph poped) it will try to recreate te parent but there were no arguments passed so it crashes.

Steps to reproduce:

Navigate from Second Fragment to Child nav graph (with non-nullable parameters).
Navigate to Third fragment using SafeArgs and the app crashes.

Crash log:

Process: cz.dels.issues, PID: 1743
java.lang.NullPointerException: null cannot be cast to non-null type kotlin.Long
at androidx.navigation.NavType$Companion$LongType$1.get(NavType.kt:352)
at androidx.navigation.NavType$Companion$LongType$1.get(NavType.kt:342)
at androidx.navigation.NavArgument.verify(NavArgument.kt:76)
at androidx.navigation.NavDestination.addInDefaultArgs(NavDestination.kt:502)
at androidx.navigation.NavController.addEntryToBackStack(NavController.kt:1865)
at androidx.navigation.NavController.addEntryToBackStack$default(NavController.kt:1813)
at androidx.navigation.NavController$navigate$4.invoke(NavController.kt:1721)
at androidx.navigation.NavController$navigate$4.invoke(NavController.kt:1719)
at androidx.navigation.NavController$NavControllerNavigatorState.push(NavController.kt:287)
at androidx.navigation.fragment.FragmentNavigator.navigate(FragmentNavigator.kt:246)
at androidx.navigation.fragment.FragmentNavigator.navigate(FragmentNavigator.kt:162)
at androidx.navigation.NavController.navigateInternal(NavController.kt:260)
at androidx.navigation.NavController.navigate(NavController.kt:1719)
at androidx.navigation.NavController.navigate(NavController.kt:1545)
at androidx.navigation.NavController.navigate(NavController.kt:1472)
at androidx.navigation.NavController.navigate(NavController.kt:1930)
at cz.dels.issues.SecondFragment.onViewCreated$lambda-0(SecondFragment.kt:38)
at cz.dels.issues.SecondFragment.$r8$lambda$XDYnOS_cYrafiNQ5rcCu1WCn0IE(Unknown Source:0)
at cz.dels.issues.SecondFragment$$ExternalSyntheticLambda0.onClick(Unknown Source:2)

Note: If in step 2 SaveArgs is not used then navigation works correctly. More information is here: https://github.com/Del-S/issues/blob/master/app/src/main/java/cz/dels/issues/SecondFragment.kt#L37.

ap...@google.com <ap...@google.com> #5Oct 4, 2021 09:09PM

Ups a typo: Navigate from ~~Second~~ First Fragment to Child nav graph (with non-nullable parameters).

Note: sorry for the spam but I am not able to edit my own comment.

jb...@google.com <jb...@google.com> #6Oct 5, 2021 04:40PM

Marked as fixed.

This has been fixed and will be available in navigation 2.6.0-alpha08

yu...@gmail.com <yu...@gmail.com> #7Oct 5, 2021 07:38PM

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

commit 6b358154b794a0456b089ac8e548bfb830dd6c22
Author: Clara Fok <clarafok@google.com>
Date: Tue Mar 14 17:56:12 2023

Fix missing non-nullable arg when rebuilding hierarchy

When navigating with NavDirections, args is populated with an empty bundle. This causes issue when we rebuild parent hierarchy while adding a new entry to NavBackStack. If the Entry being rebuilt contains a non-nullalbe arg, i.e. Long, this empty bundle will cause an exception.

Test: ./gradlew navigation:navigation-runtime:cC
Bug: 249988437
Change-Id: I5c8ce739ad9a3428c8a8de13eae391bfff0db5df

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/2488855

yu...@gmail.com <yu...@gmail.com> #8Oct 5, 2021 08:50PM

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

androidx.navigation:navigation-runtime:2.6.0-alpha08

yu...@gmail.com <yu...@gmail.com> #9Oct 6, 2021 01:05AM

I tried build #7796270 and looks like the bug is gone. Thanks!