Unable to initialize NavBackStackEntry - IllegalStateException: Method addObserver must be called on the main thread [171125856]

Fixed

Bug

Status Update

No update yet.

Description

[Deleted User]

created issue #1

Oct 19, 2020 08:57AM

Component used: Navigation

Version used: 2.2.0, 2.3.0, 2.3.1

Devices/Android versions reproduced on: 10.0, 9.0 - probably not related

Description:

I've updated two dependencies in my project:

androidx.fragment:fragment 1.3.0-alpha06 -> 1.3.0-beta01
androidx.activity.activity 1.1.0 -> 1.2.0-beta01

and now I see that NavController::navigate needs to be called from the main thread. Otherwise NavBackStackEntry throws IllegalStateException when trying to register lifecycle observer.

Stacktrace:

Caused by: java.lang.IllegalStateException: Method addObserver must be called on the main thread
    at androidx.lifecycle.LifecycleRegistry.enforceMainThreadIfNeeded(LifecycleRegistry.java:317)
    at androidx.lifecycle.LifecycleRegistry.addObserver(LifecycleRegistry.java:172)
    at androidx.savedstate.SavedStateRegistryController.performRestore(SavedStateRegistryController.java:61)
    at androidx.navigation.NavBackStackEntry.<init>(NavBackStackEntry.java:84)
    at androidx.navigation.NavBackStackEntry.<init>(NavBackStackEntry.java:69)
    at androidx.navigation.NavController.navigate(NavController.java:970)
    at androidx.navigation.NavController.navigate(NavController.java:867)

There were no changes in documentation so I assume that this behavior is unintended.

Comments

il...@google.com <il...@google.com> #2Oct 19, 2020 08:10PM

Using navigation version 2.6.0 and 2.7.1 the issue still persists.

After further investigation, the behaviour can be corrected by filtering on backstack entries where current state is at least started. In my opinion the name visibleEntries is misleading if it contains entries that are not actually visible or in transition.

[Deleted User] <[Deleted User]> #3Oct 20, 2020 07:19AM

Note that as per the visibleEntries documentation, it is expected that there are entries that are in the CREATED state - those are the entries that are in the process of being removed (i.e., they are no longer in the back stack, but have not yet marked their transition as complete).

It is a bug that those entries aren't removed when their exit animation completes and that's what we'll be looking into.

ap...@google.com <ap...@google.com> #4Apr 6, 2021 10:13PM

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

commit f61da31809827bfac89af629c88ad9b8423e88b6
Author: Clara Fok <clarafok@google.com>
Date: Wed Sep 06 14:14:11 2023

Fix entry not marked complete after view is destroyed

As part of a fix for

b/279644470

in aosp/2566210, when the fragment view is destroyed, we would mark the transitioning (outgoing) entry as complete only if the entry has also been removed from backstack. However, in the simple navigate() case where the outgoing entry is not popped and remains in the backstack, this entry is not marked complete and ends up in the visibleEntries even though the view has been destroyed.

Now the backstack check in ON_DESTROY is no longer necessary to fix the original

b/279644470

bug -- the view being destroyed should be the right signal for completing entries regardless of whether transitioning effects are used. So this check is removed.

Test: ./gradlew navigation:navigation-fragment:cC
Test: ./gradlew navigation:navigation-runtime:cC
Bug: 288520638
Change-Id: I5caa9af1b5bd7084e76d7daf9515f7430bf2489d

M navigation/navigation-fragment/src/androidTest/java/androidx/navigation/fragment/FragmentNavigatorTest.kt
M navigation/navigation-fragment/src/androidTest/java/androidx/navigation/fragment/NavControllerWithFragmentTest.kt
M navigation/navigation-fragment/src/main/java/androidx/navigation/fragment/FragmentNavigator.kt
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/2743918

il...@google.com <il...@google.com> #5Apr 6, 2021 10:17PM

Marked as fixed, reassigned to il...@google.com.

Fixed internally and will be available in navigation 2.7.3

ap...@google.com <ap...@google.com> #6Apr 12, 2021 11:58PM

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

androidx.navigation:navigation-fragment:2.7.3
androidx.navigation:navigation-runtime:2.7.3

Issue 171125856