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

Still crashing with Compose 1.7.4.
I also tried moving sharedElement to BoxWithConstraints (rather than in its content), but did not help.
So the layout hierarchy looks like this (with more details and with "..." I replaced series of "normal" layouts):
NavHost -> ... -> AnimatedVisibility -> ... -> BoxWithConstraints with sharedElement -> some content
\> ... -> AnimatedVisibility -> ... -> LazyList -> ... -> Animated Visibility -> Selection container -> BoxWithConstraints with sharedElement -> some content

Any ideas?

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

In your BoxWithConstraints do you do any conditional composition? Things like:

if (constraintsExceedsCertainThreshold) composeSomeContent() else someOtherContent()

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

No, it's just a `Text` which has different style depending on constraints.
Also note `sharedElement` is put on `BoxWithContraints` now, not on the content.
Thanks!

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

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

Based on the stacktrace, it seems like the item in question is composed but never placed. Do you use custom precompose or prefetch logic in your lazy list?

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

No, nothing custom. Just the default prefetch logic.
There is also one `AnimatedContent` above the `BoxWithConstraints`. Could this cause issues?
Thank you for looking into this.

Issue 171125856