NavGraphBuilder.dialog [206465487]

Fixed

Bug

Status Update

No update yet.

Description

ja...@deepl.com

created issue #1

Nov 16, 2021 02:51PM

Component used: Navigation

Version used: 2.4.0-beta02

Devices/Android versions reproduced on: Every device

I'm using Compose with the navigation components. I inject a ViewModel via Hilt.

I navigate with the NavGraphBuilder.composable() extension, which works.

When I open my composable within a Dialog via the NavGraphBuilder.dialog() extension I run into the following problem:

Closing the dialog with the system back button works. When I call navController.popBackstack() this exception occurs and the app crashes:

java.lang.IllegalStateException: You cannot access the NavBackStackEntry's ViewModels until it is added to the NavController's back stack (i.e., the Lifecycle of the NavBackStackEntry reaches the CREATED state).
        at androidx.navigation.NavBackStackEntry.getViewModelStore(NavBackStackEntry.kt:180)
        at androidx.lifecycle.ViewModelProvider.<init>(ViewModelProvider.java:114)
        at androidx.lifecycle.viewmodel.compose.ViewModelKt.get(ViewModel.kt:80)
        at androidx.lifecycle.viewmodel.compose.ViewModelKt.viewModel(ViewModel.kt:72)

I observed that my crashing composable is recomposed after navController.popBackstack(), which ultimately leads to the crash. Is there a reason for the additional recompositions?

Comments

jb...@google.com <jb...@google.com> #2Nov 16, 2021 03:58PM

Yigit, do you have time to fix it?

reemission of the same liveData is racy

ja...@deepl.com <ja...@deepl.com> #3Nov 18, 2021 10:13AM

yea i'll take it.

il...@google.com <il...@google.com> Nov 18, 2021 04:26PM

Assigned to jb...@google.com.

ap...@google.com <ap...@google.com> #4Nov 18, 2021 10:53PM

Thanks for the detailed analysis. This may not be an issue anymore since we've started using Main.immediate there but I' not sure; I'll try to create a test case.

jb...@google.com <jb...@google.com> #5Nov 18, 2021 10:55PM

Marked as fixed.

just emitting same live data reproduces the issue.

@Test
fun raceTest() {
val subLiveData = MutableLiveData(1)
val subject = liveData(testScope.coroutineContext) {
emitSource(subLiveData)
emitSource(subLiveData) //crashes
}
subject.addObserver().apply {
testScope.advanceUntilIdle()
}
}

ja...@deepl.com <ja...@deepl.com> #6Nov 19, 2021 08:08AM

With 2.2.0-alpha04 (that use Main.immediate), the issue seems to be still there (I tested it by calling emitSource() twice, like your test case)

Issue 206465487