IssueTracker

Component used: Navigation
Version used: androidx.navigation:navigation-compose:2.4.0-beta02
Devices/Android versions reproduced on: Google Pixel 3 with Android 12, ARM64 emulator with Android 12

Please get the attached project (Compose Blueprint). It contains two screens: Main and Subscreen. Subscreen is nested under Subgraph navigation block. So the navigation goes: Main -> Subgraph -> SubScreen. Subscreen is requesting Subgraph's ViewModel emulating the situation when this ViewModel needs to be shared between some screen within a nested flow.

Install the app and follow the next steps:

1. Enable "Don't keep activities" in Developer options.
2. Open Compose Blueprint application.
3. Click "To subgraph" button. Subscreen is opened now.
4. Press home button in order to move application to background. At this point MainActivity is destroyed.
5. Reopen the app from recent apps. MainActivity is recreated and should be showing Subscreen once again.
6. Press back. 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.kt:105)
        at androidx.lifecycle.viewmodel.compose.ViewModelKt.get(ViewModel.kt:82)
        at androidx.lifecycle.viewmodel.compose.ViewModelKt.viewModel(ViewModel.kt:72)
        at dev.olshevski.blueprint.compose.MainActivityKt$BlueprintNavHost$1$2$1.invoke(MainActivity.kt:142)
        at dev.olshevski.blueprint.compose.MainActivityKt$BlueprintNavHost$1$2$1.invoke(MainActivity.kt:69)
        at androidx.compose.runtime.internal.ComposableLambdaImpl.invoke(ComposableLambda.jvm.kt:116)
        at androidx.compose.runtime.internal.ComposableLambdaImpl.invoke(ComposableLambda.jvm.kt:34)
        at androidx.navigation.compose.NavHostKt$NavHost$4$1.invoke(NavHost.kt:150)
        at androidx.navigation.compose.NavHostKt$NavHost$4$1.invoke(NavHost.kt:149)
        at androidx.compose.runtime.internal.ComposableLambdaImpl.invoke(ComposableLambda.jvm.kt:107)
        at androidx.compose.runtime.internal.ComposableLambdaImpl.invoke(ComposableLambda.jvm.kt:34)
        at androidx.compose.runtime.CompositionLocalKt.CompositionLocalProvider(CompositionLocal.kt:215)
        at androidx.compose.runtime.saveable.SaveableStateHolderImpl.SaveableStateProvider(SaveableStateHolder.kt:84)
        at androidx.navigation.compose.NavBackStackEntryProviderKt.SaveableStateProvider(NavBackStackEntryProvider.kt:59)
        at androidx.navigation.compose.NavBackStackEntryProviderKt.access$SaveableStateProvider(NavBackStackEntryProvider.kt:1)
        at androidx.navigation.compose.NavBackStackEntryProviderKt$LocalOwnersProvider$1.invoke(NavBackStackEntryProvider.kt:51)
        at androidx.navigation.compose.NavBackStackEntryProviderKt$LocalOwnersProvider$1.invoke(NavBackStackEntryProvider.kt:50)
        at androidx.compose.runtime.internal.ComposableLambdaImpl.invoke(ComposableLambda.jvm.kt:107)
        at androidx.compose.runtime.internal.ComposableLambdaImpl.invoke(ComposableLambda.jvm.kt:34)
        at androidx.compose.runtime.CompositionLocalKt.CompositionLocalProvider(CompositionLocal.kt:215)
        at androidx.navigation.compose.NavBackStackEntryProviderKt.LocalOwnersProvider(NavBackStackEntryProvider.kt:46)
        at androidx.navigation.compose.NavHostKt$NavHost$4.invoke(NavHost.kt:149)
        at androidx.navigation.compose.NavHostKt$NavHost$4.invoke(NavHost.kt:142)
        at androidx.compose.runtime.internal.ComposableLambdaImpl.invoke(ComposableLambda.jvm.kt:116)
        at androidx.compose.runtime.internal.ComposableLambdaImpl.invoke(ComposableLambda.jvm.kt:34)
        at androidx.compose.animation.CrossfadeKt$Crossfade$1$1.invoke(Crossfade.kt:74)
        at androidx.compose.animation.CrossfadeKt$Crossfade$1$1.invoke(Crossfade.kt:69)
        at androidx.compose.runtime.internal.ComposableLambdaImpl.invoke(ComposableLambda.jvm.kt:107)
        at androidx.compose.runtime.internal.ComposableLambdaImpl.invoke(ComposableLambda.jvm.kt:34)
        at androidx.compose.animation.CrossfadeKt.Crossfade(Crossfade.kt:86)
        at androidx.navigation.compose.NavHostKt.NavHost(NavHost.kt:142)
        at androidx.navigation.compose.NavHostKt$NavHost$5.invoke(Unknown Source:13)
        at androidx.navigation.compose.NavHostKt$NavHost$5.invoke(Unknown Source:10)
        at androidx.compose.runtime.RecomposeScopeImpl.compose(RecomposeScopeImpl.kt:140)
        at androidx.compose.runtime.ComposerImpl.recomposeToGroupEnd(Composer.kt:2156)
        at androidx.compose.runtime.ComposerImpl.skipCurrentGroup(Composer.kt:2399)
        at androidx.compose.runtime.ComposerImpl$doCompose$2$5.invoke(Composer.kt:2580)
        at androidx.compose.runtime.ComposerImpl$doCompose$2$5.invoke(Composer.kt:2566)
        at androidx.compose.runtime.SnapshotStateKt.observeDerivedStateRecalculations(SnapshotState.kt:540)
        at androidx.compose.runtime.ComposerImpl.doCompose(Composer.kt:2566)
        at androidx.compose.runtime.ComposerImpl.recompose$runtime_release(Composer.kt:2542)
        at androidx.compose.runtime.CompositionImpl.recompose(Composition.kt:614)
        at androidx.compose.runtime.Recomposer.performRecompose(Recomposer.kt:764)
        at androidx.compose.runtime.Recomposer.access$performRecompose(Recomposer.kt:103)
        at androidx.compose.runtime.Recomposer$runRecomposeAndApplyChanges$2$2.invoke(Recomposer.kt:447)
        at androidx.compose.runtime.Recomposer$runRecomposeAndApplyChanges$2$2.invoke(Recomposer.kt:416)
        at androidx.compose.ui.platform.AndroidUiFrameClock$withFrameNanos$2$callback$1.doFrame(AndroidUiFrameClock.android.kt:34)
        at androidx.compose.ui.platform.AndroidUiDispatcher.performFrameDispatch(AndroidUiDispatcher.android.kt:109)
        at androidx.compose.ui.platform.AndroidUiDispatcher.access$performFrameDispatch(AndroidUiDispatcher.android.kt:41)
        at androidx.compose.ui.platform.AndroidUiDispatcher$dispatchCallback$1.doFrame(AndroidUiDispatcher.android.kt:69)
        at android.view.Choreographer$CallbackRecord.run(Choreographer.java:1035)
        at android.view.Choreographer.doCallbacks(Choreographer.java:845)
        at android.view.Choreographer.doFrame(Choreographer.java:775)
        at android.view.Choreographer$FrameDisplayEventReceiver.run(Choreographer.java:1022)
        at android.os.Handler.handleCallback(Handler.java:938)
        at android.os.Handler.dispatchMessage(Handler.java:99)
        at android.os.Looper.loopOnce(Looper.java:201)
        at android.os.Looper.loop(Looper.java:288)
        at android.app.ActivityThread.main(ActivityThread.java:7839)
        at java.lang.reflect.Method.invoke(Native Method)
        at com.android.internal.os.RuntimeInit$MethodAndArgsCaller.run(RuntimeInit.java:548)
        at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:1003)

The same crash never happen when the activity is not recreated, e.g. when "Don't keep activities" is disabled. Also, just going back and forth between screens without moving the app into the background works correctly.

So it seems there something going wrong when the navigation backstack is restored.