IssueTracker

Component used: lifecycle-viewmodel-ktx

Version used: 2.3.0

Devices/Android versions reproduced on: Pixel 4 running Android 10

Sample project to trigger the issue: https://github.com/tfcporciuncula/view-tree-owner-bug

You can repro the issue by cloning that repo, running it, and then rotating the screen causing a config change.

This is the code I'm using to create a ViewModel in a View (as you can see here):

private val viewModel by lazy {
  val factory = object : AbstractSavedStateViewModelFactory(findViewTreeSavedStateRegistryOwner()!!, null) {
    override fun <T : ViewModel?> create(key: String, modelClass: Class<T>, handle: SavedStateHandle): T {
      return MyViewModel() as T
    }
  }
  ViewModelProvider(findViewTreeViewModelStoreOwner()!!, factory).get(MyViewModel::class.java)
}

Everything works fine, but the app crashes on orientation change with the following stacktrace:

Process: com.tfcporciuncula.viewtreeownerbug, PID: 3467
    java.lang.IllegalStateException: Internal error: OnRecreation should be registered only on componentsthat implement ViewModelStoreOwner
        at androidx.lifecycle.SavedStateHandleController$OnRecreation.onRecreated(SavedStateHandleController.java:80)
        at androidx.savedstate.Recreator.reflectiveNew(Recreator.java:92)
        at androidx.savedstate.Recreator.onStateChanged(Recreator.java:64)
        at androidx.lifecycle.LifecycleRegistry$ObserverWithState.dispatchEvent(LifecycleRegistry.java:354)
        at androidx.lifecycle.LifecycleRegistry.forwardPass(LifecycleRegistry.java:265)
        at androidx.lifecycle.LifecycleRegistry.sync(LifecycleRegistry.java:307)
        at androidx.lifecycle.LifecycleRegistry.moveToState(LifecycleRegistry.java:148)
        at androidx.lifecycle.LifecycleRegistry.handleLifecycleEvent(LifecycleRegistry.java:134)
        at androidx.fragment.app.FragmentViewLifecycleOwner.handleLifecycleEvent(FragmentViewLifecycleOwner.java:62)
        at androidx.fragment.app.Fragment.restoreViewState(Fragment.java:650)
        at androidx.fragment.app.Fragment.restoreViewState(Fragment.java:2997)
        at androidx.fragment.app.Fragment.performActivityCreated(Fragment.java:2988)
        at androidx.fragment.app.FragmentStateManager.activityCreated(FragmentStateManager.java:577)
        at androidx.fragment.app.FragmentStateManager.moveToExpectedState(FragmentStateManager.java:285)
        at androidx.fragment.app.FragmentStore.moveToExpectedState(FragmentStore.java:112)
        at androidx.fragment.app.FragmentManager.moveToState(FragmentManager.java:1636)
        at androidx.fragment.app.FragmentManager.dispatchStateChange(FragmentManager.java:3112)
        at androidx.fragment.app.FragmentManager.dispatchActivityCreated(FragmentManager.java:3056)
        at androidx.fragment.app.FragmentController.dispatchActivityCreated(FragmentController.java:251)
        at androidx.fragment.app.FragmentActivity.onStart(FragmentActivity.java:473)
        at androidx.appcompat.app.AppCompatActivity.onStart(AppCompatActivity.java:210)
        at android.app.Instrumentation.callActivityOnStart(Instrumentation.java:1425)
        at android.app.Activity.performStart(Activity.java:7825)
        at android.app.ActivityThread.handleStartActivity(ActivityThread.java:3294)
        at android.app.servertransaction.TransactionExecutor.performLifecycleSequence(TransactionExecutor.java:221)
        at android.app.servertransaction.TransactionExecutor.cycleToPath(TransactionExecutor.java:201)
        at android.app.servertransaction.TransactionExecutor.executeLifecycleState(TransactionExecutor.java:173)
        at android.app.servertransaction.TransactionExecutor.execute(TransactionExecutor.java:97)
        at android.app.ActivityThread$H.handleMessage(ActivityThread.java:2016)
        at android.os.Handler.dispatchMessage(Handler.java:107)
        at android.os.Looper.loop(Looper.java:214)
        at android.app.ActivityThread.main(ActivityThread.java:7356)
        at java.lang.reflect.Method.invoke(Native Method)
        at com.android.internal.os.RuntimeInit$MethodAndArgsCaller.run(RuntimeInit.java:492)
        at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:930)

The crash has a pretty clear cause which is this:

if (!(owner instanceof ViewModelStoreOwner)) {
    throw new IllegalStateException(
            "Internal error: OnRecreation should be registered only on components"
                    + "that implement ViewModelStoreOwner");
}

So it seems there's this implicit requirement of having the SavedStateRegistryOwner also be a ViewModelStoreOwner, and that's not the case for the view when it's in a fragment: its SavedStateRegistryOwner is a FragmentViewLifecycleOwner, which is only a SavedStateRegistryOwner and not a ViewModelStoreOwner.

It feels like findViewTreeSavedStateRegistryOwner() should return the fragment itself (like findViewTreeSavedStateRegistryOwner()) instead of the FragmentViewLifecycleOwner, so this would work. Or am I doing something wrong here?

If the view is in an activity everything works fine -- findViewTreeSavedStateRegistryOwner() returns the activity in this case, which is also a ViewModelStoreOwner so everything is good.