[heecheolman]

Summary:

When a view is moved to a new parent (for example because an intermediate view is flattened or unflattened), Fabric emits a Remove from the previous parent followed by an Insert into the new one. If the view is being animated out of its previous parent at that moment (it is in that parent's transitioning views, e.g. via LayoutTransition or startViewTransition), ViewGroup removes it from its children but keeps its parent pointer until the transition ends.

addViewAt already detects that the view still has a parent and calls removeView() on it, but removeView() looks the view up in the children array, finds nothing, and silently returns. The following addView() then throws "The specified child already has a parent", which is rethrown as "addViewAt: failed to insert view [...]" and crashes the app.

If the view is still attached to the same parent after removeView(), end the view transition on that parent, which clears the parent pointer, so the view can be inserted into its new parent.

Changelog:

[Android] [Fixed] - Fix addViewAt: failed to insert view crash when a view is reparented while being animated out of its previous parent

Test Plan:

Added SurfaceMountingManagerTest.addViewAt_reparentsViewThatIsTransitioningOutOfPreviousParent, which starts a view transition on the previous parent, removes the child, and inserts it into another parent. Without this change it fails with the same exception seen in production; with it, it passes.

  ./gradlew :packages:react-native:ReactAndroid:testDebugUnitTest --tests 'com.facebook.react.fabric.*'

[javache]

React Native doesn't use Android LayoutTransition / startViewTransition though, and neither should 3rd party view managers directly alter view structures managed by React Native.

Do you have a concrete repro for this bug?