fix(Android, Stack): dispatch lifecycle events when parent is not a ScreenFragment

[collectioneur]

Description

When React Native is loaded inside a Fragment (not directly in an Activity), for example in a brownfield setup using ReactFragment, lifecycle events are never dispatched for root screen fragments. This causes transitionStart/transitionEnd events in react-navigation to never fire.

The root cause is in ScreenFragment.dispatchViewAnimationEvent(). The condition:

if (parent == null || (parent is ScreenFragment && !parent.isTransitioning))

does not account for the case where parentFragment is a regular Fragment. When RN runs inside a ReactFragment, findFragmentManagerForReactRootView returns that fragment's childFragmentManager. Root screen fragments then have parentFragment pointing to the host fragment. Since it's not null and not a ScreenFragment, the condition evaluated to false and all lifecycle events were silently dismissed.

Changes

Added parent !is ScreenFragment to the condition in ScreenFragment.dispatchViewAnimationEvent(), so that lifecycle events are correctly dispatched when the parent fragment is not a ScreenFragment (e.g. ReactFragment in brownfield apps). Such parents don't participate in screen transitions, so they should be treated the same as parent == null.

Before & after - visual documentation

Before

before.mov

After

after.mov

Test plan

Reproducing this in FabricExample without adding a brownfield component is not possible. However, I tested all events in the example app after applying the change and everything works the same as before.

Checklist

• Included code example that can be used to test this change.
• For visual changes, included screenshots / GIFs / recordings documenting the change.
• For API changes, updated relevant public types.
• Ensured that CI passes

[Copilot]

Pull request overview

Fixes missing screen lifecycle dispatch for root ScreenFragments when React Native is hosted inside a non-ScreenFragment parent (e.g., ReactFragment in brownfield apps), restoring transitionStart/transitionEnd behavior in react-navigation.

Changes:

• Update ScreenFragment.dispatchViewAnimationEvent() to dispatch lifecycle events when the parent fragment is not a ScreenFragment.
• Add explanatory comments documenting the brownfield/ReactFragment scenario and rationale.

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[Copilot]

The if condition is logically correct but redundant/verbose: parent == null is already covered by parent !is ScreenFragment, and the final (parent is ScreenFragment && ...) re-check can be avoided. Consider simplifying to if (parent !is ScreenFragment || !parent.isTransitioning) (which is also shorter and more readable).

Suggested change

	if (parent == null || parent !is ScreenFragment || (parent is ScreenFragment && !parent.isTransitioning)) {
	if (parent !is ScreenFragment || !parent.isTransitioning) {

[collectioneur]

My current version is a bit easier to read:
Case 1: If there's no parent Fragment, we simply dispatch the events.
Case 2: If a parent Fragment exists but it isn't a ScreenFragment, it won't dispatch lifecycle events on its own (since only ScreenFragments do that), so we can safely dispatch the events ourselves.
Case 3: If the parent is a ScreenFragment but isn't currently transitioning, we know there won't be any duplicates, so we dispatch the event here too.
In all other cases, we just don't.

[kkafar]

Thanks!