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fix(android): stop the FragmentManager driving fragments with a dead entry #11352

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fix(android): stop the FragmentManager driving fragments with a dead entry #11352

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62 changes: 56 additions & 6 deletions packages/core/ui/frame/frame-helper-for-android.ts
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Original file line number Diff line number Diff line change
Expand Up @@ -37,6 +37,10 @@ function findPageForFragment(fragment: androidx.fragment.app.Fragment, frame: Fr
entry = current;
} else if (executingContext && executingContext.entry && executingContext.entry.fragmentTag === fragmentTag) {
entry = executingContext.entry;
} else {
// Android also restores fragments that were only in the backstack or still queued, so
// widen the lookup before treating this fragment as an orphan.
entry = frame._findEntryForTag(fragmentTag);
}

let page: Page;
Expand All @@ -52,7 +56,41 @@ function findPageForFragment(fragment: androidx.fragment.app.Fragment, frame: Fr
entry.fragment = fragment;
_updateTransitions(entry);
} else {
throw new Error(`Could not find a page for ${fragmentTag}.`);
// Android restored a fragment no live entry owns anymore - the frame navigated on (or was
// reset) while the activity was being recreated. Throwing is fatal across the JNI boundary
// and this fragment can never produce a view, so discard it instead.
Trace.write(`Could not find a page for ${fragmentTag}. Discarding orphaned fragment.`, Trace.categories.NativeLifecycle, Trace.messageType.error);
removeFragmentIfAdded(fragment);
Comment on lines +62 to +63
}
}

/**
* Drops a fragment the JS side no longer owns from its FragmentManager, so the manager stops
* driving it through the lifecycle. The removal is always deferred - callers may be inside a
* FragmentManager transaction, where commitNow throws "already executing transactions".
*/
export function removeFragmentIfAdded(fragment: androidx.fragment.app.Fragment): void {
if (!fragment.isAdded()) {
return;
}

const manager = fragment.getParentFragmentManager();
if (manager.isDestroyed()) {
return;
}

manager.beginTransaction().remove(fragment).commitAllowingStateLoss();
}

/**
* Breaks the fragment -> BackstackEntry link so a fragment the FragmentManager is still holding
* cannot bring a discarded entry (and its torn down page) back into the frame.
*/
export function detachFragmentCallbacks(fragment: androidx.fragment.app.Fragment): void {
const callbacks: FragmentCallbacksImplementation = fragment[CALLBACKS];
if (callbacks) {
callbacks.entry = null;
callbacks.frame = null;
Comment on lines +92 to +93
}
}

Expand Down Expand Up @@ -214,7 +252,7 @@ export class FragmentCallbacksImplementation implements AndroidFragmentCallbacks
const hasRemovingParent = fragment.getRemovingParentFragment();

if (hasRemovingParent) {
const nativeFrameView = this.frame.nativeViewProtected;
const nativeFrameView = this.frame?.nativeViewProtected;
if (nativeFrameView) {
const bitmapDrawable = new android.graphics.drawable.BitmapDrawable(getNativeApp<android.app.Application>().getApplicationContext().getResources(), this.backgroundBitmap);
this.frame._originalBackground = this.frame.backgroundColor || new Color('White');
Expand All @@ -237,7 +275,10 @@ export class FragmentCallbacksImplementation implements AndroidFragmentCallbacks

const entry = this.entry;
if (!entry) {
Trace.error(`${fragment}.onDestroy: entry is null or undefined`);
// A fragment that was never bound to an entry, or whose entry has already been
// discarded, is still destroyed by the FragmentManager. Trace.error routes to the error
// handler, which rethrows and turns this teardown into a fatal exception.
Trace.write(`${fragment}.onDestroy: entry is null or undefined`, Trace.categories.NativeLifecycle, Trace.messageType.error);

return null;
}
Expand Down Expand Up @@ -270,7 +311,7 @@ export class FragmentCallbacksImplementation implements AndroidFragmentCallbacks
const hasRemovingParent = fragment.getRemovingParentFragment();

if (hasRemovingParent) {
this.backgroundBitmap = this.loadBitmapFromView(this.frame.nativeViewProtected);
this.backgroundBitmap = this.loadBitmapFromView(this.frame?.nativeViewProtected);
}
} finally {
superFunc.call(fragment);
Expand All @@ -279,7 +320,16 @@ export class FragmentCallbacksImplementation implements AndroidFragmentCallbacks

@profile
public onResume(fragment: org.nativescript.widgets.FragmentBase, superFunc: Function): void {
const frame = this.entry.resolvedPage.frame;
const frame = this.entry?.resolvedPage?.frame;
if (!frame) {
// Stale fragment the FragmentManager is still driving after its entry (or page) was
// discarded: there is no navigation left to complete, and dereferencing the missing page
// would throw across the JNI boundary.
superFunc.call(fragment);

return;
}

// on some cases during the first navigation on nested frames the animation doesn't trigger
// we depend on the animation (even None animation) to set the entry as the current entry
// animation should start between start and resume, so if we have an executing navigation here it probably means the animation was skipped
Expand All @@ -288,7 +338,7 @@ export class FragmentCallbacksImplementation implements AndroidFragmentCallbacks
const weakRef = new WeakRef(this);
setTimeout(() => {
const owner = weakRef.get();
if (!owner) {
if (!owner || !owner.entry) {
return;
}
if (!owner.entry.isAnimationRunning) {
Expand Down
14 changes: 12 additions & 2 deletions packages/core/ui/frame/index.android.ts
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Expand Up @@ -16,7 +16,7 @@ import { getAppMainEntry } from '../../application/helpers-common';
import { AndroidActivityBackPressedEventData, AndroidActivityNewIntentEventData, AndroidActivityRequestPermissionsEventData, AndroidActivityResultEventData } from '../../application/application-interfaces';
import { Application } from '../../application/application';
import { isEmbedded, setEmbeddedView } from '../embedding';
import { CALLBACKS, FRAMEID, framesCache, setFragmentCallbacks } from './frame-helper-for-android';
import { CALLBACKS, detachFragmentCallbacks, FRAMEID, framesCache, removeFragmentIfAdded, setFragmentCallbacks } from './frame-helper-for-android';
import { SDK_VERSION } from '../../utils';

export * from './frame-common';
Expand Down Expand Up @@ -459,8 +459,18 @@ export class Frame extends FrameBase {
public _removeEntry(removed: BackstackEntry): void {
super._removeEntry(removed);

if (removed.fragment) {
const fragment = removed.fragment;
if (fragment) {
_clearEntry(removed);

// The entry is gone now - its page was torn down and resolvedPage cleared - but the
// fragment can still be sitting in the FragmentManager: navigation only evicts fragments
// sharing the frame's current container, so anything left over from an activity
// recreation or a frame reset survives. Cut it loose here, or the FragmentManager keeps
// driving it through the lifecycle against a dead entry.
detachFragmentCallbacks(fragment);
removeFragmentIfAdded(fragment);

removed.fragment = null;
}

Expand Down
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