[iOS] RouterExtensions.back() fails silently after app lock/suspend mid-navigation — component stuck, native back button unresponsive on resume

Bắt đầu với RouterExtensions.back(), Frame.topmost().goBack() và vòng đời tạm dừng/tiếp tục của iOS trên thiết bị vật lý bằng cách sử dụng cửa sổ tái hiện 150ms đã mô tả. Theo dõi trạng thái bị gián đoạn của UINavigationController và frame NativeScript, sau đó xác minh rằng có thể thử lại thao tác điều hướng hoặc các trạng thái native, frame và Angular router được đồng bộ hóa lại sau khi tiếp tục.

[iOS] RouterExtensions.back() fails silently after app lock/suspend mid-navigation — component stuck, native back button unresponsive on resume

Environment

• CLI: 9.0.5
• Cross-platform modules (@nativescript/core): 8.9.9
• Android Runtime: 8.9.2
• iOS Runtime: 8.9.4
• Plugin(s): @nativescript/angular
• NativeScript-Angular: 17.0.0
• Angular: 17.0.8

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Describe the bug

This is a runtime error on iOS only.

When RouterExtensions.back() is called (e.g. on form submit after an async API operation) and the user locks the phone or backgrounds the app within the same moment, the navigation silently fails. On resume:

• The component that triggered the back navigation is still on screen
• The native ActionBar back button (top-left iOS back chevron) is also completely unresponsive
• No exception is thrown, no crash, no error log
• Calling router.back() again on resume causes the call to repeat but navigation never completes
• Frame.topmost().canGoBack() returns true but Frame.topmost().goBack() has no visible effect

The app is permanently stuck on that page until force-quit and relaunch.

Console output observed during a single "submit + lock phone" cycle (3 resume attempts):

back Called
Keyboard hidden
super.back Called
back Called
Keyboard hidden
super.back Called
back Called
Keyboard hidden
super.back Called

super.back() fires even when the app is in the background. NavigationEnd never fires. Angular router url still points to the source page on resume. Frame.topmost().goBack() on resume is silently ignored and the native back button stops responding entirely.

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To Reproduce

Setup:

A custom RouterExtensions subclass wrapping back() in a setTimeout for iOS keyboard dismiss (a common and necessary iOS pattern — navigating without first dismissing the keyboard causes visual glitches):

@Injectable()
export class BaseRouterExtension extends RouterExtensions {
  IOS_KEYBOARD_DISMISS_DELAY = 150;
override back(options?: BackNavigationOptions) {

this.zone.run(() => {

hideKeyboard();

if (isIOS) {

setTimeout(() => {

super.back(options); // fires even when app is suspended

}, this.IOS_KEYBOARD_DISMISS_DELAY);

} else {

super.back(options);

}

});

}

}

Navigation triggered by a signal/effect on API success:

effect(() => {
  if (this.successOperation()) {
    this.navigateBack();
  }
});
async navigateBack() {

await this.onStopTextToSpeech();

this.router.back();

}

Steps:

1. Navigate from Page A → Page B (a form/edit screen)
2. On Page B, submit the form — this triggers an async API call, on success router.back() is called
3. Lock the phone (press power button) within ~150ms of the back() call
4. Unlock the phone and resume the app
5. Observe: still on Page B — the programmatic back and the native ActionBar back button both do nothing

Most reliable reproduction (near 100% hit rate):

The setTimeout(150ms) creates a guaranteed window. Lock the phone immediately after tapping Submit before the toast or transition appears.

---

Expected behavior

Either:

• RouterExtensions.back() / Frame.topmost().goBack() called on resume should complete the interrupted navigation, OR
• The native UINavigationController state and NativeScript frame/Angular router state should be re-synced automatically on resume so that navigation can be retried from JS

---

Sample project

Unable to provide a Playground link as the issue requires a physical device lock action to reproduce (Simulator behaves differently for lock/sleep events). A minimal reproduction would be:

1. Page A navigates to Page B
2. Page B calls RouterExtensions.back() inside a setTimeout(150)
3. Lock the physical device during that 150ms window
4. Resume — Page B is stuck and native back button is unresponsive

---

Additional context

What was attempted as workarounds — none fully resolved the issue:

Approach	Result
Check Application.inBackground in setTimeout	Unreliable — flag not always set before setTimeout fires depending on lock timing
Own _isAppInBackground flag via suspend/resume events	Race condition — suspend event fires after navigateBack() call in some sequences
Snapshot router.url before back(), compare on resume	URL comparison is accurate, but Frame.topmost().goBack() on resume still silently fails
Frame.topmost().goBack() directly in resume handler	No visual effect — native back button is also unresponsive at this point
RouterExtensions.navigateByUrl(previousUrl) on resume	Pushes a new page onto the stack instead of popping — incorrect behaviour
page.on('navigatedFrom') to detect native completion	Does not fire when navigation is interrupted by lock

The native UINavigationController appears to enter a broken/stuck state after a lock-interrupted navigation transition that cannot be recovered from the JavaScript layer with currently available APIs.

Questions for the team:

1. After a lock-interrupted UIViewController pop, is there a supported way to re-trigger or complete the navigation from JS?
2. Is the native UINavigationController instance exposed anywhere so we can call popViewControllerAnimated: directly as a fallback?
3. Is there a navigation transition completion hook (equivalent to UINavigationControllerDelegate.navigationController:didShowViewController:animated:) accessible from NativeScript?

Related issues:

• https://github.com/NativeScript/nativescript-angular/issues/1596 — Back navigation broken after suspend/resume in TabView + nested frame scenario — closed/fixed in 2018 via PR https://github.com/NativeScript/NativeScript/pull/6528. The current issue reproduces on a simple single-frame stack with no TabView and is not addressed by that fix.