Repository: flutter
Issue: App Exits Instead of Navigating Back with StatefullShellRoute in go_router on Android (flutter >= 3.24)
Labels: c: regression,package,has reproducible steps,P1,p: go_router,fyi-android,team-go_router,triaged-go_router,:hourglass_flowing_sand:,found in release: 3.24,found in release: 3.25

### Steps to reproduce

1. Modify MainActivity.kt to use FlutterFragmentActivity instead of FlutterActivity.
2. Run the official example of StatefullShellRoute from the go_router package. The example can be found [here](https://github.com/flutter/packages/blob/main/packages/go_router/example/lib/stateful_shell_route.dart).
3. Tap the “View details” button in “Section A” to navigate to the “DetailsScreen - A” screen.
4. Switch to “Section B.”
5. Switch back to “Section A” and use the Android back button or swipe gesture to go back.
6. Issue: The app exits instead of returning to the “Root of section A.”

### Expected results

The app should navigate back to the “Root of section A” when the Android back button or swipe gesture is used.

### Actual results

The app exits instead of navigating back to the previous screen.

### Code sample

<details open><summary>Code sample</summary>

```kotlin
import io.flutter.embedding.android.FlutterFragmentActivity

class MainActivity: FlutterFragmentActivity()
```

```dart
import 'package:flutter/material.dart';
import 'package:go_router/go_router.dart';

final GlobalKey<NavigatorState> _rootNavigatorKey =
    GlobalKey<NavigatorState>(debugLabel: 'root');
final GlobalKey<NavigatorState> _sectionANavigatorKey =
    GlobalKey<NavigatorState>(debugLabel: 'sectionANav');

// This example demonstrates how to setup nested navigation using a
// BottomNavigationBar, where each bar item uses its own persistent navigator,
// i.e. navigation state is maintained separately for each item. This setup also
// enables deep linking into nested pages.

void main() {
  runApp(NestedTabNavigationExampleApp());
}

/// An example demonstrating how to use nested navigators
class NestedTabNavigationExampleApp extends StatelessWidget {
  /// Creates a NestedTabNavigationExampleApp
  NestedTabNavigationExampleApp({super.key});

  final GoRouter _router = GoRouter(
    navigatorKey: _rootNavigatorKey,
    initialLocation: '/a',
    routes: <RouteBase>[
      // #docregion configuration-builder
      StatefulShellRoute.indexedStack(
        builder: (BuildContext context, GoRouterState state,
            StatefulNavigationShell navigationShell) {
          // Return the widget that implements the custom shell (in this case
          // using a BottomNavigationBar). The StatefulNavigationShell is passed
          // to be able access the state of the shell and to navigate to other
          // branches in a stateful way.
          return ScaffoldWithNavBar(navigationShell: navigationShell);
        },
        // #enddocregion configuration-builder
        // #docregion configuration-branches
        branches: <StatefulShellBranch>[
          // The route branch for the first tab of the bottom navigation bar.
          StatefulShellBranch(
            navigatorKey: _sectionANavigatorKey,
            routes: <RouteBase>[
              GoRoute(
                // The screen to display as the root in the first tab of the
                // bottom navigation bar.
                path: '/a',
                builder: (BuildContext context, GoRouterState state) =>
                    const RootScreen(label: 'A', detailsPath: '/a/details'),
                routes: <RouteBase>[
                  // The details screen to display stacked on navigator of the
                  // first tab. This will cover screen A but not the application
                  // shell (bottom navigation bar).
                  GoRoute(
                    path: 'details',
                    builder: (BuildContext context, GoRouterState state) =>
                        const DetailsScreen(label: 'A'),
                  ),
                ],
              ),
            ],
          ),
          // #enddocregion configuration-branches

          // The route branch for the second tab of the bottom navigation bar.
          StatefulShellBranch(
            // It's not necessary to provide a navigatorKey if it isn't also
            // needed elsewhere. If not provided, a default key will be used.
            routes: <RouteBase>[
              GoRoute(
                // The screen to display as the root in the second tab of the
                // bottom navigation bar.
                path: '/b',
                builder: (BuildContext context, GoRouterState state) =>
                    const RootScreen(
                  label: 'B',
                  detailsPath: '/b/details/1',
                  secondDetailsPath: '/b/details/2',
                ),
                routes: <RouteBase>[
                  GoRoute(
                    path: 'details/:param',
                    builder: (BuildContext context, GoRouterState state) =>
                        DetailsScreen(
                      label: 'B',
                      param: state.pathParameters['param'],
                    ),
                  ),
                ],
              ),
            ],
          ),

          // The route branch for the third tab of the bottom navigation bar.
          StatefulShellBranch(
            routes: <RouteBase>[
              GoRoute(
                // The screen to display as the root in the third tab of the
                // bottom navigation bar.
                path: '/c',
                builder: (BuildContext context, GoRouterState state) =>
                    const RootScreen(
                  label: 'C',
                  detailsPath: '/c/details',
                ),
                routes: <RouteBase>[
                  GoRoute(
                    path: 'details',
                    builder: (BuildContext context, GoRouterState state) =>
                        DetailsScreen(
                      label: 'C',
                      extra: state.extra,
                    ),
                  ),
                ],
              ),
            ],
          ),
        ],
      ),
    ],
  );

  @override
  Widget build(BuildContext context) {
    return MaterialApp.router(
      title: 'Flutter Demo',
      theme: ThemeData(
        primarySwatch: Colors.blue,
      ),
      routerConfig: _router,
    );
  }
}

/// Builds the "shell" for the app by building a Scaffold with a
/// BottomNavigationBar, where [child] is placed in the body of the Scaffold.
class ScaffoldWithNavBar extends StatelessWidget {
  /// Constructs an [ScaffoldWithNavBar].
  const ScaffoldWithNavBar({
    required this.navigationShell,
    Key? key,
  }) : super(key: key ?? const ValueKey<String>('ScaffoldWithNavBar'));

  /// The navigation shell and container for the branch Navigators.
  final StatefulNavigationShell navigationShell;

  // #docregion configuration-custom-shell
  @override
  Widget build(BuildContext context) {
    return Scaffold(
      // The StatefulNavigationShell from the associated StatefulShellRoute is
      // directly passed as the body of the Scaffold.
      body: navigationShell,
      bottomNavigationBar: BottomNavigationBar(
        // Here, the items of BottomNavigationBar are hard coded. In a real
        // world scenario, the items would most likely be generated from the
        // branches of the shell route, which can be fetched using
        // `navigationShell.route.branches`.
        items: const <BottomNavigationBarItem>[
          BottomNavigationBarItem(icon: Icon(Icons.home), label: 'Section A'),
          BottomNavigationBarItem(icon: Icon(Icons.work), label: 'Section B'),
          BottomNavigationBarItem(icon: Icon(Icons.tab), label: 'Section C'),
        ],
        currentIndex: navigationShell.currentIndex,
        // Navigate to the current location of the branch at the provided index
        // when tapping an item in the BottomNavigationBar.
        onTap: (int index) => navigationShell.goBranch(index),
      ),
    );
  }
  // #enddocregion configuration-custom-shell

  /// NOTE: For a slightly more sophisticated branch switching, change the onTap
  /// handler on the BottomNavigationBar above to the following:
  /// `onTap: (int index) => _onTap(context, index),`
  // ignore: unused_element
  void _onTap(BuildContext context, int index) {
    // When navigating to a new branch, it's recommended to use the goBranch
    // method, as doing so makes sure the last navigation state of the
    // Navigator for the branch is restored.
    navigationShell.goBranch(
      index,
      // A common pattern when using bottom navigation bars is to support
      // navigating to the initial location when tapping the item that is
      // already active. This example demonstrates how to support this behavior,
      // using the initialLocation parameter of goBranch.
      initialLocation: index == navigationShell.currentIndex,
    );
  }
}

/// Widget for the root/initial pages in the bottom navigation bar.
class RootScreen extends StatelessWidget {
  /// Creates a RootScreen
  const RootScreen({
    required this.label,
    required this.detailsPath,
    this.secondDetailsPath,
    super.key,
  });

  /// The label
  final String label;

  /// The path to the detail page
  final String detailsPath;

  /// The path to another detail page
  final String? secondDetailsPath;

  @override
  Widget build(BuildContext context) {
    return Scaffold(
      appBar: AppBar(
        title: Text('Root of section $label'),
      ),
      body: Center(
        child: Column(
          mainAxisSize: MainAxisSize.min,
          children: <Widget>[
            Text('Screen $label',
                style: Theme.of(context).textTheme.titleLarge),
            const Padding(padding: EdgeInsets.all(4)),
            TextButton(
              onPressed: () {
                GoRouter.of(context).go(detailsPath, extra: '$label-XYZ');
              },
              child: const Text('View details'),
            ),
            const Padding(padding: EdgeInsets.all(4)),
            if (secondDetailsPath != null)
              TextButton(
                onPressed: () {
                  GoRouter.of(context).go(secondDetailsPath!);
                },
                child: const Text('View more details'),
              ),
          ],
        ),
      ),
    );
  }
}

/// The details screen for either the A or B screen.
class DetailsScreen extends StatefulWidget {
  /// Constructs a [DetailsScreen].
  const DetailsScreen({
    required this.label,
    this.param,
    this.extra,
    this.withScaffold = true,
    super.key,
  });

  /// The label to display in the center of the screen.
  final String label;

  /// Optional param
  final String? param;

  /// Optional extra object
  final Object? extra;

  /// Wrap in scaffold
  final bool withScaffold;

  @override
  State<StatefulWidget> createState() => DetailsScreenState();
}

/// The state for DetailsScreen
class DetailsScreenState extends State<DetailsScreen> {
  int _counter = 0;

  @override
  Widget build(BuildContext context) {
    if (widget.withScaffold) {
      return Scaffold(
        appBar: AppBar(
          title: Text('Details Screen - ${widget.label}'),
        ),
        body: _build(context),
      );
    } else {
      return ColoredBox(
        color: Theme.of(context).scaffoldBackgroundColor,
        child: _build(context),
      );
    }
  }

  Widget _build(BuildContext context) {
    return Center(
      child: Column(
        mainAxisSize: MainAxisSize.min,
        children: <Widget>[
          Text('Details for ${widget.label} - Counter: $_counter',
              style: Theme.of(context).textTheme.titleLarge),
          const Padding(padding: EdgeInsets.all(4)),
          TextButton(
            onPressed: () {
              setState(() {
                _counter++;
              });
            },
            child: const Text('Increment counter'),
          ),
          const Padding(padding: EdgeInsets.all(8)),
          if (widget.param != null)
            Text('Parameter: ${widget.param!}',
                style: Theme.of(context).textTheme.titleMedium),
          const Padding(padding: EdgeInsets.all(8)),
          if (widget.extra != null)
            Text('Extra: ${widget.extra!}',
                style: Theme.of(context).textTheme.titleMedium),
          if (!widget.withScaffold) ...<Widget>[
            const Padding(padding: EdgeInsets.all(16)),
            TextButton(
              onPressed: () {
                GoRouter.of(context).pop();
              },
              child: const Text('< Back',
                  style: TextStyle(fontWeight: FontWeight.bold, fontSize: 18)),
            ),
          ]
        ],
      ),
    );
  }
}
```

</details>


### Screenshots or Video

<details open>
<summary>Screenshots / Video demonstration</summary>

https://github.com/user-attachments/assets/b59a1e8d-0fd2-4a9a-a198-13c92fc0f463

</details>


### Logs

_No response_

### Flutter Doctor output

<details open><summary>Doctor output</summary>

```console
Doctor summary (to see all details, run flutter doctor -v):
[✓] Flutter (Channel stable, 3.24.0, on macOS 14.5 23F79 darwin-arm64, locale ja-JP)
[✓] Android toolchain - develop for Android devices (Android SDK version 34.0.0)
[!] Xcode - develop for iOS and macOS (Xcode 15.2)
    ✗ CocoaPods installed but not working.
        You appear to have CocoaPods installed but it is not working.
        This can happen if the version of Ruby that CocoaPods was installed with is different from the one being used to invoke
        it.
        This can usually be fixed by re-installing CocoaPods.
      For re-installation instructions, see https://guides.cocoapods.org/using/getting-started.html#installation
[✓] Chrome - develop for the web
[✓] Android Studio (version 2024.1)
[✓] VS Code (version 1.92.2)
[✓] Connected device (6 available)
[✓] Network resources

! Doctor found issues in 1 category.
```

</details>

### Additional Information

- This issue does not occur in Flutter SDK version 3.22.3 but starts occurring from version 3.24.0.
- The issue only occurs when using FlutterFragmentActivity. It does not occur when using FlutterActivity.