Flutter：使用不包含导航器的上下文请求导航器操作

我现在遇到了一个问题，那就是在我的Flutter 翼应用程序中无法访问Navigator.代码是这样的:

class App extends StatelessWidget {
  const App({super.key});

  @override
  Widget build(BuildContext context) {
    return MultiBlocProvider(
      providers: [
        BlocProvider<LanguageBloc>(
          create: (_) => serviceLocator<LanguageBloc>(),
        ),
        BlocProvider<MaintenanceBloc>(
          create: (_) => serviceLocator<MaintenanceBloc>(),
        ),
        BlocProvider<VersionBloc>(
          create: (_) => serviceLocator<VersionBloc>(),
        ),
        BlocProvider<AuthBloc>(
          create: (_) => serviceLocator<AuthBloc>(),
        ),
      ],
      child: const _AppView(),
    );
  }
}

class _AppView extends StatefulWidget {
  const _AppView();

  @override
  State<_AppView> createState() => _AppViewState();
}

class _AppViewState extends State<_AppView> {
  final _navigatorKey = GlobalKey<NavigatorState>();

  NavigatorState get _navigator => _navigatorKey.currentState!;

  @override
  Widget build(BuildContext context) {
    return MaterialApp(
      navigatorKey: _navigatorKey,
      title: AppConfig.appName,
      locale: context.select((LanguageBloc bloc) => bloc.state.language.toLocale()),
      supportedLocales: AppLanguage.toLocales(),
      localizationsDelegates: [
        AppLocalization.getDelegate(getAppTranslations: serviceLocator<GetAppTranslations>()),
        GlobalMaterialLocalizations.delegate,
        GlobalWidgetsLocalizations.delegate,
        GlobalCupertinoLocalizations.delegate,
      ],
      theme: AppTheme.themeData,
      onGenerateRoute: (settings) {
        return MaterialPageRoute(
          settings: settings,
          builder: (context) {
            return const Placeholder(
              color: Colors.red,
            );
          },
        );
      },
      builder: (context, child) {
        return MultiBlocListener(
          listeners: [
            BlocListener<MaintenanceBloc, MaintenanceState>(
              listener: (context, state) {
                switch (state.runtimeType) {
                  case InMaintenance:
                    _navigator.pushAndRemoveUntil<void>(
                      MaterialPageRoute(builder: (context) => const MaintenancePage()),
                      (route) => false,
                    );
                    break;
                  case NotInMaintenance:
                    break;
                }
              },
            ),
            BlocListener<VersionBloc, VersionState>(
              listener: (context, state) {
                switch (state.runtimeType) {
                  case InitialVersionState:
                    break;
                  case CheckingVersion:
                    break;
                  case Outdated:
                    _navigator.pushAndRemoveUntil<void>(
                      MaterialPageRoute(builder: (context) => const OutdatedPage()),
                      (route) => false,
                    );
                    break;
                  case UpToDate:
                    break;
                }
              },
            ),
            BlocListener<AuthBloc, AuthState>(
              listener: (context, state) {
                switch (state.status) {
                  case AuthStatus.authenticated:
                    _navigator.pushAndRemoveUntil<void>(
                      MaterialPageRoute(builder: (context) => MainPage()),
                      (route) => false,
                    );
                  case AuthStatus.unauthenticated:
                    _navigator.pushAndRemoveUntil<void>(
                      MaterialPageRoute(builder: (context) => const LoginPage()),
                      (route) => false,
                    );
                  case AuthStatus.unknown:
                    _navigator.pushAndRemoveUntil<void>(
                      MaterialPageRoute(builder: (context) => const LoginPage()),
                      (route) => false,
                    );
                }
              },
            ),
          ],
          child: child!,
        );
      },
    );
  }
}

使用我的代码，我基本上遵循了您在BLoC Login Tutorial中看到的代码.

无论出于什么原因，这都会导致Unhandled Exception: Null check operator used on a null value在NavigatorState get _navigator => _navigatorKey.currentState!;，这意味着Navigator不能被访问.

当我运行相同的代码，但没有使用_navigatorKey，而是使用Navigator.of(context)时，我收到以下错误:

Unhandled Exception: Navigator operation requested with a context that does not include a Navigator.个

The context used to push or pop routes from the Navigator must be that of a widget that is a descendant of a Navigator widget.个

再次表明我不能使用Navigator.

这一点让我感到困惑，因为MaterialApp是一个parent小部件，所以Navigator应该是可访问的.将MultiBlocListener包装在Builder中以获得最新的context并不能解决问题.不使用MultiBlocListener内部的独立BlocListener提供的context也没有帮助.

在这个阶段，我不知道这里出了什么问题，特别是因为我正在遵循上面链接的教程.