Flutter：来自后台任务的通知导航，没有上下文问题

如何解决Flutter：来自后台任务的通知导航，没有上下文问题

我的应用程序执行以下操作：它使用 Flutter Workmanager 运行后台任务，该任务检查一些值，然后通过 Flutter 本地通知抛出通知。在 Flutterlocalnotifications 插件的 initialize 方法中，我可以指定一个内联函数，它应该导航到一个页面。由于我没有 Builder 上下文，因此我必须使用带有 OnGenerateRoute 的 Navigator Key 将用户转发到站点。但是，这不起作用，我不知道为什么。我知道当应用程序被杀死时，此代码很有用。

示例代码

final NotificationApplaunchdetails? notificationApplaunchdetails =
      await FlutterlocalnotificationsPlugin.getNotificationApplaunchdetails();
  String initialRoute = HomePage.routeName;
  if (notificationApplaunchdetails?.didNotificationLaunchApp ?? false) {
    selectednotificationPayload = notificationApplaunchdetails!.payload;
    initialRoute = SecondPage.routeName;
  }

但是当应用程序还活着时该怎么办？下面列出了我的项目代码。

Main.Dart

void main() {

  WidgetsFlutterBinding.ensureInitialized();
  Workmanager().initialize(callbackdispatcher,isInDebugMode: true);
  Workmanager().registerPeriodicTask("1","test",frequency: Duration(minutes: 15));
  runApp(MyApp());
}

class MyApp extends StatefulWidget {
  @override
  State createState() => _MyAppState();
}

class _MyAppState extends State<MyApp> {
  // This widget is the root of your application.

  @override
  Widget build(BuildContext context) {
    return MaterialApp(
      title: 'Flutter Demo',theme: ThemeData(
        primarySwatch: Colors.blue,),initialRoute: "/",navigatorKey: NavigationService.navigatorKey,onGenerateRoute: RouteGenerator.generateRoute
    );
  }
}

RouteGenerator.dart

class RouteGenerator {
  static Route<dynamic> generateRoute(RouteSettings settings) {
    final args = settings.arguments;

    switch(settings.name) {
      case '/first':
        return MaterialPageRoute(builder: (_) => Page1(title: "First"));
      case '/second':
        return MaterialPageRoute(builder: (_) => Page2(title: "Second"));
      case '/third':
        return MaterialPageRoute(builder: (_) => Page3(title: "Third"));
      case '/fourth':
        return MaterialPageRoute(builder: (_) => Page4(title: "Fourth"));
    }
    return MaterialPageRoute(builder: (_) => Page0(title: "Root!"));
  }
}

class NavigationService {
  static final GlobalKey<NavigatorState> navigatorKey = new GlobalKey<NavigatorState>();

  static Future<dynamic> navigateto(String routeName) {
    return navigatorKey.currentState!.pushNamed(routeName);
  }
}

service.dart

class DevHttpOverrides extends HttpOverrides {
  @override
  HttpClient createHttpClient(SecurityContext? context) {
    return super.createHttpClient(context)
      ..badCertificateCallback = (X509Certificate cert,String host,int port) => true;
  }
}

void callbackdispatcher() {
  Workmanager().executeTask((task,inputData) async{
        HttpOverrides.global = new DevHttpOverrides();
        var url = 'https://172.16.0.100/handler.PHP?page=settings';
        http.Response response = await http.get(Uri.parse(url));
        List<dynamic> list = jsonDecode(response.body);


        SharedPreferences prefs = await SharedPreferences.getInstance();
        var usage = "Beides";
        var checkValue = "temp_out";
        var borderValueString = "14.9";
        var checktype = "Grenzwert überschreiten";

        var borderValueDouble;
        var message = "";
        if(usage != "Nur Home Widgets" && checkValue != "" && borderValueString != "" && checktype != "")
        {
          var value = list[0][checkValue];

          if (double.tryParse(borderValueString) != null && double.tryParse(value) != null)
          {
            borderValueDouble = double.parse(borderValueString);
            value = double.parse(value);
          }

          if (checktype == "Grenzwert unterschreiten")
          {
            if (borderValueDouble is double)
            {
              if (value <= borderValueDouble)
              {
                message = "Grenzwert unterschritten";
              }
            }
          }
          else if (checktype == "Grenzwert überschreiten")
          {
            if (borderValueDouble is double)
            {
              if (value >= borderValueDouble)
              {
                message = "Grenzwert überschritten";
              }
            }
          }
          else if (checktype == "Entspricht Grenzwert")
          {
            if (borderValueDouble == value)
            {
              message = "Grenzwert erreicht";
            }
          }
        }

        if(message != "")
        {
          FlutterlocalnotificationsPlugin flip = new FlutterlocalnotificationsPlugin();
          var android = new AndroidInitializationSettings('@mipmap/ic_launcher');
          var ios = new IOSInitializationSettings();

          var settings = new InitializationSettings(android: android,iOS: ios);
          flip.initialize(settings,onSelectNotification: (String? payload) async {
            await NavigationService.navigatorKey.currentState!.push(MaterialPageRoute(builder: (context) => Page4(title: "Hello")));
      
  });
            


          var androidplatformChannelSpecifics = new AndroidNotificationDetails(
              '1','weatherstation','Notify when values change',importance: Importance.max,priority: Priority.high
          );

          var iOSPlatformChannelSpecifics = new IOSNotificationDetails();

          var platformChannelSpecifics = new NotificationDetails(
              android: androidplatformChannelSpecifics,iOS: iOSPlatformChannelSpecifics);

          await flip.show(0,message,'App öffnen für weitere Details',platformChannelSpecifics,payload: 'Default_Sound'
          );
        }

    return Future.value(true);
  });
}