颤动：收到FCM时更新通知图标失败

Question

我下面使用Fire Cloud Messaging在Android应用程序的flutter中有代码，当我收到通知图标更新数字时，它可以完美地工作，但是问题是当我收到通知并且应用程序未打开时图标不会更新收到的FCM数量有什么帮助？ 并预先感谢

class MessageHandler extends StatefulWidget {
  @override
  _MessageHandlerState createState() => _MessageHandlerState();
}

class _MessageHandlerState extends State<MessageHandler> with ChangeNotifier {
  final Firestore _db = Firestore.instance;
  final FirebaseMessaging _fcm = FirebaseMessaging();

  StreamSubscription iosSubscription;

  @override
  void initState() {
    super.initState();
    if (Platform.isIOS) {
      iosSubscription = _fcm.onIosSettingsRegistered.listen((data) {
        print(data);
        _saveDeviceToken();
      });

      _fcm.requestNotificationPermissions(IosNotificationSettings());
    } else {
      _saveDeviceToken();
    }



    _fcm.configure(
      onMessage: (Map<String, dynamic> message) async {
        print("onMessage: $message");

      
        notificationCounterValueNotifer.value++;
        notificationCounterValueNotifer
            .notifyListeners(); 
            
        final snackbar = SnackBar(
          content: Text(message['notification']['title']),
          action: SnackBarAction(
            label: 'Go',
            onPressed: () => null,
          ),
        );

        Scaffold.of(context).showSnackBar(snackbar);
      
      },
      onLaunch: (Map<String, dynamic> message) async {
        print("onLaunch: $message");
     
      },
      onResume: (Map<String, dynamic> message) async {
        print("onResume: $message");

      
      },
    );
  }


  @override
  void dispose() {
    if (iosSubscription != null) iosSubscription.cancel();
    super.dispose();
  }

  @override
  Widget build(BuildContext context) {
    // _handleMessages(context);
    return MaterialApp(
        home: Scaffold(body: HomeApp()


         
            ));
  }

  /// Get the token, save it to the database for current user
  _saveDeviceToken() async {
    // Get the current user
    String uid = 'jeffd23';
    // FirebaseUser user = await _auth.currentUser();

    // Get the token for this device
    String fcmToken = await _fcm.getToken();

    // Save it to Firestore
    if (fcmToken != null) {
      var tokens = _db
          .collection('users')
          .document(uid)
          .collection('tokens')
          .document(fcmToken);

      await tokens.setData({
        'token': fcmToken,
        'createdAt': FieldValue.serverTimestamp(), // optional
        'platform': Platform.operatingSystem // optional
      });
    }
  }

  /// Subscribe the user to a topic
  _subscribeToTopic() async {
    // Subscribe the user to a topic
    _fcm.subscribeToTopic('puppies');
  }
}

class Message {
  String title;
  String body;
  String message;
  Message(title, body, message) {
    this.title = title;
    this.body = body;
    this.message = message;
  }
}

List<Message> messagesList;
Widget myAppBarIcon() {
  return ValueListenableBuilder(
    builder:
        (BuildContext context, int newNotificationCounterValue, Widget child) {
      return newNotificationCounterValue == 0
          ? Container(
              child: IconButton(
                  icon: Icon(Icons.notifications),
                  color: Colors.white,
                  // size: 40,
                  onPressed: () {
                    Navigator.push(
                      context,
                      MaterialPageRoute(
                        builder: (context) => Notifyy(),
                      ),
                    );
                  }),
            )
          : Stack(
              children: <Widget>[
                IconButton(
                    icon: Icon(Icons.notifications),
                    color: Colors.white,
                    // size: 40,
                    onPressed: () {
                      notificationCounterValueNotifer.value--;
                      Navigator.push(
                          context,
                          MaterialPageRoute(
                            builder: (context) => Notifyy(),
                          ));
                    }),
                Container(
                  width: 15,
                  height: 15,
                  alignment: Alignment.bottomRight,
                  margin: EdgeInsets.only(top: 8, left: 10),
                  child: Container(
                    width: 20,
                    height: 20,
                    decoration: BoxDecoration(
                        shape: BoxShape.circle,
                        color: Color(0xffc32c37),
                        border: Border.all(color: Colors.white, width: 1)),
                    child: Padding(
                      padding: const EdgeInsets.all(2.0),
                      child: Text(
                        newNotificationCounterValue.toString(),
                        textAlign: TextAlign.center,
                        style: TextStyle(fontSize: 8),
                      ),
                    ),
                  ),
                ),
              ],
            );
    },
    valueListenable: notificationCounterValueNotifer,
  );
}