扑：我想在Android应用中收到来自FCM的通知时更新通知徽章

Question

我在flutter中实现了以下代码，并将其连接到firebase，它可以正常工作并根据需要显示通知，但是， 问题：每当收到Firebase Cloud Messaging发出的通知时，我想更新通知徽章（红色圆圈，带有通知号）。 有什么帮助吗？

import 'package:flutter/material.dart';
import 'package:flutter/rendering.dart';
import 'package:mycafe/main.dart';
import 'Custom_Text.dart';
import 'Pasta.dart';
import 'Burger.dart';
import 'Pizza.dart';
import 'AboutUs.dart';
import 'dart:async';

import 'dart:math';
import 'package:cloud_firestore/cloud_firestore.dart';
import 'package:firebase_auth/firebase_auth.dart';
import 'ContactUs.dart';


import 'package:shared_preferences/shared_preferences.dart';
import 'dart:async';
import 'dart:io';
import 'package:flushbar/flushbar.dart';
import 'package:flushbar/flushbar_helper.dart';
// import 'package:flutter/material.dart';

import 'package:firebase_messaging/firebase_messaging.dart';
import 'package:cloud_firestore/cloud_firestore.dart';

import 'constants.dart' as Constants;
import 'ui/auth/AuthScreen.dart';
import 'ui/onBoarding/OnBoardingScreen.dart';

import 'package:flutter/cupertino.dart';

import 'package:mycafe/ui/auth/AuthScreen.dart';

var bannerItems = ["Burger", "cheesechilly", "Noodles", "Pizza"];
var bannerImages = [
  "images/burger.jpg",
  "images/cheesechilly.jpg",
  "images/noodles.jpg",
  "images/pizza.jpg"
];

class Notify extends StatelessWidget {
  @override
  Widget build(BuildContext context) {
    return MaterialApp(
      title: 'FlutterBase',
      home: Scaffold(
        body: MessageHandler(),
      ),
    );
  }
}

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

class _MessageHandlerState extends State<MessageHandler> {
  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");
        // RaisedButton(
        //   child: Text(message['notification']['title']),
        //   onPressed: () {
        //     Flushbar(
        //       flushbarPosition: FlushbarPosition.TOP,
        //       icon: Icon(
        //         Icons.notifications_active,
        //         color: Colors.white,
        //       ),
        //       mainButton: FlatButton(
        //         onPressed: () {
        //           Navigator.pop(context);
        //           //  Flush.showGoodFlushbar(context, 'login successful!');
        //         },
        //         // child: Text(
        //         //   "ADD",
        //         //   style: TextStyle(color: Colors.amber),
        //         // ),
        //       ),
        //       // duration: Duration(seconds: 7))
        //     ).show(context);
        //   },
        // );

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

        Scaffold.of(context).showSnackBar(snackbar);
        // showDialog(
        //   context: context,
        //   builder: (context) => AlertDialog(
        //     content: ListTile(
        //       title: Text(message['notification']['title']),
        //       subtitle: Text(message['notification']['body']),
        //     ),
        //     actions: <Widget>[
        //       FlatButton(
        //         color: Colors.amber,
        //         child: Text('Ok'),
        //         onPressed: () => Navigator.of(context).pop(),
        //       ),
        //     ],
        //   ),
        // );
      },
      onLaunch: (Map<String, dynamic> message) async {
        print("onLaunch: $message");
        // TODO optional
      },
      onResume: (Map<String, dynamic> message) async {
        print("onResume: $message");
        // TODO optional
      },
    );
  }

  @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');
  }
}