Flutter：本地通知插件显示两次通知

Question

我在特定时间从我的服务器收到通知，向用户显示通知。但是，每当我的设备收到来自 Firebase Cloud Messaging 的消息时，FlutterLocalNotificationsPlugin 最终会显示两个通知，如下所示。

我已经确认我从我的服务器收到了一个通知，我认为它只是在前端的某个地方处理不正确。

这是我在后台调用它的代码

main

Future<void> _firebaseMessagingBackgroundHandler(RemoteMessage message) async {
  // If you're going to use other Firebase services in the background, such as Firestore,
  // make sure you call `initializeApp` before using other Firebase services.
  await Firebase.initializeApp();
  print('Handling a background message ${message.messageId}');
  if (message.notification != null) {
    print(message.notification.title);
    print(message.notification.body);
    flutterLocalNotificationsPlugin.show(
        message.notification.hashCode,
        message.notification.title,
        message.notification.body,
        NotificationDetails(
          android: AndroidNotificationDetails(
            channel.id,
            channel.name,
            channel.description,
            icon: 'launch_background',
          ),
          iOS: IOSNotificationDetails()
        ));
  }

  // Create a notification for this
}


const AndroidNotificationChannel channel = AndroidNotificationChannel(
  'high_importance_channel', // id
  'High Importance Notifications', // title
  'This channel is used for important notifications.', // description
  importance: Importance.high,
);

final FlutterLocalNotificationsPlugin flutterLocalNotificationsPlugin =
    FlutterLocalNotificationsPlugin();

// Starting FlutterFire through the suggestion found here
// https://firebase.flutter.dev/docs/overview
Future<void> main() async {
  WidgetsFlutterBinding.ensureInitialized();
  await Firebase.initializeApp();
  FirebaseMessaging.onBackgroundMessage(_firebaseMessagingBackgroundHandler);

  /// Create an Android Notification Channel.
  /// We use this channel in the `AndroidManifest.xml` file to override the
  /// default FCM channel to enable heads up notifications.
  await flutterLocalNotificationsPlugin
      .resolvePlatformSpecificImplementation<
          AndroidFlutterLocalNotificationsPlugin>()
      ?.createNotificationChannel(channel);

  /// Update the iOS foreground notification presentation options to allow
  /// heads up notifications.
  await FirebaseMessaging.instance.setForegroundNotificationPresentationOptions(
    alert: true,
    badge: true,
    sound: true,
  );

  runApp(MyApp());
}

class MyApp extends StatefulWidget {
  MyApp({Key key}) : super(key: key);

  @override
  _MyAppState createState() => _MyAppState();
}

class _MyAppState extends State<MyApp> {
  User _user;
  FirebaseAnalytics analytics;
  bool _error = false;

  void _handleLogin(User user) {
    // print("Handle Login");
    setState(() {
      _user = user;
    });
  }

  @override
  void initState() {
    super.initState();

    // if we opened the app through a notification, it will send us via this
    FirebaseMessaging.onMessageOpenedApp.listen((RemoteMessage message) {
      print('On Message Opened!');
      print(message);
    });
  }

  @override
  Widget build(BuildContext context) {
   }
}

Answer 1

以防万一有人遇到同样的问题。我重新阅读了 FlutterFire 上的文档，其中提到如果您拥有当前最新的 Flutter SDK 和 Firebase，那么它会尝试自动显示它。我的错误是我除此之外还实施了 FlutterLocalNotifications，并且我收到了两个通知，一个是手动的，另一个是自动的。

向您的设备发送消息时，请确保它是 notification 而不是 data。该文档提到如果您发送 data 它可能会被忽略为推送通知。仅使用它来向应用程序发送数据包。

Answer 2

注释这部分代码可以解决问题。

/// 更新 iOS 前台通知显示选项以允许 /// 抬头通知。等待

FirebaseMessaging.instance.setForegroundNotificationPresentationOptions( alert: true, badge: true, sound: true, );

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