Flutter_local_notifications notificationResponse.payload is always empty string,

Question

I'm trying to setup my mobile app, so that when a user gets a FCM message, when they click on it, I can use data within the message to route them to appropriate screen.

My FCM message looks like this:

const fcmMessage = {
                notification: {
                    title: title,
                    body: message
                },
                data:{
                    type:'Chat',
                    Name: 'Mike',
                    body:'test'
                },
                android: {
                    notification: {
                        title:title,
                        body: message,
                        channel_id:'high_importance_channel'
                    }
                },
                token: msgToken,
            };

then within my main() method, I am initializing the Flutter_Local_notifications as per the code snippet below.

The issue is when I click on the notification, the payload is always an empty string? These are the code lines that perform this. Why is the NotificationResponse.payload empty string? ultimately, I need access the "data" object in the FCM message.

void onDidReceiveNotificationResponse(NotificationResponse notificationResponse) async {
  print(notificationResponse.payload);
}

Here is the full main() method.

void main() async {
  WidgetsFlutterBinding.ensureInitialized();
  await Firebase.initializeApp();

  // Set the background messaging handler early on, as a named top-level function
  FirebaseMessaging.onBackgroundMessage(_firebaseMessagingBackgroundHandler);

  if (!kIsWeb) {
    channel = const AndroidNotificationChannel(
      'high_importance_channel', // id
      'High Importance Notifications', // title/
      importance: Importance.high,
    );
  }


flutterLocalNotificationsPlugin = FlutterLocalNotificationsPlugin();

var initializationSettingsAndroid =
      AndroidInitializationSettings('@mipmap/ic_launcher');
  var initializationSettingsIOs = DarwinInitializationSettings();
  var initSettings = InitializationSettings(
      android: initializationSettingsAndroid, iOS: initializationSettingsIOs);

  void onDidReceiveNotificationResponse(NotificationResponse notificationResponse) async {
    print(notificationResponse.payload);
}
   
  await flutterLocalNotificationsPlugin.initialize(initSettings,onDidReceiveNotificationResponse: onDidReceiveNotificationResponse,);
            
  /// 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);

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


  FirebaseMessaging.onMessage.listen((RemoteMessage message) {
    print('Got a message whilst in the foreground!');
    print('Message data: ${message.data}');

    if (message.notification != null) {
      RemoteNotification? notification = message.notification;
      AndroidNotification? android = message.notification?.android;
      FlutterLocalNotificationsPlugin s = FlutterLocalNotificationsPlugin();
      s.show(
        notification.hashCode,
        notification?.title,
        notification?.body,
        NotificationDetails(
          android: AndroidNotificationDetails(channel.id, channel.name,
              icon: 'launch_background',
              channelDescription: channel.description,
              importance: Importance.max,
              priority: Priority.high,
              ongoing: true,
              styleInformation: BigTextStyleInformation('')),
        ),
      );
    }
  });


  runApp(MyApp());
}

UPDATE, found what I needed. In the LocalNotification show method, we can add the payload attribute and set it to whatever part of the message.

For my use case, I encode the message.data , and then in the didReceive method, I can decode back to JSON object and use as needed.

 s.show(
        payload: jsonEncode(message.data),
        notification.hashCode,
        notification?.title,
        notification?.body,
        NotificationDetails(
          android: AndroidNotificationDetails(channel.id, channel.name,
              icon: 'launch_background',
              channelDescription: channel.description,
              importance: Importance.max,
              priority: Priority.high,
              ongoing: true,
              styleInformation: BigTextStyleInformation('')),
        ),
      );

Answer 1

You will have to provide the payload property in the show method:

import 'dart:convert';
// ...

void main() async {
  WidgetsFlutterBinding.ensureInitialized();
  await Firebase.initializeApp();

  // Set the background messaging handler early on, as a named top-level function
  FirebaseMessaging.onBackgroundMessage(_firebaseMessagingBackgroundHandler);

  if (!kIsWeb) {
    channel = const AndroidNotificationChannel(
      'high_importance_channel', // id
      'High Importance Notifications', // title/
      importance: Importance.high,
    );
  }


flutterLocalNotificationsPlugin = FlutterLocalNotificationsPlugin();

var initializationSettingsAndroid =
      AndroidInitializationSettings('@mipmap/ic_launcher');
  var initializationSettingsIOs = DarwinInitializationSettings();
  var initSettings = InitializationSettings(
      android: initializationSettingsAndroid, iOS: initializationSettingsIOs);

  void onDidReceiveNotificationResponse(NotificationResponse notificationResponse) async {
// this should print now
    print(notificationResponse.payload);
// let's add some switch statements here
switch (notificationResponse.notificationResponseType) {
// triggers when the notification is tapped
        case NotificationResponseType.selectedNotification:
          if (notificationResponse.payload != null) {
            try {
              Map notificationPayload =
                  (jsonDecode(notificationResponse.payload!));
              print(notificationResponse.payload); // prints the decoded JSON
            } catch (error) {
              log('Notification payload error $error');
            }
          }
          break;
        default:
      }
}
   
  await flutterLocalNotificationsPlugin.initialize(initSettings,onDidReceiveNotificationResponse: onDidReceiveNotificationResponse,);
            
  /// 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);

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


  FirebaseMessaging.onMessage.listen((RemoteMessage message) {
    print('Got a message whilst in the foreground!');
    print('Message data: ${message.data}');

    if (message.notification != null) {
      RemoteNotification? notification = message.notification;
      AndroidNotification? android = message.notification?.android;
      FlutterLocalNotificationsPlugin s = FlutterLocalNotificationsPlugin();
      s.show(
        notification.hashCode,
        notification?.title,
        notification?.body,
        NotificationDetails(
          android: AndroidNotificationDetails(channel.id, channel.name,
              icon: 'launch_background',
              channelDescription: channel.description,
              importance: Importance.max,
              priority: Priority.high,
              ongoing: true,
              styleInformation: BigTextStyleInformation('')),
        ),
        // provide payload here: message.data contains the payload
        // If your payload is in json, you might also want to encode it since flutter_local_notification accepts
        // strings
payload: jsonEncode(message.data),
      );
    }
  });


  runApp(MyApp());
}