firebase-messaging - Fatal: failed to find callback

Question

I'm trying to use FCM messaging and keep getting this error.

E/FlutterFcmService( 3684): Fatal: failed to find callback

Below is the code I've used to setup.

  static Future<void> messagePiper(
      Map<String, dynamic> message,
      FilteredMap<String, ChatMessage> globalChatEntryMap,
      FilteredMap<String, ChatMessage> gameChatEntryMap,
      Subject<List<ChatMessage>> globalChatSubject,
      Subject<List<ChatMessage>> gameChatSubject,
      Map<String, Player> _playerMap) async {
    final Map<String, dynamic> data = message['data'];
    if (data.containsKey('name')) {
      final msg = ChatMessage.fromMap(data);
      globalChatEntryMap.putIfAbsent(msg.id, () => msg);
      globalChatSubject.add(globalChatEntryMap.values.toList());
    } else {
      final msg = GameChatMessage.fromMap(data);

      final chat = ChatMessage.fromGlobalChatMessage(
        msg,
        _playerMap[msg.pId].name,
        _playerMap[msg.pId].imageUrl,
      );

      print('chat: $chat');
      gameChatEntryMap.putIfAbsent(msg.id, () => chat);
      print('_gameChatEntryMap : $gameChatEntryMap');
      gameChatSubject.add(gameChatEntryMap.values.toList());
    }

    return Future<void>.value();
  }

is the callback passed in to FirebaseMessaging configuration.

  final FirebaseMessaging _fm = FirebaseMessaging();

  @override
  void initState() {

   _fm.configure(
        onMessage: (Map<String, dynamic> message) async {
          print('onMessagee : $message');
          return Utils.messagePiper(
              message,
              _globalChatEntryMap,
              _gameChatEntryMap,
              _globalChatSubject,
              _gameChatSubject,
              _playerMap);
        },
        onLaunch: (Map<String, dynamic> message) async {
          print('onLaunch : $message');
          return Utils.messagePiper(
              message,
              _globalChatEntryMap,
              _gameChatEntryMap,
              _globalChatSubject,
              _gameChatSubject,
              _playerMap);
          ;
        },
        onResume: (Map<String, dynamic> message) async {
          print('onResume : $message');
          return Utils.messagePiper(
              message,
              _globalChatEntryMap,
              _gameChatEntryMap,
              _globalChatSubject,
              _gameChatSubject,
              _playerMap);
          ;
        },
        onBackgroundMessage: null);
....

Java configuration file

package io.flutter.plugins;

import io.flutter.app.FlutterApplication;
import io.flutter.plugin.common.PluginRegistry;
import io.flutter.plugin.common.PluginRegistry.PluginRegistrantCallback;
import io.flutter.plugins.GeneratedPluginRegistrant;
import io.flutter.plugins.firebasemessaging.FlutterFirebaseMessagingService;

public class Application extends FlutterApplication implements PluginRegistrantCallback {
    @Override
    public void onCreate() {
        super.onCreate();
        FlutterFirebaseMessagingService.setPluginRegistrant(this);
    }

    @Override
    public void registerWith(PluginRegistry registry) {
        GeneratedPluginRegistrant.registerWith(registry);
    }
}

dependency versions

  random_string: 0.0.2
  firebase_auth: ^0.14.0+5
  firebase_database: ^3.0.7
  provider: 3.0.0
  rxdart: ^0.22.2
  collection: ^1.14.11
  audioplayers: ^0.13.2
  firebase_admob: ^0.5.5
  connectivity: ^0.4.4
  firebase_messaging: ^5.1.6 # tried with several different versions

I tried with several firebase_messaging versions but couldn't find a fix.

Appreciate any help to solve this issue.

Answer 1

When I was trying to send a notification from the firebase console just to test my app receives notifications, I also encountered the same error. Make sure you kill the app on your emulator so it is not running in the background. And now try sending a notification from the firebase console, wait for a couple of seconds and you should see it. This worked for me.

Answer 2

In Application class use the below code

previously it was GeneratedPluginRegistrant.registerWith(registry);,

replace it with FirebaseMessagingPlugin.registerWith(registry.registrarFor("io.flutter.plugins.firebasemessaging.FirebaseMessagingPlugin"));

import io.flutter.app.FlutterApplication;
import io.flutter.plugin.common.PluginRegistry;
import io.flutter.plugin.common.PluginRegistry.PluginRegistrantCallback;
import io.flutter.plugins.GeneratedPluginRegistrant;
import io.flutter.plugins.firebasemessaging.FirebaseMessagingPlugin;
import io.flutter.plugins.firebasemessaging.FlutterFirebaseMessagingService;

public class Application extends FlutterApplication implements PluginRegistrantCallback {

    @Override
    public void onCreate(){
        super.onCreate();
        FlutterFirebaseMessagingService.setPluginRegistrant(this);
    }

    @Override
    public void registerWith(PluginRegistry registry){
        FirebaseMessagingPlugin.registerWith(registry.registrarFor("io.flutter.plugins.firebasemessaging.FirebaseMessagingPlugin"));
    }


}

Answer 3

You should declare a backgroundMessageHandler function that is outside a class or as a static function, in order to be reached from outside, and then you pass this function to fbm.configure:

Future<dynamic> myBackgroundMessageHandler(Map<String, dynamic> message) {
  print('on background $message');
}

fbm.configure(
      onMessage: (msg) {
        print(msg);
        return;
      },
      onLaunch: (msg) {
        print(msg);
        return;
      },
      onResume: (msg) {
        print(msg);
        return;
      },
      onBackgroundMessage: myBackgroundMessageHandler
);

Also open your_project_folder/android/app/source/AndroidManifest.xml and paste this XML code after existing intent-filter code of your main Activity:

<intent-filter>
    <action android:name="FLUTTER_NOTIFICATION_CLICK" />
    <category android:name="android.intent.category.DEFAULT" />
</intent-filter>

The result will be similar to the following code:

<activity android:name=".MainActivity" android:launchMode="singleTop" android:theme="@style/LaunchTheme" android:configChanges="orientation|keyboardHidden|keyboard|screenSize|smallestScreenSize|locale|layoutDirection|fontScale|screenLayout|density|uiMode" android:hardwareAccelerated="true" android:windowSoftInputMode="adjustResize">
            <intent-filter>
                <action android:name="android.intent.action.MAIN" />
                <category android:name="android.intent.category.LAUNCHER" />
            </intent-filter>
            <intent-filter>
                <action android:name="FLUTTER_NOTIFICATION_CLICK" />
                <category android:name="android.intent.category.DEFAULT" />
            </intent-filter>
</activity>

Answer 4

Are you sending FCM using the web, not FCM console? make sure the post request is correct on your backend. I'm using Laravel

$response = Http::withHeaders([
            'Content-Type' => 'application/json',
            'Authorization'=> 'key='. $token,
        ])->post($url, [
            'notification' => [
                'body' => $request->summary,
                'title' => $request->title,
                'image' => request()->getHttpHost().$path,
                
            ],
            'priority'=> 'high',
            'data' => [
                'click_action'=> 'FLUTTER_NOTIFICATION_CLICK',
                
                'status'=> 'done',
                
            ],
            'to' => '/topics/all'
        ]);

Answer 5

This error message is coming from startBackgroundIsolate which is used for allowing handling background messages. If you don't want to handle background messages then you can safely ignore this error message. Otherwise, you need to set up a callback for handling background messages as described here

If your callback is not executed when clicking on the notification then it's because you didn't set click_action property of the message to FLUTTER_NOTIFICATION_CLICK