[Firebase_messaging] Double notification appear in release mode for some device (Flutter android)

[matteoberla]

Hi every one, I'm trying to handle notification in my Flutter App, I'll start showing all the code and then telling you more about the problem I'm facing.

Inside my main() function :

await Firebase.initializeApp(
        options: DefaultFirebaseOptions.currentPlatform,
      );
      await FirebaseApi().initNotification();

FirebaseApi.dart (Handler class with all the functions called to handle notification):

import 'dart:convert';
import 'dart:io';

import 'package:eraser/eraser.dart';
import 'package:firebase_messaging/firebase_messaging.dart';
import 'package:flutter_local_notifications/flutter_local_notifications.dart';
import 'package:logger/logger.dart';
import 'package:palladio_mobile/controllers/notification_handlers/notification_handler.dart';
import 'package:palladio_mobile/controllers/persistent_data_handlers/login_shared_preferences.dart';

const bool debugPrint = true;

@pragma('vm:entry-point')
Future handleBackgroundMessage(RemoteMessage message) async {
  if (debugPrint) {
    print("background");
    print(message.toMap());
  }
  try {
    FirebaseApi firebaseApi = FirebaseApi();
    await firebaseApi.initAndSendLocalNotification(message);
  } catch (e) {
    print(e);
  }
}

@pragma('vm:entry-point')
Future handleBackgroundMessage2(RemoteMessage message) async {
  print("BACKGROUND: ${message.toMap()}");
}

class FirebaseApi {
  final _androidChannel = const AndroidNotificationChannel(
    'high_importance_channel',
    'High Importance Notifications',
    description: "This channel is used for important notifications",
    importance: Importance.max,
  );

  final _localNotification = FlutterLocalNotificationsPlugin();

  void handleMessage(RemoteMessage? message) async {
    if (debugPrint) {
      print("handle message");
      print(message?.toMap());
    }

    if (message == null) return;
    //azione da fare al ricevimento della notifica
    NotificationHandler notificationHandler = NotificationHandler();
    await notificationHandler.updateNotificationProvider(message.data);
    notificationHandler.handleRoutes(message.data);
  }

  void handleInitialMessage(RemoteMessage? message) async {
    if (debugPrint) {
      print("initial message");
      print(message?.toMap());
    }
    if (message == null) return;
    //azione da fare al ricevimento della notifica
    NotificationHandler notificationHandler = NotificationHandler();
    await notificationHandler.updateNotificationProvider(message.data);
  }

  Future initLocalNotifications() async {
    const iOS = DarwinInitializationSettings();
    const android = AndroidInitializationSettings("@drawable/ic_launcher");
    const settings = InitializationSettings(android: android, iOS: iOS);

    await _localNotification.initialize(settings,
        onDidReceiveNotificationResponse: (response) {
      final message = RemoteMessage.fromMap(jsonDecode(response.payload!));
      handleMessage(message);
    });

    final appLaunchDetails =
        await _localNotification.getNotificationAppLaunchDetails();
    if (appLaunchDetails != null && appLaunchDetails.didNotificationLaunchApp) {
      if (appLaunchDetails.notificationResponse != null) {
        final message = RemoteMessage.fromMap(
            jsonDecode(appLaunchDetails.notificationResponse!.payload!));
        handleInitialMessage(message);
      }
    }

    final platform = _localNotification.resolvePlatformSpecificImplementation<
        AndroidFlutterLocalNotificationsPlugin>();
    await platform?.createNotificationChannel(_androidChannel);
  }

  initAndSendLocalNotification(RemoteMessage message) async {
    await initLocalNotifications();
    sendLocalNotification(message);
  }

  sendLocalNotification(RemoteMessage message) {
    final notification = message.data;

    NotificationHandler notificationHandler = NotificationHandler();
    notificationHandler.handleLocalUpdates(notification);

    //crea in autonomia la notifica locale quindi non serve fare nulla
    if (Platform.isIOS) return;

    if (debugPrint) {
      print("sendLocalNotification");
      print(message.toMap());
    }

    _localNotification.show(
      message.hashCode,
      notification["title_local_notification"],
      notification["body_local_notification"],
      NotificationDetails(
        android: AndroidNotificationDetails(
            _androidChannel.id, _androidChannel.name,
            channelDescription: _androidChannel.description,
            icon: "@drawable/ic_launcher"),
      ),
      payload: jsonEncode(
        message.toMap(),
      ),
    );
  }

  Future initPushNotifications() async {
    await FirebaseMessaging.instance
        .setForegroundNotificationPresentationOptions(
            alert: true, badge: true, sound: true);

    FirebaseMessaging.instance.getInitialMessage().then(handleInitialMessage);
    FirebaseMessaging.onMessageOpenedApp.listen(handleMessage);
    FirebaseMessaging.onBackgroundMessage(handleBackgroundMessage2);
    FirebaseMessaging.onMessage.listen(
      (message) {
        if (debugPrint) {
          print("onMessage");
          print(message.toMap());
        }
        sendLocalNotification(message);
      },
    );
  }

  Future<String?> initNotification() async {
    try {
      final firebaseMessaging = FirebaseMessaging.instance;
      await firebaseMessaging.requestPermission();
      String? fcmToken = await firebaseMessaging.getToken();
      await LoginSharedPreferences.setFcmToken(fcmToken);
      //log
      Logger log = Logger();
      log.w("FCM TOKEN: $fcmToken");

      //cancella tutte le notifiche
      Eraser.clearAllAppNotifications();

      //start notifications
      initPushNotifications();
      initLocalNotifications();

      return fcmToken;
    } catch (e) {
      print(
          "Impossibile inizializzare il gestore delle notifiche: ${e.toString()}");
    }
    return null;
  }
}

Payload sent from my php backend:

$android = array("collapseKey"=>$collapseKey, "priority"=>"high", "notification"=>array("sound" => "default", "tag"=>$tag));
        $ios = array("headers"=>array("apns-priority"=>"10", "apns-collapse-id"=>$tag), "payload" => array("aps"=>array("sound" => "default")));

// !!!  inside data there're also other parameters that are needed to be able to navigate through my app after a notification is opened
// I've added title and body just to make some testing in the past and my code is still like this
$data["title_local_notification"] = $title;
$data["body_local_notification"] = $body;

$payload = ["message" => [
                    "token" => $toToken,
                    "notification"=>[
                        "title" => $title,
                        "body"=> $body,
                        ],
                    "data"=>$data,
                    "android"=>$android,
                    "apns"=>$iOS,
                    ]
           ];

The problem I'm facing:
-On iOS everything works (or at least for all the device I've been able to test)
-On android in debug mode works fine in any device, but on release mode I've noticed that sometimes a double notification is showed.

It happens just for a device I'm testing: One Plus 8t, Android 14. Oxygen OS KB2003_14.0.0.1311.
When the app is killed or in background a double notification is sent (just in this device, just in release mode, i've tested in debug mode and it works just like any other device), while in any other device I've tried it's not happening.

I've read the documentation talking about not sending both "notification" and "data" in the payload, but it has worked without any problem and if I don't send one of them I've other problems while handling the notification actions or the notification is not showed at all.

NOTICE THAT:
Inside sendLocalNotification there's a if (Platform.isIOS) return; this because in the past I've noticed that iOS was already creating a notification in some cases by itself, and thus the local notification was not needed, if I hadn't add this return a double notification on iOS would have been sent, but on iOS every device had this behavior.

I'm attaching some debug logs to show you what is happening in debug, unfortunately I'm not able to save the same logs on release mode to see what is happening.

 # foreground Samsung - OK

[DEBUG] 2026-03-20T10:21:59.236505 [D] TIME: 2026-03-20T10:21:59.235309 onMessage
[DEBUG] 2026-03-20T10:21:59.254128 [D] TIME: 2026-03-20T10:21:59.253149 {senderId: null, category: null, collapseKey: com.sasoftware.palladio.palladio_mobile, contentAvailable: false, data: {prog_dis: DIS038, notification_tag: 1187, body_local_notification: a, title_local_notification: Messaggio da magazzino, rif: 85}, from: 473524389672, messageId: 0:1773998518625541%bb1efa7fbb1efa7f, messageType: null, mutableContent: false, notification: {title: Messaggio da magazzino, titleLocArgs: [], titleLocKey: null, body: a, bodyLocArgs: [], bodyLocKey: null, android: {channelId: null, clickAction: null, color: null, count: null, imageUrl: null, link: null, priority: 0, smallIcon: null, sound: default, ticker: null, tag: 1187, visibility: 0}, apple: null, web: null}, sentTime: 1773998518618, threadId: null, ttl: 2419200}
[DEBUG] 2026-03-20T10:21:59.267411 [D] TIME: 2026-03-20T10:21:59.266836 sendLocalNotification
[DEBUG] 2026-03-20T10:21:59.273072 [D] TIME: 2026-03-20T10:21:59.272313 {senderId: null, category: null, collapseKey: com.sasoftware.palladio.palladio_mobile, contentAvailable: false, data: {prog_dis: DIS038, notification_tag: 1187, body_local_notification: a, title_local_notification: Messaggio da magazzino, rif: 85}, from: 473524389672, messageId: 0:1773998518625541%bb1efa7fbb1efa7f, messageType: null, mutableContent: false, notification: {title: Messaggio da magazzino, titleLocArgs: [], titleLocKey: null, body: a, bodyLocArgs: [], bodyLocKey: null, android: {channelId: null, clickAction: null, color: null, count: null, imageUrl: null, link: null, priority: 0, smallIcon: null, sound: default, ticker: null, tag: 1187, visibility: 0}, apple: null, web: null}, sentTime: 1773998518618, threadId: null, ttl: 2419200}


# background - Samsung - OK

[DEBUG] 2026-03-20T10:24:35.258697 [D] TIME: 2026-03-20T10:24:35.241310 BACKGROUND: {senderId: null, category: null, collapseKey: com.sasoftware.palladio.palladio_mobile, contentAvailable: false, data: {prog_dis: DIS038, notification_tag: 1188, body_local_notification: e, title_local_notification: Messaggio da magazzino, rif: 85}, from: 473524389672, messageId: 0:1773998674718397%bb1efa7fbb1efa7f, messageType: null, mutableContent: false, notification: {title: Messaggio da magazzino, titleLocArgs: [], titleLocKey: null, body: e, bodyLocArgs: [], bodyLocKey: null, android: {channelId: null, clickAction: null, color: null, count: null, imageUrl: null, link: null, priority: 0, smallIcon: null, sound: default, ticker: null, tag: 1188, visibility: 0}, apple: null, web: null}, sentTime: 1773998674712, threadId: null, ttl: 2419200}

# killed - Samsung - OK

[DEBUG] 2026-03-20T10:25:43.092453 [D] TIME: 2026-03-20T10:25:43.040567 BACKGROUND: {senderId: null, category: null, collapseKey: com.sasoftware.palladio.palladio_mobile, contentAvailable: false, data: {prog_dis: DIS038, notification_tag: 1189, body_local_notification: f, title_local_notification: Messaggio da magazzino, rif: 85}, from: 473524389672, messageId: 0:1773998733488763%bb1efa7fbb1efa7f, messageType: null, mutableContent: false, notification: {title: Messaggio da magazzino, titleLocArgs: [], titleLocKey: null, body: f, bodyLocArgs: [], bodyLocKey: null, android: {channelId: null, clickAction: null, color: null, count: null, imageUrl: null, link: null, priority: 0, smallIcon: null, sound: default, ticker: null, tag: 1189, visibility: 0}, apple: null, web: null}, sentTime: 1773998733482, threadId: null, ttl: 2419200}

Any help would really be appreciated.

[adiprmx]

ran into this exact thing in my own app tbh. ngl the culprit is sending notification plus data together.

when the app is backgrounded or killed, android takes the notification part and shows it on its own, you dont write any code for that one. so thats already one notification. if your code shows another one on top, you get the double.

what fixed it for me: send data only, no notification block, and show the notification yourself with flutter_local_notifications in all three states, foreground, background, terminated. one path, one notification, no matter the device.

since your background handler only logs and it only happens on that one oneplus in release, two things worth checking. log the message id in the background handler. same id twice means the system redelivered it, two different ids means your backend sent it twice. btw check your backend isnt holding onto old tokens. if it keeps every token without replacing on refresh, the device gets one copy per stored token.

one more thing i noticed in your code, the handler that shows a local notification is defined but never registered, the print only one is whats actually wired up. if you ever swap them, youll get doubles everywhere, not just the oneplus.

and the fact it only happens on the oneplus in release tracks, oxygenos kills and restarts background work aggressively, and release timing is different from debug, so thats where the redelivery shows up.