I want to send multiple data messages to my flutter app. I was working with notifications as they were sent in all states (foreground, background, terminated) but found that they are being collapsed. I switched to use only-data messages and after some code modification, it works flawlessly on Android when the app is in any condition, I always receive the data message. Even if the user has no internet connection and multiple messages are sent, each one will be received after reconnecting. When testing this on iOS, I ran the app in release mode as I did in Android and everything worked in foreground, when I tried to swipe to home and send app to background and send a message, nothing is received. When I reopen the app, the data message is then received. If I send multiple data messages, only the last one is received after reopening the app.

This behaviour also exists when simply locking the iPhone

There are 2 major problems here:

1- Data messages are not being received in background/terminated states in release mode but works fine in profile mode

2- Even after re-opening the app, only the last data message is being received (similar to collapsing notifications in FCM)

I didn’t find any comments regarding this behaviour in FCM doumentation. Can someone look into this to ensure if this is a normal behaviour or not. If so, how can I overcome it or a work around ?

Data Message Sending Function:

public function sendDataMessage($deviceTokens, $data = [], $priority = "high")
{
    $messaging = app('firebase.messaging');
    $clean_data = $data;
    if (isset($data["type"]) && $data["type"] == "chat" && $data["action"] == "receiveMessage") {
        unset($clean_data["fcm_message"]);
    }
    $messages = [];
    foreach ($deviceTokens as $token) {
        try {
            if (isset($data["type"]) && $data["type"] == "chat" && $data["action"] == "receiveMessage") {
                $chat_message = $data["fcm_message"];
                $clean_data["title"] = Chats::select("name")->find($data["chat_id"])->name;
                $clean_data["body"] = $chat_message["sender"]["name"] . ": " . ($chat_message["content"]["type"] == "Text" ? $chat_message["content"]["body"] : $chat_message["content"]["type"]);
            }
            $messages[] = CloudMessage::withTarget('token', $token)
                ->withData($clean_data)
                ->withAndroidConfig(AndroidConfig::fromArray([
                    'priority' => 'high',  // Use high priority
                    'ttl' => 86400 * 28, // 4 weeks in seconds
                ]))
                ->withApnsConfig(ApnsConfig::fromArray([
                    'headers' => [
                        'apns-expiration' => strval(time() + 86400 * 28), // Expiry timestamp
                        'apns-priority' => '10',
                    ],
                    'payload' => [
                        'aps' => [
                            // 'sound' => 'default',
                            "content-available" => 1,
                            "mutable-content" => 1
                        ],
                    ],
                ]));
        } catch (Exception $e) {
            return $e;
        }
    }
    try {
        $report = $messaging->sendAll($messages);
    } catch (NotFound $e) {
        return $e;
    } catch (Exception $e) {
        return $e;
    }

    return $report->successes()->count();
}

Firebase Handler:

static void initializeFCMHandler() async {
    FirebaseMessaging.onBackgroundMessage(handleBackgroundMessage);
    FirebaseMessaging.onMessage.listen(handleMessage);
}

@pragma('vm:entry-point')
static Future<void> handleBackgroundMessage(RemoteMessage? message) async {
    if (message?.notification != null) {
      handleNotification(message, isBackground: true);
    } else {
      handleDataMessage(message, isBackground: true);
    }
}

static void handleMessage(RemoteMessage? message) async {
    if (message?.notification != null) {
      handleNotification(message);
    } else {
      handleDataMessage(message);
    }
}