[firebase_messaging] data message arrives on the native side, but is not delivered to the Dart side

[sd-timaru]

Using firebase_messaging: ^5.1.6 plugin in my application, I noticed that when the app is in the background, sometimes the messages do not reach "the destination", so i decided to do some "tracking".

In the file FlutterFirebaseMessagingService.java, at the method executeDartCallbackInBackgroundIsolate i added
"Log.i(TAG, "before handleBackgroundMessage")":

    ...
    Log.i(TAG, "before handleBackgroundMessage");
    args.put("message", messageData);
    backgroundChannel.invokeMethod("handleBackgroundMessage", args, result);
    ...

In the file firebase_messaging.dart , at the method setMethodCallHandler i added
"print('Received in Dart!');":

  backgroundChannel.setMethodCallHandler((MethodCall call) async {
    print('Received in Dart!');
    if (call.method == 'handleBackgroundMessage') {
    ...

To do some testing, i send 4 data messages, while the app was in background. 2 of them arrived successfully in the app, but the last 2 didn't, even they arrived to the java side:

If i "bring" the app in the foreground and send to it others data messages, the arrive successfully.

What could be the problem? Why the messages are not delivered always to the Dart side, when the app is in the background?

[iapicca]

Hi @sd-timaru
Could you please provide your flutter doctor -v
and your your flutter run --verbose?
Thank you

[sd-timaru]

Yes, but i just updated the flutter and dart plugin....

doc.txt

output.txt

[iapicca]

Thank you @sd-timaru

[goody-h]

I also experience this on my app.

A simple flutter logs on the connected device would show the creation of an observatory listener when a data message is received
I/flutter (24260): Observatory listening on http://127.0.0.1:46040/aO_xk0_pDeQ=/

But then the Dart background Message handler does not always execute

[Salakar]

Hey all 👋

As part of our roadmap (#2582) we've just shipped a complete rework of the firebase_messaging plugin that aims to solve this and many other issues.

If you can, please try out the dev release (see the migration guide for upgrading and for changes) and if you have any feedback then join in the discussion here.

Given the scope of the rework I'm going to go ahead and close this issue in favor of trying out the latest plugin.

Thanks everyone.