Background Callback Dispatcher to Main thread when app being launched

[matthewjs]

We are having a problem when Flutter Fire Messaging is receiving a background notification. We have setup a top level Callback Handler that is called when a background notification is received:

static Future<void> backgroundMessageHandler(RemoteMessage message) async { // initialize widgets binding for plugins WidgetsFlutterBinding.ensureInitialized(); final SendPort messagesPort = IsolateNameServer.lookupPortByName(BACKGROUND_MESSAGES_PORT_NAME); messagesPort?.send(message); }

As can be seen, this handler is designed to send a message to a SendPort that has been setup in main method. When we launch our app, then move it to the background everything works perfectly.

However, if we restart the phone (so that the app is not running) and then send a notification, we can see from LOGCAT that

I/FLTFireMsgService: FlutterFirebaseMessagingBackgroundService started!

But it seems that messagesPort? is null. I assumed that when aa message handler is called from the background, that the main method is run; is this correct?