How is onBackgroudMessage used?

[Mariana-S-Sanches]

I started using firebase last year, and recently it had an update. I am updating my app, and I would like to know how to use this method to receive notifications. What he should do, is read what comes on the data, make a decode, and according to what comes, do a navigation for a certain screen, but it has not worked. This is my code:

    Future<void> _fcmBackgroundHandler(RemoteMessage message) async {
      await Firebase.initializeApp();
      print("Handling a background message: ${message.messageId}");
      var title = message.data['title'];
        if (title == 'dash') {
          print('Data title test: ${message.data['title']}');
          Navigator.of(context).push(
            PageRouteBuilder(
              pageBuilder: (BuildContext context, _, __) {
                return Dashboard();
              },
            ),
          );
        } else {
          Navigator.of(context).push(
            PageRouteBuilder(
              pageBuilder: (BuildContext context, _, __) {
                return Dashboard();
              },
            ),
          );
        }
    }

    FirebaseMessaging.onBackgroundMessage(_fcmBackgroundHandler);