Receive messages from multiple senders (Firebase projects) in Android app using FCM

Question

I'm trying to receive messages from multiple Firebase projects(senders) using the pointers in this post . I have initialized the FirebaseApp with appropriate options and have called getToken() on each of the senders/projects. But this doesn't work. The only FCM messages that I receive are from the project whose google-services.json has been included in the project. Please let me know if I am missing something here. Thanks.

            FirebaseApp.initializeApp(context);

            FirebaseOptions options1 = new FirebaseOptions.Builder()
                    .setApiKey("apiKey1")
                    .setApplicationId("appId1")
                    .setGcmSenderId("senderId1")
                    .setStorageBucket("bucket1")
                    .setDatabaseUrl("database1")
                    .build();
            FirebaseApp.initializeApp(context, options1, "project1");

            FirebaseOptions options2 = new FirebaseOptions.Builder()
                    .setApiKey("apikey2")
                    .setApplicationId("appId2")
                    .setGcmSenderId("sender2")
                    .setStorageBucket("bucket2")
                    .setDatabaseUrl("database2")
                    .build();
            FirebaseApp.initializeApp(context, options2, "project2");

            new AsyncTask<Void, Void, Void>() {
                @Override
                protected Void doInBackground(Void... params) {

                    try {
                        String token1 = FirebaseInstanceId.getInstance(FirebaseApp.getInstance("project1")).getToken("sender1", FirebaseMessaging.INSTANCE_ID_SCOPE);
                        String token2 = FirebaseInstanceId.getInstance(FirebaseApp.getInstance("project2")).getToken("sender2", FirebaseMessaging.INSTANCE_ID_SCOPE);
                    } catch (IOException e) {
                        e.printStackTrace();
                    }
                    return null;
                }

                @Override
                protected void onPostExecute(Void result) {

                }
            }.execute();

           FirebaseMessaging fcm = FirebaseMessaging.getInstance();                

Answer 1

The way that worked for me is a little bit similar to what you did, but with a slight difference: I was keeping reference of the FirebaseApp returned from the Factory Method FirebaseApp.initializeApp and then passing the variable to the FirebaseInstanceId.getInstance() . Also, I don't think the first call for initialize app FirebaseApp.initializeApp(context) is useful since in all cases you will not need it.

My version of your code would be:

            //FirebaseApp.initializeApp(context);

            FirebaseOptions options1 = new FirebaseOptions.Builder()
                    .setApiKey("apiKey1")
                    .setApplicationId("appId1")
                    .setGcmSenderId("senderId1")
                    .setStorageBucket("bucket1")
                    .setDatabaseUrl("database1")
                    .build();
            FirebaseApp app1 = FirebaseApp.initializeApp(context, options1, "project1");

            FirebaseOptions options2 = new FirebaseOptions.Builder()
                    .setApiKey("apikey2")
                    .setApplicationId("appId2")
                    .setGcmSenderId("sender2")
                    .setStorageBucket("bucket2")
                    .setDatabaseUrl("database2")
                    .build();
            FirebaseApp app2 = FirebaseApp.initializeApp(context, options2, "project2");

            new AsyncTask<Void, Void, Void>() {
                @Override
                protected Void doInBackground(Void... params) {

                    try {
                        String token1 = FirebaseInstanceId.getInstance(app1).getToken("sender1", FirebaseMessaging.INSTANCE_ID_SCOPE);
                        String token2 = FirebaseInstanceId.getInstance(app2).getToken("sender2", FirebaseMessaging.INSTANCE_ID_SCOPE);
                    } catch (IOException e) {
                        e.printStackTrace();
                    }
                    return null;
                }

                @Override
                protected void onPostExecute(Void result) {

                }
            }.execute();

           FirebaseMessaging fcm = FirebaseMessaging.getInstance();   

I don't know if it makes sense, but I hope that it will be able to help you anyways.