Transfer data from FirebaseMessagingService to Activity using rxjava

Question

I am currently just using EventBus to transfer data from FirebaseMessagingService onMessageReceived to MainActivity , but this is getting tricky as complexity goes on and what if i get multiple notifications ? on the other hand,

Data transfer is costing 1 extra class and 2 boiler plate function due to EventBus.

So Problem is how to transfer data from FirebaseMessagingService to Activity using Rxjava , and is there any way to convert this whole service to some observables ?

Jordy Langen · Accepted Answer · 2016-11-14T13:00:55.503

You would still need to Service to receive the notifcations. However, you could use a PublishSubject to publish items like this:

class NotificationsManager {

    private static PublishSubject<Notification> notificationPublisher;

    public PublishSubject<Notification> getPublisher() {
        if (notificationPublisher == null) {
            notificationPublisher = PublishSubject.create();
        }

        return notificationPublisher;
    }

    public Observable<Notification> getNotificationObservable() {
        return getPublisher().asObservable();
    }
}

class FirebaseMessagingService {

    private PublishSubject<Notification> notificationPublisher;

    public void create() {
        notificationPublisher = NotificationsManager.getPublisher()
    }

    public void dataReceived(Notification notification) {
        notificationPublisher.onNext(notification)
    }
}

class MyActivity {

    private Observable<Notification> notificationObservable;

    public void onCreate(Bundle bundle) {
        notificationObservable = NotificationsManager.getNotificationObservable()

        notificationObservable.subscribe(...)
    }
}

Edit: expanded the example. Please note this is not the best way to do it, just an example

I didn't get it , how can you transfer `notificationPublisher` from FMS to activity , are you saying i should make it static in FMS ? , it will leak memory — Zulqurnain Jutt, Nov 14 '16 at 12:54
You could make a manager class that maintains this `notificationPublisher` and make sure to properly dispose the reference of it in the Service and Actvity — Jordy Langen, Nov 14 '16 at 12:55
Added a sample, but have a look into dependency injection & Dagger — Jordy Langen, Nov 14 '16 at 13:01

Alex Shutov · Answer 2 · 2016-11-14T13:12:24.333

yes, you can convert Service for using Observables by using PublishSubject . Just return it as observable by subject.asObservable() and pass it new event from onEvent() method by subject.onNext(). Use Service binding to bind your Service to Activity, and , whithing binding interface, return references to your subjects as observables.

PublishSubject<String> eventPipe = PublishSubject.create();

        Observable<String> pipe = eventPipe.observeOn(Schedulers.computation()).asObservable();
        // susbcribe to that source
        Subscription s =  pipe.subscribe(value -> Log.i(LOG_TAG, "Value received: " + value));

        // give next value to source (use it from onEvent())
        eventPipe.onNext("123");

        // stop receiving events (when you disconnect from Service)
        if (s != null && !s.isUnsubscribed()){
            s.unsubscribe();
            s = null;
        }

        // we're disconnected, nothing will be printed out
        eventPipe.onNext("321");

some basic example please for where exactly to use `subject.asObservable()` and why — Zulqurnain Jutt, Nov 14 '16 at 12:59

Transfer data from FirebaseMessagingService to Activity using rxjava

2 Answers2