GCM RxJava IntentService

GcmRegistrationIntentService.class

public class GcmRegistrationIntentService extends IntentService {

    private static final String TAG = "RegIntentService";
    private static final String[] TOPICS = {"global"};

    private PushNotificationManager pushNotificationManager;
    private GcmRequestManager gcmRequestManager;
    private InstanceID instanceID;

    public GcmRegistrationIntentService() {
        super(TAG);
    }

    public GcmRegistrationIntentService(String name) {
        super(TAG);
    }

    @Override
    protected void onHandleIntent(Intent intent) {

        pushNotificationManager = PushNotificationManager.getInstance(this.getApplicationContext());
        gcmRequestManager = GcmRequestManager.getInstance(this.getApplicationContext());
        instanceID = InstanceID.getInstance(this.getApplicationContext());

        //update flag to say we need to register in case of failure
        pushNotificationManager.setHasCompletedGcmRegistration(false);

        setupPushNotifications();
    }

    private void setupPushNotifications() {

        getToken().subscribeOn(Schedulers.io())
                  .flatMap(this::sendRegistrationToServer)
                  .subscribe(new GcmRegistrationSubscriber());
    }

    private Single<String> getToken() {
        return Single.defer(() -> {
            try {

                String token = instanceID.getToken(getString(R.string.gcm_sender_id), GoogleCloudMessaging.INSTANCE_ID_SCOPE, null);
                pushNotificationManager.setGcmPushToken(token);
                return Single.just(token);
            } catch (Exception exception) {
                return Single.error(exception);
            }
        });
    }

    private Single<Object> sendRegistrationToServer(String token) {

        pushNotificationManager.setGcmPushToken(token);
        return gcmRequestManager.register()
                                .toSingle()
                                .flatMap(this::registerTopics);
    }

    private Single<Void> registerTopics(Object object) {
        return Single.defer(() -> {
            try {

                GcmPubSub pubSub = GcmPubSub.getInstance(getApplicationContext());

                for (String topic : TOPICS) {
                    pubSub.subscribe(pushNotificationManager.getGcmPushToken(), "/topics/" + topic, null);
                }

                return Single.just(null);
            } catch (Exception exception) {
                return Single.error(exception);
            }
        });
    }

    private class GcmRegistrationSubscriber extends SingleSubscriber<Object> {

        @Override
        public void onSuccess(Object value) {
            pushNotificationManager.setHasCompletedGcmRegistration(true);
        }

        @Override
        public void onError(Throwable e) {
            pushNotificationManager.setHasCompletedGcmRegistration(false);
        }
    }
}