asyncTask.java

if (senderId != null) {
            new AsyncTask<Void, Void, Void>() {
                @Override
                protected Void doInBackground(Void... params) {
                    try {
                        String token = getToken(senderId);
                        GcmPubSub.getInstance(TiApplication.getInstance()).subscribe(token, topic, null);

                        if (successTopicCallback != null) {
                            // send success callback
                            HashMap<String, Object> data = new HashMap<String, Object>();
                            data.put("success", true);
                            data.put("topic", topic);
                            successTopicCallback.callAsync(getKrollObject(), data);
                        }
                    } catch (Exception ex) {
                        // error
                        Log.e(LCAT, "Error " + ex.toString());
                        if (errorTopicCallback != null) {
                            // send error callback
                            HashMap<String, Object> data = new HashMap<String, Object>();
                            data.put("success", false);
                            data.put("topic", topic);
                            data.put("error", ex.toString());
                            errorCallback.callAsync(getKrollObject(), data);
                        }
                    }
                    return null;
                }
            }.execute();
        } else {
            sendError(errorTopicCallback, "No GCM senderId specified; get it from the Google Play Developer Console");
        }