MQTT Callback context not defined during publish

Question

    public class MqttService extends Service implements MqttCallback {
                public MqttAsyncClient mClient; 
                mOpts = new MqttConnectOptions();
                mOpts.setCleanSession(MQTT_CLEAN_SESSION);
                mOpts.setUserName(String.valueOf(userMigration.getId()));
                mOpts.setPassword(userMigration.getPassword().toCharArray());
                mOpts.setAutomaticReconnect(true);
                mOpts.setKeepAliveInterval(MQTT_KEEP_ALIVE);
                mClient.connect(mOpts, this, connectListener);
                @Override
                public void messageArrived(String topic, MqttMessage message) throws Exception {
                }
                @Override
               public void deliveryComplete(IMqttDeliveryToken token) {
                //Log.e(DEBUG_TAG, "Completed Delivery");
               }

              @Override
              public void connectionLost(Throwable arg0) {
              stopKeepAlives();
              Log.e(DEBUG_TAG, "Lost");
              mClient = null;
              }
              IMqttActionListener connectListener = new IMqttActionListener() {
        public void onSuccess(IMqttToken asyncActionToken) {
            mStarted = true; // Service is now connected
            Log.i(DEBUG_TAG,"Successfully connected");
            mClient.setCallback(MqttService.this);
        }

        public void onFailure(IMqttToken asyncActionToken, Throwable exception) {
            Log.e(DEBUG_TAG, "con failed "+exception.toString());
        }
    };

 mClient.publish("message/"+jsonObject.get("userBId").getAsInt(),jsonObject.toString().getBytes(), 1, false, this, new IMqttActionListener() {
                    @Override
                    public void onSuccess(IMqttToken asyncActionToken) {


                    }

                    @Override
                    public void onFailure(IMqttToken asyncActionToken, Throwable exception) {
                        Log.e(DEBUG_TAG,"failed");
                    }
                });
    }

//If I am not setting callback after connection, it is working perfectly but message recevied is not triggering. If I set callback after connection, them message arrived is triggering but during publish, I am getting IMqttActionListener defined on null. Could you help me. I need callback just after the publish to update that data in my database.

Answer 1

Try moving the mClient.setCallback(MqttService.this); line up, before connect is initiated:

mOpts.setKeepAliveInterval(MQTT_KEEP_ALIVE);
mClient.setCallback(this);
mClient.connect(mOpts, this, connectListener);