code: public void addListener(Class<? extends VehicleMessage> messageType,
              VehicleMessage.Listener listener) {
          Log.i(TAG, "Adding listener " + listener + " for " + messageType);
          mNotifier.register(messageType, listener);
      }
docs: Register to receive asynchronous updates for a specific VehicleMessage
  type.
  
  Use this method to register an object implementing the
  VehicleMessage.Listener interface to receive real-time updates
  whenever a new value is received for the specified message type.
  
  Make sure you unregister your listeners with
  VehicleManager.removeListener(...) when your activity or service closes
  and no longer requires updates.
  
  @param messageType The class of the VehicleMessage
  (e.g. SimpleVehicleMessage.class) the listener is listening for
  @param listener An listener instance to receive the callback.