public void addListener(AirMapTrafficListener listener){
  if (listeners.isEmpty()) {
    listeners.add(listener);
    connect();
  }
 else {
    listeners.add(listener);
  }
}

public void addListener ( AirMapTrafficListener listener ) { if ( listeners . isEmpty ( ) ) { listeners . add ( listener ) ; connect ( ) ; } else { listeners . add ( listener ) ; } }
add a listener to be notified of traffic events
