public void addListener(final INaviGraphListener listener){
  super.addListener(listener);
  m_listeners.addListener(listener);
  m_synchronizer.addListener(listener);
}

public void addListener ( final INaviGraphListener listener ) { super . addListener ( listener ) ; m_listeners . addListener ( listener ) ; m_synchronizer . addListener ( listener ) ; }
adds a listener object that is notified about changes in the graph .
