public void addLifecycleListener(LifecycleListener lifecycleListener){
  if (!lifecycleListeners.contains(lifecycleListener)) {
    lifecycleListeners.add(lifecycleListener);
  }
}

public void addLifecycleListener ( LifecycleListener lifecycleListener ) { if ( ! lifecycleListeners . contains ( lifecycleListener ) ) { lifecycleListeners . add ( lifecycleListener ) ; } }
adds a listener for all of this controller ' s lifecycle events
