public void addListener( IOpFilterListener listener ) {
super.addListener(listener);
if( listeners.size()==1){
// this is the 1st listener we better watch the AOIService for change!
IAOIService aOIService = PlatformGIS.getAOIService();
aOIService.addListener( watcher );
}
}
@Override
public void removeListener( IOpFilterListener listener ) {
super.removeListener(listener);