[AS3]在as3编程用hasEventListener(Event.EventType)检测侦听是

[AS3]在as3编程用hasEventListener(Event.EventType)检测侦听是否删
if(a.hasEventListener(Event.EventType))
{
     a.removeEventListener(Event.EventType , function);
    ..........
}
例子
a.addEventListener(MouseEvent.CLICK , onClick);
function onClick(e:MouseEvent):void
{
    if(a.hasEventListener(MouseEvent.CLICK )) //判断a是否含有MouseEvent.CLICK这个事件
          a.removeEventListener(MouseEvent.CLICK  , onClick);
}