仿 jQuery 的 once 方法，在 ActionScript 中指定一个只触发一次的监听器。

package net.gerhut.eventUtils
{
    import flash.events.EventDispatcher;
	
	public class OnceEventDispatcher
	{
		public static function add(eventDispatcher:EventDispatcher, type:String, listener:Function, useCapture:Boolean=false, priority:int=0, useWeakReference:Boolean=false):void
		{
			var onceListener:OnceListener = new OnceListener(eventDispatcher, type, listener, useCapture);
			eventDispatcher.addEventListener(type, onceListener.outputListener, useCapture, priority, useWeakReference);
		}
	}
}

import flash.events.Event;
import flash.events.EventDispatcher;

class OnceListener
{
	private var type:String;
	private var eventDispatcher:EventDispatcher;
	private var originalListener:Function;
	private var useCapture:Boolean;
	
	public function OnceListener(eventDispatcher:EventDispatcher, type:String, originalListener:Function, useCapture:Boolean=false)
	{
		this.type = type;
		this.eventDispatcher = eventDispatcher;
		this.originalListener = originalListener;
		this.useCapture = useCapture;
	}
	
	public function outputListener(event:Event):void
	{
		eventDispatcher.removeEventListener(type, outputListener, useCapture);
		originalListener(event);
	}
}