ActionScript 3.0 事件机制小结

这次先把ActionScript 3.0 事件机制总结一下先吧，这里只说一下自定义类发送事件的3中方式，因为在设计模式中是比较常用的。例如MVC。

关于自定义事件，主要由于两个类：事件类（Event）,事件发送类（EventDispatcher）。我们讨论的自定义发送事件，就是如何使对象能够发送事件。

方式一：继承EventDispatcher类

package 
{
	import flash.display.Sprite;
	import flash.events.Event;
	import flash.events.EventDispatcher;
	
	/**
	 * ...
	 * @author 橡树小屋
	 */
	public class estends extends Sprite
	{
		function estends() {
			//第一种
			var dispatcher:extendsDispatcher = new extendsDispatcher();
			dispatcher.addEventListener(extendsDispatcher.ACTION, actionH);
			dispatcher.doSome();
			//第二种
			var dispatcher1:EventDispatcher = new EventDispatcher();
			dispatcher1.addEventListener("secDispatcher", actionH);
			dispatcher1.dispatchEvent(new Event("secDispatcher"));
			//或者
			dispatcher.addEventListener("thurdDispatcher", actionH);
			dispatcher.dispatchEvent(new Event("thurdDispatcher"));
		}
		private function actionH(e:Event):void {
			trace(e);
		}
	}
	
}
import flash.events.Event;
import flash.events.EventDispatcher;

class extendsDispatcher extends EventDispatcher {
	public static var ACTION:String = "action";
	public function doSome():void {
		dispatchEvent(new Event(extendsDispatcher.ACTION));
	}
}

只要继承EventDispatcher类，就可以直接用EventDispatcher类的方法发送事件，方便简单。

方式二：复合EventDispatcher对象

package 
{
	
	/**
	 * ...
	 * @author 橡树小屋
	 */
	import flash.display.Sprite;
	import flash.events.Event;
	
	public class compont extends Sprite
	{
		public function compont() {
			var dis:compont1 = new compont1();
			dis.getEventDispatch().addEventListener(compont1.ACTION, show);
			dis.doSome();
		}
		private function show(e:Event):void {
			trace(e);
		}
	}
	
}
import flash.events.Event;
import flash.events.EventDispatcher;

class compont1 {
	private var _dispatcher:EventDispatcher;
	public static var ACTION:String = "action";
	public function compont1() {
		_dispatcher = new EventDispatcher();
	}
	public function getEventDispatch():EventDispatcher {
		return _dispatcher;
	}
	public function doSome():void {
		_dispatcher.dispatchEvent(new Event(compont1.ACTION));
	}
}

所谓的复合，其实就是用EventDispatcher发送事件而已，因为EventDispatcher本身就是个事件发送类，一般情况下，用EventDispatcher发送事件反而会更简单。

方式三：实现IEventDispatcher接口

package 
{
	import flash.display.Sprite;
	import flash.events.Event;
	
	/**
	 * ...
	 * @author 橡树小屋
	 */
	public class implement extends Sprite
	{
		
		public function implement() {
			var impObj:implete = new implete();
			impObj.addEventListener(implete.ACTION, actionH);
			impObj.dispatchEvent(new Event(implete.ACTION));
		}
		private function actionH(e:Event):void {
			trace(e);
		}
	}
	
}
import flash.events.Event;
import flash.events.EventDispatcher;
import flash.events.IEventDispatcher;

class implete implements IEventDispatcher {
	public var _dispatcher:EventDispatcher;
	public static const ACTION:String = "action";
	
	public function implete() {
		_dispatcher = new EventDispatcher();
	}
	//实现5个方法
	public function addEventListener(type:String,listener:Function,useCapture:Boolean=false,priority:int=0,useWeakReference:Boolean=true):void {
		_dispatcher.addEventListener(type, listener, useCapture, priority, useWeakReference);
		
	}
	public function dispatchEvent(evt:Event):Boolean {
		return _dispatcher.dispatchEvent(evt);
	}
	public function hasEventListener(type:String):Boolean {
		return _dispatcher.hasEventListener(type);
	}
	public function removeEventListener(type:String, listener:Function, useCapture:Boolean = false):void {
		_dispatcher.removeEventListener(type,listener,useCapture);
	}
	public function willTrigger(type:String):Boolean {
		return _dispatcher.willTrigger(type);
	}
}

当类本身要继承其他类，无法继承EventDispatcher类的时候，同时又希望这个类能够成为一个单纯的事件发送类，并且可以自己添加某些方法在里面，这时候用继承IEventDispatcher接口就比较合适了，不过过程比较麻烦写，要实现IEventDispatcher接口的5个方法。

参考资料：

《flash ActionScript 3.0 殿堂之路》