Flex的mxml中调用绘图As代码

<?xml version="1.0" encoding="utf-8"?>
<s:Application xmlns:fx="http://ns.adobe.com/mxml/2009" 
			   xmlns:s="library://ns.adobe.com/flex/spark" 
			   xmlns:mx="library://ns.adobe.com/flex/mx" minWidth="955" minHeight="600"
			   applicationComplete="initView()">
	<mx:Label x="10" y="10" text="As3.0 -> Flex!">
	</mx:Label>
	<mx:Canvas x="0" y="0" id="canvas" width="100%" height="100%">
	</mx:Canvas>
	<fx:Declarations>
		<!-- 将非可视元素（例如服务、值对象）放在此处 -->
	</fx:Declarations>
	<fx:Script>
		<![CDATA[
			//需要使用Canvas来包含UIComponent，然后将自己定义的As类添加到Component中
			import mx.core.UIComponent;
			private function initView():void
			{
				var component:UIComponent=new UIComponent();
				canvas.addChild(component);
				component.addChild(new MyDemo());
			}
		]]>
	</fx:Script>
</s:Application>

MyDemo.as:

package
{
	import flash.display.Shape;
	import flash.display.Sprite;
	import flash.events.Event;
	import flash.events.KeyboardEvent;
	import flash.events.MouseEvent;
	import flash.events.TimerEvent;
	import flash.utils.Timer;
	import mx.controls.Label;
	
	/**
	 * 将上一次记录的Blog <<flex(入门)之timer的使用,键盘,鼠标的监听>> 的As代码放到flex的Web项目中去调用，这个时候会有问题
	 * 原因出在了舞台上,然后在网上搜索了一下,问题解决了。
	 * 
	 * */
	
	//窗体大小，绘制帧率
	public class MyDemo extends Sprite
	{
		private var circle:Shape;
		private var label:Label;
		private var timer:Timer;
		public function MyDemo()
		{
			super();
			label = new Label();
			label.x = 30;
			label.y = 30;
			addChild(label);
			circle = new Shape();
			circle.x = 50;
			circle.y = 100;
			addChild(circle);
			circle.graphics.beginFill(0xee2f2f);
			circle.graphics.drawCircle(circle.x,circle.y,40);
			circle.addEventListener(Event.ENTER_FRAME,changePos);//每帧调用changePos函数
			//------------------需要增加Event.ADDED_TO_STAGE时间监听-------------------//
			this.addEventListener(Event.ADDED_TO_STAGE,addToStageHandler);
			//------------------通过addToStageHandler()来添加舞台监听-------------------//
			timer = new Timer(1000,5); //设置延迟时间是1秒，循环执行5次timerExcute()
			timer.addEventListener(TimerEvent.TIMER,timerExcute);
			timer.addEventListener(TimerEvent.TIMER_COMPLETE,timerComplete);//执行完成后调用timerComplete
			timer.start();//启动timer
		}
		
		public function changePos(event:Event):void
		{
			if(circle.y >= 300)
			{
				circle.y = 1;
			}else if(0<circle.y && circle.y < 300)
			{	
				circle.y+=5;
			}
		}
		
		//不可以直接在flex文件中调用as的代码(抛空对象异常)，然后as代码中直接使用stage对象，
		public function addToStageHandler(event:Event):void
		{
			stage.addEventListener(MouseEvent.CLICK,onClick); //舞台上添加鼠标点击监听事件
			stage.addEventListener(KeyboardEvent.KEY_DOWN,keyDown);//舞台添加键盘监听
		}
		
		//在点击的地方产生绿色方形
		public function onClick(event:MouseEvent):void
		{
			var rect:Shape = new Shape();
			addChild(rect);
			rect.graphics.beginFill(0x11ff00);
			rect.graphics.drawRect(event.stageX,event.stageY,20,20);
		}
		
		
		public function keyDown(event:KeyboardEvent):void
		{
			var count:int = 0
			if(event.keyCode == 13) //监听Enter键
			{	
				var rect:Shape = new Shape();
				addChild(rect);
				rect.graphics.beginFill(0x00f1f0);
				rect.graphics.drawRect(Math.random()*400,Math.random()*300,10,10);
			}
		}
		
		public function timerExcute(event:TimerEvent):void
		{
			var rect:Shape = new Shape();
			addChild(rect);
			rect.graphics.beginFill(0x0f11f0);
			rect.graphics.drawRect(Math.random()*400,Math.random()*300,10,10);
		}
		
		public function timerComplete(event:TimerEvent):void
		{
			var rect:Shape = new Shape();
			addChild(rect);
			rect.graphics.beginFill(0x000000);
			rect.graphics.drawRect(Math.random()*400,Math.random()*300,30,60);
		}
	}
}