flex动态加载module

<?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="400" minHeight="300" applicationComplete="application1_applicationCompleteHandler(event)"> 
	<s:layout> 
		<s:BasicLayout/> 
	</s:layout> 
	
	<fx:Script> 
		<![CDATA[ 
			import mx.core.IVisualElement; 
			import mx.events.FlexEvent; 
			import mx.events.ModuleEvent; 
			import mx.modules.IModuleInfo; 
			import mx.modules.ModuleManager; 
			
			private var module:IModuleInfo; 
			private var first:Boolean=true;//是否首次加载的判断标志 
			private var moduleInstance:Object;//用于保存加载后的实例引用 
			
			protected function button1_clickHandler(event:MouseEvent):void 
			{    
				//非首次加载（先卸载） 
				if (!first) 
				{ 
					module.unload(); 
					pnl.removeElement(moduleInstance as IVisualElement); 
				} 
				initModule(); 
				module.load();   
				btn1.enabled = false; 
			} 
			
			private function onModuleReady(e:ModuleEvent):void 
			{                
				moduleInstance  = e.module.factory.create();//注：这里千万不能用as做任何的转型，否则就报null object reference错误，原因不明                 
				this.pnl.addElement(moduleInstance as IVisualElement); 
				//由于只能以Object方式操作，所以下面的代码，没办法智提示，只以盲打 
				moduleInstance.txtModule.text = Math.random().toString(); 
				moduleInstance.x = moduleInstance.y = 10; 
				trace(moduleInstance.Test()); 
				first = false; 
				btn1.enabled = true; 
				
			} 
			
			private function initModule():void 
			{ 
				module = ModuleManager.getModule("module/MyModule.swf"); 
				module.addEventListener(ModuleEvent.READY,onModuleReady);    
			} 
			
			//应用加载完成时，就预先将Module初始化（甚至这时就可以load，只是不显示而已，以改善用户体验） 
			protected function application1_applicationCompleteHandler(event:FlexEvent):void 
			{ 
				initModule(); 
			} 
			
		]]>
	</fx:Script>   
	
	<s:Panel id="pnl" title="动态加载Module" left="10" top="10" bottom="50" right="10"></s:Panel> 
	
	<s:Button click="button1_clickHandler(event)" label="load" horizontalCenter="0" bottom="10" id="btn1"> 
		
	</s:Button> 
</s:Application>