想实现一个按钮在点击后无效30秒钟时间，改如何处理?

<?xml version="1.0" encoding="utf-8"?>

<mx:Application xmlns:mx="http://www.adobe.com/2006/mxml" layout="absolute">

	<mx:Script>

		<![CDATA[

		    public var i:int = 30;

		    public var intervalId:Number;//定时器参数 

			private function clickFunction():void{

				i = 30;

				btn.enabled = false;

				setTimeout(clickBack,30000);//三十秒

				intervalId = setInterval(NumAdd,1000);

			}

			

			private function clickBack():void{

				btn.enabled  = true;

			}

			

			private function NumAdd():void{

				i--;

				if(i==0){

					clearInterval(intervalId);

					show.text="";

				}

				else

					show.text = "距离按钮恢复还有" + i + "秒";

			}

		]]>

	</mx:Script>

	<mx:Canvas id="main" width="100%" height="100%">

		<mx:Button id="btn" x="100" y="100" label="点击" click="clickFunction()" />

		<mx:Label id="show" x="100" y="120" />

	</mx:Canvas>

</mx:Application>

<?xml version="1.0" encoding="utf-8"?>

<mx:Application xmlns:mx="http://www.adobe.com/2006/mxml" layout="absolute">

	<mx:Script>

		<![CDATA[

			private function clickFunction():void{

				btn.enabled = false;

				setTimeout(clickBack,30000);//三十秒

			}

			

			private function clickBack():void{

				btn.enabled  = true;

			}

		]]>

	</mx:Script>

	<mx:Canvas id="main" width="100%" height="100%">

		<mx:Button id="btn" label="点击" click="clickFunction()" />

	</mx:Canvas>

</mx:Application>