flex计算器

<?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/halo" minWidth="1024" minHeight="768" xmlns:tudou="components.*"><fx:Declarations><!-- Place non-visual elements (e.g., services, value objects) here --></fx:Declarations><fx:Script><![CDATA[import mx.collections.ArrayCollection;import mx.controls.Alert;private var mydp:ArrayCollection=new ArrayCollection([{text:"加法",value:"+"},{text:"减法",value:"-"},{text:"乘法",value:"*"},{text:"除法",value:"/"}]);protected function calc_clickHandler(event:MouseEvent):void{var m:int=this.mark.selectedIndex;var num1:Number=Number(this.firstnum.text);var num2:Number=Number(this.secondnum.text);if(m==-1){Alert.show("请选择运算符","信息");return;}var res:Number;switch(m){case 0:res=num1+num2;break;case 1:res=num1-num2;break;case 2:res=num1*num2;break;case 3:res=num1/num2;break;}this.result.text=res.toFixed(2);}protected function clear_clickHandler(event:MouseEvent):void{this.firstnum.text=null;this.secondnum.text=null;this.result.text=null;this.mark.selectedIndex=-1;}]]></fx:Script><s:Label text="第一个数:" x="171" y="87"/><s:TextInput id="firstnum" x="261" y="82"/><s:Label text="第二个数:" x="171" y="122"/><s:TextInput id="secondnum" x="261" y="122"/><s:Label text=" 结 果:" x="189" y="205"/><s:TextInput id="result" x="261" y="195"/><s:Button label="计算"  x="261" y="244" click="calc_clickHandler(event)"/><s:Button x="382" y="244" label="清空" click="clear_clickHandler(event)"/><tudou:closeWindowBtn /><s:Label x="183" y="153" text="运算符:"/><s:DropDownList x="261" y="153" prompt="--请选择运算符--" width="128" id="mark" dataProvider="{mydp}" labelField="text" selectedIndex="-1"></s:DropDownList></s:Application>