使用flex4开发一个计算器

<?xml version="1.0" encoding="utf-8"?>
<s:WindowedApplication xmlns:fx="http://ns.adobe.com/mxml/2009" creationComplete="windowedapplication1_creationCompleteHandler()"
					   xmlns:s="library://ns.adobe.com/flex/spark" 
					   xmlns:mx="library://ns.adobe.com/flex/mx">
	<s:layout>
		<s:VerticalLayout horizontalAlign="center" verticalAlign="middle" />
	</s:layout>
	<fx:Script>
		<![CDATA[
			import mx.controls.Alert;
			
			private var num1:Number;					// 前一个数的值
			private var hasOver:Boolean = false;		// 是否按了计算符号
			private var operator:String;				// 运算符
			
			protected function windowedapplication1_creationCompleteHandler():void
			{
				hasOver = false;
				result.text="0";
				operator = "";
			}
			
			private function showNumber(str:String):void {
				if(str == ‘.‘ && result.text.indexOf(".") != -1) return;
				if(result.text.length >= 9)	return;
				if(result.text == "0" && str == "0")	return;
				if(result.text == "NaN" || result.text == "0") {
					result.text = "";
				}
				result.text += str;
				hasOver = false;
			}
			
			private function saveNumber(oper:String):void {	
				if(hasOver && oper == "-") {
					result.text = "-";
					return;
				}
				num1 = Number(result.text);
				result.text = "0";
				hasOver = true;
				operator = oper;
			}
					
			private function calculate():void {
				switch(operator) {
					case "+":
						result.text = String(num1 + Number(result.text));
						break;
					case "-":
						result.text = String(num1 - Number(result.text));
						break;
					case "*":
						result.text = String(num1 * Number(result.text));
						break;
					case "/":
						result.text = result.text == "0" ? "NaN" : String(num1 / Number(result.text));
						break;
					default:
						break;
				}
			}
			
			private function simpleCal(type:String):void {
				switch(type) {
					case "sqrt":
						result.text = String(Math.sqrt(Number(result.text)));
						break;
					case "square":
						result.text = String(Math.pow(Number(result.text), 2));
						break;
					case "divided":
						result.text = result.text == "0" ? "NaN" : String(1 / Number(result.text));
						break;
					default:
						break;
				}
			}
		]]>
	</fx:Script>
	<fx:Declarations>
		<!-- 将非可视元素（例如服务、值对象）放在此处 -->
	</fx:Declarations>
	<!--布局：Panel-->
	<s:Panel width="220" height="260" title="计算器">
		<s:layout>
			<s:VerticalLayout horizontalAlign="center" verticalAlign="middle" />
		</s:layout>
		<s:TextInput id="result" width="80%" height="25"/>
		<s:HGroup width="100%" height="30" paddingLeft="5" paddingRight="5" verticalAlign="middle" horizontalAlign="center">		<!-- paddingLeft左边距 paddingRight右边距 -->
			<s:Button width="40" label="S" click="simpleCal(‘sqrt‘)"/>		<!--求平方根-->
			<s:Button width="40" label="G" click="simpleCal(‘square‘)"/>	<!--求平方-->
			<s:Button width="40" label="N" click="simpleCal(‘divided‘)"/>	<!--求1/N-->
			<s:Button width="40" label="C" click="windowedapplication1_creationCompleteHandler()"/>
		</s:HGroup>
		<s:HGroup width="100%" height="30" paddingLeft="5" paddingRight="5" verticalAlign="middle" horizontalAlign="center">		<!-- paddingLeft左边距 paddingRight右边距 -->
			<s:Button width="40" label="1" click="showNumber(‘1‘)"/>
			<s:Button width="40" label="2" click="showNumber(‘2‘)"/>
			<s:Button width="40" label="3" click="showNumber(‘3‘)"/>
			<s:Button width="40" label="=" click="calculate()"/>
		</s:HGroup>
		<s:HGroup width="100%" height="30" paddingLeft="5" paddingRight="5" verticalAlign="middle" horizontalAlign="center">		<!-- paddingLeft左边距 paddingRight右边距 -->
			<s:Button width="40" label="4" click="showNumber(‘4‘)"/>
			<s:Button width="40" label="5" click="showNumber(‘5‘)"/>
			<s:Button width="40" label="6" click="showNumber(‘6‘)"/>
			<s:Button width="40" label="+" click="saveNumber(‘+‘)"/>
		</s:HGroup>
		<s:HGroup width="100%" height="30" paddingLeft="5" paddingRight="5" verticalAlign="middle" horizontalAlign="center">		<!-- paddingLeft左边距 paddingRight右边距 -->
			<s:Button width="40" label="7" click="showNumber(‘7‘)"/>
			<s:Button width="40" label="8" click="showNumber(‘8‘)"/>
			<s:Button width="40" label="9" click="showNumber(‘9‘)"/>
			<s:Button width="40" label="-" click="saveNumber(‘-‘)"/>
		</s:HGroup>
		<s:HGroup width="100%" height="30" paddingLeft="5" paddingRight="5" verticalAlign="middle" horizontalAlign="center">		<!-- paddingLeft左边距 paddingRight右边距 -->
			<s:Button width="40" label="0" click="showNumber(‘0‘)"/>
			<s:Button width="40" label="." click="showNumber(‘.‘)"/>
			<s:Button width="40" label="/" click="saveNumber(‘/‘)"/>
			<s:Button width="40" label="*" click="saveNumber(‘*‘)"/>
		</s:HGroup>
	</s:Panel>
</s:WindowedApplication>