flex制作一个用户登录框(含验证码)

<?xml version="1.0" encoding="utf-8"?>
<mx:Application xmlns:mx="http://www.adobe.com/2006/mxml" layout="absolute"
             fontSize="12" horizontalAlign="center" creationComplete="init()">
             
 <mx:Script>
  <![CDATA[
   import mx.controls.Alert;
   
   private function init():void{
    generate.text=generateCheckCode();
   }
   
   //login identifying 
   private function loginHandler():void{
      if(user.text==""||pass.text==""){
       Alert.show("user or pass is empty","tips");
      }else{
       if(user.text=="shane"&&pass.text=="shane"
          &&identify.text.toLowerCase()==generate.text.toLowerCase()){
           
        Alert.show("login is OK","tips");
           currentState="hollow";
        
       }else{
        if(identify.text.toLowerCase()!=generate.text.toLowerCase()){
          Alert.show("indentifyCode is error","tips");
          generate.text=generateCheckCode();
        }else{
        Alert.show("user or pass error","tips");
        }
       }
      }
   }
   
   
   //clear 
   private function clearHandler():void{
    user.text=pass.text="";
   }
   
   //generate identifying coder
   
   private function generateCheckCode():String{
    //init
    var num:Number;
    var code:String;
    var checkCode:String="";
    
    for(var i:int=0;i<5;i++){
     num=Math.round(Math.random()*100000);
     if(num%2==0){
      code=String.fromCharCode(48+(num%10));
     }else{
      code=String.fromCharCode(65+(num%26));
     }
     checkCode +=code;
    }
    return checkCode;
   }
  ]]>
 </mx:Script>
             
 <mx:Panel id="panel" x="143" y="115" width="350" height="229" layout="absolute" title="login">
 
  <mx:Button id="btnLogin" x="73" y="141" label="login" click="loginHandler()"/>
  <mx:Button id="btnClear" x="167" y="141" label="clear" click="clearHandler()"/>
  
  <mx:Label x="44" y="31" text="user"/>
  <mx:Label x="44" y="64" text="pass"/>
  
  <mx:TextInput id="user" x="81" y="31"/>
  <mx:TextInput id="pass" x="81" y="62" displayAsPassword="true"/>
  <mx:Text x="28" y="100" text="identify"/>
  <mx:TextInput x="81" y="98" width="50" id="identify"/>
  <mx:Label x="139" y="100" width="48" id="generate"/>
  <mx:Label x="195" y="100" text="看不清楚 换个~~" click="generateCheckCode()"/>
  
 </mx:Panel>
 
   <mx:states>
    <mx:State name="hollow">
     <mx:RemoveChild target="{panel}"/>
     <mx:AddChild position="lastChild">
      <mx:Label text="hollow marshane" x="0" y="200" fontSize="200" color="red"/>
     </mx:AddChild>
    </mx:State>
   </mx:states>
 
</mx:Application>