用flash builder4做一个带验证码的用户登录框

1、用panel,label,button,textinput组建布局，如下图：
 
2、设用户名、密码、验证码所对应的textinput的id分别为userName、pasWord、inVal;设用于显示验证码的label组建的id为：val.
     布局代码如下：
 <s:Panel x="126" y="98" width="250" height="200" id="login" title="用户登录" includeIn="login">
  <s:Label x="26" y="21" text="用户名："/>
  <s:Label x="26" y="51" text="密    码："/>
  <s:TextInput id="userName" x="82" y="19"/>
  <s:TextInput id="pasWord" x="82" y="46"/>
  <s:Button x="26" y="104" label="提交"/>
  <s:Button x="140" y="104" label="重设" />
  <s:Label x="26" y="79" text="验证码："/>
  <s:TextInput x="82" y="73" width="52" id="inVal"/>
  <s:Label x="140" y="80" id="val" color="red"/>
  <s:Button x="178" y="73" label="换" width="32"/>
 </s:Panel>
3、生成4位随机数：
  protected function valdetorNumber():String
   {
    var digtal1:Number;
    var digtal2:Number;
    var str1:Number;
    var str2:Number;
    var code:String;
    digtal1=Math.random()*10;
    digtal2=Math.random()*10;
    str1=Math.random()*26;
    str2=Math.random()*26;
    code=String.fromCharCode(65+str1)+String.fromCharCode(48+digtal1)
         +String.fromCharCode(65+str2)+String.fromCharCode(48+digtal2);
    
    return code;
   }
 4、将随机数绑定到val：
protected function initApp():void
   {
    val.text=valdetorNumber();
   }
5、网页加载时运行initApp()函数：
 <s:App