flex模拟登陆验证

<?xml version="1.0" encoding="utf-8"?>
<mx:Application xmlns:mx="http://www.adobe.com/2006/mxml" layout="absolute" creationComplete="initApp()">
        <mx:states>
            <!--新建“index”State-->
                <mx:State name="index">
                    <!--移除“登录框”-->
                        <mx:RemoveChild target="{panel1}"/>
                        <!--添加新的组件-->
                        <mx:AddChild position="lastChild">
                                <mx:Label x="231" y="174" text="欢迎来到主页" fontFamily="Georgia" fontSize="20" />
                        </mx:AddChild>
                </mx:State>
        </mx:states>
        <mx:Script>
                <![CDATA[
                    import mx.controls.Alert;
                    private function initApp():void
                    {
                            //显示校验码
                       lblCheckCode.text=GenerateCheckCode();
                    }
                        private function loginHandle():void
                        {
                                //空的情况
                                if(txtUsername.text==""||txtPassword.text=="")
                                {
                                        Alert.show("请输入完整数据!");
                                }
                                else
                                {
                                        //合法用户
                                        if(txtUsername.text=="Administrator"&&txtPassword.text=="123456"&&txtCheckCode.text.toLocaleLowerCase()==lblCheckCode.text.toLowerCase())
                                        {
                                                currentState="index";
                                        }
                                        //登录失败
                                        else
                                        {
                                                //校验码错误
                                                if(txtCheckCode.text.toLowerCase()!=lblCheckCode.text.toLowerCase())
                                            {
                                               Alert.show("校验码错误!");
                                               //重新生成校验码
                                               lblCheckCode.text=GenerateCheckCode();
                                            }
                                            //用户名或密码错误
                                            else
                                                  Alert.show("用户名或密码错误!");
                                        }
                                }
                        }
                        private function resetHandle():void
                        {
                                txtUsername.text="";
                                txtPassword.text="";
                                txtCheckCode.text="";
                        }

            //生成随机码
                        private function GenerateCheckCode():String
                        {
                                //初始化
                                var ran:Number;
                                var number:Number;
                                var  code:String;
                                var checkCode:String ="";
                                //生成四位随机数
                                for(var i:int=0; i<4; i++)
                                {
                                        //Math.random生成数为类似为0.1234
                                        ran=Math.random();
                                        number =Math.round(ran*10000);
                                        //如果是2的倍数生成一个数字
                                        if(number % 2 == 0)
                                          //"0"的ASCII码是48
                                          code = String.fromCharCode(48+(number % 10));
                                        //生成一个字母
                                        else
                                          //"A"的ASCII码为65
                                          code = String.fromCharCode(65+(number % 26)) ;
                                        checkCode += code;
                                }
                                return checkCode;
                        }

                ]]>
        </mx:Script>
        <mx: Panel x="108" y="71" width="349" height="257" layout="absolute" title="用户登录" fontFamily="Georgia" fontSize="12" id="panel1">
                <!--  "用户名"标签  -->
                <mx:Label x="41.5" y="33" text="用户名"/>
                <!--  "密码"标签  -->
                <mx:Label x="42.5" y="81" text="密码"/>
                <!--  "用户名"输入框  -->
                <mx:TextInput x="94.5" y="33" id="txtUsername"/>
                <!--  "密码"输入框  -->
                <mx:TextInput x="95.5" y="81" id="txtPassword" displayAsPassword="true"/>
                <!--  "登录"按钮  -->
                <mx:Button x="82.5" y="159" label="登录" id="btnLogin" click="loginHandle()"/>
        <!--  "重置"按钮  -->
                <mx:Button x="181.5" y="159" label="重置" id="btnReset" click="resetHandle()"/>
                <!--  "校验码"标签  -->
                <mx:Label x="165.5" y="125" id="lblCheckCode" width="42.5" color="#377CD0"/>
                <mx:LinkButton x="216" y="123" label="看不清楚?" id="linkbtnReGenerate" click="lblCheckCode.text=GenerateCheckCode();" fontFamily="Georgia" fontSize="11"/>
                <mx:Label x="39.5" y="123" text="校验码"/>
                <!--  "校验码"输入框  -->
                <mx:TextInput x="96.5" y="121" id="txtCheckCode" width="61" maxChars="4"/>
        </mx:Panel>
</mx:Application>