简单表单布局及验证

<?xml version="1.0" encoding="utf-8"?>
<mx:Application xmlns:mx="http://www.adobe.com/2006/mxml" layout="absolute">
    <mx:Script>
        <![CDATA[
            import mx.controls.Alert;
            private function clearInputValue():void{
                _username.text = "";
                _pas.text = "";
                _email.text = "";
                radiogroup1.selectedValue = "男";
            }
            
            private function showInputValue():void{
                var str:String = _username.text + "\r";
                str += _pas.text + "\r";
                str += this.radiogroup1.selectedValue + "\r";
                str += _email.text;
                Alert.show(str);
            } 
        ]]>
    </mx:Script>
    <mx:Panel x="86" y="54" width="306" height="284" layout="absolute" title="用户注册">
        <mx:Form x="10" y="10">
            <mx:FormHeading label="用户资料"/>
            <mx:FormItem label="用户名称" required="true">
                <mx:TextInput id="_username"/>
            </mx:FormItem>
            <mx:FormItem label="用户口令">
                <mx:TextInput id="_pas" displayAsPassword="true"/>
            </mx:FormItem>
            <mx:FormItem label="性别">
                <mx:HBox width="100%">
                    <mx:RadioButtonGroup id="radiogroup1"/>
                    <mx:RadioButton label="男" groupName="radiogroup1" selected="true"/>
                    <mx:RadioButton label="女" groupName="radiogroup1"/>
                </mx:HBox>
            </mx:FormItem>
            <mx:FormItem label="邮箱">
                <mx:TextInput id="_email"/>
            </mx:FormItem>
            <mx:FormItem>
                <mx:HBox width="100%">
                    <mx:Button label="注册" click="showInputValue();"/>
                    <mx:Button label="重写" click="clearInputValue();"/>
                </mx:HBox>
            </mx:FormItem>
        </mx:Form>
    </mx:Panel>
    <mx:StringValidator source="{_username}" property="text" requiredFieldError="用户名称不能为空!" />
    <mx:EmailValidator source="{_email}" property="text" /> 
</mx:Application>