數據驗證
內置Validator類
<?xml version="1.0" encoding="utf-8"?>
<mx:Application xmlns:mx="http://www.adobe.com/2006/mxml"
   backgroundColor="#FFFFFF" width="550" height="300">
  
  <mx:Validator required="true" source="{fnametxt}" property="text"
    trigger="{validatebtn}" triggerEvent="click" listener="{fnametxt}"/>
  <mx:Validator required="true" source="{lnametxt}" property="text"
    trigger="{validatebtn}" triggerEvent="click" listener="{lnametxt}"/>
  <mx:Validator required="true" source="{addresstxt}" property="text"
    trigger="{validatebtn}" triggerEvent="click" listener="{addresstxt}"/>
  <mx:Validator required="true" source="{citytxt}" property="text"
    trigger="{validatebtn}" triggerEvent="click" listener="{citytxt}"/>
  <mx:Validator required="true" source="{statetxt}" property="text"
    trigger="{validatebtn}" triggerEvent="click" listener="{statetxt}"/> 
  <mx:ZipCodeValidator required="true" source="{ziptxt}" property="text"
    trigger="{validatebtn}" triggerEvent="click" listener="{ziptxt}"/>
  <mx:EmailValidator source="{emailtxt}" property="text"
    trigger="{validatebtn}" triggerEvent="click" listener="{emailtxt}"/>
  <mx:PhoneNumberValidator source="{phonetxt}" property="text"
    trigger="{validatebtn}" triggerEvent="click" listener="{phonetxt}"/>
   
  <mx:Panel title="Contact Info" width="500" height="250">
  <mx:Form>
    <mx:FormItem label="Name" direction="horizontal">
      <mx:TextInput id="fnametxt" />
      <mx:TextInput id="lnametxt" />
    </mx:FormItem>
    <mx:FormItem label="Address">
      <mx:TextInput id="addresstxt"/>
    </mx:FormItem>
    <mx:FormItem label="City State, Zip" direction="horizontal">
      <mx:TextInput id="citytxt"/>
      <mx:TextInput id="statetxt" width="20"/>
      <mx:TextInput id="ziptxt" width="50"/>
    </mx:FormItem>
    <mx:FormItem label="Phone">
      <mx:TextInput id="phonetxt"/>
    </mx:FormItem>
    <mx:FormItem label="Email">
      <mx:TextInput id="emailtxt"/>
    </mx:FormItem>
    <mx:Button id="validatebtn" label="Validate"/>
  </mx:Form>
  </mx:Panel>
</mx:Application>

使用errorString進行數據驗證
如果Flex自帶的驗證組件無法滿足要求，可用ActionScript自定義，errorString屬性將以默認的紅色邊框和包括錯誤信息顯示
<?xml version="1.0" encoding="utf-8"?>
<mx:Application xmlns:mx="http://www.adobe.com/2006/mxml"
   backgroundColor="#FFFFFF" width="300" height="150">
   <mx:Script>
    <![CDATA[
     private function validate():void{
       // check for length of 10
       if(myText.text.length < 10){
         // assign errorString to TextInput
         myText.errorString = "This field requires at least 100 characters";
       } else {
         // remove errorString
         myText.errorString = null;
       }
     }
     ]]>
   </mx:Script>
   <mx:Panel title="Simple AS Validate" width="210" height="75">
     <mx:HBox width="100%" height="100%" paddingLeft="3" paddingTop="3">
       <mx:TextInput id="myText" width="100"/>
       <mx:Button label="Validate" click="validate()" />
     </mx:HBox>
   </mx:Panel>
</mx:Application>