Flex中用state来表示不同的状态的经典的例子

<?xml version="1.0" encoding="utf-8"?>
<mx:Application xmlns:mx="http://www.adobe.com/2006/mxml">

<mx:states>
<mx:State name="Register">
<mx:AddChild relativeTo="{loginForm}" position="lastChild">
<mx:target>
<mx:FormItem id="confirm" label="Confirm:">
<mx:TextInput/>
</mx:FormItem>
</mx:target>
</mx:AddChild>
<mx:SetProperty target="{loginPanel}" name="title" value="Register"/>
<mx:SetProperty target="{loginButton}" name="label" value="Register"/>
<mx:SetStyle target="{loginButton}"
name="color" value="blue"/>
<mx:RemoveChild target="{registerLink}"/>
<mx:AddChild relativeTo="{spacer1}" position="before">
<mx:target>
<mx:LinkButton id="loginLink" label="Return to Login" click="currentState=''"/>
</mx:target>
</mx:AddChild>
</mx:State>
</mx:states>

<!-- Define a Panel container that defines the login form.-->
<mx:Panel title="Login" id="loginPanel"
horizontalScrollPolicy="off" verticalScrollPolicy="off"
paddingTop="10" paddingLeft="10" paddingRight="10" paddingBottom="10">

<mx:Text width="100%" color="blue"
text="Click the 'Need to Register?' link to change state. Click the 'Return to Login' link to return to the base state."/>

<mx:Form id="loginForm" >
<mx:FormItem label="Username:">
<mx:TextInput/>
</mx:FormItem>
<mx:FormItem label="Password:">
<mx:TextInput displayAsPassword="true"/>
</mx:FormItem>
</mx:Form>
<mx:ControlBar>
<mx:LinkButton id="registerLink"   label="Need to Register?"
click="currentState='Register'"/>
<mx:Spacer width="100%" id="spacer1"/>
<mx:Button label="Login" id="loginButton"/>
</mx:ControlBar>
</mx:Panel>

</mx:Application>