AddChildAction  - AS3 Flex

<?xml version="1.0" ?>
<!-- Simple example to demonstrate the Transition class. -->
<s:Application xmlns:fx="http://ns.adobe.com/mxml/2009"
    xmlns:s="library://ns.adobe.com/flex/spark"
    xmlns:mx="library://ns.adobe.com/flex/mx" currentState="Login">
 
    <!-- Define the view states -->
    <s:states>
        <s:State name="Login" />
        <s:State name="Register" />
    </s:states>

    <s:transitions>
        <!-- Define the transition from the base state to the Register state.-->
        <s:Transition id="toRegister" fromState="*" toState="Register">
            <s:Sequence targets="{[loginPanel, registerLink, confirm, loginLink]}">
                <s:RemoveAction />
                <s:Fade />
                <s:SetAction target="{loginPanel}" property="title" />
                <s:SetAction target="{loginButton}" property="label" />
                <s:SetAction target="{loginButton}" property="color" />
                <s:Resize target="{loginPanel}"/>
                <s:AddAction />
                <s:Fade />
            </s:Sequence>
        </s:Transition>

        <!-- Define the transition from the Register state to the base state.-->
        <s:Transition id="toDefault" fromState="Register" toState="*">
            <s:Sequence targets="{[loginPanel, registerLink, 
                    confirm, loginLink]}">
                <s:RemoveAction/>
                <s:SetAction target="{loginPanel}" property="title"/>
                <s:SetAction  target="{loginButton}" property="label"/>
                <s:SetAction target="{loginButton}" property="color"/>
                <s:Resize target="{loginPanel}"/>
                <s:AddAction/>
            </s:Sequence>
        </s:Transition>
    </s:transitions>

    <!-- Define a Panel container that defines the login form. The title of the Panel
         changes depending on the state. -->
    <s:Panel title="Login" title.Register="Register" id="loginPanel" 
            width="75%" horizontalCenter="0" verticalCenter="0">
    <s:controlBarLayout >
        <s:BasicLayout />
    </s:controlBarLayout>
    <s:layout>
        <s:VerticalLayout paddingTop="10" paddingBottom="10" paddingRight="10" paddingLeft="10" />
    </s:layout>
        <s:Label color="blue" width="100%"
            text="Click the 'Need to Register?' link to change state. Click the 'Return to Login' link to return to the base state."/>

        <!-- The following form has  two TextInputs in the Login state and three TextInputs
             in the Register state. -->
        <s:Form id="loginForm" >
            <s:FormItem label="Username:">
                <s:TextInput/>
            </s:FormItem>
            <s:FormItem label="Password:">
                <s:TextInput/>
            </s:FormItem>
            <s:FormItem id="confirm" label="Confirm:" includeIn="Register" includeInLayout="false" includeInLayout.Register="true">
                <s:TextInput/>
            </s:FormItem>
        </s:Form>
       
        <!-- The controlBar includes two visible items in each state. Which LinkButton is visible is determined
             by the state -->
        <s:controlBarContent>
            <mx:LinkButton id="registerLink"  label="Need to Register?" top="10" bottom="10"
                click="currentState='Register'" left="10" includeIn="Login" />
            <mx:LinkButton id="loginLink" label="Return to Login" click="currentState=''" includeIn="Register" left="10"  top="10" bottom="10"/>
            <s:Button label="Login" label.Register="Register" id="loginButton" right="10" color.Register="0x0000FF"  top="10" bottom="10"/>
        </s:controlBarContent>
    </s:Panel>
</s:Application>