<?xml version="1.0" encoding="utf-8"?>
<s:Skin xmlns:fx="http://ns.adobe.com/mxml/2009" xmlns:s="library://ns.adobe.com/flex/spark" 
        xmlns:fb="http://ns.adobe.com/flashbuilder/2009" 
		alpha.disabled="0.5" xmlns:skins="org.corlan.dialog.skins.*">
    
    <fx:Metadata>
    <![CDATA[ 
        /** 
         * @copy spark.skins.spark.ApplicationSkin#hostComponent
         */
        [HostComponent("spark.components.SkinnablePopUpContainer")]
    ]]>
    </fx:Metadata> 
    
    <s:states>
        <s:State name="normal"/>
        <s:State name="disabled"/>
        <s:State name="closed" stateGroups="closedGroup"/>
        <s:State name="disabledAndClosed" stateGroups="closedGroup"/>
    </s:states>
    
    <!-- Transitions for open and close -->
    <s:transitions>
        <s:Transition fromState="closed" toState="normal" autoReverse="true">
            <s:Fade duration="150" target="{chrome}"/>
        </s:Transition>

        <s:Transition fromState="disabledAndClosed" toState="disabled" autoReverse="true">
            <s:Fade duration="150" target="{chrome}"/>
        </s:Transition>
        
        <s:Transition fromState="normal" toState="closed" autoReverse="true">
            <s:Fade duration="150" target="{chrome}"/>
        </s:Transition>

        <s:Transition fromState="disabled" toState="disabledAndClosed" autoReverse="true">
            <s:Fade duration="150" target="{chrome}"/>
        </s:Transition>
    </s:transitions>
        
    <!--- Defines the background and content group used by this skin. -->
    <s:Group id="chrome" left="0" right="0" top="0" bottom="0" visible.closedGroup="false">
        <!--- 
		Defines the appearance of the SkinnablePopUpContainer class's background. 
		In this case a FXG file is used to draw the background.
		-->
		<skins:BackGroundAlert id="background" left="0" right="0" top="0" bottom="0"/>
        <!--- @copy spark.components.SkinnableContainer#contentGroup -->
        <s:Group id="contentGroup" left="0" right="0" top="0" bottom="0" minWidth="0" minHeight="0">
            <s:layout>
                <s:BasicLayout/>
            </s:layout>
        </s:Group>
    </s:Group>
    
</s:Skin>

http://corlan.org/?p=3088

SkinnablePopUpContainer Skin Class

mobile, Flex

ActionScript 3