<?xml version="1.0" encoding="utf-8"?>
<!-- http://blog.flexexamples.com/2007/11/01/creating-unique-identifiers-with-flex/ -->
<mx:Application xmlns:mx="http://www.adobe.com/2006/mxml"
        layout="vertical"
        verticalAlign="middle"
        backgroundColor="white"
        creationComplete="generateUID();">

    <mx:Script>
        <![CDATA[
            import mx.utils.UIDUtil;

            private function generateUID():void {
                lbl.text = UIDUtil.createUID();
            }
        ]]>
    </mx:Script>

    <mx:ApplicationControlBar dock="true">
        <mx:Button id="btn"
                label="Create UID"
                click="generateUID();" />
    </mx:ApplicationControlBar>

    <mx:Label id="lbl"
            fontSize="20"
            selectable="true" />

</mx:Application>