<?xml version="1.0" encoding="utf-8"?>
<!-- http://blog.flexexamples.com/2008/04/27/setting-a-custom-tool-tip-field-on-a-buttonbar-control-in-flex/ -->
<mx:Application xmlns:mx="http://www.adobe.com/2006/mxml"
        layout="vertical"
        verticalAlign="middle"
        backgroundColor="white" viewSourceURL="srcview/index.html">

    <mx:Array id="arr">
        <mx:Object label="Accordion"
                toolTip="Le Accordion"
                icon="@Embed('assets/Accordion.png')" />
        <mx:Object label="ApplicationControlBar"
                toolTip="Le ApplicationControlBar"
                icon="@Embed('assets/ApplicationControlBar.png')" />
        <mx:Object label="Box"
                toolTip="Le Box"
                icon="@Embed('assets/Box.png')" />
        <mx:Object label="Canvas"
                toolTip="Le Canvas"
                icon="@Embed('assets/Canvas.png')" />
        <mx:Object label="ControlBar"
                toolTip="Le ControlBar"
                icon="@Embed('assets/ControlBar.png')" />
    </mx:Array>

    <mx:ButtonBar id="buttonBar"
            dataProvider="{arr}"
            labelField="label"
            toolTipField="toolTip"
            height="32" />

</mx:Application>