<?xml version="1.0" encoding="utf-8"?>
<!-- http://blog.flexexamples.com/2008/01/07/setting-the-button-corner-radius-in-a-flex-buttonbar-control/ -->
<mx:Application xmlns:mx="http://www.adobe.com/2006/mxml"
        layout="vertical"
        verticalAlign="middle"
        backgroundColor="white" viewSourceURL="srcview/index.html">

    <mx:Style>
        .myCustomButtonStyleName {
            cornerRadius: 16;
        }
    </mx:Style>

    <mx:Array id="arr">
        <mx:Object label="Button" />
        <mx:Object label="ButtonBar" />
        <mx:Object label="CheckBox" />
        <mx:Object label="ColorPicker" />
    </mx:Array>

    <mx:ButtonBar id="buttonBar"
            buttonStyleName="myCustomButtonStyleName"
            dataProvider="{arr}"
            height="32" />

</mx:Application>