<?xml version="1.0" encoding="utf-8"?>
<!-- http://blog.flexexamples.com/2008/09/26/setting-a-custom-label-function-on-a-piechart-in-flex/ -->
<mx:Application name="PieSeries_labelFunction_test"
        xmlns:mx="http://www.adobe.com/2006/mxml"
        layout="vertical"
        verticalAlign="middle"
        backgroundColor="white" viewSourceURL="srcview/index.html">

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

            private function pieSeries_labelFunc(item:Object, field:String, index:Number, percentValue:Number):String {
                return StringUtil.substitute("{0} ({1}%)",
                            item.@label,
                            percentValue.toFixed(1));
            }
        ]]>
    </mx:Script>

    <mx:XMLListCollection id="dp">
        <mx:source>
            <mx:XMLList>
                <product label="Product 1" data="3" />
                <product label="Product 2" data="1" />
                <product label="Product 3" data="4" />
                <product label="Product 4" data="1" />
                <product label="Product 5" data="5" />
                <product label="Product 6" data="9" />
            </mx:XMLList>
        </mx:source>
    </mx:XMLListCollection>

    <mx:Panel styleName="opaquePanel"
            width="100%"
            height="100%">
        <mx:PieChart id="pieChart"
                dataProvider="{dp}"
                showDataTips="false"
                height="100%"
                width="100%">
            <mx:series>
                <mx:PieSeries id="pieSeries"
                        field="@data"
                        nameField="@label"
                        labelPosition="callout"
                        labelFunction="pieSeries_labelFunc" />
            </mx:series>
        </mx:PieChart>
        <mx:ControlBar width="100%">
            <mx:Legend dataProvider="{pieChart}"
                    direction="horizontal"
                    horizontalGap="100"
                    width="100%" />
        </mx:ControlBar>
    </mx:Panel>

</mx:Application>