Setting a custom label function on a PieChart in Flex

The following example shows how you can set a custom label function on a Flex PieChart control by setting the labelFunction property on the PieSeries object.

Full code after the jump.

View MXML

<?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">

    <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>

View source is enabled in the following example.

Due to popular demand, here is the “same” example in a more ActionScript friendly format:

View MXML

<?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"
        initialize="init();">

    <mx:Script>
        <![CDATA[
            import mx.charts.Legend;
            import mx.charts.PieChart;
            import mx.charts.chartClasses.Series;
            import mx.charts.series.PieSeries;
            import mx.collections.XMLListCollection;
            import mx.containers.ControlBar;
            import mx.containers.Panel;
            import mx.containers.TileDirection;
            import mx.utils.StringUtil;

            private var dp:XMLListCollection;
            private var legend:Legend;
            private var panel:Panel;
            private var pieChart:PieChart;
            private var pieSeries:PieSeries;

            private function init():void {
                var productsXML:XML = <products>
                            <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" />
                        </products>;

                dp = new XMLListCollection(productsXML.product);

                pieSeries = new PieSeries();
                pieSeries.field = "@data";
                pieSeries.nameField = "@label";
                pieSeries.labelFunction = pieSeries_labelFunc;
                pieSeries.setStyle("labelPosition", "callout");

                pieChart = new PieChart();
                pieChart.dataProvider = dp;
                pieChart.showDataTips = false;
                pieChart.percentWidth = 100;
                pieChart.percentHeight = 100;
                pieChart.series = [pieSeries];

                legend = new Legend();
                legend.dataProvider = pieChart;
                legend.direction = TileDirection.HORIZONTAL;
                legend.setStyle("horizontalGap", 100);
                legend.percentWidth = 100;

                var controlBar:ControlBar = new ControlBar();
                controlBar.percentWidth = 100;
                controlBar.addChild(legend);

                panel = new Panel();
                panel.styleName = "opaquePanel";
                panel.percentWidth = 100;
                panel.percentHeight = 100;
                panel.addChild(pieChart);
                panel.addChild(controlBar);
                addChild(panel);
            }

            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:Application>