Creating a linear gradient fill on a ColumnChart control’s column series in Flex

The following example shows how you can create a linear gradient fill for a ColumnSeries in Flex.

Full code after the jump.

View MXML

<?xml version="1.0"?>
<!-- http://blog.flexexamples.com/2007/11/20/creating-a-linear-gradient-fill-on-a-columnchart-controls-column-series-in-flex/ -->
<mx:Application xmlns:mx="http://www.adobe.com/2006/mxml"
        layout="vertical"
        verticalAlign="middle"
        backgroundColor="white">

    <mx:Script>
        <![CDATA[
            import mx.charts.chartClasses.IAxis;

            private function linearAxis_labelFunc(item:Object, prevValue:Object, axis:IAxis):String {
                return currencyFormatter.format(item);
            }

            private function categoryAxis_labelFunc(item:Object, prevValue:Object, axis:CategoryAxis, categoryItem:Object):String {
                var datNum:Number = Date.parse(item);
                var tempDate:Date = new Date(datNum);
                return dateFormatter.format(tempDate).toUpperCase();
            }
        ]]>
    </mx:Script>

    <mx:DateFormatter id="dateFormatter" formatString="DD" />
    <mx:CurrencyFormatter id="currencyFormatter" precision="2" />

    <mx:XMLListCollection id="dp">
        <mx:source>
            <mx:XMLList>
                <quote date="8/1/2007" open="40.29" close="39.58" />
                <quote date="8/2/2007" open="39.4" close="39.52" />
                <quote date="8/3/2007" open="39.47" close="38.75" />
                <quote date="8/6/2007" open="38.71" close="39.38" />
                <quote date="8/7/2007" open="39.08" close="39.42" />
                <quote date="8/8/2007" open="39.61" close="40.23" />
                <quote date="8/9/2007" open="39.9" close="40.75" />
                <quote date="8/10/2007" open="41.3" close="41.06" />
                <quote date="8/13/2007" open="41" close="40.83" />
                <quote date="8/14/2007" open="41.01" close="40.41" />
                <quote date="8/15/2007" open="40.22" close="40.18" />
                <quote date="8/16/2007" open="39.83" close="39.96" />
                <quote date="8/17/2007" open="40.18" close="40.32" />
                <quote date="8/20/2007" open="40.55" close="40.74" />
                <quote date="8/21/2007" open="40.41" close="40.13" />
                <quote date="8/22/2007" open="40.4" close="40.77" />
                <quote date="8/23/2007" open="40.82" close="40.6" />
                <quote date="8/24/2007" open="40.5" close="40.41" />
                <quote date="8/27/2007" open="40.38" close="40.81" />
            </mx:XMLList>
        </mx:source>
    </mx:XMLListCollection>

    <mx:ColumnChart id="columnChart"
            showDataTips="true"
            dataProvider="{dp}"
            width="100%"
            height="100%">

        <!-- vertical axis -->
        <mx:verticalAxis>
            <mx:LinearAxis baseAtZero="false"
                    labelFunction="linearAxis_labelFunc" />
        </mx:verticalAxis>

        <!-- horizontal axis -->
        <mx:horizontalAxis>
            <mx:CategoryAxis id="ca"
                    categoryField="@date"
                    title="August 2007"
                    labelFunction="categoryAxis_labelFunc" />
        </mx:horizontalAxis>

        <!-- horizontal axis renderer -->
        <mx:horizontalAxisRenderers>
            <mx:AxisRenderer axis="{ca}"
                    canDropLabels="true" />
        </mx:horizontalAxisRenderers>

        <!-- series -->
        <mx:series>
            <mx:ColumnSeries displayName="Open"
                    xField="@date"
                    yField="@open">
                <mx:fill>
                    <mx:LinearGradient id="linearGradient">
                        <mx:entries>
                            <mx:Array>
                                <mx:GradientEntry color="red"
                                        ratio="0.0"
                                        alpha="1.0" />
                                <mx:GradientEntry color="black"
                                        ratio="1.0"
                                        alpha="1.0" />
                            </mx:Array>
                        </mx:entries>
                    </mx:LinearGradient>
                </mx:fill>
            </mx:ColumnSeries>
        </mx:series>

        <!-- series filters -->
        <mx:seriesFilters>
            <mx:Array />
        </mx:seriesFilters>
    </mx:ColumnChart>

</mx:Application>

View source is enabled in the following example.

By default, the gradient goes left-to-right, if you want to create a vertical gradient or 45° gradient (or any arbitrary number), you can set the angle property in the LinearGradient tag, as seen in the following snippet:

<mx:LinearGradient id="linearGradient" angle="90">
    <mx:entries>
        <mx:Array>
            <mx:GradientEntry color="red"
                    ratio="0.0"
                    alpha="1.0" />
            <mx:GradientEntry color="black"
                    ratio="1.0"
                    alpha="1.0" />
        </mx:Array>
    </mx:entries>
</mx:LinearGradient>