Setting a custom icon on the Spark DropDownList control in Flex 4

The following example shows how you can use a custom icon on the Spark DropDownList control in Flex 4 by creating a custom skin and setting the skinClass style.

The following example(s) require Flash Player 10 and the Adobe Flex 4 SDK. To download the Adobe Flash Builder 4 trial, see www.adobe.com/products/flex/. To download the latest nightly build of the Flex 4 SDK, see opensource.adobe.com/wiki/display/flexsdk/Download+Flex+4.

For more information on getting started with Flex 4 and Flash Builder 4, see the official Adobe Flex Team blog.

<?xml version="1.0" encoding="utf-8"?>
<!-- http://blog.flexexamples.com/2009/04/12/setting-a-custom-icon-on-the-spark-dropdownlist-control-in-flex-gumbo/ -->
<s:Application name="Spark_DropDownList_skinClass_DropDownListButtonSkin_test"
        xmlns:fx="http://ns.adobe.com/mxml/2009"
        xmlns:s="library://ns.adobe.com/flex/spark"
        xmlns="library://ns.adobe.com/flex/mx">
 
    <s:DropDownList id="dropDownList"
            labelField="label"
            requireSelection="true"
            skinClass="skins.CustomDropDownListSkin"
            width="100"
            horizontalCenter="0"
            top="20">
        <s:dataProvider>
            <s:ArrayList>
                <fx:Object label="The" />
                <fx:Object label="Quick" />
                <fx:Object label="Brown" />
                <fx:Object label="Fox" />
                <fx:Object label="Jumps" />
                <fx:Object label="Over" />
                <fx:Object label="The" />
                <fx:Object label="Lazy" />
                <fx:Object label="Dog" />
            </s:ArrayList>
        </s:dataProvider>
    </s:DropDownList>
 
</s:Application>

View source is enabled in the following example.

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Next, create a custom skin for the Spark DropDownList control, skins/CustomDropDownListSkin.mxml:

<?xml version="1.0" encoding="utf-8"?>
<!-- http://blog.flexexamples.com/2009/04/12/setting-a-custom-icon-on-the-spark-dropdownlist-control-in-flex-gumbo/ -->
<s:SparkSkin name="CustomDropDownListSkin"
        xmlns:fx="http://ns.adobe.com/mxml/2009"
        xmlns:s="library://ns.adobe.com/flex/spark"
        xmlns:fb="http://ns.adobe.com/flashbuilder/2009"
        alpha.disabled="0.5">
    <!-- states -->
    <s:states>
        <s:State name="normal" />
        <s:State name="open" />
        <s:State name="disabled" />
    </s:states>
 
    <!-- host component -->
    <fx:Metadata>
        [HostComponent("spark.components.DropDownList")]
    </fx:Metadata>
 
    <fx:Script fb:purpose="styling">
        <![CDATA[
            /* Define the content fill items that should be colored by the "contentBackgroundColor" style. */
            static private const contentFill:Array = ["bgFill"];
 
            override public function get contentItems():Array {
                return contentFill;
            }
 
            override protected function updateDisplayList(unscaledWidth:Number, unscaledHeight:Number):void {
                if (getStyle("borderVisible") == false) {
                    if (border) {
                        border.visible = false;
                    }
                    if (background) {
                        background.left = background.top = background.right = background.bottom = 0;
                    }
                    if (scroller) {
                        scroller.minViewportInset = 0;
                    }
                } else {
                    if (border) {
                        border.visible = true;
                    }
                    if (background) {
                        background.left = background.top = background.right = background.bottom = 1;
                    }
                    if (scroller) {
                        scroller.minViewportInset = 1;
                    }
                }
 
                if (dropShadow) {
                    dropShadow.visible = getStyle("dropShadowVisible");
                }
 
                openButton.setStyle("cornerRadius", getStyle("cornerRadius"));
 
                if (borderStroke) {
                    borderStroke.color = getStyle("borderColor");
                    borderStroke.alpha = getStyle("borderAlpha");
                }
                super.updateDisplayList(unscaledWidth, unscaledHeight);
            }
        ]]>
    </fx:Script>
 
    <s:PopUpAnchor id="popUp"
            displayPopUp.normal="false"
            displayPopUp.open="true"
            includeIn="open"
            left="0" right="0" top="0" bottom="0"
            itemDestructionPolicy="auto"
            popUpPosition="below"
            popUpWidthMatchesAnchorWidth="true">
        <s:Group id="dropDown" maxHeight="134" minHeight="22">
            <s:RectangularDropShadow id="dropShadow"
                    blurX="20" blurY="20"
                    alpha="0.45"
                    distance="7"
                    angle="90"
                    color="#000000"
                    left="0" top="0" right="0" bottom="0" />
            <s:Rect id="border"
                    left="0" right="0" top="0" bottom="0">
                <s:stroke>
                    <s:SolidColorStroke id="borderStroke" weight="1"/>
                </s:stroke>
            </s:Rect>
 
            <!-- fill -->
            <s:Rect id="background"
                    left="1" right="1" top="1" bottom="1">
                <s:fill>
                    <s:SolidColor id="bgFill" color="0xFFFFFF" />
                </s:fill>
            </s:Rect>
 
            <s:Scroller id="scroller"
                    left="0" top="0" right="0" bottom="0"
                    hasFocusableChildren="false"
                    minViewportInset="1">
                <s:DataGroup id="dataGroup"
                        itemRenderer="spark.skins.spark.DefaultItemRenderer">
                    <s:layout>
                        <s:VerticalLayout gap="0" horizontalAlign="contentJustify" />
                    </s:layout>
                </s:DataGroup>
            </s:Scroller>
        </s:Group>
    </s:PopUpAnchor>
 
    <s:Button id="openButton"
            left="0" right="0" top="0" bottom="0"
            focusEnabled="false"
            skinClass="skins.CustomDropDownListButtonSkin" />
 
    <s:Label id="labelDisplay"
            verticalAlign="middle"
            maxDisplayedLines="1"
            mouseEnabled="false" mouseChildren="false"
            left="7" right="30" top="2" bottom="2"
            width="75"
            verticalCenter="1" />
 
</s:SparkSkin>

And finally, a custom skin for the Spark DropDownListButton Button control, skins/CustomDropDownListButtonSkin.mxml:

<?xml version="1.0" encoding="utf-8"?>
<!-- http://blog.flexexamples.com/2009/04/12/setting-a-custom-icon-on-the-spark-dropdownlist-control-in-flex-gumbo/ -->
<s:SparkSkin name="CustomDropDownListButtonSkin"
        xmlns:fx="http://ns.adobe.com/mxml/2009"
        xmlns:s="library://ns.adobe.com/flex/spark"
        xmlns:fb="http://ns.adobe.com/flashbuilder/2009"
        minWidth="21" minHeight="21">
 
    <!-- states -->
    <s:states>
        <s:State name="up" />
        <s:State name="over" />
        <s:State name="down" />
        <s:State name="disabled" />
    </s:states>
 
    <fx:Metadata>
        [HostComponent("spark.components.Button")]
    </fx:Metadata>
 
    <fx:Script fb:purpose="styling">
        <![CDATA[
            static private const exclusions:Array = ["arrow"];
 
            override public function get colorizeExclusions():Array {
                return exclusions;
            }
 
            static private const symbols:Array = [];
 
            override public function get symbolItems():Array {
                return symbols;
            }
 
            override protected function initializationComplete():void {
                useChromeColor = true;
                super.initializationComplete();
            }
 
            override protected function updateDisplayList(unscaledWidth:Number, unscaledHeight:Number):void {
                var cr:Number = getStyle("cornerRadius");
 
                if (cornerRadius != cr) {
                    cornerRadius = cr;
                    shadow.radiusX = cornerRadius;
                    fill.radiusX = cornerRadius;
                    lowlight.radiusX = cornerRadius;
                    highlight.radiusX = cornerRadius;
                    border.radiusX = cornerRadius;
                }
 
                if (highlightStroke) {
                    highlightStroke.radiusX = cornerRadius;
                }
                if (hldownstroke1) {
                    hldownstroke1.radiusX = cornerRadius;
                }
                if (hldownstroke2) {
                    hldownstroke2.radiusX = cornerRadius;
                }
 
                super.updateDisplayList(unscaledWidth, unscaledHeight);
            }
 
            private var cornerRadius:Number = 2;
        ]]>
    </fx:Script>
 
    <!-- layer 1: shadow -->
    <s:Rect id="shadow" left="-1" right="-1" top="-1" bottom="-1" radiusX="2">
        <s:fill>
            <s:LinearGradient rotation="90">
                <s:GradientEntry color="0x000000" color.down="0xFFFFFF" alpha="0.01" alpha.down="0" />
                <s:GradientEntry color="0x000000" color.down="0xFFFFFF" alpha="0.07" alpha.down="0.5" />
            </s:LinearGradient>
        </s:fill>
    </s:Rect>
 
    <!-- layer 2: fill -->
    <s:Rect id="fill" left="1" right="1" top="1" bottom="1" radiusX="2">
        <s:fill>
            <s:LinearGradient rotation="90">
                <s:GradientEntry color="0xFFFFFF" color.over="0xBBBDBD" color.down="0xAAAAAA" alpha="0.85" />
                <s:GradientEntry color="0xD8D8D8" color.over="0x9FA0A1" color.down="0x929496" alpha="0.85" />
            </s:LinearGradient>
        </s:fill>
    </s:Rect>
 
    <!-- layer 3: fill lowlight -->
    <s:Rect id="lowlight" left="1" right="1" top="1" bottom="1" radiusX="2">
        <s:fill>
            <s:LinearGradient rotation="270">
                <s:GradientEntry color="0x000000" ratio="0.0" alpha="0.0627" />
                <s:GradientEntry color="0x000000" ratio="0.48" alpha="0.0099" />
                <s:GradientEntry color="0x000000" ratio="0.48001" alpha="0.0" />
            </s:LinearGradient>
        </s:fill>
    </s:Rect>
 
    <!-- layer 4: fill highlight -->
    <s:Rect id="highlight" left="1" right="1" top="1" bottom="1" radiusX="2">
        <s:fill>
            <s:LinearGradient rotation="90">
                <s:GradientEntry color="0xFFFFFF" ratio="0.0" alpha="0.33" alpha.over="0.22" alpha.down="0.12"/>
                <s:GradientEntry color="0xFFFFFF" ratio="0.48" alpha="0.33" alpha.over="0.22" alpha.down="0.12" />
                <s:GradientEntry color="0xFFFFFF" ratio="0.48001" alpha="0.0" />
            </s:LinearGradient>
        </s:fill>
    </s:Rect>
 
    <!-- layer 5: highlight stroke (all states except down) -->
    <s:Rect id="highlightStroke" left="1" right="1" top="1" bottom="1" excludeFrom="down" radiusX="2">
        <s:stroke>
            <s:LinearGradientStroke rotation="90" weight="1">
                <s:GradientEntry color="0xFFFFFF" alpha.over="0.22" />
                <s:GradientEntry color="0xD8D8D8" alpha.over="0.22" />
            </s:LinearGradientStroke>
        </s:stroke>
    </s:Rect>
 
    <!-- layer 6: highlight stroke (down state only) -->
    <s:Rect id="hldownstroke1" left="1" right="1" top="1" bottom="1" radiusX="2" includeIn="down">
        <s:stroke>
            <s:LinearGradientStroke rotation="90" weight="1">
                <s:GradientEntry color="0x000000" alpha="0.25" ratio="0.0" />
                <s:GradientEntry color="0x000000" alpha="0.25" ratio="0.001" />
                <s:GradientEntry color="0x000000" alpha="0.07" ratio="0.0011" />
                <s:GradientEntry color="0x000000" alpha="0.07" ratio="0.965" />
                <s:GradientEntry color="0x000000" alpha="0.00" ratio="0.9651" />
            </s:LinearGradientStroke>
        </s:stroke>
    </s:Rect>
 
    <s:Rect id="hldownstroke2" left="2" right="2" top="2" bottom="2" radiusX="2" includeIn="down">
        <s:stroke>
            <s:LinearGradientStroke rotation="90" weight="1">
                <s:GradientEntry color="0x000000" alpha="0.09" ratio="0.0" />
                <s:GradientEntry color="0x000000" alpha="0.00" ratio="0.0001" />
            </s:LinearGradientStroke>
        </s:stroke>
    </s:Rect>
 
    <!-- layer 7: border - put on top of the fill so it doesn't disappear when scale is less than 1 -->
    <s:Rect id="border" left="0" right="0" top="0" bottom="0" width="69" height="20" radiusX="2">
        <s:stroke>
            <s:LinearGradientStroke rotation="90" weight="1">
                <s:GradientEntry color="0x000000" alpha="0.5625" alpha.down="0.6375" />
                <s:GradientEntry color="0x000000" alpha="0.75" alpha.down="0.85" />
            </s:LinearGradientStroke>
        </s:stroke>
    </s:Rect>
 
    <s:Rect right="18" top="1" bottom="1" width="1">
        <s:fill>
            <s:LinearGradient rotation="90">
                <s:GradientEntry color="0x000000" alpha="0.5625" alpha.down="0.6375" />
                <s:GradientEntry color="0x000000" alpha="0.75" alpha.down="0.85" />
            </s:LinearGradient>
        </s:fill>
    </s:Rect>
 
    <!-- layer 8: arrow -->
    <!--- The arrow graphic displayed in the anchor button. -->
    <s:BitmapImage id="arrow"
            source="@Embed('skins/bullet_red.png')"
            right="2" verticalCenter="0" />
 
</s:SparkSkin>

This entry is based on a beta version of the Flex 4 SDK and therefore is very likely to change as development of the Flex SDK continues. The API can (and will) change causing examples to possibly not compile in newer versions of the Flex 4 SDK.