Setting the width of the pop up on a Spark DropDownList control in Flex 4

The following example shows how you can set the drop down menu width on a Spark DropDownList control by setting the width property within a custom DropDownList skin.

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/2009/04/13/setting-the-width-of-the-pop-up-on-a-spark-dropdownlist-control-in-flex-gumbo/ -->
<s:Application name="Spark_DropDownList_skinClass_width_test"
        xmlns:fx="http://ns.adobe.com/mxml/2009"
        xmlns:s="library://ns.adobe.com/flex/spark"
        xmlns:mx="library://ns.adobe.com/flex/mx">
 
    <s:DropDownList id="dropDownList"
            labelField="label"
            requireSelection="true"
            skinClass="skins.CustomDropDownListSkin"
            horizontalCenter="0"
            top="20">
        <s:dataProvider>
            <s:ArrayList>
                <fx:Object label="Adobe AIR" />
                <fx:Object label="ColdFusion" />
                <fx:Object label="Dreamweaver" />
                <fx:Object label="Flash" />
                <fx:Object label="Flash Player" />
                <fx:Object label="Fireworks" />
                <fx:Object label="Flex" />
                <fx:Object label="Illustrator" />
            </s:ArrayList>
        </s:dataProvider>
    </s:DropDownList>
 
</s:Application>

And the custom skin class, skins/CustomDropDownListSkin.mxml, is as follows:

<?xml version="1.0" encoding="utf-8"?>
<!-- http://blog.flexexamples.com/2009/04/13/setting-the-width-of-the-pop-up-on-a-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>
        <![CDATA[
            [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>
 
    <!---
    The PopUpAnchor control that opens the drop-down list.
 
    <p>In a custom skin class that uses transitions, set the
    <code>itemDestructionPolicy</code> property to <code>none</code>.</p>
    -->
    <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="false">
        <!--- This includes borders, background colors, scrollers, and filters. -->
        <s:Group id="dropDown"
                minHeight="22"
                maxHeight="134"
                width="300">
            <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>
                    <!--- border stroke -->
                    <s:SolidColorStroke id="borderStroke" weight="1" />
                </s:stroke>
            </s:Rect>
 
            <!-- fill -->
            <!--- Defines the appearance of drop-down list's background fill. -->
            <s:Rect id="background"
                    left="1" right="1" top="1" bottom="1" >
                <s:fill>
                    <!--- The color of the drop down's background fill. The default color is 0xFFFFFF. -->
                    <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>
 
    <!---  The default skin is DropDownListButtonSkin. -->
    <s:Button id="openButton"
            left="0" right="0" top="0" bottom="0"
            focusEnabled="false"
            skinClass="spark.skins.spark.DropDownListButtonSkin" />
 
    <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>

[GoogleAdsWide]

View source is enabled in the following example.

You can also set the skinClass style in an advanced .CSS file or <Style> block, as seen in the following example:

<?xml version="1.0" encoding="utf-8"?>
<!-- http://blog.flexexamples.com/2009/04/13/setting-the-width-of-the-pop-up-on-a-spark-dropdownlist-control-in-flex-gumbo/ -->
<s:Application name="Spark_DropDownList_skinClass_width_test"
        xmlns:fx="http://ns.adobe.com/mxml/2009"
        xmlns:s="library://ns.adobe.com/flex/spark"
        xmlns:mx="library://ns.adobe.com/flex/mx">
 
    <fx:Style>
        @namespace s "library://ns.adobe.com/flex/spark";
        @namespace mx "library://ns.adobe.com/flex/mx";
 
        s|DropDownList {
            skinClass: ClassReference("skins.CustomDropDownListSkin");
        }
    </fx:Style>
 
    <s:DropDownList id="dropDownList"
            labelField="label"
            requireSelection="true"
            horizontalCenter="0"
            top="20">
        <s:dataProvider>
            <s:ArrayList>
                <fx:Object label="Adobe AIR" />
                <fx:Object label="ColdFusion" />
                <fx:Object label="Dreamweaver" />
                <fx:Object label="Flash" />
                <fx:Object label="Flash Player" />
                <fx:Object label="Fireworks" />
                <fx:Object label="Flex" />
                <fx:Object label="Illustrator" />
            </s:ArrayList>
        </s:dataProvider>
    </s:DropDownList>
 
</s:Application>

Or you can set the skinClass style using ActionScript, as seen in the following example:

<?xml version="1.0" encoding="utf-8"?>
<!-- http://blog.flexexamples.com/2009/04/13/setting-the-width-of-the-pop-up-on-a-spark-dropdownlist-control-in-flex-gumbo/ -->
<s:Application name="Spark_DropDownList_skinClass_width_test"
        xmlns:fx="http://ns.adobe.com/mxml/2009"
        xmlns:s="library://ns.adobe.com/flex/spark"
        xmlns:mx="library://ns.adobe.com/flex/mx">
    <s:controlBarContent>
        <s:Button id="btn"
                label="Set DropDownList skinClass"
                click="btn_clickHandler(event);" />
    </s:controlBarContent>
 
    <fx:Script>
        <![CDATA[
            import skins.CustomDropDownListSkin;
 
            protected function btn_clickHandler(evt:MouseEvent):void {
                dropDownList.setStyle("skinClass", CustomDropDownListSkin);
            }
        ]]>
    </fx:Script>
 
    <s:DropDownList id="dropDownList"
            labelField="label"
            requireSelection="true"
            horizontalCenter="0"
            top="20">
        <s:dataProvider>
            <s:ArrayList>
                <fx:Object label="Adobe AIR" />
                <fx:Object label="ColdFusion" />
                <fx:Object label="Dreamweaver" />
                <fx:Object label="Flash" />
                <fx:Object label="Flash Player" />
                <fx:Object label="Fireworks" />
                <fx:Object label="Flex" />
                <fx:Object label="Illustrator" />
            </s:ArrayList>
        </s:dataProvider>
    </s:DropDownList>
 
</s:Application>

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.