Displaying a border on specific sides of a HorizontalList control in Flex

The following example shows how you can toggle which sides of a Flex HorizontalList control display the border outline by setting the borderSides style.

Full code after the jump.

<?xml version="1.0" encoding="utf-8"?>
<!-- http://blog.flexexamples.com/2009/07/26/displaying-a-border-on-specific-sides-of-a-horizontallist-control-in-flex/ -->
<mx:Application name="HorizontalList_borderSides_test"
        xmlns:mx="http://www.adobe.com/2006/mxml"
        layout="vertical"
        verticalAlign="middle"
        backgroundColor="white">
 
    <mx:HorizontalList id="hList"
            borderColor="red"
            borderSides="left right"
            labelField="label"
            horizontalScrollPolicy="on"
            columnWidth="120"
            columnCount="5"
            rowHeight="90">
        <mx:dataProvider>
            <mx:ArrayCollection>
                <mx:Object label="One" />
                <mx:Object label="Two" />
                <mx:Object label="Three" />
                <mx:Object label="Four" />
                <mx:Object label="Five" />
                <mx:Object label="Six" />
                <mx:Object label="Seven" />
                <mx:Object label="Eight" />
                <mx:Object label="Nine" />
            </mx:ArrayCollection>
        </mx:dataProvider>
    </mx:HorizontalList>
 
</mx:Application>

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

<?xml version="1.0" encoding="utf-8"?>
<!-- http://blog.flexexamples.com/2009/07/26/displaying-a-border-on-specific-sides-of-a-horizontallist-control-in-flex/ -->
<mx:Application name="HorizontalList_borderSides_test"
        xmlns:mx="http://www.adobe.com/2006/mxml"
        layout="vertical"
        verticalAlign="middle"
        backgroundColor="white">
 
    <mx:Style>
        HorizontalList {
            borderSides: "top bottom";
        }
    </mx:Style>
 
    <mx:HorizontalList id="hList"
            borderColor="red"
            labelField="label"
            horizontalScrollPolicy="on"
            columnWidth="120"
            columnCount="5"
            rowHeight="90">
        <mx:dataProvider>
            <mx:ArrayCollection>
                <mx:Object label="One" />
                <mx:Object label="Two" />
                <mx:Object label="Three" />
                <mx:Object label="Four" />
                <mx:Object label="Five" />
                <mx:Object label="Six" />
                <mx:Object label="Seven" />
                <mx:Object label="Eight" />
                <mx:Object label="Nine" />
            </mx:ArrayCollection>
        </mx:dataProvider>
    </mx:HorizontalList>
 
</mx:Application>

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

<?xml version="1.0" encoding="utf-8"?>
<!-- http://blog.flexexamples.com/2009/07/26/displaying-a-border-on-specific-sides-of-a-horizontallist-control-in-flex/ -->
<mx:Application name="HorizontalList_borderSides_test"
        xmlns:mx="http://www.adobe.com/2006/mxml"
        layout="vertical"
        verticalAlign="middle"
        backgroundColor="white">
 
    <mx:Script>
        <![CDATA[
            private function checkBox_change(evt:Event):void {
                var sides:String = "";
                if (leftCh.selected) {
                    sides += " left";
                }
                if (rightCh.selected) {
                    sides += " right";
                }
                if (topCh.selected) {
                    sides += " top";
                }
                if (bottomCh.selected) {
                    sides += " bottom";
                }
                hList.setStyle("borderSides", sides);
            }
        ]]>
    </mx:Script>
 
    <mx:ApplicationControlBar dock="true">
        <mx:Form styleName="plain">
            <mx:FormItem label="left:">
                <mx:CheckBox id="leftCh"
                        selected="true"
                        change="checkBox_change(event);" />
            </mx:FormItem>
            <mx:FormItem label="right:">
                <mx:CheckBox id="rightCh" 
                        selected="true"
                        change="checkBox_change(event);" />
            </mx:FormItem>
            <mx:FormItem label="top:">
                <mx:CheckBox id="topCh"
                        selected="true"
                        change="checkBox_change(event);" />
            </mx:FormItem>
            <mx:FormItem label="bottom:">
                <mx:CheckBox id="bottomCh"
                        selected="true"
                        change="checkBox_change(event);" />
            </mx:FormItem>
        </mx:Form>
    </mx:ApplicationControlBar>
 
    <mx:HorizontalList id="hList"
            borderColor="red"
            labelField="label"
            horizontalScrollPolicy="on"
            columnWidth="120"
            columnCount="5"
            rowHeight="90">
        <mx:dataProvider>
            <mx:ArrayCollection>
                <mx:Object label="One" />
                <mx:Object label="Two" />
                <mx:Object label="Three" />
                <mx:Object label="Four" />
                <mx:Object label="Five" />
                <mx:Object label="Six" />
                <mx:Object label="Seven" />
                <mx:Object label="Eight" />
                <mx:Object label="Nine" />
            </mx:ArrayCollection>
        </mx:dataProvider>
    </mx:HorizontalList>
 
</mx:Application>