Changing the letter spacing on a Spark Button control in Flex 4

The following example shows how you can change the letter spacing on the Spark Button control in Flex 4 by setting the trackingLeft or trackingRight styles.

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/2010/04/05/changing-the-letter-spacing-on-a-spark-button-control-in-flex-4/ -->
<s:Application name="Spark_Button_trackingRight_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>
        <mx:Form>
            <mx:FormItem label="trackingLeft:">
                <s:HSlider id="sldrL" minimum="0" maximum="10" />
            </mx:FormItem>
            <mx:FormItem label="trackingRight:">
                <s:HSlider id="sldrR" minimum="0" maximum="10" />
            </mx:FormItem>
        </mx:Form>
    </s:controlBarContent>
 
    <s:Button id="btn"
            label="Spark Button label"
            trackingLeft="{sldrL.value}"
            trackingRight="{sldrR.value}"
            maxWidth="600"
            horizontalCenter="0" verticalCenter="0" />
 
</s:Application>

You can also set the trackingLeft and trackingRight styles 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/2010/04/05/changing-the-letter-spacing-on-a-spark-button-control-in-flex-4/ -->
<s:Application name="Spark_Button_trackingRight_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|Button {
            trackingLeft: 10;
            trackingRight: 10;
        }
    </fx:Style>
 
    <s:Button id="btn"
            label="Spark Button label"
            maxWidth="600"
            horizontalCenter="0" verticalCenter="0" />
 
</s:Application>

Or you can set the trackingLeft and trackingRight using ActionScript, as seen in the following example:

<?xml version="1.0" encoding="utf-8"?>
<!-- http://blog.flexexamples.com/2010/04/05/changing-the-letter-spacing-on-a-spark-button-control-in-flex-4/ -->
<s:Application name="Spark_Button_trackingRight_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>
        <mx:Form>
            <mx:FormItem label="trackingLeft:">
                <s:HSlider id="sldrL"
                        minimum="0" maximum="10"
                        change="sldrL_changeHandler(event);"/>
            </mx:FormItem>
            <mx:FormItem label="trackingRight:">
                <s:HSlider id="sldrR"
                        minimum="0" maximum="10"
                        change="sldrR_changeHandler(event);"/>
            </mx:FormItem>
        </mx:Form>
    </s:controlBarContent>
 
    <fx:Script>
        <![CDATA[
            protected function sldrL_changeHandler(event:Event):void {
                btn.setStyle("trackingLeft", sldrL.value);
            }
 
            protected function sldrR_changeHandler(event:Event):void {
                btn.setStyle("trackingRight", sldrR.value);
            }
        ]]>
    </fx:Script>
 
    <s:Button id="btn"
            label="Spark Button label"
            maxWidth="600"
            horizontalCenter="0" verticalCenter="0" />
 
</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.