Full code after the jump.

The following example(s) require Flash Player 10 and the Adobe Flex 4 SDK. To download the Adobe Flash Builder 4 trial, see http://www.adobe.com/products/flex/. To download the latest nightly build of the Flex 4 SDK, see http://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/2009/09/08/setting-the-focus-alpha-on-a-spark-textarea-control-in-flex-4/ -->
<s:Application name="Spark_TextArea_focusAlpha_test"
        xmlns:fx="http://ns.adobe.com/mxml/2009"
        xmlns:s="library://ns.adobe.com/flex/spark"
        xmlns:mx="library://ns.adobe.com/flex/halo">
    <s:controlBarContent>
        <mx:Form contentBackgroundAlpha="0">
            <mx:FormItem label="focusAlpha:">
                <s:HSlider id="slider"
                        minimum="0.0"
                        maximum="1.0"
                        value="0.8"
                        snapInterval="0.1"
                        stepSize="0.1"
                        change="txtArea.setFocus();" />
            </mx:FormItem>
            <mx:FormItem label="focusColor:">
                <mx:ColorPicker id="colorPicker"
                        selectedColor="haloBlue"
                        change="callLater(txtArea.setFocus);" />
            </mx:FormItem>
        </mx:Form>
    </s:controlBarContent>
 
    <s:TextArea id="txtArea"
            focusAlpha="{slider.value}"
            focusColor="{colorPicker.selectedColor}"
            horizontalCenter="0" verticalCenter="0"
            creationComplete="txtArea.setFocus();"/>
 
</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.

 

Full code after the jump.

View MXML

<?xml version="1.0" encoding="utf-8"?>
<!-- http://blog.flexexamples.com/2008/05/23/setting-the-focus-alpha-on-a-numericstepper-control-in-flex/ -->
<mx:Application xmlns:mx="http://www.adobe.com/2006/mxml"
        layout="vertical"
        verticalAlign="middle"
        backgroundColor="white">

    <mx:Script>
        <![CDATA[
            import mx.events.NumericStepperEvent;

            private function numericStepper_change(evt:NumericStepperEvent):void {
                // reset focus
                focusManager.setFocus(btn);
                focusManager.setFocus(numericStepper);
            }
        ]]>
    </mx:Script>

    <mx:ApplicationControlBar dock="true">
        <mx:Button id="btn" label="click here to remove focus" />
    </mx:ApplicationControlBar>

    <mx:NumericStepper id="numericStepper"
            minimum="0.0"
            maximum="1.0"
            value="0.5"
            stepSize="0.1"
            textAlign="center"
            focusAlpha="{numericStepper.value}"
            change="numericStepper_change(event);" />

</mx:Application>

View source is enabled in the following example.

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

View MXML

<?xml version="1.0" encoding="utf-8"?>
<!-- http://blog.flexexamples.com/2008/05/23/setting-the-focus-alpha-on-a-numericstepper-control-in-flex/ -->
<mx:Application xmlns:mx="http://www.adobe.com/2006/mxml"
        layout="vertical"
        verticalAlign="middle"
        backgroundColor="white">

    <mx:Style>
        NumericStepper {
            focusAlpha: 1.0;
        }
    </mx:Style>

    <mx:ApplicationControlBar dock="true">
        <mx:Button id="btn" label="click here to remove focus" />
    </mx:ApplicationControlBar>

    <mx:NumericStepper id="numericStepper"
            minimum="0.0"
            maximum="1.0"
            value="1.0"
            stepSize="0.1"
            textAlign="center"/>

</mx:Application>

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

View MXML

<?xml version="1.0" encoding="utf-8"?>
<!-- http://blog.flexexamples.com/2008/05/23/setting-the-focus-alpha-on-a-numericstepper-control-in-flex/ -->
<mx:Application xmlns:mx="http://www.adobe.com/2006/mxml"
        layout="vertical"
        verticalAlign="middle"
        backgroundColor="white">

    <mx:Script>
        <![CDATA[
            import mx.events.NumericStepperEvent;

            private function numericStepper_change(evt:NumericStepperEvent):void {
                numericStepper.setStyle("focusAlpha", evt.value);
                // reset focus
                focusManager.setFocus(btn);
                focusManager.setFocus(numericStepper);
            }
        ]]>
    </mx:Script>

    <mx:ApplicationControlBar dock="true">
        <mx:Button id="btn" label="click here to remove focus" />
    </mx:ApplicationControlBar>

    <mx:NumericStepper id="numericStepper"
            minimum="0.0"
            maximum="1.0"
            value="0.5"
            stepSize="0.1"
            textAlign="center"
            change="numericStepper_change(event);" />

</mx:Application>