Changing the background alpha on the Halo TextArea control in Flex 4

The following example shows how you can set the background alpha on the Halo TextArea control’s Spark skin in Flex 4 by setting the borderSkin style. As you may have noticed, the Halo components have new “Spark” themed skins in Flex 4 (basically so you can use Halo+Spark components in the same Flex project and have a consistent look-and-feel). You may also have noticed that several styles on the Halo controls don’t appear to work any more when using the Spark skins. For example, if you want to change the background fill alpha on the Halo TextArea control in Flex 4, you can no longer set the backgroundAlpha style, you’ll now need to create a custom skin and set the borderSkin style.

The various Halo component’s new Spark skins can be found in your Flex 4 SDK installation in the following location: <Flex SDK>\frameworks\projects\sparkskins\src\mx\skins\spark\…

If you want to set the border skin on the Halo TextArea control, you’ll need to copy the TextInputBorderSkin.mxml file.

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.

View MXML

<?xml version="1.0" encoding="utf-8"?>
<!-- http://blog.flexexamples.com/2009/06/09/changing-the-background-alpha-on-the-halo-textarea-control-in-flex-4/ -->
<s:Application name="TextArea_SparkSkin_backgroundAlpha_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"
        backgroundColor="red">

    <mx:TextArea id="textArea"
            borderSkin="skins.CustomHaloTextAreaBorderSkin"
            left="50" right="50"
            top="50" bottom="50">
        <mx:htmlText><fx:String source="lorem.html" /></mx:htmlText>
    </mx:TextArea>

</s:Application>

And the custom skin class, CustomHaloTextAreaBorderSkin.mxml, is as follows:

View skins/CustomHaloTextAreaBorderSkin.mxml

<?xml version="1.0" encoding="utf-8"?>
<!-- http://blog.flexexamples.com/2009/06/09/changing-the-background-alpha-on-the-halo-textarea-control-in-flex-4/ -->
<local:SparkSkinForHalo name="CustomHaloTextAreaBorderSkin"
        xmlns:fx="http://ns.adobe.com/mxml/2009"
        xmlns:s="library://ns.adobe.com/flex/spark"
        xmlns:local="mx.skins.spark.*"
        implements="mx.core.IBorder">

    <fx:Script>
        <![CDATA[
            import mx.core.EdgeMetrics;
            import mx.core.IUIComponent;

            /* Define the skin elements that should not be colorized. */
            static private const exclusions:Array = ["background"];
            override public function get colorizeExclusions():Array {return exclusions;}

            /* 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};

            /* Define the border items.*/
            static private const borderItem:Array = ["borderEntry1", "borderEntry2"];
            override protected function get borderItems():Array {return borderItem;}

            static private const metrics:EdgeMetrics = new EdgeMetrics(2, 2, 2, 2);

            public function get borderMetrics():EdgeMetrics {
                return metrics;
            }

            override protected function updateDisplayList(unscaledWidth:Number, unscaledHeight:Number):void {
                super.updateDisplayList(unscaledWidth, unscaledHeight);

                if (parent && (parent is IUIComponent) && !IUIComponent(parent).enabled) {
                    alpha = 0.5;
                } else {
                    alpha = 1;
                }
            }
        ]]>
    </fx:Script>

    <!-- border -->
    <s:Rect left="0" right="0" top="0" bottom="0">
        <s:stroke>
            <s:LinearGradientStroke rotation="90" weight="1">
                <s:GradientEntry id="borderEntry1" alpha="0.5525" />
                <s:GradientEntry id="borderEntry2" alpha="0.6375" />
            </s:LinearGradientStroke>
        </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" alpha="0.4" />
        </s:fill>
    </s:Rect>

    <!-- shadow -->
    <s:Rect left="1" top="1" right="1" height="1">
        <s:fill>
            <s:SolidColor color="0x000000" alpha="0.12" />
        </s:fill>
    </s:Rect>

</local:SparkSkinForHalo>

The default Spark skins for the MX/Halo controls/containers can be found in the Flex SDK at:
%Flex SDK%\frameworks\projects\sparkskins\src\mx\skins\spark\*.

View source is enabled in the following example.

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

View MXML

<?xml version="1.0" encoding="utf-8"?>
<!-- http://blog.flexexamples.com/2009/06/09/changing-the-background-alpha-on-the-halo-textarea-control-in-flex-4/ -->
<s:Application name="TextArea_SparkSkin_backgroundAlpha_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"
        backgroundColor="red">

    <fx:Style>
        @namespace mx "library://ns.adobe.com/flex/halo";

        mx|TextArea {
            borderSkin: ClassReference("skins.CustomHaloTextAreaBorderSkin");
            left: 50;
            right: 50;
            top: 50;
            bottom: 50;
        }
    </fx:Style>

    <mx:TextArea id="textArea">
        <mx:htmlText><fx:String source="lorem.html" /></mx:htmlText>
    </mx:TextArea>

</s:Application>

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

View MXML

<?xml version="1.0" encoding="utf-8"?>
<!-- http://blog.flexexamples.com/2009/06/09/changing-the-background-alpha-on-the-halo-textarea-control-in-flex-4/ -->
<s:Application name="TextArea_SparkSkin_backgroundAlpha_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"
        backgroundColor="red">

    <fx:Script>
        <![CDATA[
            import skins.CustomHaloTextAreaBorderSkin;

            private function btn_click(evt:MouseEvent):void {
                textArea.setStyle("borderSkin", CustomHaloTextAreaBorderSkin);
            }
        ]]>
    </fx:Script>

    <s:Button id="btn"
            label="Set border skin"
            click="btn_click(event);"
            left="10"
            top="10" />

    <mx:TextArea id="textArea"
            left="50" right="50"
            top="50" bottom="50">
        <mx:htmlText><fx:String source="lorem.html" /></mx:htmlText>
    </mx:TextArea>

</s:Application>

Due to popular demand, here is the “same” example in a more ActionScript friendly format:

View MXML

<?xml version="1.0" encoding="utf-8"?>
<!-- http://blog.flexexamples.com/2009/06/09/changing-the-background-alpha-on-the-halo-textarea-control-in-flex-4/ -->
<s:Application name="TextArea_SparkSkin_backgroundAlpha_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"
        backgroundColor="red"
        initialize="init();">

    <fx:Script>
        <![CDATA[
            import mx.controls.TextArea;
            import skins.CustomHaloTextAreaBorderSkin;

            [Embed(source="lorem.html", mimeType="application/octet-stream")]
            private const lorem:Class;

            private var textArea:TextArea;

            private function init():void {
                textArea = new TextArea();
                textArea.htmlText = new lorem();
                textArea.left = 50;
                textArea.right = 50;
                textArea.top = 50;
                textArea.bottom = 50;
                textArea.setStyle("borderSkin", CustomHaloTextAreaBorderSkin);
                addElement(textArea);
            }
        ]]>
    </fx:Script>

</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.