Changing the background alpha of a TextArea control in Flex

The following example shows how you can set the background alpha for a Flex TextArea control by setting the backgroundAlpha style.

Full code after the jump.

View MXML

<?xml version="1.0" encoding="utf-8"?>
<!-- http://blog.flexexamples.com/2008/08/18/changing-the-background-alpha-of-a-textarea-control-in-flex/ -->
<mx:Application name="TextArea_backgroundDisabledColor_test"
        xmlns:mx="http://www.adobe.com/2006/mxml"
        layout="vertical"
        verticalAlign="middle">

    <mx:String id="lorem" source="lorem.txt" />

    <mx:ApplicationControlBar dock="true">
        <mx:Form styleName="plain" backgroundAlpha="0.0">
            <mx:FormItem label="backgroundAlpha:">
                <mx:HSlider id="slider"
                        minimum="0.0"
                        maximum="1.0"
                        value="1.0"
                        snapInterval="0.01"
                        tickInterval="0.1"
                        liveDragging="true" />
            </mx:FormItem>
            <mx:FormItem label="enabled:">
                <mx:CheckBox id="checkBox"
                        selected="true" />
            </mx:FormItem>
        </mx:Form>
    </mx:ApplicationControlBar>

    <mx:TextArea id="textArea"
            text="{lorem}"
            backgroundAlpha="{slider.value}"
            enabled="{checkBox.selected}"
            width="100%"
            height="100%" />

</mx:Application>

View source is enabled in the following example.

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

View MXML

<?xml version="1.0" encoding="utf-8"?>
<!-- http://blog.flexexamples.com/2008/08/18/changing-the-background-alpha-of-a-textarea-control-in-flex/ -->
<mx:Application name="TextArea_backgroundDisabledColor_test"
        xmlns:mx="http://www.adobe.com/2006/mxml"
        layout="vertical"
        verticalAlign="middle">

    <mx:Style>
        TextArea {
            backgroundAlpha: 0.0;
        }
    </mx:Style>

    <mx:String id="lorem" source="lorem.txt" />

    <mx:ApplicationControlBar dock="true">
        <mx:Form styleName="plain" backgroundAlpha="0.0">
            <mx:FormItem label="enabled:">
                <mx:CheckBox id="checkBox"
                        selected="true" />
            </mx:FormItem>
        </mx:Form>
    </mx:ApplicationControlBar>

    <mx:TextArea id="textArea"
            text="{lorem}"
            enabled="{checkBox.selected}"
            width="100%"
            height="100%" />

</mx:Application>

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

View MXML

<?xml version="1.0" encoding="utf-8"?>
<!-- http://blog.flexexamples.com/2008/08/18/changing-the-background-alpha-of-a-textarea-control-in-flex/ -->
<mx:Application name="TextArea_backgroundDisabledColor_test"
        xmlns:mx="http://www.adobe.com/2006/mxml"
        layout="vertical"
        verticalAlign="middle">

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

            private function slider_change(evt:SliderEvent):void {
                textArea.setStyle("backgroundAlpha", evt.value);
            }
        ]]>
    </mx:Script>

    <mx:String id="lorem" source="lorem.txt" />

    <mx:ApplicationControlBar dock="true">
        <mx:Form styleName="plain" backgroundAlpha="0.0">
            <mx:FormItem label="backgroundAlpha:">
                <mx:HSlider id="slider"
                        minimum="0.0"
                        maximum="1.0"
                        value="1.0"
                        snapInterval="0.01"
                        tickInterval="0.1"
                        liveDragging="true"
                        change="slider_change(event);" />
            </mx:FormItem>
            <mx:FormItem label="enabled:">
                <mx:CheckBox id="checkBox"
                        selected="true" />
            </mx:FormItem>
        </mx:Form>
    </mx:ApplicationControlBar>

    <mx:TextArea id="textArea"
            text="{lorem}"
            enabled="{checkBox.selected}"
            width="100%"
            height="100%" />

</mx:Application>