Setting the corner radius on the Halo Alert control in Flex 4

The following example shows how you can set the corner radius on the Halo TextArea control (with default Spark skin) in Flex 4 by creating a custom skin and setting the radiusX and radiusY properties on the Rect objects (in Flex 3 and earlier this was done by setting the cornerRadius style directly).

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/2009/06/20/setting-the-corner-radius-on-the-halo-control-in-flex-4/ -->
<s:Application name="Alert_SparkSkin_cornerRadius_test"
        xmlns:fx="http://ns.adobe.com/mxml/2009"
        xmlns:mx="library://ns.adobe.com/flex/halo"
        xmlns:s="library://ns.adobe.com/flex/spark">

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

        mx|Alert {
            borderSkin: ClassReference("skins.CustomAlertSkin");
        }
    </fx:Style>

    <fx:Script>
        <![CDATA[
            import mx.controls.Alert;
        ]]>
    </fx:Script>

    <s:Button id="btn"
            label="show Alert"
            click="Alert.show('The quick brown fox jumps over the lazy dog.', 'Alert title');"
            horizontalCenter="0"
            verticalCenter="0" />

</s:Application>

And the custom Alert skin class is as follows:

View skins/CustomAlertSkin.mxml

<?xml version="1.0" encoding="utf-8"?>
<!-- http://blog.flexexamples.com/2009/06/20/setting-the-corner-radius-on-the-halo-control-in-flex-4/ -->
<s:SparkSkin name="CustomAlertSkin"
        xmlns:fx="http://ns.adobe.com/mxml/2009"
        xmlns:s="library://ns.adobe.com/flex/spark"
        implements="mx.core.IRectangularBorder">

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

        /* Define the skin elements that should not be colorized.
           For panel, border and title backround are skinned, but the content area and title text are not. */
        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};

        private var _metrics:EdgeMetrics = new EdgeMetrics(1, 32, 1, 1);
        public function get borderMetrics():EdgeMetrics {
            var hasPanelParent:Boolean = isPanel(parent);
            var controlBar:IUIComponent = hasPanelParent ? Object(parent).mx_internal::_controlBar : null;

            if (controlBar && controlBar.includeInLayout) {
                _metrics.bottom = controlBar.getExplicitOrMeasuredHeight() + 1;
            } else {
                _metrics.bottom = 1;
            }
            return _metrics;
        }

        public function get backgroundImageBounds():Rectangle {
            return null;
        }

        public function set backgroundImageBounds(value:Rectangle):void {
        }

        public function get hasBackgroundImage():Boolean {
            return false;
        }

        public function layoutBackgroundImage():void {
        }

        override protected function updateDisplayList(unscaledWidth:Number, unscaledHeight:Number):void {
            var em:EdgeMetrics = borderMetrics;

            if (em.bottom > 1) {
                cbbg.height = em.bottom - 1;
                cbdiv.bottom = cbbg.height;
                cbbg.visible = cbdiv.visible = true;
            } else {
                cbbg.visible = cbdiv.visible = false;
            }
            super.updateDisplayList(unscaledWidth, unscaledHeight);
        }

        private static var panels:Object = {};

        private static function isPanel(parent:Object):Boolean {
            var s:String = getQualifiedClassName(parent);
            if (panels[s] == 1) {
                return true;
            }
            if (panels[s] == 0) {
                return false;
            }
            if (s == "mx.containers::Panel") {
                panels[s] == 1;
                return true;
            }

            var x:XML = describeType(parent);
            var xmllist:XMLList = x.extendsClass.(@type == "mx.containers::Panel");
            if (xmllist.length() == 0) {
                panels[s] = 0;
                return false;
            }
            panels[s] = 1;
            return true;
        }
        ]]>
    </fx:Script>

    <fx:Declarations>
        <fx:Number id="rad">10</fx:Number>
    </fx:Declarations>

    <!-- drop shadow -->
    <s:Rect left="0" top="0" right="0" bottom="0" radiusX="{rad}" radiusY="{rad}">
        <s:filters>
            <s:DropShadowFilter blurX="20" blurY="20" alpha="0.32" distance="11" angle="90" knockout="true" />
        </s:filters>
        <s:fill>
            <s:SolidColor color="0" />
        </s:fill>
    </s:Rect>

    <!-- layer 1: border -->
    <s:Rect left="0" right="0" top="0" bottom="0" radiusX="{rad}" radiusY="{rad}">
        <s:stroke>
            <s:SolidColorStroke color="0" alpha="0.50" weight="1" />
        </s:stroke>
    </s:Rect>

    <!-- layer 2: background fill -->
    <s:Rect id="background" left="1" top="1" right="1" bottom="1" radiusX="{rad}" radiusY="{rad}">
        <s:fill>
            <s:SolidColor color="0xFFFFFF" id="bgFill" />
        </s:fill>
    </s:Rect>

    <!-- layer 5: control bar background -->
    <s:Rect id="cbbg" left="1" right="1" bottom="1" height="20" radiusX="{rad}" radiusY="{rad}">
        <s:fill>
            <s:SolidColor color="0xE8E8E8" />
        </s:fill>
    </s:Rect>

    <!-- layer 6: control bar divider line -->
    <s:Rect id="cbdiv" left="1" right="1" bottom="20" height="1">
        <s:fill>
            <s:SolidColor color="0xCDCDCD" />
        </s:fill>
    </s:Rect>

</s:SparkSkin>

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.