Setting a linear gradient background on a Spark Application container in Flex 4

The following example shows how you can create a linear gradient background on a Flex 4 Spark Application container by setting the skinClass style to a custom Application skin class which has a LinearGradient fill.

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 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/2009/03/13/setting-a-linear-gradient-background-on-an-fxapplication-container-in-flex-gumbo/ -->
<s:Application name="Spark_Application_skinClass_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"
        skinClass="skins.CustomApplicationSkin">
 
    <s:Label text="I'm a Spark Application with a custom skinClass."
            horizontalCenter="0"
            verticalCenter="0" />
 
</s:Application>

The custom skin, skins/CustomApplicationSkin.mxml, is as follows:

<?xml version="1.0" encoding="utf-8"?>
<!-- http://blog.flexexamples.com/2009/03/13/setting-a-linear-gradient-background-on-an-fxapplication-container-in-flex-gumbo/ -->
<s:Skin xmlns:fx="http://ns.adobe.com/mxml/2009"
        xmlns:s="library://ns.adobe.com/flex/spark"
        xmlns:fb="http://ns.adobe.com/flashbuilder/2009"
        alpha.disabled="0.5"
        alpha.disabledWithControlBar="0.5">
    <s:states>
        <s:State name="normal" />
        <s:State name="disabled" />
        <s:State name="normalWithControlBar" />
        <s:State name="disabledWithControlBar" />
    </s:states>
 
    <fx:Metadata>
        <![CDATA[
            [HostComponent("spark.components.Application")]
        ]]>
    </fx:Metadata>
 
    <!-- fill -->
    <!---
        A rectangle with a solid color fill that forms the background of the application.
        The color of the fill is set to the Application's backgroundColor property.
    -->
    <s:Rect id="backgroundRect" left="0" right="0" top="0" bottom="0"  >
        <s:fill>
            <s:LinearGradient rotation="90">
                <s:GradientEntry color="white" />
                <s:GradientEntry color="haloBlue" />
            </s:LinearGradient>
        </s:fill>
    </s:Rect>
 
    <s:Group left="0" right="0" top="0" bottom="0">
        <s:layout>
            <s:VerticalLayout gap="0" horizontalAlign="justify" />
        </s:layout>
 
        <s:Group id="topGroup" minWidth="0" minHeight="0"
                    includeIn="normalWithControlBar, disabledWithControlBar" >
 
            <!-- layer 0: control bar highlight -->
            <s:Rect left="0" right="0" top="0" bottom="1" >
               <s:stroke>
                    <s:LinearGradientStroke rotation="90" weight="1">
                        <s:GradientEntry color="0xFFFFFF" />
                        <s:GradientEntry color="0xD8D8D8" />
                    </s:LinearGradientStroke>
               </s:stroke>
            </s:Rect>
 
            <!-- layer 1: control bar fill -->
            <s:Rect left="1" right="1" top="1" bottom="2" >
               <s:fill>
                    <s:LinearGradient rotation="90">
                        <s:GradientEntry color="0xEDEDED" />
                        <s:GradientEntry color="0xCDCDCD" />
                    </s:LinearGradient>
               </s:fill>
            </s:Rect>
 
            <!-- layer 2: control bar divider line -->
            <s:Rect left="0" right="0" bottom="0" height="1" alpha="0.55">
                <s:fill>
                    <s:SolidColor color="0x000000" />
                </s:fill>
            </s:Rect>
 
            <!-- layer 3: control bar -->
            <s:Group id="controlBarGroup" left="0" right="0" top="1" bottom="1" minWidth="0" minHeight="0">
                <s:layout>
                    <s:HorizontalLayout paddingLeft="10" paddingRight="10" paddingTop="7" paddingBottom="7" gap="10" />
                </s:layout>
            </s:Group>
        </s:Group>
 
        <s:Group id="contentGroup" width="100%" height="100%" minWidth="0" minHeight="0" />
 
    </s:Group>
 
</s:Skin>

View source is enabled in the following example.

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You can also set the skinClass style 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/2009/03/13/setting-a-linear-gradient-background-on-an-fxapplication-container-in-flex-gumbo/ -->
<s:Application name="Spark_Application_skinClass_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">
 
    <fx:Style>
        @namespace s "library://ns.adobe.com/flex/spark";
 
        s|Application {
            skinClass: ClassReference("skins.CustomApplicationSkin");
        }
    </fx:Style>
 
    <s:Label text="I'm a Spark Application with a custom skinClass."
            horizontalCenter="0"
            verticalCenter="0" />
 
</s:Application>

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

<?xml version="1.0" encoding="utf-8"?>
<!-- http://blog.flexexamples.com/2009/03/13/setting-a-linear-gradient-background-on-an-fxapplication-container-in-flex-gumbo/ -->
<s:Application name="Spark_Application_skinClass_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>
        <s:Button id="btn"
                label="Set skin class"
                click="btn_click(event);" />
    </s:controlBarContent>
 
    <fx:Script>
        <![CDATA[
            import skins.CustomApplicationSkin;
 
            protected function btn_click(evt:MouseEvent):void {
                setStyle("skinClass", CustomApplicationSkin);
                btn.enabled = false;
            }
        ]]>
    </fx:Script>
 
    <s:Label text="I'm a Spark Application with a custom skinClass."
            horizontalCenter="0"
            verticalCenter="0" />
 
</s:Application>

Finally, you can set the Flex application’s background fill by setting the fill property on the Spark Application container’s default skin using ActionScript, as seen in the following example:

<?xml version="1.0" encoding="utf-8"?>
<!-- http://blog.flexexamples.com/2009/03/13/setting-a-linear-gradient-background-on-an-fxapplication-container-in-flex-gumbo/ -->
<s:Application name="Spark_Application_skinClass_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>
        <s:Button id="btn"
                label="Set linear gradient fill"
                click="btn_click(event);" />
    </s:controlBarContent>
 
    <fx:Script>
        <![CDATA[
            import spark.skins.spark.ApplicationSkin;
 
            protected function btn_click(evt:MouseEvent):void {
                ApplicationSkin(skin).backgroundRect.fill = linearGrad;
                btn.enabled = false;
            }
        ]]>
    </fx:Script>
 
    <fx:Declarations>
        <s:LinearGradient id="linearGrad" rotation="90">
            <s:GradientEntry color="white" />
            <s:GradientEntry color="haloBlue" />
        </s:LinearGradient>
    </fx:Declarations>
 
    <s:Label text="I'm a Spark Application with a custom skinClass."
            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.