Using graphical and text primitives in Flex Gumbo

The following example shows you how to draw an ellipse in a Flex Gumbo application using the new Ellipse graphic primitive in FXG.

Full code after the jump.

To use the following code, you must have Flash Player 10 and a Flex Gumbo SDK installed in your Flex Builder 3. For more information on downloading and installing the Gumbo SDK into Flex Builder 3, see “Using the beta Gumbo SDK in Flex Builder 3″.

View MXML

<?xml version="1.0" encoding="utf-8"?>
<!-- http://blog.flexexamples.com/2008/10/30/using-graphical-and-text-primitives-in-flex-gumbo/ -->
<FxApplication name="FXG_test"
        xmlns="http://ns.adobe.com/mxml/2009">
    <layout>
        <BasicLayout />
    </layout>

    <Ellipse id="ellipse"
            width="100"
            height="100"
            horizontalCenter="0"
            verticalCenter="0">
        <fill>
            <SolidColor color="red" />
        </fill>
    </Ellipse>

</FxApplication>

View source is enabled in the following example.

You could also create a custom component from the Ellipse with the FXG namespace, as seen in the following example:

View MXML

<?xml version="1.0" encoding="utf-8"?>
<!-- http://blog.flexexamples.com/2008/10/30/using-graphical-and-text-primitives-in-flex-gumbo/ -->
<FxApplication name="FXG_test"
        xmlns="http://ns.adobe.com/mxml/2009"
        xmlns:comps="comps.*">
    <layout>
        <BasicLayout />
    </layout>

    <comps:RedEllipse id="ellipse"
            horizontalCenter="0"
            verticalCenter="0" />

</FxApplication>

comps/RedEllipse.fxg

<?xml version="1.0" encoding="utf-8"?>
<!-- http://blog.flexexamples.com/2008/10/30/using-graphical-and-text-primitives-in-flex-gumbo/ -->
<Ellipse xmlns="http://ns.adobe.com/fxg/2008"
        width="100"
        height="100">
    <fill>
        <SolidColor color="red" />
    </fill>
</Ellipse>

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/2008/10/30/using-graphical-and-text-primitives-in-flex-gumbo/ -->
<FxApplication name="FXG_test"
        xmlns="http://ns.adobe.com/mxml/2009"
        initialize="init();">
    <layout>
        <BasicLayout />
    </layout>

    <Script>
        <![CDATA[
            import mx.graphics.Ellipse;
            import mx.graphics.SolidColor;

            private var ellipse:Ellipse;

            private function init():void {
                ellipse = new Ellipse();
                ellipse.fill = new SolidColor(0xFF0000);
                ellipse.width = 100;
                ellipse.height = 100;
                ellipse.horizontalCenter = 0;
                ellipse.verticalCenter = 0;
                addItem(ellipse);
            }
        ]]>
    </Script>

</FxApplication>

However, if you were using the <Application /> tag instead of the <FxApplication /> tag, the syntax is slightly different.
First, if you tried to use an Ellipse graphic primitive as a direct child of a Halo container (Application, Panel, Canvas, etc.), you would currently get a compiler error saying the following:

‘Ellipse’ declaration must be contained within the <Declarations> tag since it does not implement mx.core.IUIComponent.

To get around this you need to wrap the Ellipse (or other graphic primitives such as BitmapGraphic, Path, Rect, TextGraphic, TextBox, etc) in within a Group class instance (or one of its subclasses such as HGroup, VGroup, Graphic, MXMLComponent, or Skin).

View MXML

<?xml version="1.0" encoding="utf-8"?>
<!-- http://blog.flexexamples.com/2008/10/30/using-graphical-and-text-primitives-in-flex-gumbo/ -->
<Application name="FXG_test"
        xmlns="http://ns.adobe.com/mxml/2009"
        layout="absolute"
        backgroundColor="white">

    <Group id="group"
            horizontalCenter="0"
            verticalCenter="0">
        <Ellipse id="ellipse"
                width="100"
                height="100">
            <fill>
                <SolidColor color="red" />
            </fill>
        </Ellipse>
    </Group>

</Application>

You could also create a custom component from the Ellipse with the FXG namespace, as seen in the following example:

View MXML

<?xml version="1.0" encoding="utf-8"?>
<!-- http://blog.flexexamples.com/2008/10/30/using-graphical-and-text-primitives-in-flex-gumbo/ -->
<Application name="FXG_test"
        xmlns="http://ns.adobe.com/mxml/2009"
        xmlns:comps="comps.*"
        layout="absolute"
        backgroundColor="white">

    <Group id="group"
            horizontalCenter="0"
            verticalCenter="0">
        <comps:RedEllipse id="ellipse" />
    </Group>

</Application>

comps/RedEllipse.fxg

<?xml version="1.0" encoding="utf-8"?>
<!-- http://blog.flexexamples.com/2008/10/30/using-graphical-and-text-primitives-in-flex-gumbo/ -->
<Ellipse xmlns="http://ns.adobe.com/fxg/2008"
        width="100"
        height="100">
    <fill>
        <SolidColor color="red" />
    </fill>
</Ellipse>

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/2008/10/30/using-graphical-and-text-primitives-in-flex-gumbo/ -->
<Application name="FXG_test"
        xmlns="http://ns.adobe.com/mxml/2009"
        layout="absolute"
        backgroundColor="white"
        initialize="init();">

    <Script>
        <![CDATA[
            import mx.components.Group;
            import mx.graphics.Ellipse;
            import mx.graphics.SolidColor;

            private var group:Group;
            private var ellipse:Ellipse;

            private function init():void {
                ellipse = new Ellipse();
                ellipse.fill = new SolidColor(0xFF0000);
                ellipse.width = 100;
                ellipse.height = 100;

                group = new Group();
                group.setStyle("horizontalCenter", 0);
                group.setStyle("verticalCenter", 0);
                group.addItem(ellipse);
                addChild(group);
            }
        ]]>
    </Script>

</Application>

This entry is based on a beta version of the Flex Gumbo 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 Gumbo SDK.

For more information see the FXG 1.0 Specification page at opensource.adobe.com.