SmartLogic Logo (443) 451-3001

The SmartLogic Blog

SmartLogic is a web and mobile product development studio based in Baltimore. Contact us for help building your product or visit our website to learn more about what we do.

New Flex 4 Theme and Class Renaming

October 8th, 2008 by

NOTE: See my comment below about updating this example until I have the chance to.

A few times a day I update my subversion checkout of the Gumbo trunk. Last night I noticed a major overhaul which renamed all the Flex 4 classes, repackaged them into the mx package instead of flex. The new classes are now all (at least temporarily) prefixed with Fx, so if you are trying to compile your previously working Flex 4 code against the up-to-date SDK and suddenly see the following error:

Error: Could not resolve <Application> to a component implementation.

your issue will be resolved by changing Application to FxApplication. You’ll need to do the same for most of the other Flex 4 controls (Group, VGroup, and HGroup are exceptions that don’t need to be prefixed with Fx).

Spark Theme

You may also notice the new spark folder added in the skins directory. Below is an example application showing what these new skins look like for some of the Gumbo components:

[flash /wp-content/uploads/2008/10/spark_controls.swf]

As usual here is the code:


<?xml version="1.0" encoding="utf-8"?>
<FxApplication xmlns="">

    <VGroup horizontalCenter="0" verticalCenter="0">

        <FxButton label="Button" />

        <FxCheckBox label="Check Box" />

        <FxRadioButton label="Radio Button" />

        <FxHScrollBar />

        <FxNumericStepper />

        <FxHSlider />

        <FxTextInput />



Remember, you’ll need Flash Player 10 in order to run this SWF after you’ve compiled it.

I hope everyone’s enjoying their Gumbo!

  • Dev

    FxApplication is very strange, I think mx:Application is better, why Adobe changes it ? Using namespace is much more readable than adding prefix to the class name.

  • Greg Jastrab

    This is only a guess on my part, but I believe this is just a temporary solution since they merged the Gumbo classes into the mx package from the flex package. I may be wrong, but this is my guess as I agree with you that it looks strange.

    Remember, Gumbo isn’t even in a beta stage yet, so class names can be expected to change regularly until then.

  • Dev

    Oh I see, thanks for your reply !!!

  • Pingback: Ryan Stewart - Rich Internet Application Mountaineer » Blog Archive » New Prefixes for Flex 4 Components

  • Greg Jastrab

    Looks like Ryan is hinting (click the trackback above) that the Fx prefix is more long term than I thought…

  • Pingback: New Prefixes for Flex 4 Components | Rich Internet Applications Blog

  • Pingback: CS4 is out…

  • Greg Lafrance

    Using the Flex 4 SDK available as of this date, it seems this is how this app will be coded:

  • Greg Lafrance

    My code did not come through in my previous comment:

  • Greg Lafrance

    Oh well. So much for posting updated code. :-(

  • Greg Jastrab

    Refer to the previous posts you have commented on, I’ve updated some examples which will probably help you figure out how these all should work now.

    The main difference between the posted code and the current SDK is to add the


    namespace declaration, and preface most of the tags with s:

Greg Jastrab was a developer and project manager at SmartLogic from 2006 to 2011. Follow @gjastrab on twitter

Greg Jastrab's posts