Dealing with the MX namespace in the FX world


So one day, you decide you're not going to use an mx DataGrid, because you know it's just not necessary; all you want to do is display a list, and if you haven't heard (...if you haven't, why are you reading this article...), Spark components are all the rage. So you set up a stub project, use an s:List, set up an item renderer, fake some data, do a little style work, and it all works great. 


Then you try to integrate it into a Flex 3.5 project. You're already using the "both mx/fx" setting in the project properties, but there's a lot of files in there that were built before Spark. 


You can end up with all kind if problems:

•  If you have any interface implementations in your top-level element (usually a Canvas or some such), suddenly the interface methods will come up as "not implemented".
• Your style for the List won't work, any number of odd errors, like "mobile theme only" and some such appear. 
• Namespaces will be called undeclared.
• "Only one language may be specified" sorts of errors. 

Here's what you need to make sure of:

• Declare your top-level mx and fx namespaces this way (you'll also need the "s" namespace for Spark components):

xmlns:fx="http://ns.adobe.com/mxml/2009"
xmlns:mx="library://ns.adobe.com/flex/mx"
xmlns:s="library://ns.adobe.com/flex/spark"

• If you have inline style problems, this is an example of making it work. Note that I'm styling all s:List components with this, and even though the "s" namespace is declared above, you'll still need it below in the style declaration.

<fx:style>
@namespace s "library://ns.adobe.com/flex/spark";
s|List { baseColor: #e5e5e5; }
</fx:style>

• And the big one...make sure you change the namespace of your script tags if you are seeing problems with interface implementations and whatnot.

<fx:script></fx:script>

That should do it, these things have solved most of problems when dealing with the mx namespace in the fx world. 

As always, thanks for visiting.