"'borderThickness' is only supported by the halo theme" Flex namespace warning

I'm trying to understand what is going on with my namespaces since I upgraded to flash builder 4.

xmlns:mx="http://www.adobe.com/2006/mxml" in the application

and in the stylesheets:

@namespace mx "library://ns.adobe.com/flex/mx";

Everything seems to be recognized correctly, however, I get a warning that says:

"borderThickness" is only supported by the halo theme

(which I thought was in the mx theme).

Now, when I try 开发者_Python百科xmlns:s="library://ns.adobe.com/flex/mx" then it doesn't recognize anything. Is there something I might be doing wrong here or confusing?

mx is the default prefix for mx components - they're the components you're used to from flex 3. it's URI should be library://ns.adobe.com/flex/mx

s is the default prefix for spark components. They're the new components added in flex 4. It's URI should be library://ns.adobe.com/flex/spark

for more info, see this document: http://www.adobe.com/devnet/flex/articles/flex3and4_differences_03.html

as quoo stated above, you need to make sure you change the ns declarations in your mxml files to:

xmlns:fx="http://ns.adobe.com/mxml/2009"

xmlns:mx="library://ns.adobe.com/flex/mx"

xmlns:s="library://ns.adobe.com/flex/spark"

That being said however, I have noticed some wonkiness with FB4 when you add these namespaces for the first time to a file that was originally built in FB3. Sometimes it will not code-complete some old halo components. On mine, it will mysteriously create a fictitious "mx1" namespace that I haven't even declared. Most times I've found that closing the editor window and doing a project clean, then re-opening the file seems to fix the problem.