PureMVC is an MVC framework with a flex port (actually, the original was developed in flex and later ported to other platforms). It was one of the first frameworks (along with Cairngorm) to be released for flex. I find it to be a little restrictive myself with a learning curve.
You'll find AS3 to be somewhat natural for a Java developer. The syntax may be a little funky, but you will have most of what you want directly translated to AS3. AS3 source files end in *.as and the output is either a *.swf (executable) or a *.swc (library).
If you pick up flex, you'll also find *.mxml files which is its markup language. The fundamental difference between MXML and programming in Android's XML template or webdevelopment with HTML is that the MXML file actually compiles to a pure actionscript class.
For a Java developer, I would recommend that you take a look at spring actionscript. It one of the first (if not the first) dependency injection frameworks and comes out of the port directly from Java Spring. You will get your annotation-based injection or injection through XML configuration.
Personally, if I were to start from scratch as a beginner, my framework of choice is swiz for its simplicity.