I've just started using libgdx (http://code.google.com/p/libgdx/) for Android development. They have a JNI wrapper for Box2D (java wrapper for the native code). They also have plenty of example code which you can look at to see how they use Box2D.
If you view the video at their Google code page, it will explain how to easily setup a project. Then you may want to go to the wiki, or I found that the guy at http://steigert.blogspot.com.au/ is working his way through an extremely comprehensive but easy to understand tutorial.
If you are interested in looking straight at some Box2D code which runs on Android, here are plenty of tests here:
There is also source code for complete games, some which use Box2D:
You'll find development quite fast, because you can run your games on a PC as well as on the phone, so most of your debugging will be done on the PC. The process for setting up both the PC and the Android code is described nicely in the video I described above (the guy narrating is quite funny).