I think if you follow this tutorial carefully, you should get there without any problem.
i think something in the sdk has changed.
It was Version 2 of the dropbox-core when i developed the library.
The SDK is now at Version 6 of dropbox-core.
I may need to find out what of the dropbox SDK needs to get wrapped to support the new refreshtoken.
If you found some examples (in java) which used the authentification in Android i can help wrapping them.
I did not had the time to search for - working - examples for Android so far....