I know it is too late. But this might help. I had similar issues for the past few weeks connecting and communicating the mega adk and Android.
As I got succeeded now, I wrote blog posts which might help you and others with similar issues. I did run the application on Kitkat and Lollipop without any issues, but not sure about Jellybean.
Here are few changes that are to be made to make the android application work on most of the devices.
Change import com.android.future.usb.UsbAccessory;
to
import android.hardware.usb.UsbAccessory;
Change UsbAccessory accessory = UsbManager.getAccessory(intent);
to
UsbAccessory accessory = (UsbAccessory) intent.getParcelableExtra(UsbManager.EXTRA_ACCESSORY);
And Here is the link to the blog post http://blog.srichakram.in/2015/09/arduino-mega-adk-and-android.html