This repo is a simple communication library for Arduino and Android with using Usb Shield. Project also contains an example.With this library you can achieve :
*Connect an Arduino to Android with usb cable as accessory.
*With accessory support on android you can get higher baud rates.
*Set commands and define a function to answer these commands.
This project is created on Xcode with using embedXcode. For info about how to install embedXcode(https://arduandro.wordpress.com/2015/10/02/a-better-development-environment-for-arduino-embedxcode/) You can upload directly an Arduino uno and test library with this apk:https://www.dropbox.com/s/o27bp8mgnwplbwz/ADKLibraryCom.apk?dl=0 It sends "getBV" with clicking message button and Arduino answers it.
Detailed info about how to use this library is at : https://arduandro.wordpress.com/2015/10/04/arduino-meets-android-usb-host-shield-and-adk-serial-communication-library/