Android on ROS

These are the steps with start with Android over ROS (Hydro)
First, install ROS development environment
Second, install Android Studio.
Then, download the Android SDK and put it in your home directory. If you put it in /opt/ you may not be have write access to add required packages. If you need to put in /opt/, use sudo chmod 777 -R /opt/android-studio/ if your sdk folder is inside /opt/android-studio/ folder.
Now, we assume that the android studio is installed in /opt/android-studio/ and the sdk is in /opt/android-studio/sdk/. Make sure that you have write access in both folder and their subfolder.
To be able to compile android_core you will need to download the SDK APIs android-10, android-11, android-12 and android-13. For this, go to /opt/android-studio/sdk/tools/ and run ./android. You will have the SDK Manager launched. Select the above APIs and download them. You must first add the folder /opt/android-studio/sdk/.
When download finish, go to ~/android/ and execute catkin_make. It will take a while until android_core compile. Just wait ...
Useful ROS Android Links

Getting started with ROS Android Apps
ROS Listener Question