An example of the android joystick library at https://github.com/controlwear/virtual-joystick-android.
A screenshot of this example is
Note: this repository has been changed to use the OFFLINE COMPILED LOCAL aar library file in the app/libs directory, instead of the online one at io.github.controlwear:virtualjoystick.
Note: This app uses the default empty app configuration of Android Studio, so change the SDK version in the app/build.gradle script as you like, or install the one specified in the file.