Android : How to scroll background in games?

I have some basic programming skills but Im new in game programming. Know that every game needs a game loop, something like while (true) { //do things } in separate thread. But i wonder how is a scrollabe background (2D) used to be realized (when pressing arrow, main character is in the middle of screen, but background and things are moving). How could a simplest example of code for android platform looks like?