Question

Using libgdx, how can I intercept the android BACK key in order to do some preprocessing (e.g. asking for confirmation from user), before actually performing the command to exit the game?

Answer 1

1. Enable catching of Back Key.

In the class that implements ApplicationListener

   @Override
   public void create() {
        ...
        Gdx.input.setCatchBackKey(true);
        ...
   }

2. Handle catching of Back Key.

In a class that implements the InputProcessor

   @Override
   public boolean keyDown(int keycode) {
        ...
        if(keycode == Keys.BACK){
           // Optional back button handling (e.g. ask for confirmation)
           ...
           if (shouldReallyQuit)
             Gdx.app.exit();
        }
        return false;
   }