android: button for scrolling at a certain position


I was planning to create a function where there’s a 2 button at the side of the screen for up and down. I want it to just scroll up or down a little if I tap/touch it once and not totally at the top or bottom of the screen. I tried to search how to do it but all I saw was about getting at the top/bottom. Can you guys suggest me how can I implement this kind of function?

Source: Android Questions