This project was born for answering this stackoverflow question. Implemented two ViewPager scrolling together, i.e. one ViewPager following another ViewPager's scrolling motions by some rules. As that question said, this effect just like an iOS contacts list. Consist of an alphabet and a contact list. Alphabet scroll simultaneously if the coming contact of contact list not longer belong to current alpha.
Describing maybe not very clear, just take a look at below illustration.
