Android as a platform offers a lot of different components to be used around. In a single Activity you might find yourself with a stack of Fragments, Views, Model data, adapters, Action bar actions, View actions (click), context menus and more.
Aiming to combine them all in an elegant way that will guarantee you with flexible and modular code will require you to “decouple” them from each other. That way, you will have the opportunity to re-use them, and make future changes easier.
