There are two areas where our choices differ from what you might see elsewhere in the Android community:
This is mostly a matter of opinion. We find it makes for cleaner code in the applications in this book because it puts the listener’s method implementations right where you want to see them. In high-performance contexts or large applications, anonymous inner classes may cause problems, but for most circumstances they work fine.
Fragments are not an absolutely necessary tool, but we find that, when used correctly, they are a valuable tool in any Android developer’s toolkit. Once you get comfortable with fragments, they are not that difficult to work with. Fragments have clear advantages over activities that make them worth the effort, including flexibility in building and presenting your user interfaces.