Fragments

Fragments will likely become a staple of almost every app you make. They are so useful, there are so many reasons to use them, and—once you get used to them—they are so simple, that there is almost no reason not to use them.

Fragments are reusable elements of an app, just like any class, but, as we mentioned previously, they have special features—such as the ability to load their own view/layout, as well as their very own lifecycle functions—which make them perfect for achieving the goals we discussed in the Real-world apps section.

Let's dig a bit deeper into fragments, one feature at a time.

Fragments have a life cycle too

We can set up and control fragments, very much like we do with activities, by overriding the appropriate lifecycle functions.

The onCreate function

In the onCreate function, we can initialize variables and do almost all the things we typically do in the Activity onCreate function. The big exception to this is initializing our UI...