Fragment reality check
So, what does this Fragment stuff really do for us? Our first Fragment mini-app would have the same appearance and functionality had we not bothered with the Fragment at all.
In fact, using the Fragment class has made the whole thing more complicated! Why would we want to do this?
We know that a Fragment instance or fragments can be added to the layout of an Activity.
We know that a Fragment not only contains its own layout (view) but also its very own code (controller), which, although hosted by an Activity, the Fragment instance is virtually independent.
Our quick app only showed one Fragment instance in action, but we could have an Activity that hosts two or more fragments. We then effectively have two almost independent controllers displayed on a single screen.
What is most useful about this, however, is that when the Activity starts, we can detect attributes of the device our app is running on – perhaps phone or tablet; portrait or...