Android fragments vs compound controls

Question

Why should Android 3.0 fragments be used instead of compound controls? One can create a View inheritor or compound control once and use it everywhere.

I've read http://android-developers.blogspot.com/2011/02/android-30-fragments-api.html but did not find the answer.

Answer 1

The difference is that fragments have a life cycle (onPause, onCreate, onStart...) of their own. By having a life cycle, fragments can respond independently to events, save their state through onSaveInstanceState, and be brought back (i.e. such as when resuming after an incoming call or when the user clicks the back button). The life cycle is summarized in the fragment documentation:

https://developer.android.com/guide/components/fragments.html#Lifecycle

You can always wrap a fragment or activity around a compound view, so just think of fragments as containers to your compound views that give them an independent life cycle.

Answer 2

The reason would be to have the same code work on tablets and phones. There are different layout considerations for these devices and Fragments allow you to take that into consideration and have your app behave differently without having to rewrite any code.