Javadoc
A TabListener receives event callbacks from the action bar as tabs
are deselected, selected, and reselected. A FragmentTransaction
is provided to each of these callbacks; if any operations are added
to it, it will be committed at the end of the full tab switch operation.
This lets tab switches be atomic without the app needing to track
the interactions between different tabs.
NOTE: This is a very simple implementation that does not retain
fragment state of the non-visible tabs across activity instances.
Look at the FragmentTabs example for how to do a more complete
implementation.