Understanding the fragment lifecycle

One of the challenges of developing Android applications is assuring that our applications effectively handle the lifecycle of the application's activities. During the lifetime of an application, a given activity may be created, destroyed, and recreated many times. A simple action such as a user rotating a device from a portrait to landscape orientation, or vice-versa, normally causes the visible activity to be completely destroyed and recreated using the appropriate resources for the new orientation. Applications that do not cooperate effectively with this natural lifecycle will often crash or behave in some other undesirable manner.

As we know, each fragment instance exists within a single activity; therefore, that fragment must cooperate in some way with the activity lifecycle. In fact, not only do fragments cooperate with the activity lifecycle but also they are intimately connected.

In both the setup and display phase and hide and teardown phase, fragments...