13. Handling Android Activity State Changes

Based on the information outlined in the chapter entitled “Understanding Android Application and Activity Lifecycles” it is now evident that the activities and fragments that make up an application pass through a variety of different states during the course of the application’s lifespan. The change from one state to the other is imposed by the Android runtime system and is, therefore, largely beyond the control of the activity itself. That does not, however, mean that the app cannot react to those changes and take appropriate actions.

The primary objective of this chapter is to provide a high-level overview of the ways in which an activity may be notified of a state change and to outline the areas where it is advisable to save or restore state information. Having covered this information, the chapter will then touch briefly on the subject of activity lifetimes.