13.3 Dynamic State vs. Persistent State

A key objective of lifecycle management is ensuring that the state of the activity is saved and restored at appropriate times. When talking about state in this context we mean the data that is currently being held within the activity and the appearance of the user interface. The activity might, for example, maintain a data model in memory that needs to be saved to a database, content provider or file. Such state information, because it persists from one invocation of the application to another, is referred to as the persistent state.

The appearance of the user interface (such as text entered into a text field but not yet committed to the application’s internal data model) is referred to as the dynamic state, since it is typically only retained during a single invocation of the application (and also referred to as user interface state or instance state).

Understanding the differences between these two states is important because...