Android has many different ways for you to store data for long-term use by your activity. The simplest to use is the preferences system, which is the focus of this chapter.
Android allows activities and applications to keep preferences, in the form of key/value pairs (akin to a
Map), that will hang around between invocations of an activity. As the name suggests, the primary purpose of preferences is to enable you to store user-specified configuration details, such as the last feed the user looked at in your feed reader, the sort order to use by default on a list, or whatever. Of course, you can store in the preferences whatever you like, as long as it is keyed by a
String and has a primitive value (