Android Mobile computing for the rest of us.* *Prepare to be sued by Apple.

Android Process Life Cycle  Process  Comprised of one or more  Activities  Services  Broadcast Receivers  Android O.S. calls all shots  Processes may be terminated if resources become scarce

Process States  Process States – Highest to Lowest Priority  Foreground Process  Process interacting with the user  Visible Process  Process the user can see or service bound to such a process  Service Process  Executing service process  Background Process  Not visible or service process – likely to be killed in order of least recently seen.  Empty Process  Processes ready to serve as hosts to newly launched applications

The Activity Stack  When an activity is started it is pushed on to the activity stack  When an activity ends it is popped off the activity stack  Activities at the bottom might be terminated if resources are needed

The Activity States  Active/Running  At the top of the activity stack  Has focus  Paused  Partially visible  Held in Memory  Ready to restart quickly  Stopped  Not at all visible  Held in Memory  Might be killed  Killed  terminated

Configuration Changes  Configuration Changes  Rotation  Changing fonts  Activity is restarted on configuration changes!!!

Dynamic vs Persistent State  Persistent State  File Data  Database Data  Dynamic State  User-Interface State

Android Activity Lifecycle Methods  onCreate(Bundle savedInstanceState)  Bundle contains dynamic state (UI state)  onRestart()  onStart()  Always called after onCreate() or onRestart(). Activity is about to become visible.  Next call will be onResume() or onStop()  onResume()  Activity is on the top of the activity stack  onPause() Another Activity is about to become foreground Store persistent state Stop animations or other cpu-intensive tasks  onStop()  The activity is no longer visible. It will either be followed by onRestart() or onDestroy()  OnDestroy()  The application has called finish() or is being destroyed to reclaim resources  No guarantee that this method will be called

More Activity Lifecycle Methods  onRestoreInstanceState(Bundle savedInstanceState)  Called immediately after onStart() if the activitiy is restarting  OnSaveInstanceState(Bundle outstate)  Called before an activity is destroyed  Provides a chance to save dynamic state

Don’t forget to tell the base “super” class  protected void onRestart()  {  super.onRestart();  // stuff you want to do here.  }

Entire Lifetime and Foreground Lifetime

Model-View-Controller (MVC)  Model – contains the program state that will be displayed  View – provides a rendering of the state  Controller – handles user interaction, usually via events *Diagram from Head First Design Patterns, by Freeman, Robson, Sierra, and Bates