Easy Understand Activity life cycle

States of an activity

An activity can be in different states depending how it is interacting with the user. These states are described by the following table.

State	Description
Running	Activity is visible and interacts with the user.
Paused	Activity is still visible but partially obscured, instance is running but might be killed by the system.
Stopped	Activity is not visible, instance is running but might be killed by the system.
Killed	Activity has been terminated by the system of by a call to its finish() method.

The live cycle methods

The Android system defines a life-cycle for activities via predefined life-cycle methods. The most important methods are: .Important Activity lifecycle methods:

Method	Purpose
onCreate()	Called then the activity is created. Used to initialize the activity, for example create the user interface.
onResume()	Called if the activity get visible again and the user starts interacting with the activity again. Used to initialize fields, register listeners, bind to services, etc.
onPause()	Called once another activity gets into the foreground. Always called before the activity is not visible anymore. Used to release resources or save application data. For example you unregister listeners, intent receivers, unbind from services or remove system service listeners.
onStop()	Called once the activity is no longer visible. Time or CPU intensive shut-down operations, such as writing information to a database should be down in the onStop() method. This method is guaranteed to be called as of API 11.