Understand the Activity Lifecycle

Fig. A simplified illustration of the activity lifecycle

When user navigates from one activity to another or even in single-page activity, the application will pass through various states. These states are onCreate, onStart, onResume, onPause, onStop, onDestroy. Which are totally responsible for behavior of the activities in application.


Activity Lifecycle States (Methods)

onCreate()

Called when the activity is first created. This is where you should do all of your normal static set up: create views, bind data to lists, etc. This method also provides you with a Bundle containing the activity’s previously frozen state, if there was one. Always followed by onStart().

onRestart()

Called after your activity has been stopped, prior to it being started again. Always followed by onStart()

onStart()

Called when the activity is becoming visible to the user. Followed by onResume() if the activity comes to the foreground, or onStop() if it becomes hidden.

onResume()

Called when the activity will start interacting with the user. At this point your activity is at the top of the activity stack, with user input going to it. Always followed by onPause().

onPause()

Called as part of the activity lifecycle when an activity is going into the background, but has not (yet) been killed. The counterpart to onResume(). When activity B is launched in front of activity A, this callback will be invoked on A. B will not be created until A’s onPause() returns, so be sure to not do anything lengthy here.

onStop()

Called when you are no longer visible to the user. You will next receive either onRestart(), onDestroy(), or nothing, depending on later user activity.

onDestroy()

The final call you receive before your activity is destroyed. This can happen either because the activity is finishing (someone called finish() on it, or because the system is temporarily destroying this instance of the activity to save space. You can distinguish between> these two scenarios with the isFinishing() method.


Activity Lifecycle Example

simple code shows the the behavior of activity. use this code snippet and check your log. You will get the better idea how the these activity lifecycle states work.


Some Situations

  • When open the app

onCreate() --> onStart() --> onResume()

  • When back button pressed and exit the app

onPaused() -- > onStop() --> onDestory()

  • When home button pressed

onPaused() --> onStop()

  • After pressed home button when again open app from recent task list or clicked on icon

onRestart() --> onStart() --> onResume()

  • When open app another app from notification bar or open settings

onPaused() --> onStop()

  • Back button pressed from another app or settings then used can see our app

onRestart() --> onStart() --> onResume()

  • When any dialog open on screen

onPause()

  • After dismiss the dialog or back button from dialog

onResume()


Simplified Meanings

onCreate()
on Create And Prepare To Display
onRestart()
on Prepare To Display
onStart()
on Visible
onResume()
on Begin Interaction
onPause()
on Pause Interaction
onStop()
on Invisible
onDestroy()
on Finish

for more information checkout Android Developer Documentation