When you minimize the application (for example, by pressing the Home button), the activity stops. It is very important that when you maximize the application back, the activity is correctly restored and the data is saved.
Please, note:
the process of minimizing and maximizing the application must be checked on each screen. This case is especially useful for the input forms. Simply take the user's side: it is very unpleasant if you typed a letter, then switched the mail app to answer the call, but when you returned, you did not find your text. Also, this should not happen with a data entry form containing a large number of fields. Finding it empty again, the user can go insane. We DO NOT code like that. Period.
When you exit the application (using the hardware "back" button) in addition to step 1 and step 2, step 3 is performed. Activity is destroyed and the next time you start the application, it is recreated.
Test-case #5. Screen rotation (pic.8)