Question

I make a test app and runs it on device. At frist launch everything works fine. Then I press home button to exit, then press the app icon. It seems that viewWillAppear is not called this time. In my understanding, viewWillAppear is called every time the view shows up on screen no matter it’s triggered by dismiss view controller or by pressing home button then relaunched.

Answer 1

According to the documentation:

This method is called before the receiver’s view is about to be added
to a view hierarchy and before any animations are configured for
showing the view. You can override this method to perform custom tasks
associated with displaying the view. For example, you might use this
method to change the orientation or style of the status bar to
coordinate with the orientation or style of the view being presented.
If you override this method, you must call super at some point in your
implementation.

To get notified, when your application resumes you should use:
- (void)applicationDidBecomeActive:(UIApplication *)application
This method is implemented in your AppDelegate.m