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The method viewWillAppear: is triggered in response to a change in the state of the application, indicating that the view controller is becoming “active.” The reason viewDidLoad exists – the only reason – is that it sometimes isn't possible or efficient to configure 100% of an interface in a XIB.
In other words, if someone looks at another application or takes a phone call, then switches back to your app which was earlier on backgrounded, your UIViewController which was already visible when you left your app 'doesn't care' so to speak -- as far as it is concerned, it's never disappeared and it's still visible ...
Notifies the view controller that its view is about to be added to a view hierarchy.
There is a noticeable pause after row selection and before the new view is pushed. Some logging indicates that all of my code is reasonably quick, from row selection until the pushed controller's viewWillAppear . But then the time between viewWillAppear and viewDidAppear is logged at around 0.7 seconds.
If you use a navigation controller and set its delegate, then the view{Will,Did}{Appear,Disappear} methods are not invoked.
You need to use the navigation controller delegate methods instead:
navigationController:willShowViewController:animated:
navigationController:didShowViewController:animated:
I've run into this same problem. Just send a viewWillAppear message to your view controller before you add it as a subview. (There is one BOOL parameter which tells the view controller if it's being animated to appear or not.)
[myViewController viewWillAppear:NO];
Look at RootViewController.m in the Metronome example.
(I actually found Apple's example projects great. There's a LOT more than HelloWorld ;)
I finally found a solution for this THAT WORKS!
UINavigationControllerDelegate
I think the gist of it is to set your nav control's delegate to the viewcontroller it is in, and implement UINavigationControllerDelegate and it's two methods. Brilliant! I'm so excited i finally found a solution!
Thanks iOS 13.
ViewWillDisappear,ViewDidDisappear,ViewWillAppearandViewDidAppearwon't get called on a presenting view controller on iOS 13 which uses a new modal presentation that doesn't cover the whole screen.
Credits are going to Arek Holko. He really saved my day.
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