(This is both question and answer since it took quite a bit of digging to find the real answer.)
Symptom: viewWillAppear
, viewDidAppear
were not being called in my UIViewController.
Cause: Embedding a UINavigationController
or UITabBarController
(my case) in a UIViewController
somehow interrupts with the calling of these methods.
Solution: Call them manually in the UIViewController
that contains the aforementioned UINavigationController
/ UITabBarController
.
For example (assuming projectNavigationController
is your UINavigationController
):
-(void)viewWillAppear:(BOOL)animated { [super viewWillAppear:animated]; [projectNavigationController viewWillAppear:animated]; } -(void)viewWillDisappear:(BOOL)animated { [super viewWillDisappear:animated]; [projectNavigationController viewWillDisappear:animated]; } -(void)viewDidAppear:(BOOL)animated { [super viewDidAppear:animated]; [projectNavigationController viewDidAppear:animated]; } -(void)viewDidDisappear:(BOOL)animated { [super viewDidDisappear:animated]; [projectNavigationController viewDidDisappear:animated]; }
In my case I had an inner UITabBarController
and I called the methods accordingly and all was solved.
(Attribution on the solution: http://davidebenini.it/2009/01/03/viewwillappear-not-being-called-inside-a-uinavigationcontroller/)
Best Answer
I'm going to go ahead and disagree with @St3fan, and use
UIKit
as the counter-example.However, the wisdom (or lack thereof), of embedding controllers in general should be guided by sane UI design principles.
The easiest counter-example is
UINavigationControllers
embedded inUITabBarControllers
. These appear all over the place. Just off the top of my head, the iPod app on iPhone, and Contacts within the Phone app on iPhone.I was curious enough to bother to check what they do with the views (add to the "super-controller" view or to the
UIWindow
. I was pretty sure I was going to find that the sub-controller views were descendants of the super-controller views in the view hierarchy, which is contrary to St3fan's recommendation.I whipped up a very quick iPhone app hooking everything up in InterfaceBuilder to create a
UITabBarController
based app with two tabs, the first of which was aUINavigationController
with a plain oleUIViewController
as it's root view controller, and a 2nd tab with a plain oldUIViewController
just so I had a 2nd tab to click later.Sprinkle in some
NSLog
statements to output the variousUIView's
for the controllers we see this:The lines prefixed with "Superview" were the output from walking up the
rootViewController.view's
superview chain until hitting nil.Then of course a quick glance at the call stack in a couple of places where
viewDidDisappear
would get called on the root view controller.First, the call stack when
viewDidDisappear
is called on the root controller as a result of a new controller being pushed on to the stack:Second, the call stack when another tab is selected in the top-most UITabBarController:
So in all cases, it seems that Apple decided that controllers should be calling the various
viewDidAppear
, etc methods on their embedded subcontrollers and that the view's should be embedded similarly. I think the OP hit this nail right on the head if we're to takeUIKit
design as a good lead to follow.