Iphone – viewDidLoad gets called, viewWillAppear does not get called, view does not appear on screen

cocoa-touchiphoneuikit

Update

It has been mentioned that viewWillAppear and viewDidAppear do not get called per the docs.
However, I perform no initialization within these methods and no adding UI elements to the view.

I was just using them to place break points to try to debug this.

Any other ideas?

Original Question

I'm stumped. I'm refactoring some code and have come across some strange behavior….

I initialize viewController A without a nib and set the view programmatically.

viewDidLoad in controller A gets called.

Inside viewDidLoad of viewController A, I initialize viewController B from a nib.

I add viewControllerB.view as a subview of viewControllerA.view

viewDidload of controller B gets called.

Then it gets weird:

viewWillAppear and viewDidAppear of
viewController B never get
called.
viewControllerB.view never makes
it on screen.
No errors.

Things I checked:

The name of the viewControllerBs Nib is correct.

The view outlet of viewControllerB is connected to a view.

viewControllerB and its view both are non-nil.

And to top it off, everything works great in SDK [redacted] beta 5!

Any ideas?
It's got to be something silly..

Best Answer

If the view controller is added to a view hierarchy through code, the view controller will not get viewWillAppear (or viewDidAppear) messages. If you add it yourself you have to send the view controller the message yourself.

Related Solutions

Iphone – View Controllers: How to switch between views programmatically

There's a nice example of switching views in Chapter 6 of Beginning iPhone Development. You can see the source code for it here: http://iphonedevbook.com/

SwitchViewController has the code to change views programatically.


- (IBAction)switchViews:(id)sender
{

    if (self.yellowViewController == nil)
    {
        YellowViewController *yellowController = [[YellowViewController alloc]
                initWithNibName:@"YellowView" bundle:nil];
        self.yellowViewController = yellowController;
        [yellowController release];
    }

    [UIView beginAnimations:@"View Flip" context:nil];
    [UIView setAnimationDuration:1.25];
    [UIView setAnimationCurve:UIViewAnimationCurveEaseInOut];

    UIViewController *coming = nil;
    UIViewController *going = nil;
    UIViewAnimationTransition transition;

    if (self.blueViewController.view.superview == nil) 
    {   
        coming = blueViewController;
        going = yellowViewController;
        transition = UIViewAnimationTransitionFlipFromLeft;
    }
    else
    {
        coming = yellowViewController;
        going = blueViewController;
        transition = UIViewAnimationTransitionFlipFromRight;
    }

    [UIView setAnimationTransition: transition forView:self.view cache:YES];
    [coming viewWillAppear:YES];
    [going viewWillDisappear:YES];
    [going.view removeFromSuperview];
    [self.view insertSubview: coming.view atIndex:0];
    [going viewDidDisappear:YES];
    [coming viewDidAppear:YES];

    [UIView commitAnimations];

}

Iphone – UIViewController: viewWillAppear is called, viewDidAppear not

I had this issue happen to me: viewWillAppear was being called but viewDidAppear was not!

I finally figured out that this was because I had a tabBarController where I overloaded it's own viewDidAppear and forgot the [super viewDidAppear:animated];

It threw off every VC in every tab! adding that line back in fixed it for my other VC's.

Hope this helps someone!

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