Bartu Bartu - 1 year ago 89
iOS Question

UI blocks while pushing view controller on to navigation controller

I have just moved my iOS 5 project to iOS 6 environment (since Apple made it mandatory to support 4-inch device compability) and now I am having a bit of a problem while pushing a

on to

After I push my custom
, my user interface blocks for 5 to 20 seconds, only when I am pushing that custom
for the first time. If I pop my
and push it again, there is no delay or UI block.

Here is what happens;

First I am pushing my UIViewController from UITableViewController's didSelectRowAtIndexPath (custom init works fine, no issue there)

CampaignDetailViewController *detailViewController = [[CampaignDetailViewController alloc] initWithProduct:selectedProduct];
[self.navigationController pushViewController:detailViewController animated:YES];

Than I am logging everything (I cleared all code in
, which means pushing the controller should only load nib)

On the pushed

- (id)initWithProduct:(Product *)selectedProduct
NSLog(@"starting init");
self = [super initWithNibName:@"CampaignDetailViewController" bundle:nil];
NSLog(@"nib loaded");
if (self) {
self.navigationItem.title =;
self.product = selectedProduct;
NSLog(@"finishing init");
return self;

- (void)viewDidLoad
NSLog(@"starting viewdidload");
[super viewDidLoad];
NSLog(@"finishing viewdidload");

- (void)viewWillAppear:(BOOL)animated
NSLog(@"view will appear");

- (void)viewDidAppear:(BOOL)animated
NSLog(@"view did appear");

Debugger Log;

2013-05-03 12:33:49.678 my-app[1429:707] starting init
2013-05-03 12:33:49.680 my-app[1429:707] nib loaded
2013-05-03 12:33:49.683 my-app[1429:707] finishing init
2013-05-03 12:33:49.808 my-app[1429:707] starting viewdidload
2013-05-03 12:33:49.855 my-app[1429:707] finishing viewdidload
2013-05-03 12:33:49.861 my-app[1429:707] view will appear
2013-05-03 12:35:28.501 my-app[1429:707] view did appear

There is over 30 seconds of delay between viewWillAppear and viewDidAppear.

Further Info

  • I have tried to use regular
    and removed the nib file, nothing changed.

  • Nothing gets loaded in between of pushViewController and loading the UIViewController.

  • This issue happens on my iPhone 4 - iOS 5 device. Everything works fine on iOS 5 and 6 simulators also works fine on my iPhone 5 - iOS 6 device.

  • I am pushing other view controllers on other parts of my project as well, but this UIViewController seems to be the only issue.

  • View controller is pushed on the main thread, and therefore view controller is loaded on the main thread

  • During this blocked period, XCode (4.6.1) also gets blocked and does not responds as well

Answer Source

Two hints:

1 - is this issue happening on the simulator or on a real device? I've experienced many unexpected delays on the simulator.

2 - remember to call

[super viewWillAppear:animated];


[super viewDidAppear:animated];

inside the impelentations.

From Apple documentation:

If you override this method, you must call super at some point in your implementation.

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