Unbalanced calls to begin/end appearance transitions for UITabBarController

Question

I have an UITabBarController, when initial run, I want to overlay a login view controller but received error.

Unbalanced calls to begin/end appearance transitions for < UITabBarController: 0x863ae00 >.

Below is the code.

- (BOOL)application:(UIApplication *)application didFinishLaunchingWithOptions:(NSDictionary *)launchOptions
{
    // Override point for customization after application launch.
    self.window = [[[UIWindow alloc] initWithFrame:[[UIScreen mainScreen] bounds]] autorelease];

    // Override point for customization after application launch.

    UIViewController *lessonVC = [[[LessonViewController alloc] initWithNibName:@"LessonViewController" bundle:nil] autorelease];

    UIViewController *programVC = [[[ProgramViewController alloc] initWithNibName:@"ProgramViewController" bundle:nil] autorelease];

    UIViewController *flashcardVC = [[[FlashCardViewController alloc] initWithNibName:@"FlashCardViewController" bundle:nil] autorelease];

    UIViewController *moreVC = [[[MoreViewController alloc] initWithNibName:@"MoreViewController" bundle:nil] autorelease];

    UINavigationController *lessonNVC = [[[UINavigationController alloc] initWithRootViewController:lessonVC] autorelease];

    UINavigationController *programNVC = [[[UINavigationController alloc] initWithRootViewController:programVC] autorelease];

    UINavigationController *flashcardNVC = [[[UINavigationController alloc] initWithRootViewController:flashcardVC] autorelease];

    UINavigationController *moreNVC = [[[UINavigationController alloc] initWithRootViewController:moreVC] autorelease];

    self.tabBarController = [[[UITabBarController alloc] init/*WithNibName:nil bundle:nil*/] autorelease];
    self.tabBarController.viewControllers = [NSArray arrayWithObjects:lessonNVC, programNVC, flashcardNVC, moreNVC, nil];
    self.tabBarController.selectedIndex = 0;
    self.window.rootViewController = self.tabBarController;

    [self.window makeKeyAndVisible];

    if (![[ZYHttpRequest sharedRequest] userID]) 
    {
        // should register or login firstly
        LoginViewController *loginVC = [[LoginViewController alloc] initWithNibName:@"LoginViewController"
                                                                             bundle:nil];
        loginVC.modalTransitionStyle = UIModalTransitionStyleFlipHorizontal;
        [self.tabBarController presentModalViewController:loginVC animated:YES];
        ZY_SAFE_RELEASE(loginVC);
    }

    return YES;
}

Anyone who can help me? Thanks in advance!

Also, I'v checked this[http://stackoverflow.com/q/7886096/527539]. But no luck. — ZYiOS, Dec 19 '11 at 15:25

score 78 · Accepted Answer · edited May 13 '16 at 18:07

78

You need to wait to present the modal view controller until the next run loop. I ended up using a block (to make things more simple) to schedule the presentation for the next run loop:

Update:
As mentioned by Mark Amery below, just a simple dispatch_async works, there's no need for a timer:

dispatch_async(dispatch_get_main_queue(), ^(void){     
  [self.container presentModalViewController:nc animated:YES]; 
});

/* Present next run loop. Prevents "unbalanced VC display" warnings. */
double delayInSeconds = 0.1;
dispatch_time_t popTime = dispatch_time(DISPATCH_TIME_NOW, delayInSeconds * NSEC_PER_SEC);
dispatch_after(popTime, dispatch_get_main_queue(), ^(void){
    [self.container presentModalViewController:nc animated:YES];
});

edited May 13 '16 at 18:07

Ozgur Vatansever

49,246
17
84
119

answered Dec 27 '11 at 22:50

Maurizio

4,143
1
29
28

4

No need for a timer here, at least in the case I had (in which your answer solved my warning). Just do `dispatch_async(dispatch_get_main_queue(), ^(void){ [self.container presentModalViewController:nc animated:YES]; });` which is simpler and less hacky. – Mark Amery Sep 18 '13 at 15:27
I totally agree with Mark, it's easier just to use ` dispatch_async(dispatch_get_main_queue(), { code block }) – netwire Jul 24 '14 at 23:53
7

`dispatch_async()` didn't work on iOS8 for me but `dispatch_after()` worked. The downside of it is that I see the rootViewController for a moment (because of 0.1f delay). – SoftDesigner Sep 22 '14 at 11:41
@SoftDesigner I have the same problem, the rootViewController is shown for a moment. Did you find a solution to this? – entropid Oct 17 '14 at 03:12
@Entropid nope, I had to change the structure of view controllers to avoid that. – SoftDesigner Oct 17 '14 at 11:11
1

I'm using [[NSRunLoop currentRunLoop] runUntilDate:[NSDate date]]; before presentViewController:, it looks better for me, since you are sure, that loop ran before presenting. – Povilas Dec 17 '14 at 11:57
@Entropid on iOS8 I had to delay the first presentation to `viewDidAppear` on the root view controller (which must be done loading by that point). Unfortunately there is a brief delay and, alas, `viewWillAppear` is too soon. – wcochran Jul 15 '15 at 20:24

score 10 · Answer 2 · answered Dec 21 '11 at 04:11

I suspect the problem is that you're trying to call presentModalViewController: before the tab bar is done loading. Try moving the final logic onto the next event loop:

  [self.window makeKeyAndVisible];
  [self performSelector:(handleLogin) withObject:nil afterDelay:0];
}

- (void)handleLogin
{
  if (![[ZYHttpRequest sharedRequest] userID]) 
    {
        // should register or login firstly
        LoginViewController *loginVC = [[LoginViewController alloc] initWithNibName:@"LoginViewController"
                                                                             bundle:nil];
        loginVC.modalTransitionStyle = UIModalTransitionStyleFlipHorizontal;
        [self.tabBarController presentModalViewController:loginVC animated:YES];
        ZY_SAFE_RELEASE(loginVC);
    }
}

[self performSelector:(handleLogin) withObject:nil afterDelay:0.1]; work in my iPod 4G, if delay time is 0, will only work on simulator but get the same warning in device. — ZYiOS, Dec 28 '11 at 15:08
Thank you, thank you, thank you. The selected answer has the same idea, but much more complicated, and this worked great for me. — Le Mot Juiced, Jul 20 '13 at 21:45

score 5 · Answer 3 · edited Sep 26 '12 at 08:27

5

[self.tabBarController presentModalViewController:loginVC animated:**NO**];

edited Sep 26 '12 at 08:27

danielbeard

9,120
3
44
58

answered Aug 30 '12 at 14:15

Rio V

59
1
1

score 2 · Answer 4 · answered Nov 09 '12 at 20:20

2

I had a similar problem when tried to presentModalViewController (my welcome screen) in main view's viewWillAppear. Is was solved just by moving the modal VC call to viewDidAppear.

answered Nov 09 '12 at 20:20

Arseniy

487
4
14

score 0 · Answer 5 · edited Feb 25 '13 at 06:04

0

[self performSelector:@selector(modaltheView) withObject:self afterDelay:0.1];
-(void)modaltheView
{
    [self.container presentModalViewController:nc animated:YES];
}

edited Feb 25 '13 at 06:04

DD_

7,230
11
38
59

answered Feb 25 '13 at 05:42

swamy

9
1

Unbalanced calls to begin/end appearance transitions for UITabBarController

5 Answers5

Linked