Warning for two navigation controllers that are presented as modal

Question

I created two UIViewControll that are presented as modal. Suppose that for the first 5 attempts, the modal will display normally, but then it will give me:

 Warning: Attempt to dismiss from view controller <UINavigationController: 0x76a8450> while a presentation or dismiss is in progress! 

Below is the code for rejecting the current view controller and presenting another

 [customAlertLoad dismissViewControllerAnimated:NO completion:^{ CustomAlertMsg *cust = [[CustomAlertMsg alloc] init]; cust.modalTransitionStyle = UIModalTransitionStyleCoverVertical; cust.modalPresentationStyle = UIModalPresentationFormSheet; cust.delegate = self; [self.navigationController presentModalViewController:cust animated:YES]; cust.view.superview.frame = CGRectMake(0, 0, 458, 230); cust.view.superview.center = self.view.center; }]; 

Any help would be greatly appreciated.

Answer 1

change

I recalled another similar problem a few weeks ago. You are experiencing a race condition that can probably be solved with GCD (Grand Central Dispatch). This is similar to @rakeshNS solution, but less dangerous. (Using timers is bad practice for handling race conditions, although in many languages ​​calling a method with a 0 second timer is a trick used to call this method at the end of the call stack, which also made it asynchronous). Apple provides a mechanism for this.

I would try to make this small change:

 [customAlertLoad dismissViewControllerAnimated:NO completion:^{ dispatch_async(dispatch_get_main_queue(), ^(void) { CustomAlertMsg *cust = [[CustomAlertMsg alloc] init]; cust.modalTransitionStyle = UIModalTransitionStyleCoverVertical; cust.modalPresentationStyle = UIModalPresentationFormSheet; cust.delegate = self; [self.navigationController presentModalViewController:cust animated:YES]; cust.view.superview.frame = CGRectMake(0, 0, 458, 230); cust.view.superview.center = self.view.center; }); }]; 

The dispatch_async call puts the block at the end of the execution stack. It is not possible to run this before the modal version is fired. It also allows animation when firing and presenting two modals.

However, I must mention that in this particular problem it is a hack. You have a problem somewhere else . If I reproduce your installation in a test project, I can create / fire as many modals from completion blocks as possible without running into your error (as long as the reject code is called from the delegate custom callback used to reject the modal, as the apple says ) I would look at your custom alert download and custom alert code.

end edit

It may not be the same as your problem, I ran into this problem before popovers appeared after moving my code base to ARC. There were strange things when my Popover was released too soon or too long. The solution was to create an instance variable to hold Popover and manage it manually. Then it all started with honkey dory.

So, I would do:

 @interface YourClass:UIViewController @property (nonatomic,strong) CustomAlertMsg *cust; @end @implementation YourClass ... Codey Code.... -(void)pushView{ // For the sake of sanity, nil the modal here if(self.cust != nil) self.cust = nil; self.cust = [[CustomAlertMsg alloc] init]; self.cust.modalTransitionStyle = UIModalTransitionStyleCoverVertical; self.cust.modalPresentationStyle = UIModalPresentationFormSheet; self.cust.delegate = self; [self.navigationController presentModalViewController:self.cust animated:YES]; self.cust.view.superview.frame = CGRectMake(0, 0, 458, 230); self.cust.view.superview.center = self.view.center; } // Then where you dismiss it, or in the delegate callback that is // called when you dismiss it, if you are using one anyway, // nil it out - (void)methodThatDismissesModal { [self dismissModalViewControllerAnimated:YES]; // This is pretty important if(self.cust != nil) self.cust = nil; } ... Codey Code.... @end 

Answer 2

As stated in the error message, the problem occurs when rejected. So this is not a presentModalViewController problem, it is dismissViewControllerAnimated .

If you could insert some context for this call, we could find a solution.

Answer 3

Try changing to this:

 [self.navigationController presentModalViewController:cust animated:NO]; 

Answer 4

Perhaps try rejecting the navigation controller instead of customAlertLoad :

 [self.navigationController dismissViewControllerAnimated:NO completion:^{ CustomAlertMsg *cust = [[CustomAlertMsg alloc] init]; cust.modalTransitionStyle = UIModalTransitionStyleCoverVertical; cust.modalPresentationStyle = UIModalPresentationFormSheet; cust.delegate = self; [self.navigationController presentModalViewController:cust animated:YES]; cust.view.superview.frame = CGRectMake(0, 0, 458, 230); cust.view.superview.center = self.view.center; }]; 

Answer 5

Try it,

 [customAlertLoad dismissViewControllerAnimated:NO completion:^{ [self performSelector:@selector(pushView) withObject:ni afterDelay:0.4]; } -(void)pushView{ CustomAlertMsg *cust = [[CustomAlertMsg alloc] init]; cust.modalTransitionStyle = UIModalTransitionStyleCoverVertical; cust.modalPresentationStyle = UIModalPresentationFormSheet; cust.delegate = self; [self.navigationController presentModalViewController:cust animated:YES]; cust.view.superview.frame = CGRectMake(0, 0, 458, 230); cust.view.superview.center = self.view.center; }