Question

I have two views that need to be shown modally, one after the other. This doesn’t work if we dismiss and show consecutively, like this:

[rootController dismissModalViewControllerAnimated: YES];
[rootController presentModalViewController: psvc animated: YES];

The second modal view simply doesn’t show up.

I’ve seen a fix that was something like this:

[rootController dismissModalViewControllerAnimated: YES];
[[UIApplication sharedApplication] beginIgnoringInteractionEvents];
[self performSelector: @selector(seekModal) withObject: nil afterDelay: 0.5];
[[UIApplication sharedApplication] endIgnoringInteractionEvents];

The problem is that this won’t work all the time (the delay needed is superior, sometimes).

Another possible fix would be to eliminate the animation:

[rootController dismissModalViewControllerAnimated: NO];
[rootController presentModalViewController: psvc animated: YES];

But I’d really like to keep the animation, to keep the feel that the first modal is out of the way. Any suggestions?

Answer 1

EDIT: The “correct” mechanism to do this in iOS5+ would be to use the – dismissViewControllerAnimated:completion: method, and present the sequential view controller from the completion block.

---

The viewcontroller that is being shown modally will have its viewDidDisappear:animated: method called once the modal-dismissal-animation is complete. AFIK this is the only place you can hook to initiate a subsequent presentModalViewController:animated: call.

I have a class that I use for presenting modal view controllers and it implements the logic you’re looking for via a callback to the presenting view controller once the dismissal is complete. To use this class, simply alloc/init an instance and present using the normal presentViewController:animated: call. Implement the following method on the presenting view controller:

- (void) modalViewControllerDidDismiss:(UIViewController *)modalViewController

This will be called at once the modal view controller is gone, and you can present a new modal view controller at this time.

One nice thing too – since this class is a specialization of UINavigationController, you can configure the navigationBar on/off as you like. The class also has built-in logic to show a dismiss button, as you like.

Here’s the class definition:

@protocol TSModalViewControllerDelegate

- (void) modalViewControllerDidDismiss: (UIViewController*) modalViewController;

@end

@interface TSModalViewController : UINavigationController 
{
    UIViewController*   _originalParentViewController;
}
@property BOOL dismissButtonHidden;

- (id) initWithViewController: (UIViewController*) vc;
- (id) initWithClass: (Class) c;
- (id) initWithClass: (Class) c nibName:(NSString *)nibNameOrNil bundle:(NSBundle *)nibBundleOrNil;

@end

And the class implementation:

@implementation TSModalViewController
@synthesize dismissButtonHidden;

- (id) initWithViewController: (UIViewController *)vc
{
    return [super initWithRootViewController: vc];
}

- (id) initWithClass:(Class)c
{
    UIViewController* vc = [[[c alloc] init] autorelease];
    return [self initWithViewController: vc];
}

- (id) initWithClass: (Class) c nibName:(NSString *)nibNameOrNil bundle:(NSBundle *)nibBundleOrNil
{
    UIViewController* vc = [[[c alloc] initWithNibName:nibNameOrNil bundle:nibBundleOrNil] autorelease];
    return [self initWithViewController: vc];
}

- (void) viewDidAppear: (BOOL) animated
{
    [super viewDidAppear: animated];

    [_originalParentViewController release];
    _originalParentViewController = [self.parentViewController retain];

    if (!self.dismissButtonHidden)
    {
        UIBarButtonItem* dismissButton = [[[UIBarButtonItem alloc] initWithBarButtonSystemItem: UIBarButtonSystemItemStop
                                                                                        target: self 
                                                                                        action: @selector(onDismiss:)] autorelease];

        UIViewController* rootViewController = [self.viewControllers objectAtIndex:0];

        rootViewController.navigationItem.leftBarButtonItem = dismissButton;
        self.navigationBarHidden = NO;
    }   
}

- (void) viewDidDisappear:(BOOL)animated
{
    [super viewDidDisappear: animated];
    if ( [_originalParentViewController respondsToSelector: @selector(modalViewControllerDidDismiss:)] )
    {
        [_originalParentViewController performSelector: @selector(modalViewControllerDidDismiss:) withObject: self];
    }
}

- (void) dismissModalViewControllerAnimated:(BOOL)animated
{
    return [self.parentViewController dismissModalViewControllerAnimated: animated];
}

- (void) onDismiss: (id) sender
{
    [self.parentViewController dismissModalViewControllerAnimated: YES];
}

- (void) didReceiveMemoryWarning 
{
    [super didReceiveMemoryWarning];
}

- (void) viewDidUnload 
{
    [super viewDidUnload];
}

- (void)dealloc 
{
    [_originalParentViewController release];
    [super dealloc];
}

@end

and, here’s how you can use it (in the context of some normal view controller):

- (void) onShowIt:(id)sender
{
    TSModalViewController* mvc = [[[TSModalViewController alloc] initWithClass: [MyModalViewController class] nibName: @"MyModalViewController" bundle:nil] autorelease];
    mvc.dismissButtonHidden = YES;  // set to no if you don't want an "automatic" close button

    [self presentModalViewController: mvc animated: YES];
}

and, here is the dismissal callback method, which presents a new modal view controller:

- (void) modalViewControllerDidDismiss:(UIViewController *)modalViewController
{
    MyModalViewController* vc = [[[MyModalViewController alloc] initWithNibName: @"MyModalViewController" bundle:nil] autorelease];
    vc.modalTransitionStyle = UIModalTransitionStyleFlipHorizontal;

    TSModalViewController* mvc = [[[TSModalViewController alloc] initWithViewController: vc] autorelease];

    [self presentModalViewController: mvc animated: YES];
}