Nice slide transition between non-fullscreen and fullscreen UIViewController

Question

I have a view controller which is not fullscreen (has a status bar) and want to present a modal view controller which is fullscreen.

If I hide the status bar at the beginning of the animation (parent's viewWillDisappear or modal's viewWillAppear) then for a moment the parent will be visible without a status bar, looking like a bug.

If I do it at the end of the animation (parent's viewDidDisappear or modal's viewDidAppear) then the status bar will be visible for a moment over the modal view, i.e. it won't appear as the modal view "covered it".

Is there a way to do this nicely?

edit:

One possibility would be to create a UIWindow with windowLevel=alert for at least the duration of the animation. The sample iAd ad seems to cover the status bar nicely without another window, so it must be possible somehow.

Answer 1

Another fun little project. This was the best I could come up with. It's not too bad if you don't mind using your own container controller to manage presenting/dismissing view controllers. I try to do things in a general way but this could be rolled into an app w/ the ContainerViewController if desired.

Note that I only implemented the equivalent of UIModalTransitionStyleCoverVertical. You can customize the animation however you like as well.

Relevant animation code:

- (void)presentViewController:(UIViewController *)viewControllerToPresent
{   
    // do nothing if no controller
    if (!viewControllerToPresent) return;

    [__viewControllers addObject:viewControllerToPresent];
    CGRect toFrame = viewControllerToPresent.view.frame;
    toFrame.origin = CGPointMake(0, CGRectGetMaxY(self.view.bounds));
    viewControllerToPresent.view.frame = toFrame;

    [UIView transitionWithView:self.view
                      duration:0.2
                       options:UIViewAnimationOptionTransitionNone
                    animations:^{
                        [[UIApplication sharedApplication] setStatusBarHidden:viewControllerToPresent.wantsFullScreenLayout withAnimation:UIStatusBarAnimationSlide];
                        [self.view addSubview:viewControllerToPresent.view];
                        viewControllerToPresent.view.frame = [UIScreen mainScreen].applicationFrame;
                    }
                    completion:nil];
}

- (void)dismissViewController
{
    // nothing to dismiss if showing first controller
    if (__viewControllers.count <= 1) return;

    UIViewController *currentViewController = [__viewControllers lastObject];
    UIViewController *previousViewController = [__viewControllers objectAtIndex:__viewControllers.count - 2];

    [UIView transitionWithView:self.view
                      duration:0.2
                       options:UIViewAnimationOptionTransitionNone
                    animations:^{
                        [[UIApplication sharedApplication] setStatusBarHidden:previousViewController.wantsFullScreenLayout withAnimation:UIStatusBarAnimationSlide];
                        CGRect toFrame = currentViewController.view.frame;
                        toFrame.origin = CGPointMake(0, CGRectGetMaxY(self.view.bounds));
                        currentViewController.view.frame = toFrame;
                    }
                    completion:^(BOOL finished) {
                        [currentViewController.view removeFromSuperview];
                        [__viewControllers removeLastObject];
                    }];
}