Incorrect frame when dismissing modally presented view controller

Question

I am presenting a UIViewController using a custom transition and a custom UIPresentationController. The view controller's view does not cover the entire screen, so the presenting view controller is still visible.

Next, I present an instance of UIImagePickerController on top of this view controller. The problem is that when I dismiss the image picker, the presenting view controller's frame covers the entire screen instead of just the portion I want it to cover. The frame specified by frameOfPresentedViewInContainerView in my custom UIPresentationController seems to be completely ignored.

Only if present the image picker with a modalPresentationStyle of UIModalPresentationOverCurrentContext my frames remain intact (which makes sense since no views are removed from the view hierarchy in the first place). Unfortunately that's not what I want. I want the image picker to be presented full screen, which - for whatever reason - seems to mess up my layout. Anything that I might be doing wrong or forgetting here? Any suggestions?

Answer 1

I tried both wrapper approaches mentioned. One side effect of using this wrapping approach is that device rotation doesn't display well - introducing black boxes around the presented view.

Instead of doing the wrapping trick, try setting the modalPresentationStyle of the presented UIImagePickerController to UIModalPresentationOverFullScreen. This means the views underneath the image picker won't be removed/restored from the view hierarchy during presentation/dismissal.

Answer 2

This is expected because the fullscreen presentation does not restore the original frame computed by frameOfPresentedViewInContainerView. The recommended way to fix this is to create a wrapper view in which you will insert the presented view controller's view. Here is the relevant code for your custom presentation controller:

- (void)presentationTransitionWillBegin {
    // wrapper is a property defined in the custom presentation controller.
    self.wrapper = [UIView new];
    [self.wrapper addSubview:self.presentedViewController.view];
}

- (CGRect)frameOfPresentedViewInContainerView {
    CGRect result = self.containerView.frame;

    // In this example we are doing a half-modal presentation
    CGFloat height = result.size.height/2;
    result.origin.y = height;
    result.size.height = height;

    return result;
}

- (UIView *)presentedView {
    return self.wrapper;
}

- (BOOL)shouldPresentInFullscreen {
    return NO;
}

- (void)containerViewWillLayoutSubviews {
    self.wrapper.frame = self.containerView.frame;
    self.presentedViewController.view.frame = [self frameOfPresentedViewInContainerView];
}

Note that we override presentedView to return the wrapper view instead of the default value – the presented view controller's view. This way, even if the second presentation modifies the wrapper's frame the presented view controller's view will not change.

Answer 3

This worked for me, in UIPresentationController:

override func containerViewWillLayoutSubviews() {

     super.containerViewWillLayoutSubviews()
     presentedViewController.view.frame = frameOfPresentedViewInContainerView
}

Answer 4

erudel's solution didn't work for me as is, but adding another view in between wrapperView and presentedViewController.view did the trick (I have no idea why):

- (instancetype)initWithPresentedViewController:(UIViewController *)presentedViewController
                       presentingViewController:(UIViewController *)presentingViewController {
    if (self = [super initWithPresentedViewController:presentedViewController
                             presentingViewController:presentingViewController]) {
        _wrapperView = [[UIView alloc] init];
        _wrapperView2 = [[UIView alloc] init]; // <- new view
    }
    return self;
}

- (CGRect)frameOfPresentedViewInContainerView {
    return self.containerView.bounds;
}

- (UIView *)presentedView {
    return self.wrapperView;
}

- (BOOL)shouldPresentInFullscreen {
    return NO;
}

- (void)containerViewWillLayoutSubviews {
    self.wrapperView.frame = self.containerView.frame;
    self.wrapperView2.frame = /* your custom frame goes here */;
    self.presentedViewController.view.frame = self.wrapperView2.bounds;
}

- (void)presentationTransitionWillBegin {
    [self.wrapperView addSubview:self.wrapperView2];
    [self.wrapperView2 addSubview:self.presentedViewController.view];

    // Set up a dimming view, etc
}

Tested this on iOS 9.3.

Answer 5

I tried containerViewWillLayoutSubviews but it wasn't quite working. I wanted to avoid the extra wrapper views if possible. I came up with this strategy of correcting the frame on the view using the presentedView. In addition I was able to remove containerViewWillLayoutSubviews. forceFrame is tuned to our particular use case. presentedFrame is set by our custom animator.

class CustomModalPresentationController: UIPresentationController {

        var presentedFrame = CGRect.zero
        var forceFrame = false

        override func dismissalTransitionWillBegin() {
            forceFrame = false
        }
        override func presentationTransitionDidEnd(_ completed: Bool) {
            forceFrame = true
        }
        override var presentedView: UIView? {
            if forceFrame {
                presentedViewController.view.frame = presentedFrame
            }
            return presentedViewController.view
        }
        override var frameOfPresentedViewInContainerView: CGRect {
            return presentedFrame
        }
    }