UIViewController在模态表示后更改维度

Question

I have a UIViewController which is presented using a custom transition, and by design it only fills 90% of the screen's height.

This appears fine, and I've never had any issues with it. Let's call it View A. Now I am trying to present a full screen modal view on top of this, let's call that View B. This appearance works, but when View B is dismissed, View A reappears, but has been expanded to fill the entire bounds of the screen.

Here's the presentation code I'm using:

- (void)animateTransition:(id <UIViewControllerContextTransitioning>)transitionContext
{
    ...
    // Presentation
    const CGFloat viewHeight = (screenBounds.size.height * 0.9);
    const CGRect beginFrame = CGRectMake(0, screenBounds.size.height, screenBounds.size.width, viewHeight);
    const CGRect finalFrame = CGRectMake(0, (screenBounds.size.height - viewHeight), screenBounds.size.width, viewHeight);

    // Dim
    self.dimmedView.alpha = 0.0;
    [transitionContext.containerView addSubview:self.dimmedView];
    [transitionContext.containerView addConstraints:[NSLayoutConstraint allConstraintsFromViewToSuperview:self.dimmedView inset:UIOffsetZero]];

    // Prepare
    UIView * const toView = toVC.view;
    toView.frame = beginFrame;
    [transitionContext.containerView addSubview:toView];

    // Animate
    [UIView animateWithDuration:kAnimationDuration delay:0.0 usingSpringWithDamping:0.8 initialSpringVelocity:0.25 options:0 animations:^{
        toView.frame = finalFrame;

        self.dimmedView.alpha = 0.6;

        self.tabBarController.view.layer.cornerRadius = 8.0;
        self.tabBarController.view.transform = CGAffineTransformMakeScale(0.95, 0.95);
    } completion:^(BOOL finished) {
        [transitionContext completeTransition:!transitionContext.transitionWasCancelled];
        [offshootView removeFromSuperview];
    }];
    ...
}

Has anyone seen this before, and know how to stop the system from resizing View A?

Answer 1

I think the problem is that you modify the size of the view controller's root view, although it is handled by the view controller. The documentation for UIViewController says:

A view controller's root view is always sized to fit its assigned space.

Why not add another (fully transparent) view as a child to the root view, where you place all your content? Doing so let's you keep the root view at 100% while changing the new view's size to 90% when you want to. If I understand you correctly this will accomplish the same thing without touching the root view.

For this to work you should set the view controllers Presentation property in the Storyboard attribute inspector to Over Full Screen . If you want to set it by code you set the view controller's .modalPresentationStyle = UIModalPresentationOverFullScreen . By setting this the underlying view controller will stay on screen after you have presented your view controller and continue to be visible where you have transparency in your view.

Documentation for UIViewController

Documentation for UIModalPresentationOverFullScreen