UIPresentationController底部弹窗取消保存后短暂全屏问题求助

嘿，这个坑我之前踩过！用UIPresentationController做底部自定义弹窗时，调用系统的“保存到文件”后确实会出现弹窗先闪全屏再恢复的情况，本质是系统处理模态转场时临时修改了presentedView的尺寸，而原来的布局逻辑没跟上。下面是我亲测有效的解决思路：

核心解决思路 #

• 用约束替代直接设置Frame：别再只在containerViewWillLayoutSubviews()里硬写frame了，直接给presentedView添加明确的宽度、高度和位置约束，让系统无法随意修改它的尺寸。
• 重写尺寸计算方法：在自定义的PresentationController里重写size(forChildContentContainer:withParentContainerSize:)，返回你想要的弹窗尺寸，告诉系统这才是弹窗的理想大小。
• 避免布局逻辑滞后：系统在关闭“保存到文件”视图后才触发containerViewWillLayoutSubviews()，这时候已经晚了，提前用约束和尺寸方法锁定布局，就能避免临时全屏的闪屏。

修改后的关键代码 #

自定义PresentationController #

class SlideInPresentationController: UIPresentationController {
    private let direction: PresentationDirection
    private let disableCompactHeight: Bool
    
    init(presentedViewController: UIViewController,
         presenting presentingViewController: UIViewController?,
         direction: PresentationDirection,
         disableCompactHeight: Bool) {
        self.direction = direction
        self.disableCompactHeight = disableCompactHeight
        super.init(presentedViewController: presentedViewController, presenting: presentingViewController)
    }
    
    // 告诉系统弹窗的理想尺寸
    override func size(forChildContentContainer container: UIContentContainer, withParentContainerSize parentSize: CGSize) -> CGSize {
        // 根据你的需求返回自定义尺寸，比如高度300，宽度和父容器一致
        if disableCompactHeight && traitCollection.horizontalSizeClass == .compact && traitCollection.verticalSizeClass == .regular {
            return CGSize(width: parentSize.width, height: 300)
        }
        return super.size(forChildContentContainer: container, withParentContainerSize: parentSize)
    }
    
    override func containerViewWillLayoutSubviews() {
        super.containerViewWillLayoutSubviews()
        guard let presentedView = presentedView else { return }
        
        // 禁用自动转译，用约束控制布局
        presentedView.translatesAutoresizingMaskIntoConstraints = false
        NSLayoutConstraint.activate([
            presentedView.widthAnchor.constraint(equalTo: containerView!.widthAnchor),
            presentedView.heightAnchor.constraint(equalToConstant: 300), // 替换成你的弹窗高度
            presentedView.bottomAnchor.constraint(equalTo: containerView!.bottomAnchor) // 底部弹出的位置约束
        ])
    }
    
    // 可选：添加背景遮罩（如果需要的话）
    override func presentationTransitionWillBegin() {
        super.presentationTransitionWillBegin()
        let dimmingView = UIView()
        dimmingView.backgroundColor = UIColor.black.withAlphaComponent(0.5)
        dimmingView.frame = containerView!.bounds
        dimmingView.autoresizingMask = [.flexibleWidth, .flexibleHeight]
        containerView?.insertSubview(dimmingView, at: 0)
    }
}

确保TransitioningDelegate返回正确的PresentationController #

class SlideInPresentationManager: NSObject, UIViewControllerTransitioningDelegate {
    var direction: PresentationDirection = .bottom
    var disableCompactHeight = true
    
    func presentationController(forPresented presented: UIViewController, presenting: UIViewController?, source: UIViewController) -> UIPresentationController? {
        return SlideInPresentationController(presentedViewController: presented, presenting: presenting, direction: direction, disableCompactHeight: disableCompactHeight)
    }
}

为什么这样有效？ #

系统在处理“保存到文件”这种系统级模态视图时，会临时调整presentedView的尺寸来适配转场，但我们通过size(forChildContentContainer:)明确告诉了系统弹窗的理想尺寸，再加上约束锁定了位置和大小，系统就不会随便把弹窗拉成全屏了，关闭后也能保持正确的布局，不会出现闪屏。

内容的提问来源于stack exchange，提问作者alex