拖动以关闭 UIPresentationController

Question

我使用本教程制作了一个适合任何视图控制器并显示在屏幕的一半上的 UIPresentationController 。现在我想添加阻力来消除这个问题。我试图让拖动感觉自然且响应灵敏，就像 Apple iOS 13 股票应用程序上“热门故事”的拖动体验一样。我认为 iOS 13 模式拖动关闭会被保留，但它不会转移到这个控制器，但事实并非如此。

我发现的每一点代码和教程都有糟糕的拖动体验。有谁知道如何做到这一点？过去一周我一直在尝试/寻找。先感谢您

这是我的演示控制器代码

class SlideUpPresentationController: UIPresentationController {
    // MARK: - Variables
    private var dimmingView: UIView!
    
    //MARK: - View functions
    override init(presentedViewController: UIViewController, presenting presentingViewController: UIViewController?) {
        super.init(presentedViewController: presentedViewController, presenting: presentingViewController)
        setupDimmingView()
    }
    
    override func containerViewWillLayoutSubviews() {
      presentedView?.frame = frameOfPresentedViewInContainerView
    }
    
    override var frameOfPresentedViewInContainerView: CGRect {
        guard let container = containerView else { return super.frameOfPresentedViewInContainerView }
        let width = container.bounds.size.width
        let height : CGFloat = 300.0
        
        return CGRect(x: 0, y: container.bounds.size.height - height, width: width, height: height)
    }
    
    override func presentationTransitionWillBegin() {
        guard let dimmingView = dimmingView else { return }
        
        containerView?.insertSubview(dimmingView, at: 0)
      
      NSLayoutConstraint.activate(NSLayoutConstraint.constraints(withVisualFormat: "V:|[dimmingView]|",
                                                                 options: [],
                                                                 metrics: nil,
                                                                 views: ["dimmingView": dimmingView]))
      
      NSLayoutConstraint.activate(NSLayoutConstraint.constraints(withVisualFormat: "H:|[dimmingView]|",
                                                                 options: [],
                                                                 metrics: nil,
                                                                 views: ["dimmingView": dimmingView]))
      
      guard let coordinator = presentedViewController.transitionCoordinator else {
        dimmingView.alpha = 1.0
        return
      }
      
      coordinator.animate(alongsideTransition: { _ in
        self.dimmingView.alpha = 1.0
      })
    }
    
    override func dismissalTransitionWillBegin() {
      guard let coordinator = presentedViewController.transitionCoordinator else {
        dimmingView.alpha = 0.0
        return
      }
      
      coordinator.animate(alongsideTransition: { _ in
        self.dimmingView.alpha = 0.0
      })
    }
    
    func setupDimmingView() {
      dimmingView = UIView()
      dimmingView.translatesAutoresizingMaskIntoConstraints = false
      dimmingView.backgroundColor = UIColor(white: 0.0, alpha: 0.5)
      dimmingView.alpha = 0.0
      
      let recognizer = UITapGestureRecognizer(target: self,
                                              action: #selector(handleTap(recognizer:)))
      dimmingView.addGestureRecognizer(recognizer)
    }
    
    @objc func handleTap(recognizer: UITapGestureRecognizer) {
      presentingViewController.dismiss(animated: true)
    }
}

Answer 1

由于您对想要的拖动体验的描述不太清楚，希望我没有误解您的意思。

我试图让拖动感觉自然且响应灵敏，就像 Apple iOS 13 股票应用程序上“热门故事”的拖动体验一样。

我得到的是，您希望能够拖动呈现的视图，如果它到达某个点则将其关闭，否则返回到其原始位置（并且因为您可以将视图带到您想要的任何位置）。为了实现这一点，我们可以向presentedViewController添加一个UIPanGesture，然后

1. 根据手势移动presentedView

2. 关闭/移回presentedView

    class SlideUpPresentationController: UIPresentationController {
        // MARK: - Variables
        private var dimmingView: UIView!
        private var originalX: CGFloat = 0
   
        //MARK: - View functions
        override init(presentedViewController: UIViewController, presenting presentingViewController: UIViewController?) {
            super.init(presentedViewController: presentedViewController, presenting: presentingViewController)
            setupDimmingView()
        }
   
        override func containerViewWillLayoutSubviews() {
            presentedView?.frame = frameOfPresentedViewInContainerView
        }
   
        override var frameOfPresentedViewInContainerView: CGRect {
            guard let container = containerView else { return super.frameOfPresentedViewInContainerView }
            let width = container.bounds.size.width
            let height : CGFloat = 300.0
   
            return CGRect(x: 0, y: container.bounds.size.height - height, width: width, height: height)
        }
   
        override func presentationTransitionWillBegin() {
            guard let dimmingView = dimmingView else { return }
   
            containerView?.insertSubview(dimmingView, at: 0)
            // add PanGestureRecognizer for dragging the presented view controller
            let viewPan = UIPanGestureRecognizer(target: self, action: #selector(viewPanned(_:)))
            containerView?.addGestureRecognizer(viewPan)
   
            NSLayoutConstraint.activate(NSLayoutConstraint.constraints(withVisualFormat: "V:|[dimmingView]|", options: [], metrics: nil, views: ["dimmingView": dimmingView]))
   
            NSLayoutConstraint.activate(NSLayoutConstraint.constraints(withVisualFormat: "H:|[dimmingView]|", options: [], metrics: nil, views: ["dimmingView": dimmingView]))
   
            guard let coordinator = presentedViewController.transitionCoordinator else {
                dimmingView.alpha = 1.0
                return
            }
   
            coordinator.animate(alongsideTransition: { _ in
                self.dimmingView.alpha = 1.0
            })
        }
   
        @objc private func viewPanned(_ sender: UIPanGestureRecognizer) {
            // how far the pan gesture translated
            let translate = sender.translation(in: self.presentedView)
            switch sender.state {
                case .began:
                    originalX = presentedViewController.view.frame.origin.x
                case .changed:
                    // move the presentedView according to pan gesture
                    // prevent it from moving too far to the right
                    if originalX + translate.x < 0 {
                        presentedViewController.view.frame.origin.x = originalX + translate.x
                    }
                case .ended:
                    let presentedViewWidth = presentedViewController.view.frame.width
                    let newX = presentedViewController.view.frame.origin.x
   
                    // if the presentedView move more than 0.75 of the presentedView's width, dimiss it, else bring it back to original position
                    if presentedViewWidth * 0.75 + newX > 0 {
                        setBackToOriginalPosition()
                    } else {
                        moveAndDismissPresentedView()
                    }
                default:
                    break
            }
        }
   
        private func setBackToOriginalPosition() {
            // ensure no pending layout change in presentedView
            presentedViewController.view.layoutIfNeeded()
            UIView.animate(withDuration: 0.25, delay: 0.0, options: .curveEaseIn, animations: {
                self.presentedViewController.view.frame.origin.x = self.originalX
                self.presentedViewController.view.layoutIfNeeded()
            }, completion: nil)
        }
   
        private func moveAndDismissPresentedView() {
            // ensure no pending layout change in presentedView
            presentedViewController.view.layoutIfNeeded()
            UIView.animate(withDuration: 0.25, delay: 0.0, options: .curveEaseIn, animations: {
                self.presentedViewController.view.frame.origin.x = -self.presentedViewController.view.frame.width
                self.presentedViewController.view.layoutIfNeeded()
            }, completion: { _ in
                // dimiss when the view is completely move outside the screen
                self.presentingViewController.dismiss(animated: true, completion: nil)
            })
         }
   
        override func dismissalTransitionWillBegin() {
            guard let coordinator = presentedViewController.transitionCoordinator else {
                dimmingView.alpha = 0.0
                return
            }
   
            coordinator.animate(alongsideTransition: { _ in
                self.dimmingView.alpha = 0.0
            })
        }
   
        func setupDimmingView() {
            dimmingView = UIView()
            dimmingView.translatesAutoresizingMaskIntoConstraints = false
            dimmingView.backgroundColor = UIColor(white: 0.0, alpha: 0.5)
            dimmingView.alpha = 0.0
   
            let recognizer = UITapGestureRecognizer(target: self,
                                          action: #selector(handleTap(recognizer:)))
            dimmingView.addGestureRecognizer(recognizer)
        }
   
       @objc func handleTap(recognizer: UITapGestureRecognizer) {
           presentingViewController.dismiss(animated: true)
       }
   
    }
   

上面的代码只是基于您提供的代码的示例，但我希望能够解释您所谓的拖动体验的幕后发生的情况。希望这可以帮助 ;）

这是示例结果：

通过 GIPHY