拖动以关闭 UIPresentationController

Question

我制作了一个适用于任何视图控制器的 UIPresentationController，并使用此 tutorial 显示在屏幕的一半上。现在我很想添加阻力以消除这一点。我试图让拖动感觉自然且反应灵敏，就像 Apple iOS 13 股票应用程序上“Top Stories”的拖动体验一样。我认为 iOS 13 模态拖动解雇会被结转，但它不会到这个控制器，但它不会。

我发现的每一段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/搜索。提前谢谢你

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

由于你对拖拽体验的描述不是很清楚，希望我没有误会你。

I'm trying to have the drag feel natural and responsive like the drag experience for "Top Stories" on the Apple iOS 13 stocks app.

我得到的是，你希望能够拖动呈现的视图，如果它到达某个点则将其关闭，否则返回到它的原始位置（当然你可以将视图带到你想要的任何位置). 为此，我们可以在presentedViewController中添加一个UIPanGesture，然后

根据手势移动presentedView

关闭/移回呈现的视图

 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)
    }

 }

以上代码只是基于您提供的代码的一个示例，但我希望它能解释您所谓的拖动体验背后发生的事情。希望这会有所帮助 ;)

示例结果如下：

via GIPHY

拖动以关闭 UIPresentationController

Drag to dismiss a UIPresentationController

draggable

ios

uipangesturerecognizer

swift

uipresentationcontroller