在iOS中，如何向下拖动以关闭模态？

时间：2015-03-26 22:52:34

标签： ios viewcontroller gesture-recognition

解雇模态的常用方法是向下滑动 - 我们如何允许用户向下拖动模态，如果距离足够远，则模态被解除，否则它会动画回到原始位置？

例如，我们可以在Twitter应用的照片视图或Snapchat的“发现”模式中找到这个。

类似的线程指出，当用户向下滑动时，我们可以使用UISwipeGestureRecognizer和[self dismissViewControllerAnimated ...]来关闭模态VC。但这只能处理一次滑动，而不是让用户拖动模态。

15 个答案:

答案 0 :(得分：85)

我刚刚创建了一个教程，用于交互式拖动模式以解除它。

http://www.thorntech.com/2016/02/ios-tutorial-close-modal-dragging/

我发现这个主题起初很混乱，因此本教程逐步构建了这个主题。

enter image description here

如果你只是想自己运行代码，那就是repo：

https://github.com/ThornTechPublic/InteractiveModal

这是我使用的方法：

查看控制器

使用自定义动画覆盖消除动画。如果用户正在拖动模态，则interactor会启动。

import UIKit

class ViewController: UIViewController {
    let interactor = Interactor()
    override func prepareForSegue(segue: UIStoryboardSegue, sender: AnyObject?) {
        if let destinationViewController = segue.destinationViewController as? ModalViewController {
            destinationViewController.transitioningDelegate = self
            destinationViewController.interactor = interactor
        }
    }
}

extension ViewController: UIViewControllerTransitioningDelegate {
    func animationController(forDismissed dismissed: UIViewController) -> UIViewControllerAnimatedTransitioning? {
        return DismissAnimator()
    }
    func interactionControllerForDismissal(animator: UIViewControllerAnimatedTransitioning) -> UIViewControllerInteractiveTransitioning? {
        return interactor.hasStarted ? interactor : nil
    }
}

解雇Animator

您可以创建自定义动画制作工具。这是一个自定义动画，您可以在UIViewControllerAnimatedTransitioning协议中打包。

import UIKit

class DismissAnimator : NSObject {
}

extension DismissAnimator : UIViewControllerAnimatedTransitioning {
    func transitionDuration(transitionContext: UIViewControllerContextTransitioning?) -> NSTimeInterval {
        return 0.6
    }

    func animateTransition(transitionContext: UIViewControllerContextTransitioning) {
        guard
            let fromVC = transitionContext.viewControllerForKey(UITransitionContextFromViewControllerKey),
            let toVC = transitionContext.viewControllerForKey(UITransitionContextToViewControllerKey),
            let containerView = transitionContext.containerView()
            else {
                return
        }
        containerView.insertSubview(toVC.view, belowSubview: fromVC.view)
        let screenBounds = UIScreen.mainScreen().bounds
        let bottomLeftCorner = CGPoint(x: 0, y: screenBounds.height)
        let finalFrame = CGRect(origin: bottomLeftCorner, size: screenBounds.size)

        UIView.animateWithDuration(
            transitionDuration(transitionContext),
            animations: {
                fromVC.view.frame = finalFrame
            },
            completion: { _ in
                transitionContext.completeTransition(!transitionContext.transitionWasCancelled())
            }
        )
    }
}

交互器

您将UIPercentDrivenInteractiveTransition子类化，以便它可以充当您的状态机。由于两个VC都访问了交互器对象，因此使用它来跟踪平移进度。

import UIKit

class Interactor: UIPercentDrivenInteractiveTransition {
    var hasStarted = false
    var shouldFinish = false
}

模态视图控制器

这将平移手势状态映射到交互方法调用。 translationInView() y值确定用户是否超过阈值。当平移手势为.Ended时，交互者将完成或取消。

import UIKit

class ModalViewController: UIViewController {

    var interactor:Interactor? = nil

    @IBAction func close(sender: UIButton) {
        dismissViewControllerAnimated(true, completion: nil)
    }

    @IBAction func handleGesture(sender: UIPanGestureRecognizer) {
        let percentThreshold:CGFloat = 0.3

        // convert y-position to downward pull progress (percentage)
        let translation = sender.translationInView(view)
        let verticalMovement = translation.y / view.bounds.height
        let downwardMovement = fmaxf(Float(verticalMovement), 0.0)
        let downwardMovementPercent = fminf(downwardMovement, 1.0)
        let progress = CGFloat(downwardMovementPercent)
        guard let interactor = interactor else { return }

        switch sender.state {
        case .Began:
            interactor.hasStarted = true
            dismissViewControllerAnimated(true, completion: nil)
        case .Changed:
            interactor.shouldFinish = progress > percentThreshold
            interactor.updateInteractiveTransition(progress)
        case .Cancelled:
            interactor.hasStarted = false
            interactor.cancelInteractiveTransition()
        case .Ended:
            interactor.hasStarted = false
            interactor.shouldFinish
                ? interactor.finishInteractiveTransition()
                : interactor.cancelInteractiveTransition()
        default:
            break
        }
    }

}

答案 1 :(得分：53)

我将分享我在Swift 3中的表现：

结果

实施

class MainViewController: UIViewController {

  @IBAction func click() {
    performSegue(withIdentifier: "showModalOne", sender: nil)
  }

}

class ModalOneViewController: ViewControllerPannable {
  override func viewDidLoad() {
    super.viewDidLoad()

    view.backgroundColor = .yellow
  }

  @IBAction func click() {
    performSegue(withIdentifier: "showModalTwo", sender: nil)
  }
}

class ModalTwoViewController: ViewControllerPannable {
  override func viewDidLoad() {
    super.viewDidLoad()

    view.backgroundColor = .green
  }
}

模态视图控制器继承自我构建的class（ViewControllerPannable）以使其在达到特定速度时可拖动和不可接受。

ViewControllerPannable类

class ViewControllerPannable: UIViewController {
  var panGestureRecognizer: UIPanGestureRecognizer?
  var originalPosition: CGPoint?
  var currentPositionTouched: CGPoint?

  override func viewDidLoad() {
    super.viewDidLoad()

    panGestureRecognizer = UIPanGestureRecognizer(target: self, action: #selector(panGestureAction(_:)))
    view.addGestureRecognizer(panGestureRecognizer!)
  }

  func panGestureAction(_ panGesture: UIPanGestureRecognizer) {
    let translation = panGesture.translation(in: view)

    if panGesture.state == .began {
      originalPosition = view.center
      currentPositionTouched = panGesture.location(in: view)
    } else if panGesture.state == .changed {
        view.frame.origin = CGPoint(
          x: translation.x,
          y: translation.y
        )
    } else if panGesture.state == .ended {
      let velocity = panGesture.velocity(in: view)

      if velocity.y >= 1500 {
        UIView.animate(withDuration: 0.2
          , animations: {
            self.view.frame.origin = CGPoint(
              x: self.view.frame.origin.x,
              y: self.view.frame.size.height
            )
          }, completion: { (isCompleted) in
            if isCompleted {
              self.dismiss(animated: false, completion: nil)
            }
        })
      } else {
        UIView.animate(withDuration: 0.2, animations: {
          self.view.center = self.originalPosition!
        })
      }
    }
  }
}

答案 2 :(得分：15)

创建了一个演示，用于交互式拖动以关闭视图控制器，如Snapchat的发现模式。检查此github以获取示例项目。

enter image description here

答案 3 :(得分：9)

Swift 4.x，使用Pangesture

简单方法

垂直

class ViewConrtoller: UIViewController {
    override func viewDidLoad() {
        super.viewDidLoad()
        view.addGestureRecognizer(UIPanGestureRecognizer(target: self, action: #selector(onDrage(_:))))
    }

    @objc func onDrage(_ sender:UIPanGestureRecognizer) {
        let percentThreshold:CGFloat = 0.3
        let translation = sender.translation(in: view)

        let newX = ensureRange(value: view.frame.minX + translation.x, minimum: 0, maximum: view.frame.maxX)
        let progress = progressAlongAxis(newX, view.bounds.width)

        view.frame.origin.x = newX //Move view to new position

        if sender.state == .ended {
            let velocity = sender.velocity(in: view)
           if velocity.x >= 300 || progress > percentThreshold {
               self.dismiss(animated: true) //Perform dismiss
           } else {
               UIView.animate(withDuration: 0.2, animations: {
                   self.view.frame.origin.x = 0 // Revert animation
               })
          }
       }

       sender.setTranslation(.zero, in: view)
    }
}

辅助功能 

func progressAlongAxis(_ pointOnAxis: CGFloat, _ axisLength: CGFloat) -> CGFloat {
        let movementOnAxis = pointOnAxis / axisLength
        let positiveMovementOnAxis = fmaxf(Float(movementOnAxis), 0.0)
        let positiveMovementOnAxisPercent = fminf(positiveMovementOnAxis, 1.0)
        return CGFloat(positiveMovementOnAxisPercent)
    }

    func ensureRange<T>(value: T, minimum: T, maximum: T) -> T where T : Comparable {
        return min(max(value, minimum), maximum)
    }

艰难的方式

参考此 - ＆gt; https://github.com/satishVekariya/DraggableViewController

答案 4 :(得分：8)

大量更新 Swift 4 的回购。

对于 Swift 3 ，我创建了以下内容以从右到左呈现UIViewController并通过平移手势将其解除。我已将其上传为GitHub repository。

enter image description here

DismissOnPanGesture.swift档案：

//  Created by David Seek on 11/21/16.
//  Copyright © 2016 David Seek. All rights reserved.

import UIKit

class DismissAnimator : NSObject {
}

extension DismissAnimator : UIViewControllerAnimatedTransitioning {
    func transitionDuration(using transitionContext: UIViewControllerContextTransitioning?) -> TimeInterval {
        return 0.6
    }

    func animateTransition(using transitionContext: UIViewControllerContextTransitioning) {

        let screenBounds = UIScreen.main.bounds
        let fromVC = transitionContext.viewController(forKey: UITransitionContextViewControllerKey.from)
        let toVC = transitionContext.viewController(forKey: UITransitionContextViewControllerKey.to)
        var x:CGFloat      = toVC!.view.bounds.origin.x - screenBounds.width
        let y:CGFloat      = toVC!.view.bounds.origin.y
        let width:CGFloat  = toVC!.view.bounds.width
        let height:CGFloat = toVC!.view.bounds.height
        var frame:CGRect   = CGRect(x: x, y: y, width: width, height: height)

        toVC?.view.alpha = 0.2

        toVC?.view.frame = frame
        let containerView = transitionContext.containerView

        containerView.insertSubview(toVC!.view, belowSubview: fromVC!.view)


        let bottomLeftCorner = CGPoint(x: screenBounds.width, y: 0)
        let finalFrame = CGRect(origin: bottomLeftCorner, size: screenBounds.size)

        UIView.animate(
            withDuration: transitionDuration(using: transitionContext),
            animations: {
                fromVC!.view.frame = finalFrame
                toVC?.view.alpha = 1

                x = toVC!.view.bounds.origin.x
                frame = CGRect(x: x, y: y, width: width, height: height)

                toVC?.view.frame = frame
            },
            completion: { _ in
                transitionContext.completeTransition(!transitionContext.transitionWasCancelled)
            }
        )
    }
}

class Interactor: UIPercentDrivenInteractiveTransition {
    var hasStarted = false
    var shouldFinish = false
}

let transition: CATransition = CATransition()

func presentVCRightToLeft(_ fromVC: UIViewController, _ toVC: UIViewController) {
    transition.duration = 0.5
    transition.type = kCATransitionPush
    transition.subtype = kCATransitionFromRight
    fromVC.view.window!.layer.add(transition, forKey: kCATransition)
    fromVC.present(toVC, animated: false, completion: nil)
}

func dismissVCLeftToRight(_ vc: UIViewController) {
    transition.duration = 0.5
    transition.timingFunction = CAMediaTimingFunction(name: kCAMediaTimingFunctionEaseInEaseOut)
    transition.type = kCATransitionPush
    transition.subtype = kCATransitionFromLeft
    vc.view.window!.layer.add(transition, forKey: nil)
    vc.dismiss(animated: false, completion: nil)
}

func instantiatePanGestureRecognizer(_ vc: UIViewController, _ selector: Selector) {
    var edgeRecognizer: UIScreenEdgePanGestureRecognizer!
    edgeRecognizer = UIScreenEdgePanGestureRecognizer(target: vc, action: selector)
    edgeRecognizer.edges = .left
    vc.view.addGestureRecognizer(edgeRecognizer)
}

func dismissVCOnPanGesture(_ vc: UIViewController, _ sender: UIScreenEdgePanGestureRecognizer, _ interactor: Interactor) {
    let percentThreshold:CGFloat = 0.3
    let translation = sender.translation(in: vc.view)
    let fingerMovement = translation.x / vc.view.bounds.width
    let rightMovement = fmaxf(Float(fingerMovement), 0.0)
    let rightMovementPercent = fminf(rightMovement, 1.0)
    let progress = CGFloat(rightMovementPercent)

    switch sender.state {
    case .began:
        interactor.hasStarted = true
        vc.dismiss(animated: true, completion: nil)
    case .changed:
        interactor.shouldFinish = progress > percentThreshold
        interactor.update(progress)
    case .cancelled:
        interactor.hasStarted = false
        interactor.cancel()
    case .ended:
        interactor.hasStarted = false
        interactor.shouldFinish
            ? interactor.finish()
            : interactor.cancel()
    default:
        break
    }
}

易于使用：

import UIKit

class VC1: UIViewController, UIViewControllerTransitioningDelegate {

    let interactor = Interactor()

    @IBAction func present(_ sender: Any) {
        let vc = self.storyboard?.instantiateViewController(withIdentifier: "VC2") as! VC2
        vc.transitioningDelegate = self
        vc.interactor = interactor

        presentVCRightToLeft(self, vc)
    }

    func animationController(forDismissed dismissed: UIViewController) -> UIViewControllerAnimatedTransitioning? {
        return DismissAnimator()
    }

    func interactionControllerForDismissal(using animator: UIViewControllerAnimatedTransitioning) -> UIViewControllerInteractiveTransitioning? {
        return interactor.hasStarted ? interactor : nil
    }
}

class VC2: UIViewController {

    var interactor:Interactor? = nil

    override func viewDidLoad() {
        super.viewDidLoad()
        instantiatePanGestureRecognizer(self, #selector(gesture))
    }

    @IBAction func dismiss(_ sender: Any) {
        dismissVCLeftToRight(self)
    }

    func gesture(_ sender: UIScreenEdgePanGestureRecognizer) {
        dismissVCOnPanGesture(self, sender, interactor!)
    }
}

答案 5 :(得分：8)

这是一个基于@ wilson答案（谢谢）的单文件解决方案，具有以下改进：

先前解决方案的改进列表

  • 限制平移以使视图仅下降：
    • 仅通过更新y
      • 的view.frame.origin坐标来避免水平翻译
    • 使用let y = max(0, translation.y)
      • 向上滑动时，请避免平移屏幕
  • 同时根据手指被释放的位置（默认为屏幕的下半部分）而不仅仅基于滑动的速度来关闭视图控制器
  • 将视图控制器显示为模态以确保前一个视图控制器出现在后面并避免黑色背景（应该回答您的问题@nguyễn-anh-việt）
  • 删除不需要的currentPositionTouched和originalPosition
  • 公开以下参数：
    • minimumVelocityToHide：什么速度足以隐藏（默认为1500）
    • minimumScreenRatioToHide：隐藏得足够低（默认为0.5）
    • animationDuration：我们隐藏/显示的速度有多快（默认为0.2秒）

解决方案

斯威夫特3＆amp;斯威夫特4：

//
//  PannableViewController.swift
//

import UIKit

class PannableViewController: UIViewController {
    public var minimumVelocityToHide = 1500 as CGFloat
    public var minimumScreenRatioToHide = 0.5 as CGFloat
    public var animationDuration = 0.2 as TimeInterval

    override func viewDidLoad() {
        super.viewDidLoad()

        // Listen for pan gesture
        let panGesture = UIPanGestureRecognizer(target: self, action: #selector(onPan(_:)))
        self.view.addGestureRecognizer(panGesture)
    }

    func slideViewVerticallyTo(_ y: CGFloat) {
        self.view.frame.origin = CGPoint(x: 0, y: y)
    }

    @objc func onPan(_ panGesture: UIPanGestureRecognizer) {
        switch panGesture.state {
        case .began, .changed:
            // If pan started or is ongoing then
            // slide the view to follow the finger
            let translation = panGesture.translation(in: view)
            let y = max(0, translation.y)
            self.slideViewVerticallyTo(y)
            break
        case .ended:
            // If pan ended, decide it we should close or reset the view
            // based on the final position and the speed of the gesture
            let translation = panGesture.translation(in: view)
            let velocity = panGesture.velocity(in: view)
            let closing = (translation.y > self.view.frame.size.height * minimumScreenRatioToHide) ||
                          (velocity.y > minimumVelocityToHide)

            if closing {
                UIView.animate(withDuration: animationDuration, animations: {
                    // If closing, animate to the bottom of the view
                    self.slideViewVerticallyTo(self.view.frame.size.height)
                }, completion: { (isCompleted) in
                    if isCompleted {
                        // Dismiss the view when it dissapeared
                        self.dismiss(animated: false, completion: nil)
                    }
                })
            } else {
                // If not closing, reset the view to the top
                UIView.animate(withDuration: animationDuration, animations: {
                    self.slideViewVerticallyTo(0)
                })
            }
            break
        default:
            // If gesture state is undefined, reset the view to the top
            UIView.animate(withDuration: animationDuration, animations: {
                self.slideViewVerticallyTo(0)
            })
            break
        }
    }

    override init(nibName nibNameOrNil: String?, bundle nibBundleOrNil: Bundle?)   {
        super.init(nibName: nil, bundle: nil)
        self.modalPresentationStyle = .overFullScreen;
        self.modalTransitionStyle = .coverVertical;
    }

    required init?(coder aDecoder: NSCoder) {
        super.init(coder: aDecoder)
        self.modalPresentationStyle = .overFullScreen;
        self.modalTransitionStyle = .coverVertical;
    }
}

答案 6 :(得分：6)

您要描述的是交互式自定义转换动画。您正在定制过渡的动画和驾驶手势，即解除（或不解除）呈现的视图控制器。实现它的最简单方法是将UIPanGestureRecognizer与UIPercentDrivenInteractiveTransition组合。

我的书解释了如何做到这一点，我已经发布了一些例子（来自书中）。这个特殊的例子是一个不同的情况 - 过渡是横向的，而不是向下的，它是一个标签栏控制器，而不是一个呈现的控制器 - 但基本的想法是完全相同的：

https://github.com/mattneub/Programming-iOS-Book-Examples/blob/master/bk2ch06p296customAnimation2/ch19p620customAnimation1/AppDelegate.swift

如果您下载该项目并运行它，您将看到正在发生的事情正是您所描述的，除了它是横向的：如果拖动超过一半，我们转换，但如果没有，我们取消和重新回到原位。

答案 7 :(得分：6)

我创建了一个易于使用的扩展程序。

只是固有你的UIViewController和InteractiveViewController，你就完成了 InteractiveViewController

从控制器调用showInteractive（）方法以显示为Interactive。

enter image description here

答案 8 :(得分：4)

仅垂直解雇

func panGestureAction(_ panGesture: UIPanGestureRecognizer) {
    let translation = panGesture.translation(in: view)

    if panGesture.state == .began {
        originalPosition = view.center
        currentPositionTouched = panGesture.location(in: view)    
    } else if panGesture.state == .changed {
        view.frame.origin = CGPoint(
            x:  view.frame.origin.x,
            y:  view.frame.origin.y + translation.y
        )
        panGesture.setTranslation(CGPoint.zero, in: self.view)
    } else if panGesture.state == .ended {
        let velocity = panGesture.velocity(in: view)
        if velocity.y >= 150 {
            UIView.animate(withDuration: 0.2
                , animations: {
                    self.view.frame.origin = CGPoint(
                        x: self.view.frame.origin.x,
                        y: self.view.frame.size.height
                    )
            }, completion: { (isCompleted) in
                if isCompleted {
                    self.dismiss(animated: false, completion: nil)
                }
            })
        } else {
            UIView.animate(withDuration: 0.2, animations: {
                self.view.center = self.originalPosition!
            })
        }
    }

答案 9 :(得分：4)

我想出了超级简单的方法。只需将以下代码放入视图控制器：

Swift 4 

override func viewDidLoad() {
    super.viewDidLoad()
    let gestureRecognizer = UIPanGestureRecognizer(target: self,
                                                   action: #selector(panGestureRecognizerHandler(_:)))
    view.addGestureRecognizer(gestureRecognizer)
}

@IBAction func panGestureRecognizerHandler(_ sender: UIPanGestureRecognizer) {
    let touchPoint = sender.location(in: view?.window)
    var initialTouchPoint = CGPoint.zero

    switch sender.state {
    case .began:
        initialTouchPoint = touchPoint
    case .changed:
        if touchPoint.y > initialTouchPoint.y {
            view.frame.origin.y = touchPoint.y - initialTouchPoint.y
        }
    case .ended, .cancelled:
        if touchPoint.y - initialTouchPoint.y > 200 {
            dismiss(animated: true, completion: nil)
        } else {
            UIView.animate(withDuration: 0.2, animations: {
                self.view.frame = CGRect(x: 0,
                                         y: 0,
                                         width: self.view.frame.size.width,
                                         height: self.view.frame.size.height)
            })
        }
    case .failed, .possible:
        break
    }
}

答案 10 :(得分：3)

在目标C中： 这是代码

在viewDidLoad 

UISwipeGestureRecognizer *swipeRecognizer = [[UISwipeGestureRecognizer alloc]
                                             initWithTarget:self action:@selector(swipeDown:)];
swipeRecognizer.direction = UISwipeGestureRecognizerDirectionDown;
[self.view addGestureRecognizer:swipeRecognizer];

//Swipe Down Method

- (void)swipeDown:(UIGestureRecognizer *)sender{
[self dismissViewControllerAnimated:YES completion:nil];
}

答案 11 :(得分：2)

这是我基于@Wilson回答的扩展：

// MARK: IMPORT STATEMENTS
import UIKit

// MARK: EXTENSION
extension UIViewController {

    // MARK: IS SWIPABLE - FUNCTION
    func isSwipable() {
        let panGestureRecognizer = UIPanGestureRecognizer(target: self, action: #selector(handlePanGesture(_:)))
        self.view.addGestureRecognizer(panGestureRecognizer)
    }

    // MARK: HANDLE PAN GESTURE - FUNCTION
    @objc func handlePanGesture(_ panGesture: UIPanGestureRecognizer) {
        let translation = panGesture.translation(in: view)
        let minX = view.frame.width * 0.135
        var originalPosition = CGPoint.zero

        if panGesture.state == .began {
            originalPosition = view.center
        } else if panGesture.state == .changed {
            view.frame.origin = CGPoint(x: translation.x, y: 0.0)

            if panGesture.location(in: view).x > minX {
                view.frame.origin = originalPosition
            }

            if view.frame.origin.x <= 0.0 {
                view.frame.origin.x = 0.0
            }
        } else if panGesture.state == .ended {
            if view.frame.origin.x >= view.frame.width * 0.5 {
                UIView.animate(withDuration: 0.2
                     , animations: {
                        self.view.frame.origin = CGPoint(
                            x: self.view.frame.size.width,
                            y: self.view.frame.origin.y
                        )
                }, completion: { (isCompleted) in
                    if isCompleted {
                        self.dismiss(animated: false, completion: nil)
                    }
                })
            } else {
                UIView.animate(withDuration: 0.2, animations: {
                    self.view.frame.origin = originalPosition
                })
            }
        }
    }

}

<强> USAGE

在视图控制器中，您希望可以移动：

override func viewDidLoad() {
    super.viewDidLoad()

    self.isSwipable()
}

并且可以通过从视图控制器的最左侧滑动作为导航控制器来禁用。

答案 12 :(得分：2)

对于真正想深入了解Custom UIViewController Transition的用户，我建议使用this great tutorial from raywenderlich.com。

原始的最终示例项目包含错误。因此，我对其进行了修复并将其上传到Github repo。该项目位于Swift 5中，因此您可以轻松地运行和播放它。

这是预览：

它也是交互式的！

黑客愉快！

答案 13 :(得分：1)

这是我的简单类，用于从轴拖动ViewController 。只是继承了来自DraggableViewController的课程。

MyCustomClass: DraggableViewController

仅适用于显示的ViewController。

// MARK: - DraggableViewController

public class DraggableViewController: UIViewController {

    public let percentThresholdDismiss: CGFloat = 0.3
    public var velocityDismiss: CGFloat = 300
    public var axis: NSLayoutConstraint.Axis = .horizontal
    public var backgroundDismissColor: UIColor = .black {
        didSet {
            navigationController?.view.backgroundColor = backgroundDismissColor
        }
    }

    // MARK: LifeCycle

    override func viewDidLoad() {
        super.viewDidLoad()
        view.addGestureRecognizer(UIPanGestureRecognizer(target: self, action: #selector(onDrag(_:))))
    }

    // MARK: Private methods

    @objc fileprivate func onDrag(_ sender: UIPanGestureRecognizer) {

        let translation = sender.translation(in: view)

        // Movement indication index
        let movementOnAxis: CGFloat

        // Move view to new position
        switch axis {
        case .vertical:
            let newY = min(max(view.frame.minY + translation.y, 0), view.frame.maxY)
            movementOnAxis = newY / view.bounds.height
            view.frame.origin.y = newY

        case .horizontal:
            let newX = min(max(view.frame.minX + translation.x, 0), view.frame.maxX)
            movementOnAxis = newX / view.bounds.width
            view.frame.origin.x = newX
        }

        let positiveMovementOnAxis = fmaxf(Float(movementOnAxis), 0.0)
        let positiveMovementOnAxisPercent = fminf(positiveMovementOnAxis, 1.0)
        let progress = CGFloat(positiveMovementOnAxisPercent)
        navigationController?.view.backgroundColor = UIColor.black.withAlphaComponent(1 - progress)

        switch sender.state {
        case .ended where sender.velocity(in: view).y >= velocityDismiss || progress > percentThresholdDismiss:
            // After animate, user made the conditions to leave
            UIView.animate(withDuration: 0.2, animations: {
                switch self.axis {
                case .vertical:
                    self.view.frame.origin.y = self.view.bounds.height

                case .horizontal:
                    self.view.frame.origin.x = self.view.bounds.width
                }
                self.navigationController?.view.backgroundColor = UIColor.black.withAlphaComponent(0)

            }, completion: { finish in
                self.dismiss(animated: true) //Perform dismiss
            })
        case .ended:
            // Revert animation
            UIView.animate(withDuration: 0.2, animations: {
                switch self.axis {
                case .vertical:
                    self.view.frame.origin.y = 0

                case .horizontal:
                    self.view.frame.origin.x = 0
                }
            })
        default:
            break
        }
        sender.setTranslation(.zero, in: view)
    }
}

答案 14 :(得分：0)

您可以使用UIPanGestureRecognizer检测用户的拖动并使用它移动模态视图。如果结束位置足够远，则视图可以被解除，或以其他方式动画回到其原始位置。

查看this answer以获取有关如何实施此类内容的更多信息。

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