ios - 向 UIScrollView 添加垂直两指滑动手势

Question

根据 How to add a vertical swipe gesture to iPhone app for all screens ，我向 window 添加了一个双指向下滑动手势，这在整个应用程序的普通页面上都可以正常工作。但它在页面上失败了 UIScrollView(如 UITableViewController)。当我在 UIScrollView 上用两根手指向下滑动时，它只是像往常一样滚动。如果我从 UIScrollView 上方的 UINavigationBar 滑动，它再次正常工作。

理想的结果是我可以正常用一根手指滚动tableview，不用滚动tableview用两根手指滑动页面调用一些方法。这在 TweetBot 中用于切换黑暗模式，效果很好。

根据 Apple 文档:Using Responders and the Responder Chain to Handle Events ，我想我了解响应链是如何工作的，所以我想请 UIScrollView 忽略两指滑动手势，以便它可以将此事件传递给 UIWindow。但我不知道如何:

我试图实现来自 Apple 的 UIGestureRecognizerDelegate 的 func gestureRecognizer(_:, shouldRequireFailureOf otherGestureRecognizer:) document ，或通过继承 UITableView 覆盖 gestureRecognizerShouldBegin(_)。但都没有用。

欢迎任何解决方案或建议。

更新 - 最终解决方案

我简化了 joern 的解决方案，这里是。

在AppDelegate

中

// It's not necessary to keep a reference to gesture unless you want to do something further.
lazy var gesture: UIPanGestureRecognizer = {
    let gesture = UIPanGestureRecognizer(target: self, action: #selector(twoFingerDidSwipe(recognizer:)))
    gesture.minimumNumberOfTouches = 2
    gesture.maximumNumberOfTouches = 2
    return gesture
}()

func application(_ application: UIApplication, didFinishLaunchingWithOptions launchOptions: [UIApplication.LaunchOptionsKey: Any]?) -> Bool {
    gesture.delegate = AppDelegate
    window.addGestureRecognizer(gesture)
    return true
}

@objc func twoFingerDidSwipe(recognizer: UIPanGestureRecognizer) {
    let swipeThreshold: CGFloat = 50

    if recognizer.state == .changed { // 1
      switch recognizer.translation(in: window).y { // 2
      case ...(-swipeThreshold):
        print("Swipe Up")
        recognizer.state = .cancelled // 3
      case swipeThreshold...:
        print("Swipe Down")
        recognizer.state = .cancelled
      default:
        break
      }
    }
}

和

extension AppDelegate: UIGestureRecognizerDelegate {
  func gestureRecognizer(_ gestureRecognizer: UIGestureRecognizer, shouldRecognizeSimultaneouslyWith otherGestureRecognizer: UIGestureRecognizer) -> Bool {
    return true
  }
}

关于与 joern 解决方案差异的一些解释:

1. 只关注recognizer.state == .change。
2. recognizer.translation(in:) 的参数应该是 window 这样我就不能对特定的 VC 做任何事情。
3. 此识别器触发某些方法后，应将其取消，以防止继续触发它们。

而且没有必要对任何特定的 VC 做任何事情。

有了这个，双指滑动手势在普通 VC 和滚动 VC 上都可以正常工作。

Answer 1

当您将 UISwipeGestureRecognizer 添加到您的窗口时，保留对它的引用，以便您稍后可以通过 AppDelegate 访问它:

class AppDelegate: UIResponder, UIApplicationDelegate {

    var window: UIWindow?
    var twoFingerSwipeDownRecognizer: UISwipeGestureRecognizer?

    func application(_ application: UIApplication, didFinishLaunchingWithOptions launchOptions: [UIApplication.LaunchOptionsKey: Any]?) -> Bool {

        let twoFingerSwipeDownRecognizer = UISwipeGestureRecognizer(target: self, action: #selector(didRecognizeTwoFingerSwipeDown))
        twoFingerSwipeDownRecognizer.numberOfTouchesRequired = 2
        twoFingerSwipeDownRecognizer.direction = .down
        window?.addGestureRecognizer(twoFingerSwipeDownRecognizer)
        self.twoFingerSwipeDownRecognizer = twoFingerSwipeDownRecognizer

        return true
    }

    @objc func didRecognizeTwoFingerSwipeDown(recognizer: UISwipeGestureRecognizer) {
        print("SWIPE DOWN")
    }
}

然后，在包含 UITableView(或 UIScrollView)的 UIViewController 中，您必须调用 require(toFail:) 在 UITableView 的平移手势识别器上:

func enableTwoFingerSlideDown() {
    guard
        let appDelegate = UIApplication.shared.delegate as? AppDelegate,
        let twoFingerGestureRecognizer = appDelegate.twoFingerSwipeDownRecognizer
        else {
            return
        }
    tableView.panGestureRecognizer.require(toFail: twoFingerGestureRecognizer)
}

现在，两根手指向下的手势适用于 UITableView。

更新

因为滑动是一个离散的手势，所以上面的解决方案可能不是完美的解决方案。当您用一根 手指缓慢向下滚动时，您会注意到UITableView 不会立即向下滚动。有一个短暂的延迟，因为 UITableView 的 UIPanGestureDelagate 必须等到(双指)SwipeDelegate 失败。这需要一些时间。

更好的解决方案可能是使用 UIPanGestureRecognizer 来识别双指平移，然后在用户使用两根手指平移时禁用 UITableView 上的滚动。

可以这样实现:

在您的 AppDelegate 中:

class AppDelegate: UIResponder, UIApplicationDelegate {

    var window: UIWindow?
    var twoFingerPanRecognizer: UIPanGestureRecognizer?

    func application(_ application: UIApplication, didFinishLaunchingWithOptions launchOptions: [UIApplication.LaunchOptionsKey: Any]?) -> Bool {

        let twoFingerSwipeDownRecognizer = UIPanGestureRecognizer(target: self, action: #selector(didRecognizeTwoFingerPan))
        twoFingerSwipeDownRecognizer.minimumNumberOfTouches = 2
        twoFingerSwipeDownRecognizer.maximumNumberOfTouches = 2
        twoFingerPanRecognizer?.delegate = self
        window?.addGestureRecognizer(twoFingerSwipeDownRecognizer)
        self.twoFingerPanRecognizer = twoFingerSwipeDownRecognizer

        return true
    }

    @objc func didRecognizeTwoFingerPan(recognizer: UIPanGestureRecognizer) {
        let tableView = recognizer.view as? UITableView
        switch recognizer.state {
        case .began:
            tableView?.isScrollEnabled = false
        case .changed:
            let swipeThreshold: CGFloat = 50
            switch recognizer.translation(in: nil).y {
            case ...(-swipeThreshold):
                print("Swipe UP")
                recognizer.isEnabled = false
            case swipeThreshold...:
                print("Swipe DOWN")
                recognizer.isEnabled = false
            default:
                break
            }
        case .cancelled, .ended, .failed, .possible:
            tableView?.isScrollEnabled = true
            recognizer.isEnabled = true
        }
    }
}

extension AppDelegate: UIGestureRecognizerDelegate {
    func gestureRecognizer(_ gestureRecognizer: UIGestureRecognizer, shouldRecognizeSimultaneouslyWith otherGestureRecognizer: UIGestureRecognizer) -> Bool {
        return true
    }
}

在您的 ViewController 中:

func enableTwoFingerSlideDown() {
        guard
            let appDelegate = UIApplication.shared.delegate as? AppDelegate,
            let twoFingerGestureRecognizer = appDelegate.twoFingerPanRecognizer
            else {
                return
            }
        tableView.addGestureRecognizer(twoFingerGestureRecognizer)
    }

您必须从 AppDelegate 中获取 UIPanGestureRecognizer 并将其添加到 UITableView。否则这是行不通的。请记住在关闭此 UIViewController 之前将其添加回 UIWindow。

使用此解决方案，UITableView 的正常滚动行为保持不变。