将UIPanGesture添加到UITableView会阻止Xcode11.3中的UITableView滚动

Question

我和UITableView有UIViewController。当用户拉下表格时，我想取消UIViewController。通过将UIPanGestureRecognizer添加到UIViewController，只有在表内容较少且表不可滚动的情况下，才能使用控制器的视图。所以我在tableView中添加了UIPanGestureRecognizer：

self.detailTableView.bounces = true
let gesture = UIPanGestureRecognizer(target: self, action: #selector(onPan(_:)))
gesture.delegate = self
self.detailTableView.gestureRecognizers = [gesture]

onPan方法：

@objc func onPan(_ panGesture: UIPanGestureRecognizer) {
    guard self.detailTableView.contentOffset.y <= 0 else {
        return
    }

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

    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 yPoint = max(0, translation.y)
        slideViewVerticallyTo(yPoint)

    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 / 2) ||
            (velocity.y > minimumVelocityToHide)

        if closing {
            UIView.animate(withDuration: animationDuration, animations: {
                // If closing, animate to the bottom of the view
                slideViewVerticallyTo(self.view.frame.size.height)
            }, completion: { (isCompleted) in
                if isCompleted {
                    // Dismiss the view when it disappeared
                    // Dismiss UIViewController here....
                }
            })
        } else {
            // If not closing, reset the view to the top
            UIView.animate(withDuration: animationDuration, animations: {
                slideViewVerticallyTo(0)
            })
        }

    default:
        // If gesture state is undefined, reset the view to the top
        UIView.animate(withDuration: animationDuration, animations: {
            slideViewVerticallyTo(0)
        })
    }
}

也在委托之后实现，因为当tableView退回属性设置为true时，表在所有方向上都会退回。通过仅启用垂直方向的反弹不起作用。

public func gestureRecognizerShouldBegin(_ gestureRecognizer: UIGestureRecognizer) -> Bool {
        if let panRecognizer = gestureRecognizer as? UIPanGestureRecognizer {
            // Ensure it's a Vertical drag
            let velocity = panRecognizer.velocity(in: self.view)
            if abs(velocity.y) < abs(velocity.x) {
                return false
            }
        } else {
            return false
        }
        return true
    }

这段代码在Xcode10.2.1中工作得很好。现在我已经更新到Xcode11.3，dismiss正在工作，但它阻止了tableView的滚动。

有人能提供解决方案吗？

提前谢谢你。

Answer 1

您可以尝试使用以下方法来处理手势识别器。通过这样做，一旦找到附加的视图手势和手势类型，您就可以实现向下拖动以取消功能。

extension ViewController: UIGestureRecognizerDelegate {

    func gestureRecognizer(_ gestureRecognizer: UIGestureRecognizer, shouldRequireFailureOf otherGestureRecognizer: UIGestureRecognizer) -> Bool {

        if gestureRecognizer.isKind(of: UIPanGestureRecognizer.self) && otherGestureRecognizer.isKind(of: UIPanGestureRecognizer.self) && gestureRecognizer.view == tableview && gestureRecognizer.view == tableview {
            // your logic here
        }
        return true
    }

    func gestureRecognizer(_ gestureRecognizer: UIGestureRecognizer, shouldBeRequiredToFailBy otherGestureRecognizer: UIGestureRecognizer) -> Bool {

        if gestureRecognizer.isKind(of: UIPanGestureRecognizer.self) && otherGestureRecognizer.isKind(of: UIPanGestureRecognizer.self) && gestureRecognizer.view == tableview && gestureRecognizer.view == tableview {
            // your logic here
        }
        return true
    }

}