如何禁用 UIScrollView 到平移手势识别器？答案

【问题标题】：How to disable UIScrollView to a pan gesture recognizer?如何禁用 UIScrollView 到平移手势识别器？
【发布时间】：2017-09-01 21:33:43
【问题描述】：

当调用平移手势识别器（我们称之为SomePanGestureRecognizer）时，如何禁用或强制失败UIScrollView 中的手势识别器？

gestureRecognizer(_:shouldBeRequiredToFailBy:) 方法采用手势识别器参数，而不是平移手势识别器，我不知道这是否是我无法让它工作的原因，还是因为我犯了语法错误。

我有UIScrollView 的子类，用于强制失败的方法在下面的委托中：

class CustomScrollView: UIScrollView {

    override init(frame: CGRect) {
        super.init(frame: frame)

        configure()

    }

    required init?(coder aDecoder: NSCoder) {
        super.init(coder: aDecoder)

        configure()

    }

    private func configure() {

        isScrollEnabled = true
        showsHorizontalScrollIndicator = false
        showsVerticalScrollIndicator = false
        isPagingEnabled = true
        bounces = false
        alwaysBounceVertical = false
        alwaysBounceHorizontal = false

    }

}

// gesture recognizer delegate
extension CustomScrollView: UIGestureRecognizerDelegate {   

    // allow simultaneous gestures
    func gestureRecognizer(_ gestureRecognizer: UIGestureRecognizer, shouldRecognizeSimultaneouslyWith otherGestureRecognizer: UIGestureRecognizer) -> Bool {
        return true
    }

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

        // TLDR: disable uiscrollview when SomePanGestureRecognizer is called

    }

}

这是平移手势识别器，需要强制UIScrollView 中的手势识别器失败：

func addSomePanGestureRecognizer() {
    SomePanGestureRecognizer = UIPanGestureRecognizer(target: self, action: #selector(oneBPanGestureHandler(gesture:)))
    oneBHandle.addGestureRecognizer(SomePanGestureRecognizer)
}

更新我将 UIPanGestureRecognizer 子类化并使用同步委托使其工作，但我担心这是一种不稳定的方式，因为我依赖 UIKit始终在自定义平移手势之前禁用 UIScrollView。

// gesture recognizer delegate
extension CustomScrollView: UIGestureRecognizerDelegate {

    // simultaneous gestures
    func gestureRecognizer(_ gestureRecognizer: UIGestureRecognizer, shouldRecognizeSimultaneouslyWith otherGestureRecognizer: UIGestureRecognizer) -> Bool {

        if otherGestureRecognizer is CustomPanGestureRecognizer {
            return false
        } else {
            return true
        }

    }

}

更新 2 这也有效，但我不知道为什么，因为我觉得它不应该。不应该反过来吗？

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

    if otherGestureRecognizer is CustomPanGestureRecognizer {
        return true
    } else {
        return false
    }

}

【问题讨论】：

UIPanGestureRecognizers 是 UIGestureRecognizer 的子类。这不是问题。

标签： ios swift uiscrollview uipangesturerecognizer

【解决方案1】：

我相信这就是您要找的：

func gestureRecognizer(_ gestureRecognizer: UIGestureRecognizer, shouldRecognizeSimultaneouslyWith otherGestureRecognizer: UIGestureRecognizer) -> Bool {
   let isPanAndOtherRecognizer = gestureRecognizer is UIPanGestureRecognizer && otherGestureRecognizer is SomePanGestureRecognizer
   return !isPanAndOtherRecognizer
}

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

   let isPanAndOtherRecognizer = gestureRecognizer is UIPanGestureRecognizer && otherGestureRecognizer is SomePanGestureRecognizer
   return isPanAndOtherRecognizer
}

【讨论】：

编译错误：SomePanGestureRecognizer 是一个未声明的类型
这是您指定的类。使用你自己的子类。
我希望 UIScrollView 中未命名的手势识别器无法平移手势识别器 SomePanGestureRecognizer。我们不能在同一个页面上，因为这行不通。
我认为这里混淆的根源是 SomePanGestureRecognizer 是一个实例变量，而不是一个类。我认为 PeejWeej 可能已经看到它大写并认为它是一个类。
我对它进行了子类化，但不幸的是，它仍然不起作用。