ios: 如何让 UIPickerView(UIView) 在 UITouchRecognizer 之前捕获触摸事件？

Question

Event Handling Guide for iOS 说 "There may be times when you want a view to receive a touch before a gesture recognizer. "，但我找不到该怎么做。

我试过 delaysTouchesEnded = false，但没有任何效果。

@IBOutlet weak var myPickerView: UIPickerView!

override func viewDidLoad() {
    super.viewDidLoad()

    let tapGesture:UITapGestureRecognizer = UITapGestureRecognizer(target: self, action: #selector(MyViewController.pickerViewTapped(_:)))
    tapGesture.delegate = self
    tapGesture.delaysTouchesEnded = false
    myPickerView.addGestureRecognizer(tapGesture)
}

func pickerView(_ pickerView: UIPickerView, didSelectRow row: Int, inComponent component: Int){
    // called by UIPickerView 
    print("pickerView called!")
}

func pickerViewTapped(_ sender: UITapGestureRecognizer) {
    // called by UITapGestureRecognizer
    print("pickerViewTapped called!")
}

当我点击 myPickerView 时，控制台将是

pickerViewTapped called!
pickerView called!

但我希望它们的顺序相反。怎么做？

Answer 1

简答：

你不能只使用 UIGestureRecognizer 来完成。

长答案：

UIPickerView 的 select 行的操作与方法 didSelectRow 的调用之间总是存在延迟，因为将行移动到 UIPickerView 的中心需要动画本身。

另请注意，如果您点击中间的行，则不会调用 didSelectRow 方法，而只会调用 pickerViewTapped。

这个延迟必然会导致这个执行顺序：

pickerViewTapped
pickerView(_ pickerView: UIPickerView, didSelectRow row: Int, inComponent component: Int){

我找到的解决方案是这样的：

func pickerViewTapped(_ sender: UITapGestureRecognizer) {
    // called by UITapGestureRecognizer

    let timeDelay = 0.6
    //0.6 is arbitrary value, depends on you
    DispatchQueue.main.asyncAfter(deadline: .now() + timeDelay) {
        print("pickerViewTapped called!")
    }
}

我知道这可能不是您要找的答案，我也不知道您为什么会有这样的行为，但这是我找到的最接近的解决方案。

ios: 如何让 UIPickerView(UIView) 在 UITouchRecognizer 之前捕获触摸事件？

ios: How to make UIPickerView(UIView) catch touch event before UITouchRecognizer?

uipickerview

uiview

uigesturerecognizer

ios

uitapgesturerecognizer