1 用户点击屏幕后产生的一个触摸事件，经过一系列的传递过程后，会找到最合适的视图控件来处理这个事件
2 找到最合适的视图控件后，就会调用控件的touches方法来作具体的事件处理。touchesBegan…touchesMoved…touchedEnded…
3 这些touches方法的默认做法是将事件顺着响应者链条向上传递，将事件交给上一个响应者进行处理
我们可以试验一下，一个简单的VC的View只有一个SubView的App，对touches的处理，
如果我们不写next?.touchesBegan(touches, with: event)，那么点击SubView只有一个print，因为当前的响应者就是那个subview
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| extension UIApplication {
open override func touchesBegan(_ touches: Set<UITouch>, with event: UIEvent?) {
print("UIApplication touchesBegan")
next?.touchesBegan(touches, with: event)
}
}
extension UIViewController {
open override func touchesBegan(_ touches: Set<UITouch>, with event: UIEvent?) {
print("UIViewController touchesBegan")
next?.touchesBegan(touches, with: event)
}
}
extension UIView {
open override func touchesBegan(_ touches: Set<UITouch>, with event: UIEvent?) {
print("UIView touchesBegan")
next?.touchesBegan(touches, with: event)
}
}
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带上next?.touchesBegan(touches, with: event)，可以看到输出如下
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| UIView touchesBegan
UIViewController touchesBegan
UIView touchesBegan
UIView touchesBegan
UIView touchesBegan
UIApplication touchesBegan
|
我们也可以按照系统的思路实现自己的hitTest
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| class HitTestExampleView: UIView {
override func hitTest(_ point: CGPoint, with event: UIEvent?) -> UIView? {
if !isUserInteractionEnabled || isHidden || alpha <= 0.01 {
return nil
}
if self.point(inside: point, with: event) {
for subview in subviews.reversed() {
let convertedPoint = subview.convert(point, from: self)
let resultView = subview.hitTest(convertedPoint, with: event)
if resultView != nil { return resultView }
}
return self
}
return nil
}
}
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