如何在 SwiftUI 中检测点击手势位置? [英] How to detect a tap gesture location in SwiftUI?

问题描述

(对于 SwiftUI，而不是 vanilla UIKit)非常简单的示例代码，例如，在灰色背景上显示红色框:

(For SwiftUI, not vanilla UIKit) Very simple example code to, say, display red boxes on a gray background:

struct ContentView : View {
    @State var points:[CGPoint] = [CGPoint(x:0,y:0), CGPoint(x:50,y:50)]
    var body: some View {
        return ZStack {
            Color.gray
                .tapAction {
                   // TODO: add an entry to self.points of the location of the tap
                }
            ForEach(self.points.identified(by: \.debugDescription)) {
                point in
                Color.red
                    .frame(width:50, height:50, alignment: .center)
                    .offset(CGSize(width: point.x, height: point.y))
            }
        }
    }
}

我假设不是 tapAction，而是 TapGesture 之类的东西?但即使在那里，我也看不到任何方法来获取有关水龙头位置的信息.我该怎么办?

I'm assuming instead of tapAction, I need to have a TapGesture or something? But even there I don't see any way to get information on the location of the tap. How would I go about this?

推荐答案

好吧，经过一些修补并感谢 这个答案 对于我的另一个问题，我想出了一种使用 UIViewRepresentable 的方法(但无论如何，如果有更简单的方法，请告诉我！)这段代码对我有用！

Well, after some tinkering around and thanks to this answer to a different question of mine, I've figured out a way to do it using a UIViewRepresentable (but by all means, let me know if there's an easier way!) This code works for me!

struct ContentView : View {
    @State var points:[CGPoint] = [CGPoint(x:0,y:0), CGPoint(x:50,y:50)]
    var body: some View {
        return ZStack(alignment: .topLeading) {
            Background {
                   // tappedCallback
                   location in
                    self.points.append(location)
                }
                .background(Color.white)
            ForEach(self.points.identified(by: \.debugDescription)) {
                point in
                Color.red
                    .frame(width:50, height:50, alignment: .center)
                    .offset(CGSize(width: point.x, height: point.y))
            }
        }
    }
}

struct Background:UIViewRepresentable {
    var tappedCallback: ((CGPoint) -> Void)

    func makeUIView(context: UIViewRepresentableContext<Background>) -> UIView {
        let v = UIView(frame: .zero)
        let gesture = UITapGestureRecognizer(target: context.coordinator,
                                             action: #selector(Coordinator.tapped))
        v.addGestureRecognizer(gesture)
        return v
    }

    class Coordinator: NSObject {
        var tappedCallback: ((CGPoint) -> Void)
        init(tappedCallback: @escaping ((CGPoint) -> Void)) {
            self.tappedCallback = tappedCallback
        }
        @objc func tapped(gesture:UITapGestureRecognizer) {
            let point = gesture.location(in: gesture.view)
            self.tappedCallback(point)
        }
    }

    func makeCoordinator() -> Background.Coordinator {
        return Coordinator(tappedCallback:self.tappedCallback)
    }

    func updateUIView(_ uiView: UIView,
                       context: UIViewRepresentableContext<Background>) {
    }

}

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