SwiftUI拖拽优先触发时阻塞UIKit UITouch的多点触控问题求助

问题场景 #

在UIView绘图表面叠加SwiftUI控件的多点触控场景中：

• 先触发UIKit触摸（红色方块外拖拽），再操作SwiftUI控件（红色方块内拖拽）：两者均可正常响应触摸事件
• 先触发SwiftUI拖拽手势（红色方块内拖拽），再操作UIKit区域（红色方块外拖拽）：UIKit的UITouch事件被完全阻塞，仅能收到SwiftUI的触摸日志

问题原因 #

SwiftUI的DragGesture默认以.first模式独占触摸事件（第一个激活的手势会拦截所有后续触摸，阻止底层视图接收事件），导致先触发SwiftUI手势时，底层UIView无法获取其他手指的触摸信号。

解决方案 #

修改SwiftUI的DragGesture初始化参数，将独占模式改为.never，允许手势与其他触摸事件同时响应：

.gesture(DragGesture(minimumDistance: 0, exclusively: .never)
    .updating($touchXY) { (value, touchXY, _) in 
        touchXY = value.location
    })

完整修改后的代码 #

import SwiftUI
struct ContentView: View {
    @GestureState private var touchXY: CGPoint = .zero
    var body: some View {
        ZStack {
            TouchRepresentable()
            Rectangle()
                .foregroundColor(.red)
                .frame(width: 128, height: 128)
                .gesture(DragGesture(minimumDistance: 0, exclusively: .never)
                    .updating($touchXY) { (value, touchXY, _) in 
                        touchXY = value.location
                    })
                .onChange(of: touchXY) {
                    print(String(format:"SwiftUI(%.2g,%.2g)", $0.x,$0.y), terminator: " ") 
                }
        }
    }
}
struct TouchRepresentable: UIViewRepresentable {
    typealias Context = UIViewRepresentableContext<TouchRepresentable>
    public func makeUIView(context: Context) -> TouchView { 
        return TouchView() 
    }
    public func updateUIView(_ uiView: TouchView, context: Context) {}
}
class TouchView: UIView {
    func updateTouches(_ touches: Set<UITouch>, with event: UIEvent?) {
        for touch in touches {
            let location = touch.location(in: nil)
            print(String(format: "UIKit(%g,%g) ", round(location.x), round(location.y)), terminator: " ") 
        }
    }
    override func touchesBegan(_ touches: Set<UITouch>, with event: UIEvent?) { 
        updateTouches(touches, with: event) 
    }
    override func touchesMoved(_ touches: Set<UITouch>, with event: UIEvent?) { 
        updateTouches(touches, with: event) 
    }
    override func touchesEnded(_ touches: Set<UITouch>, with event: UIEvent?) { 
        updateTouches(touches, with: event) 
    }
    override func touchesCancelled(_ touches: Set<UITouch>, with event: UIEvent?) { 
        updateTouches(touches, with: event) 
    }
}

验证效果 #

修改后执行测试序列B：

1. 手指1在红色方块内开始拖拽（触发SwiftUI手势）
2. 手指2在红色方块外拖拽（触发UIKit触摸）
   → 控制台会同时输出SwiftUI和UIKit的触摸位置日志，两种交互正常响应

内容的提问来源于stack exchange，提问作者Warren Stringer