官网说明：https://developer.apple.com/design/human-interface-guidelines/watchos/interaction/digital-crown/

有时，我们希望二次开发Digital Crown，比如点击Digital Crown时，App响应一些动作，但是不幸的是，这个手势已经是IOS系统占用的手势了，没法进行自定义开发。但是我们可以捕捉到Digital Crown旋转的数值，从而做一些事情。

下面是具体的Demo：

https://dev.to/no2s14/how-to-use-wkcrowndelegate-in-watchos-development-1lj9

• UIkit的情况

import WatchKit
import Foundation

class InterfaceController: WKInterfaceController {

    override func awake(withContext context: Any?) {
        // Configure interface objects here.
    }

    override func willActivate() {
        // This method is called when watch view controller is about to be visible to user
    }

    override func didAppear() {
        super.didAppear()
        crownSequencer.delegate = self
        crownSequencer.focus()
    }

    override func didDeactivate() {
        // This method is called when watch view controller is no longer visible
    }

}

extension InterfaceController : WKCrownDelegate {
    func crownDidRotate(_ crownSequencer: WKCrownSequencer?, rotationalDelta: Double) {
        print(rotationalDelta)
    }
}

• SwiftUI的情况

SwiftUI实现起来就比较简单了

import SwiftUI

struct ContentView: View {

    @State var rotationValue = 0.0

    var body: some View {
        VStack {

            Text(("\(self.rotationValue)"))
                .padding()
                 // 这里把表冠旋转的数值绑定到rotationValue
                .focusable(true)
                // 这里把表冠旋转的数值绑定到rotationValue
                .digitalCrownRotation($rotationValue)
                // 这里监听到rotationValue的变化，可以做一些事情
                .onChange(of: rotationValue) {
                    value in
                // 打印rotationValue的值
                print(value)

            }

        }

    }
}