SwiftUI 运行按住按钮时定期编码；运行刚点击时代码不同？

Question

我想做的是实现一个按钮，当它被按住时运行每 0.5 秒执行一次特定的代码行（它可以无限期地被按住，因此运行打印语句无限期）。我希望它在被点击时有不同的行为。这是代码：

struct ContentView: View {
@State var timeRemaining = 0.5
let timer = Timer.publish(every: 0.5, on: .main, in: .common).autoconnect()
@State var userIsPressing = false //detecting whether user is long pressing the screen

var body: some View {
    VStack {
       Image(systemName: "chevron.left").onReceive(self.timer) { _ in
           if self.userIsPressing == true {
             if self.timeRemaining > 0 {
                self.timeRemaining -= 0.5
              }
            //resetting the timer every 0.5 secdonds and executing code whenever //timer reaches 0

     if self.timeRemaining == 0 {
            print("execute this code")
            self.timeRemaining = 0.5
         }
        }
    }.gesture(LongPressGesture(minimumDuration: 0.5)
                   .onChanged() { _ in
                       //when longpressGesture started
                   self.userIsPressing = true
                   }
                   .onEnded() { _ in
                       //when longpressGesture ended
                   self.userIsPressing = false

                   }
                   )
           }
}
}

目前，这与我需要它做的有点相反；上面的代码运行当我单击按钮时无限期地打印语句但是当我按住它时，它只执行一次...我该如何解决这个问题？

Answer 1

这是一个解决方案 - 要获得连续按压，需要将长按手势与顺序拖动相结合，并在处理程序中添加计时器。

更新： 使用 Xcode 11.4 / iOS 13.4（在预览和模拟器中）测试

struct TimeEventGeneratorView: View {
    var callback: () -> Void
    private let timer = Timer.publish(every: 0.5, on: .main, in: .common).autoconnect()

    var body: some View {
        Color.clear
            .onReceive(self.timer) { _ in
                self.callback()
            }
    }
}

struct TestContinuousPress: View {

    @GestureState var pressingState = false // will be true till tap hold
    var pressingGesture: some Gesture {
        LongPressGesture(minimumDuration: 0.5).sequenced(before:
              DragGesture(minimumDistance: 0, coordinateSpace:
              .local)).updating($pressingState) { value, state, transaction in
                switch value {
                    case .second(true, nil):
                        state = true
                    default:
                        break
                }
            }.onEnded { _ in
            }
    }

    var body: some View {
        VStack {
            Image(systemName: "chevron.left")
                .background(Group { if self.pressingState { TimeEventGeneratorView {
                    print(">>>> pressing: \(Date())")
                }}})
            .gesture(TapGesture().onEnded {
                print("> just tap ")
            })
            .gesture(pressingGesture)
        }
    }
}

SwiftUI 运行按住按钮时定期编码；运行刚点击时代码不同？

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SwiftUI 运行 按住按钮时定期编码； 运行 刚点击时代码不同？

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SwiftUI 运行按住按钮时定期编码；运行刚点击时代码不同？