Question

我正在尝试在SwiftUI视图中自动显示一系列图像。我可以创建一个固定的具有预定“每个”值的计时器，并在.onReceive中触发视图更新关闭，但我无法构造一个带有间隔属性的计时器用户可以使用滑块对其进行调整。以下代码适用于固定计时器。订阅会正确触发，但我似乎找不到对应的订阅 .onReceive以订阅更新图像。我也尝试创建自己的 TimerPublisher，但是我有同样的问题-如果不指定，则无法初始化固定值。

我的观点：

struct ImageStream2: View {
    @Environment(\.managedObjectContext) var managedObjectContext
    @FetchRequest(fetchRequest: DermPhoto.getAllDermPhotos()) var dermPhotos: FetchedResults<DermPhoto>
    @State private var activeImageIndex = 0
    @State private var animateSpeed: Double = 1.0
    @State private var startTimer = false

    let timer = Timer.publish(every: 1.0, on: .main, in: .default).autoconnect()
    @State private var mst: MyTimerSubscription!

    var body: some View {
        GeometryReader { geo in
            VStack {
                Text("Time Sequence")
                    .foregroundColor(.blue)
                    .font(.system(size: 25))
                Image(uiImage: UIImage(data: self.dermPhotos[self.activeImageIndex].myImage!)!)
                    .resizable()
                    .aspectRatio(contentMode: .fill)
                    .frame(width: geo.size.width - 20, height: geo.size.width - 20, alignment: .center)
                    .cornerRadius(20)
                    .shadow(radius: 10, x: 10, y: 10)

                    .onReceive(self.timer) { t in
                        print("in fixed timer")
                        if self.startTimer {
                            self.activeImageIndex = (self.activeImageIndex + 1) % self.dermPhotos.count
                        }
                    }
                Group {
                    HStack {
                        Text("0.5").foregroundColor(.blue)
                        Slider(value: self.$animateSpeed, in: 0.5...5.0, step: 0.5)
                        Text("5.0").foregroundColor(.blue)
                    }
                    .padding()
                    Text("Replay at: " + "\(self.animateSpeed) " + (self.animateSpeed == 1.0 ? "second" : "seconds") + " per frame")
                        .foregroundColor(.blue)
                    HStack {
                        Button(action: {
                            self.startTimer.toggle()
                            if self.startTimer {
                                self.mst = MyTimerSubscription(interval: 5.0)
                            } else {
                                self.mst.subscription.cancel()
                            }
                        }) {
                            ZStack {
                                RoundedRectangle(cornerRadius: 20)
                                    .fill(Color.yellow)
                                    .frame(width: 200, height: 40)
                                Text(self.startTimer ? "Stop" : "Start").font(.headline)
                            }
                        }
                    }
                    .padding()
                }//group
            }//top VStack
        }.onDisappear{ self.startTimer = false }
    }
}

订阅文件：

class MyTimerSubscription {
    let subscription: AnyCancellable
    let interval: Double
    init(interval: Double) {
        subscription =
            Timer.publish(every:interval, on:.main, in:.default)
                .autoconnect()
                .sink { _ in
                    print("in MyTimerSubscription print")
        }
        self.interval = interval
    }

    deinit {
        subscription.cancel()
    }
}

任何指导将不胜感激。 Xcode 11.3（11C29）

Answer 1

这似乎有点糊涂，但是我做了一个解决方案。更改计时器初始化成为国家财产。

@State var timer = Timer.publish(every: 1.0, on: .main, in: .default).autoconnect()

然后在我用来启动图像流的按钮操作中：

self.timer = Timer.publish(every: self.animateSpeed, on: .main, in: .default).autoconnect()

然后在按钮操作中停止流：

self.timer.upstream.connect().cancel()

无法为SwiftUI计时器设置变量间隔

1 个答案: