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ios - 列表滚动后计时器中断

问题描述

我有一个带计时器的课程（每毫秒更新一次）。

class TimeCount {
    let currentTimePublisher = Timer.TimerPublisher(interval: 0.001, runLoop: .main, mode: .common)
    let cancellable: AnyCancellable?

    init() {
        self.cancellable = currentTimePublisher.connect() as? AnyCancellable
    }

    deinit {
        self.cancellable?.cancel()
    }
}

我还有一个 TimerView 对象的 List()

List() {
    ForEach(self.timers) { timer in
        TimerPlusView(timer: timer)
    }
}

在每个对象内部，我都有一个 Text 可以更新其内容并监听计时器

Text("\(currentTime.timeIntervalSince(timer.time ?? Date()))")
    .font(.largeTitle)
    .fontWeight(.bold)
    .foregroundColor(.black)
    .opacity(0.5)
    .onReceive(timeCount.currentTimePublisher) { newCurrentTime in
        self.currentTime = newCurrentTime
    }

事情是，在（不是同时）滚动列表大约 100px 之后，计时器停止工作并且标签停止更新，我不知道为什么。

我得到的行为： 在此处输入图像描述

UPD：这是完整项目的链接以供参考。 https://www.dropbox.com/s/47zoizfqp6upz1e/TimerMinimal.zip?dl=0

标签： iosswiftxcodeswiftuicombine

解决方案

I think the problem is a bug in Xcode. Or at least something very undocumented. Or just a mystery.

The issue seems to occur when the views are being re-used from the table view (like the old dequeue-stuff) which then somehow causes the subscription to get lost, and no timer events are published any more.

Nevertheless, I found something like a work-around.

In TimerPlusView.swift, move the .onReceive handler to the very bottom of the body view, e.g.

var body: some View {

    Button(action: {
        self.timer.title = "Tapped"
    }) {
        VStack(alignment: .leading) {
            Text(timer.title ?? "New Timer")
                .font(.largeTitle)
                .fontWeight(.bold)
                .foregroundColor(.black)
            Text("\(currentTime.timeIntervalSince(timer.time ?? Date()))")
                .font(.largeTitle)
                .fontWeight(.bold)
                .foregroundColor(.black)
                .opacity(0.5)
            // onReceive doesn't seem to work here:
            //.onReceive(timeCount.currentTimePublisher) { newCurrentTime in
            //  self.currentTime = newCurrentTime
            // }

        }
    }
    .buttonStyle(BorderlessButtonStyle())
    .contextMenu {
        Button(action: {
            self.context.delete(self.timer)
        }) {
            Text("Delete")
        }
    }
    // here, onReceive works:
    .onReceive(timeCount.currentTimePublisher) { newCurrentTime in
      self.currentTime = newCurrentTime
    }
}

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