Ios SwiftUI 每秒从 Timer 更新单个 @State 属性，每秒也重绘整个视图

发布于03月29日

我不确定我是否正确使用了它，但情况如下:

我有一个观点:

struct TimerView: View {
    @State private var numberOfVideos: Int
    @State private var time = ""
    private let timer = Timer.publish(every: 1, on: .main, in: .common).autoconnect()

    init(numberOfVideos: Int) {
        _numberOfVideos = State(initialValue: numberOfVideos)
    }

    var body: some View {
        Text(time)
            .onReceive(timer) { _ in
                // it is called every second
                time = "00:00"
            }
        ReportView(numberOfVideos: $numberOfVideos)
    }
}

struct ReportView: View {
    @Binding private var numberOfVideos: Int
    init(numberOfVideos: Binding<Int>) {
        // ❌ this is called every second, I don't want it.
        self._numberOfVideos = numberOfVideos
    }

    var body: some View {
        Text(String(numberOfVideos))
    }
}

用途:

TimerView(numberOfVideos: 5)

每秒实例化ReportView个，这不是我需要的.我怎么才能解决这个问题呢？

推荐答案

在单独的视图中突出移动计时器逻辑，如下所示:

struct TimerView: View {
    @State private var numberOfVideos: Int
    @State private var time = ""

    init(numberOfVideos: Int) {
        _numberOfVideos = State(initialValue: numberOfVideos)
    }

    var body: some View {
        TimeText(text: $time)
        ReportView(numberOfVideos: $numberOfVideos)
            // .background(.debug)
    }
}

struct ReportView: View {
    @Binding private var numberOfVideos: Int
    init(numberOfVideos: Binding<Int>) {
        // ❌ this is called every second, I dont want it.
        self._numberOfVideos = numberOfVideos
    }

    var body: some View {
        Text(String(numberOfVideos))
    }
}

struct TimeText: View {
    @Binding var text: String
    private let timer = Timer.publish(every: 1, on: .main, in: .common).autoconnect()
    
    var body: some View {
        Text(text)
            .onReceive(timer) { t in
                // it is called every second
                text = t.debugDescription
            }
    }
}