如何在 iOS 14 Home Widget 中显示当前时间（实时）

Question

我正在为 ios 14 Home Widget 开发应用程序，但在显示当前时间（数字时钟）时遇到问题，该小部件没有每秒更新一次。众所周知，Apple 不允许每秒触发时间轴，还有其他方法可以通过实时更新显示当前时间吗？

我尝试了这些方法，但没有按预期工作

class NetworkManager: ObservableObject {
    @Published var dateIs = Date()
    
    init() {
        startTimer() // fetch data must be called at least once
    }
    private  func startTimer() { 
        let t = RepeatingTimer(timeInterval: 3)
                t.eventHandler = {
                    DispatchQueue.main.async() {
                        // your UI update code
                        print("Timer Fired")
                     self.dateIs = Date()
                        WidgetCenter.shared.reloadAllTimelines() // reload timelines
                    }
                    if(false){   //I know this makes no sense, but it works. Go figure...
                        t.suspend()
                    }
                }
                t.resume()

    }
}


struct Provider: TimelineProvider {

    init() {
        networkManager = NetworkManager()
    }

    
    @AppStorage("storedData", store: UserDefaults(suiteName: "group.com.name"))
    var data: Data  = Data()
    
    func placeholder(in context: Context) -> WidgetEntry {
        let entry = WidgetEntry(date: Date(), storedData: storedData[0], dateIs: networkManager.dateIs)
        return entry
    }
    
    func getSnapshot(in context: Context, completion: @escaping (WidgetEntry) -> Void) {
        
        guard let storedData: WidgetTemplate = try? JSONDecoder().decode(WidgetTemplate.self, from: data) else { return }
        let entry = WidgetEntry(date: Date(), storedData: storedData, dateIs: networkManager.dateIs)
          
        completion(entry)
    }
    
    func getTimeline(in context: Context, completion: @escaping (Timeline<WidgetEntry>) -> Void) {
    
        guard let storedData: WidgetTemplate = try? JSONDecoder().decode(WidgetTemplate.self, from: data) else { return }
        let entry = WidgetEntry(date: Date(), storedData: storedData, dateIs: networkManager.dateIs)
        
        let currentDate = Date()
        let refreshDate = Calendar.current.date(byAdding: .minute, value: 5, to: currentDate)!
        
        let timeline = Timeline(entries: [entry], policy:  .after(refreshDate))
        completion(timeline)
    }
    
}

Answer 1

您不能每秒刷新 Widget。这就是 Apple 的限制。

你能做的最好的就是用秒显示一个日期 使用timer 日期样式：

/// A style displaying a date as timer counting from now.
///
///     Text(event.startDate, style: .timer)
///
/// Example output:
///    2:32
///    36:59:01
public static let timer: Text.DateStyle

---

1. 您需要一个简单的 Entry 和 Date 属性：

struct SimpleEntry: TimelineEntry {
    let date: Date
}

1. 在Entry 中传递给定日期的午夜日期，并在下一个午夜之后刷新时间线：

struct SimpleProvider: TimelineProvider {
    ...

    func getTimeline(in context: Context, completion: @escaping (Timeline<Entry>) -> Void) {
        let midnight = Calendar.current.startOfDay(for: Date())
        let nextMidnight = Calendar.current.date(byAdding: .day, value: 1, to: midnight)!
        let entries = [SimpleEntry(date: midnight)]
        let timeline = Timeline(entries: entries, policy: .after(nextMidnight))
        completion(timeline)
    }
}

1. 使用timer 样式显示日期：

struct SimpleWidgetEntryView: View {
    var entry: SimpleProvider.Entry

    var body: some View {
        Text(entry.date, style: .timer)
    }
}

---

请注意，当您刷新时间线时（通过指定 TimelineReloadPolicy 或通过调用 WidgetCenter），您设置了 最早 小部件的时间刷新。

不保证在特定时间刷新。