ios - 在 SwiftUI WidgetKit 中的何处添加观察者

Question

我正在尝试构建一个更好的 WidgetKit ，我希望每次电池状态或电量变化时都能刷新 WidgetKit 。我知道两者都需要添加通知。所以我的逻辑是，当有关电池状态的通知发生变化时，我想刷新时间线。

但是我无法理解将观察者放在 TimelineProvider 或 Widget View 下的什么位置？

struct timeWidgetEntryView : View {
    var entry: Provider.Entry
    let NC = NotificationCenter.default
    
    init(entry:Provider.Entry) {
        self.entry = entry

    }

    func batteryLevelDidChange(_ notification: Notification) {
        UIDevice.current.isBatteryMonitoringEnabled = true
        var level = UIDevice.current.batteryLevel
        level = level * 100
        WidgetCenter.shared.reloadAllTimelines()
        NSLog("Level changed / state changed")
    }
    
    var body: some View {
        VStack {
            Text(entry.date, style: .time).foregroundColor(.black).frame(minWidth: /*@START_MENU_TOKEN@*/0/*@END_MENU_TOKEN@*/, idealWidth: 100, maxWidth: 100, minHeight: /*@START_MENU_TOKEN@*/0/*@END_MENU_TOKEN@*/, idealHeight: /*@START_MENU_TOKEN@*/100/*@END_MENU_TOKEN@*/, maxHeight: 50, alignment: /*@START_MENU_TOKEN@*/.center/*@END_MENU_TOKEN@*/)
            Text("Battery : \(entry.batteryState)").foregroundColor(.black).frame(minWidth: /*@START_MENU_TOKEN@*/0/*@END_MENU_TOKEN@*/, idealWidth: /*@START_MENU_TOKEN@*/100/*@END_MENU_TOKEN@*/, maxWidth: /*@START_MENU_TOKEN@*/.infinity/*@END_MENU_TOKEN@*/, minHeight: /*@START_MENU_TOKEN@*/0/*@END_MENU_TOKEN@*/, idealHeight: /*@START_MENU_TOKEN@*/100/*@END_MENU_TOKEN@*/, maxHeight: 50, alignment: /*@START_MENU_TOKEN@*/.center/*@END_MENU_TOKEN@*/)
        }
        .cornerRadius(10)
        .frame(width:.infinity, height:.infinity, alignment: .center)
        .onReceive(NotificationCenter.default.publisher(for: UIDevice.batteryStateDidChangeNotification))
               { obj in
                  // Change key as per your "userInfo"
                  if let userInfo = obj.userInfo, let info = userInfo["info"] {
                     print(info)
                  }
            
            WidgetCenter.shared.reloadAllTimelines()
        }
    }
}

但它没有按预期工作，所以我的问题是我是否应该将观察者移至时间线提供者？如果是，在哪里？

Answer 1

您需要改为在主应用程序中收听通知 - 如 Apple 教程中所述:

• Keeping a Widget Up To Date

然后，当您收到 UIDevice.batteryStateDidChangeNotification 时，只需调用:

WidgetCenter.shared.reloadAllTimelines()

要在您的应用不可见时继续收到通知，您可能需要启用后台通知。看到这个线程:

• Check battery level in background?