Swift 当主机应用程序关闭时，如何在小部件iOS 14中重新加载从CoreData获取数据

我目前正在使用SwiftUI开发一个应用程序

我想从

小部件中的
CoreData
重新加载数据，以便在每次关闭主机应用程序时更新较新的数据

但在我的代码中，数据不会被重新加载

我怎样才能解决这个问题


TimerApp.swift（主机应用程序）

TimerWidget.swift（小部件扩展）


Xcode:12.0.1版

iOS:14.0

生命周期：SwiftUI应用程序
负责获取数据的代码仅在
init
中：

struct Provider: TimelineProvider {
    var moc = PersistenceController.shared.managedObjectContext
    var timerEntity:TimerEntity?
    
    init(context : NSManagedObjectContext) {
        self.moc = context
        let request = NSFetchRequest<TimerEntity>(entityName: "TimerEntity")
        
        do{
            let result = try moc.fetch(request)
            timerEntity = result.first
        }
        catch let error as NSError{
            print("Could not fetch.\(error.userInfo)")
        }
    }
    ...
}

注意：我建议在
WidgetCenter.shared.reloadAllTimelines（）
周围添加一些保护措施，以确保不经常刷新它。
感谢您的回答，尽管我根据您的回答更改了代码，但提取数据从未更新过。。。我看不到数据更新过一次。只有在我构建项目时，
小部件中的数据才会更新。@Tio我更新了我的答案，基本上你也需要在
getTimeline
中重新加载
timerenty
（不仅仅是在init中）。谢谢你更新你的答案，我试着按照你的建议更改了我的代码。但是我的代码不起作用，出现了一些错误。我更新了我的问题，您是否介意建议我如何在
getTimeline
函数中更改代码以执行
NSFetchRequest
？最后，我还可以在
getTimeline
函数中重新加载执行
NSFetchRequest
的数据。
import WidgetKit
import SwiftUI
import CoreData

struct Provider: TimelineProvider {
    
    var moc = PersistenceController.shared.managedObjectContext
    var timerEntity:TimerEntity?
    
    init(context : NSManagedObjectContext) {
        self.moc = context
        let request = NSFetchRequest<TimerEntity>(entityName: "TimerEntity")
        
        do{
            let result = try moc.fetch(request)
            timerEntity = result.first
        }
        catch let error as NSError{
            print("Could not fetch.\(error.userInfo)")
        }
    }
    
    func placeholder(in context: Context) -> SimpleEntry {
        return SimpleEntry(date: Date(), timerEntity: timerEntity!)
    }
    
    func getSnapshot(in context: Context, completion: @escaping (SimpleEntry) -> ()) {
        let entry = SimpleEntry(date: Date(), timerEntity: timerEntity!)
        return completion(entry)
    }
    
    func getTimeline(in context: Context, completion: @escaping (Timeline<Entry>) -> ()) {
        var entries: [SimpleEntry] = []
        
        let currentDate = Date()
        for hourOffset in 0 ..< 5 {
            let entryDate = Calendar.current.date(byAdding: .minute, value: hourOffset, to: currentDate)!
            let entry = SimpleEntry(date: entryDate, timerEntity: timerEntity!)
            entries.append(entry)
        }
        
        let timeline = Timeline(entries: entries, policy: .atEnd)
        completion(timeline)
    }
}

struct SimpleEntry: TimelineEntry {
    let date: Date
    let timerEntity:TimerEntity
}

struct TimerWidgetEntryView : View {
        
    var entry: Provider.Entry
    
    var body: some View {
        return (
            VStack{
                Text(entry.timerEntity.task ?? "")
            }
        )
    }
}

@main
struct TimerWidget: Widget {
    let kind: String = "TimerWidget"
    
    var body: some WidgetConfiguration {
        StaticConfiguration(kind: kind, provider: Provider(context: PersistenceController.shared.managedObjectContext)) { entry in
            TimerWidgetEntryView(entry: entry)
                .environment(\.managedObjectContext, PersistenceController.shared.managedObjectContext)
        }
    }
}

struct Provider: TimelineProvider {
    
    var moc = PersistenceController.shared.managedObjectContext
    @State var timerEntity:TimerEntity?
    
    init(context : NSManagedObjectContext) {
        self.moc = context
        let request = NSFetchRequest<TimerEntity>(entityName: "TimerEntity")
        
        do{
            let result = try moc.fetch(request)
            timerEntity = result.first
        }
        catch let error as NSError{
            print("Could not fetch.\(error.userInfo)")
        }
    }
    
    func placeholder(in context: Context) -> SimpleEntry {
        return SimpleEntry(date: Date(), timerEntity: timerEntity ?? TimerEntity())
    }
    
    func getSnapshot(in context: Context, completion: @escaping (SimpleEntry) -> ()) {
        let entry = SimpleEntry(date: Date(), timerEntity: timerEntity!)
        return completion(entry)
    }
    
    func getTimeline(in context: Context, completion: @escaping (Timeline<Entry>) -> ()) {
        var entries: [SimpleEntry] = []
        let currentDate = Date()
        
        let request = NSFetchRequest<TimerEntity>(entityName: "TimerEntity")
        do{
            let result = try moc.fetch(request)
            timerEntity = result.first
        }
        catch let error as NSError{
            print("Could not fetch.\(error.userInfo)")
        }
        
        for hourOffset in 0 ..< 5 {
            let entryDate = Calendar.current.date(byAdding: .minute, value: hourOffset, to: currentDate)!
            let entry = SimpleEntry(date: entryDate, timerEntity: timerEntity ?? TimerEntity())
            entries.append(entry)
        }
        
        let timeline = Timeline(entries: entries, policy: .atEnd)
        completion(timeline)
    }
}

struct Provider: TimelineProvider {
    var moc = PersistenceController.shared.managedObjectContext
    var timerEntity:TimerEntity?
    
    init(context : NSManagedObjectContext) {
        self.moc = context
        let request = NSFetchRequest<TimerEntity>(entityName: "TimerEntity")
        
        do{
            let result = try moc.fetch(request)
            timerEntity = result.first
        }
        catch let error as NSError{
            print("Could not fetch.\(error.userInfo)")
        }
    }
    ...
}

.onChange(of: scenePhase) { newScenePhase in
    if newScenePhase == .background {
        WidgetCenter.shared.reloadAllTimelines()
    }
}