如何在宿主应用程序关闭时从 Widget iOS 14 中的 CoreData 重新加载获取数据

Question

我目前正在使用 SwiftUI 开发应用程序。

我想在 widget 中重新加载来自 CoreData 的数据，以便在每次关闭主机应用程序时更新更新的数据。

但在我的代码中，数据不会重新加载...

我该如何解决？

TimerApp.swift（主机APP）

import SwiftUI
import WidgetKit

@main
struct TimerApp: App {
    @Environment(\.scenePhase) private var scenePhase
    
    let persistenceController = PersistenceController.shared.managedObjectContext
    
    var body: some Scene {
        WindowGroup {
            ContentView()
                .environment(\.managedObjectContext, persistenceController)
                .onChange(of: scenePhase) { newScenePhase in
                    if newScenePhase == .inactive {
                        WidgetCenter.shared.reloadAllTimelines()
                    }
                }
        }
    }
}

TimerWidget.swift（插件扩展）

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)
        }
    }
}

已更新

我更新了我的代码以在 getTimeline 函数和下面执行 NSFetchRequest。

但是在我的代码中，当我构建这个项目时出现如下错误：

*** Terminating app due to uncaught exception 'NSInvalidArgumentException', reason: '-[TimerEntity task]: unrecognized selector sent to instance 0x600003175400' terminating with uncaught exception of type NSException

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)
    }
}

Xcode：版本 12.0.1

iOS: 14.0

生命周期：SwiftUI 应用程序

Answer 1

负责取数据的代码只在init:

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)")
        }
    }
    ...
}

只有在初始化Provider时才为运行。您还需要在 getTimeline 函数中执行此 NSFetchRequest，因此您的 timerEntity 已更新。

此外，如果您每次都执行 WidgetCenter.shared.reloadAllTimelines() scenePhase == .inactive，这可能太频繁了，您的 Widget 可能会停止更新。

inactive 每当您的应用程序从后台移动到前台（双向）时都会调用。

尝试改用 background - 只有当您的应用程序最小化或终止时才会调用它：

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

注意：我建议在 WidgetCenter.shared.reloadAllTimelines() 周围添加一些保护措施，以确保不会 过于频繁地刷新它 。

如何在宿主应用程序关闭时从 Widget iOS 14 中的 CoreData 重新加载获取数据

How to reload fetch data from CoreData in Widget iOS 14 when host App closes

swift

core-data

swiftui

widgetkit