Ios swift 4:从未调用后台提取

我已经在调试->模拟后台抓取中设置了后台抓取，它工作得很好。然而，当它涉及到真正的设备是永远不会被调用！！！我已经等了将近一个星期了，但没有什么新的

这是我的代码和设置 首先：我已经从capabilities选项卡打开了后台获取功能，并检查了它在info.plist中的反映

<key>UIBackgroundModes</key>
<array>
    <string>fetch</string>
</array>

第三：我正在运行在performFetchWithCompletionHandler中调用后台获取时要处理的进程

func application(_ application: UIApplication, performFetchWithCompletionHandler completionHandler: @escaping (UIBackgroundFetchResult) -> Void) {
            let content =  UserNotifications.UNMutableNotificationContent()

    let documentsPath = try! FileManager.default.url(for: .documentDirectory, in: .userDomainMask, appropriateFor: nil, create: false)
    let destinationSqliteURL = documentsPath.appendingPathComponent("MyDB.db")
    let db = FMDatabase(path: destinationSqliteURL.path)

    if !db.open() {
        print("Unable to open database")
        completionHandler(UIBackgroundFetchResult.failed)
        return
    }
    var title : String!
    if let rs = db.executeQuery("select _Title from Questions ORDER BY RANDOM() LIMIT 1;", withArgumentsIn: []){
        while (rs.next()){
            title = rs.string(forColumn: "_Title")
        }
    } else {
        print("select failed: \(db.lastErrorMessage())")
        completionHandler(UIBackgroundFetchResult.failed)
    }
    content.title = "Q&A of the Day"
    content.body = title!
    content.sound = UNNotificationSound.default()

    var dateComponents = DateComponents()
    dateComponents.calendar = Calendar.current

    dateComponents.hour = 8   // 8:00 hours

    let trigger = UNCalendarNotificationTrigger(
        dateMatching: dateComponents, repeats: true)

    let uuidString = UUID().uuidString
    let request = UNNotificationRequest(identifier: uuidString,
                                        content: content, trigger: trigger)


    let notificationCenter = UNUserNotificationCenter.current()
    notificationCenter.removeAllPendingNotificationRequests()
    notificationCenter.add(request) { (error) in
        if error != nil {
            print("ERROR in setting up the scheduled notification request")
            completionHandler(UIBackgroundFetchResult.failed)
        }
        else{
            print("Notification is Sent")
            completionHandler(UIBackgroundFetchResult.newData)
        }
     }
 }

---

当从模拟后台获取调试它时，它可以完美地工作，然而，在真实设备上测试它时，它甚至不会被调用一次。我知道，如果它只被调用一次，那么我应该在每天早上8:00发送通知，这在真正的设备上不是这样的。

也许这是沙箱问题。您可能没有权限。iOS不会承诺后台获取的时间，但是它应该至少每周执行一次。也许还有其他因素使iOS推迟/取消应用程序的后台提取。@AliIhsanURAL，如果是沙盒问题，那么为什么它在调试时工作。。。请详细说明。。。谢谢你，我也是这么说的。也许是许可问题。在真实设备中需要一些权限，但在模拟器中不需要。@AliIhsanURAL我已经检查了我正在测试的设备的所有权限，我认为所有权限都满足要求（除非我不知道还需要另一个权限，我会请您为我澄清）。我甚至在设备设置->我的应用程序名称->后台应用程序刷新中检查了后台应用程序刷新是否打开

func application(_ application: UIApplication, performFetchWithCompletionHandler completionHandler: @escaping (UIBackgroundFetchResult) -> Void) {
            let content =  UserNotifications.UNMutableNotificationContent()

    let documentsPath = try! FileManager.default.url(for: .documentDirectory, in: .userDomainMask, appropriateFor: nil, create: false)
    let destinationSqliteURL = documentsPath.appendingPathComponent("MyDB.db")
    let db = FMDatabase(path: destinationSqliteURL.path)

    if !db.open() {
        print("Unable to open database")
        completionHandler(UIBackgroundFetchResult.failed)
        return
    }
    var title : String!
    if let rs = db.executeQuery("select _Title from Questions ORDER BY RANDOM() LIMIT 1;", withArgumentsIn: []){
        while (rs.next()){
            title = rs.string(forColumn: "_Title")
        }
    } else {
        print("select failed: \(db.lastErrorMessage())")
        completionHandler(UIBackgroundFetchResult.failed)
    }
    content.title = "Q&A of the Day"
    content.body = title!
    content.sound = UNNotificationSound.default()

    var dateComponents = DateComponents()
    dateComponents.calendar = Calendar.current

    dateComponents.hour = 8   // 8:00 hours

    let trigger = UNCalendarNotificationTrigger(
        dateMatching: dateComponents, repeats: true)

    let uuidString = UUID().uuidString
    let request = UNNotificationRequest(identifier: uuidString,
                                        content: content, trigger: trigger)


    let notificationCenter = UNUserNotificationCenter.current()
    notificationCenter.removeAllPendingNotificationRequests()
    notificationCenter.add(request) { (error) in
        if error != nil {
            print("ERROR in setting up the scheduled notification request")
            completionHandler(UIBackgroundFetchResult.failed)
        }
        else{
            print("Notification is Sent")
            completionHandler(UIBackgroundFetchResult.newData)
        }
     }
 }