Question

我尝试让我的应用程序弹出viewControllers，每天到达9:00 UTC时间。我不希望它使用当地时间，因为它可以在不同地区改变，并且可以改变。我想过使用服务器时间，但是我在解决这个问题时遇到了问题。我有一个纪元时间戳并将其转换为日期。

let ref = FIRDatabase.database().reference()   
let timestamp = FIRServerValue.timestamp()
  ref.setValue(timestamp)

    ref.observe(.value, with: {
        snap in
        if let t = snap.value as? TimeInterval {
            // Cast the value to an NSTimeInterval
            // and divide by 1000 to get seconds.
            print("this is the time in seconds \(t)")
            let date = Date(timeIntervalSince1970: t)
            print("this is the time \(Date(timeIntervalSince1970: t/1000))")

打印出this is the time 2016-10-10 18:40:21 +0000。

问题是弄清楚如何只获得小时分钟和秒数，这样我就可以比较时间日期。

Answer 1

其中一个选项可能是：

在应用程序启动时从服务器请求当前时间。
计算9:00 UTC与当前时间之间的差异。
设置一个计时器（Function getPowerPoints(eventID, resultTime) As String Dim cn As ADODB.Connection Dim rs As ADODB.Recordset strFile = ThisWorkbook.FullName strCon = "Provider=Microsoft.Jet.OLEDB.4.0;Data Source=" & strFile _ & ";Extended Properties=""Excel 8.0;HDR=Yes;IMEX=1"";" Set cn = CreateObject("ADODB.Connection") Set rs = CreateObject("ADODB.Recordset") cn.Open strCon strSQL = "SELECT max(POINTS) FROM PowerPoints WHERE EVENT = " & eventID & " and TIME >= " & resultTime ''Named range rs.Open strSQL, cn getPowerPoints = rs.GetString cn.Close Set rs = Nothing Set cn = Nothing End Function），当差异过去时会触发。
最后，以您喜欢的任何方式处理回调：弹出屏幕，显示弹出窗口等。

Answer 2

您可以使用以下内容：

let calendar = Calendar.current
let components = NSDateComponents()
components.hour = 9

let nineOClock = calendar.nextDate(after: Date(), matching: components as DateComponents, matchingPolicy: .strict)

let timer = Timer(fireAt: nineOClock!, interval: 0, target: self, selector: #selector(doSomething), userInfo: nil, repeats: true)
RunLoop.main.add(timer, forMode: RunLoopMode.commonModes)

func doSomething(){
    print("Doing something")
}

Answer 3

根据当前时间（1970年的秒数）计算到下一个上午9点的时间（以秒为单位）的方法。

func untilNineAmSeconds(now: Int) -> Int {

    let todaySeconds = now % 86400
    let hourSeconds = 3600
    let nineAmSeconds = 9 * hourSeconds
    let daySeconds = 24 * hourSeconds

    if todaySeconds < nineAmSeconds {
        return nineAmSeconds - todaySeconds
    } else {
        return (daySeconds - todaySeconds) + nineAmSeconds
    }
}

现在你（1）从Firebase请求当前时间，（2）在上午9点之前获得一个时间间隔，以及（3）安排一个计时器。

let ref = FIRDatabase.database().reference()   
let timestamp = FIRServerValue.timestamp()
ref.setValue(timestamp)

ref.observe(.value, with: { snap in
    guard let ts = snap.value as? TimeInterval else {
        return
    }

    let seconds = untilNineAmSeconds(now: Int(ts))

    let timer = Timer.scheduledTimer(withTimeInterval: TimeInterval(seconds), repeats: false) { _ in
        // TODO: pop view controllers
    }

    // ...
}

Answer 4

感谢Artem和他的帮助，我被指引在正确的道路上。花了很多时间研究日期转换后，我想出了这一点。最终目标是将两个值转换为整数，这样我就可以在几秒钟内对它们进行比较，并在计时器中使用它们来计算剩余的时间。

  ref.observe(.value, with: {
        snap in
        if let t = snap.value as? TimeInterval {

     let FinalTimeInterval = self.convertStringToDateToIntStartTime() - self.convertEpochTimeStampToDateToStringToDateToIntEndTime(timeInterval: t)

            if FinalTimeInterval < 0 {
                print("less than zero")
            } else {

            let timer = Timer.scheduledTimer(withTimeInterval: TimeInterval(FinalTimeInterval), repeats: false) { _ in
                // TODO: pop view controllers
                print("i'm so happy this is working")
            }
RunLoop.current.add(timer, forMode: RunLoopMode.commonModes)

            }

        }
    })


  func convertEpochTimeStampToDateToStringToDateToIntEndTime(timeInterval: TimeInterval) -> Int {
    let date = Date(timeIntervalSince1970: timeInterval/1000)

    var dateFormater = DateFormatter()
    dateFormater.timeZone = TimeZone(identifier: "UTC")
    dateFormater.dateFormat = "HH:mm:ss"
    let dateString = dateFormater.string(from: date)

    let endTime = dateFormater.date(from: dateString)


        dateFormater.dateFormat = "HH"
        let endHours = Int(dateFormater.string(from: endTime!))
        dateFormater.dateFormat = "mm"
        let endMinutes = Int(dateFormater.string(from: endTime!))
        dateFormater.dateFormat = "ss"
        let endSeconds = Int(dateFormater.string(from: endTime!))



    return endSeconds! + endMinutes! * 60 + endHours! * 3600


}
func convertStringToDateToIntStartTime() -> Int {

    var dateFormater = DateFormatter()
    dateFormater.timeZone = TimeZone(identifier: "UTC")
    dateFormater.dateFormat = "HH:mm:ss"

    let startTime = dateFormater.date(from: "09:00:00")
    dateFormater.dateFormat = "HH"

    let startHours = Int(dateFormater.string(from: startTime!))
    dateFormater.dateFormat = "mm"

    let startMinutes = Int(dateFormater.string(from: startTime!))
    dateFormater.dateFormat = "ss"

    let startSeconds = Int(dateFormater.string(from: startTime!))



    return startSeconds! + startMinutes! * 60 + startHours! * 3600

}

我试图让我的应用程序在每天UTC时间到达9:00时弹出viewControllers

4 个答案: