我无法弄清楚如何制作倒数计时器？

Question

我是新来的IOS和迅速，但不幸的是我不知道如何莳萝倒计时器。我做了什么？如果我从当前机器时间开始设置，则完全可以。但不会化装时间。我知道它不应该工作。但我不知道如何才能让它工作。感谢

// MARK:- Timer 

    let startFormatter = NSDateFormatter() 
    let endFormatter = NSDateFormatter() 
    let userClander = NSCalendar.currentCalendar() 

    let requestComponent: NSCalendarUnit = [ 
     NSCalendarUnit.Month, 
     NSCalendarUnit.Day, 
     NSCalendarUnit.Hour, 
     NSCalendarUnit.Minute, 
     NSCalendarUnit.Second 

    ] 

    func printTime(){ 
     //let startTime = NSDate() 

     startFormatter.dateFormat = "yyyy-MM-dd HH:mm:ss" 
     endFormatter.dateFormat = "yyyy-MM-dd HH:mm:ss" 

     let requestTimeString = "2017-01-16 12:55:27" 
     let requestTime = startFormatter.dateFromString(requestTimeString) 

     let endTimeString = "2017-01-16 12:58:27" 
     let endTime = endFormatter.dateFromString(endTimeString) 


     print(endTime) 

     let timeDifferance = userClander.components(requestComponent, fromDate: requestTime!, toDate: endTime!, options: []) 

     print(timeDifferance.minute) 


     displayCountDownTimerLabel.text = "\(timeDifferance.minute):\(timeDifferance.second)" 

    } 

    func start() { 

     let timer = NSTimer.scheduledTimerWithTimeInterval(0.01, target: self, selector: #selector(ViewController.printTime), userInfo: nil, repeats: true) 
     timer.fire() 
    } 

Answer 1

let aSelector : Selector = #selector(updateTime) 

     timer = NSTimer.scheduledTimerWithTimeInterval(1.0, target: self, selector: aSelector, userInfo: labelCalIndex, repeats: true) 

func updateTime() 
{ 
    let currentTime = NSDate.timeIntervalSinceReferenceDate() 
     /* ---------------------------------------------------------------- 

       Find the difference between current time and start time. 

     ---------------------------------------------------------------- */ 

     var elapsedTime: NSTimeInterval = currentTime - startTime 

     /* ------------------------------------------------ 

       calculate the hours in elapsed time. 

      ------------------------------------------------ */ 

     let hour = Int32(elapsedTime/3600.0) 

     elapsedTime -= (NSTimeInterval(hour) * 3600) 
     /* ------------------------------------------------ 

       calculate the minutes in elapsed time. 

      ------------------------------------------------ */ 

     let minutes = Int32(elapsedTime/60.0) 

     elapsedTime -= (NSTimeInterval(minutes) * 60) 

     /* ------------------------------------------------ 

       calculate the seconds in elapsed time. 

      ------------------------------------------------ */ 

     let seconds = Int32(elapsedTime) 

     elapsedTime -= NSTimeInterval(seconds) 

     /* ------------------------------------------------------------------------------------------------------ 

       Add the leading zero for minutes, seconds and millseconds and store them as string constants 

      ------------------------------------------------------------------------------------------------------ */ 

     let strMinutes = String(format: "%02d", minutes) 

     let strSeconds = String(format: "%02d", seconds) 

     let strHour = String(format: "%02d", hour) 

     /* ------------------------------------------------------------------------------------------- 

       Concatenate minuets, seconds and milliseconds as assign it to the UILabel 

      ------------------------------------------------------------------------------------------- */ 

     let timerSting = "\(strHour):\(strMinutes):\(strSeconds)" 

     if minutes == 3 
     { 
      InvalidateTimer() 

     } 
    } 

保存在NSInterval的开始时间。

Answer 2

如果您需要3分钟的计时器或计时器持续指定的时间，则不需要使用NSDate。

对于斯威夫特3

如果你想有一个3分钟的计时器：

@IBOutlet weak var timerLabel: UILabel! 

var currentTime : Int! 

var timer : Timer! 

override func viewDidLoad() { 

    super.viewDidLoad() 

    //total time in seconds. 
    currentTime = 180 

    timerLabel.text = convertSecondsToMinutes(currentTime) 

    timer = Timer.scheduledTimer(timeInterval: 1, target: self, selector: #selector(updateLabel), userInfo: nil, repeats: true) 
} 

func updateLabel(){ 

    currentTime = currentTime - 1 

    timerLabel.text = convertSecondsToMinutes(currentTime) 

    //0 seconds left so kill the timer 
    if(currentTime == 0){ 

     timer.invalidate() 
    } 
} 

func convertSecondsToMinutes(_ seconds:Int) -> String{ 

    //one minute has 60 seconds soo :D 

    let minutes = seconds/60 

    let secondsvalue = Double(seconds).truncatingRemainder(dividingBy: 60) 

    //return string in appropriate format 
    return "\(minutes):\(Int(secondsvalue))" 
} 

Answer 3

// MARK： - 定时器

let startFormatter = NSDateFormatter() 
let endFormatter = NSDateFormatter() 
let userClander = NSCalendar.currentCalendar() 

let requestComponent: NSCalendarUnit = [ 
    NSCalendarUnit.Month, 
    NSCalendarUnit.Day, 
    NSCalendarUnit.Hour, 
    NSCalendarUnit.Minute, 
    NSCalendarUnit.Second 

] 

var count = 0 

func printTime(){ 

     if(count > 0){ 
      let minutes = String(count/60) 
      let seconds = String(count % 60) 

      print(minutes) 
      print(seconds) 
      displayCountDownTimerLabel.text = minutes + ":" + seconds 
      count -= 1 
     } 
     else{ 
       displayCountDownTimerLabel.text = "00:00" 
     } 

} 

func start() { 

    startFormatter.dateFormat = "yyyy-MM-dd HH:mm:ss" 
    endFormatter.dateFormat = "yyyy-MM-dd HH:mm:ss" 

    let requestTimeString = "2017-01-16 12:58:27" 
    let requestTime = startFormatter.dateFromString(requestTimeString) 

    let endTimeString = "2017-01-16 12:58:56" 
    let endTime = endFormatter.dateFromString(endTimeString) 

    let timeDifferance = userClander.components(requestComponent, fromDate: requestTime!, toDate: endTime!, options: []) 

    print("\(timeDifferance.hour):\(timeDifferance.minute):\(timeDifferance.second)") 


    if timeDifferance.hour == 0 && timeDifferance.minute <= 3 { 

     count = (timeDifferance.minute * 60) + timeDifferance.second 


    let timer = NSTimer.scheduledTimerWithTimeInterval(1.0, target: self, selector: #selector(ViewController.printTime), userInfo: nil, repeats: true) 

    timer.fire() 

    }else{ 
     print("request time out ") 
    } 
}