How can I make a countdown with NSTimer?

问题

How can I make a countdown with an NSTimer using Swift?

回答1:

Question 1:

@IBOutlet var countDownLabel: UILabel!

var count = 10

override func viewDidLoad() {
    super.viewDidLoad()

    var timer = Timer.scheduledTimer(timeInterval: 0.4, target: self, selector: #selector(UIMenuController.update), userInfo: nil, repeats: true)
}

func update() {
    if(count > 0) {
        countDownLabel.text = String(count--)
    }
}

Question 2:

You can do both. SpriteKit is the SDK you use for scene, motion, etc. Simple View Application is the project template. They should not conflict

回答2:

In Swift 5.1 this will work:

var counter = 30

override func viewDidLoad() {
    super.viewDidLoad()

    Timer.scheduledTimer(timeInterval: 1.0, target: self, selector: #selector(updateCounter), userInfo: nil, repeats: true)
}



@objc func updateCounter() {
    //example functionality
    if counter > 0 {
        print("\(counter) seconds to the end of the world")
        counter -= 1
    }
}

回答3:

Variable for your timer

var timer = 60

NSTimer with 1.0 as interval

var clock = NSTimer.scheduledTimerWithTimeInterval(1.0, target: self, selector: "countdown", userInfo: nil, repeats: true)

Here you can decrease the timer

func countdown() {
    timer--
}

回答4:

Swift 3

private let NUMBER_COUNT_DOWN   = 3

var countDownLabel = UILabel()
var countDown = NUMBER_COUNT_DOWN
var timer:Timer?


private func countDown(time: Double)
{
    countDownLabel.frame = CGRect(x: 0, y: 0, width: 300, height: 300)
    countDownLabel.font = UIFont.systemFont(ofSize: 300)
    countDownLabel.textColor = .black
    countDownLabel.center = CGPoint(x: self.view.frame.width / 2, y: self.view.frame.height / 2)

    countDownLabel.textAlignment = .center
    self.view.addSubview(countDownLabel)
    view.bringSubview(toFront: countDownLabel)

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

func updateCountDown() {
    if(countDown > 0) {
        countDownLabel.text = String(countDown)
        countDown = countDown - 1
    } else {
        removeCountDownLable()
    }
}

private func removeCountDownLable() {
    countDown = NUMBER_COUNT_DOWN
    countDownLabel.text = ""
    countDownLabel.removeFromSuperview()

    timer?.invalidate()
    timer = nil
}

回答5:

Swift 4.1 and Swift 5. The updatetime method will called after every second and seconds will display on UIlabel.

     var timer: Timer?
     var totalTime = 60

     private func startOtpTimer() {
            self.totalTime = 60
            self.timer = Timer.scheduledTimer(timeInterval: 1.0, target: self, selector: #selector(updateTimer), userInfo: nil, repeats: true)
        }

    @objc func updateTimer() {
            print(self.totalTime)
            self.lblTimer.text = self.timeFormatted(self.totalTime) // will show timer
            if totalTime != 0 {
                totalTime -= 1  // decrease counter timer
            } else {
                if let timer = self.timer { 
                    timer.invalidate()
                    self.timer = nil
                }
            }
        }
    func timeFormatted(_ totalSeconds: Int) -> String {
        let seconds: Int = totalSeconds % 60
        let minutes: Int = (totalSeconds / 60) % 60
        return String(format: "%02d:%02d", minutes, seconds)
    }

Copied from [https://teamtreehouse.com/community/swift-countdown-timer-of-60-seconds]

回答6:

Swift 4

Timer.scheduledTimer(timeInterval: 1.0, target: self, selector: #selector(self.updateTime), userInfo: nil, repeats: true)

Update function

@objc func updateTime(){
    debugPrint("jalan")
}

回答7:

XCode 10 with Swift 4.2

import UIKit

class ViewController: UIViewController {

   var timer = Timer()
   var totalSecond = 10

   override func viewDidLoad() {
       super.viewDidLoad()
       startTimer()
   }


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

   @objc func updateTime() {

        print(timeFormatted(totalSecond))

        if totalSecond != 0 {
           totalSecond -= 1
        } else {
           endTimer()
        }
    }

    func endTimer() {
        timer.invalidate()
    }

    func timeFormatted(_ totalSeconds: Int) -> String {
        let seconds: Int = totalSeconds % 60
        return String(format: "0:%02d", seconds)
    }

}

回答8:

Swift4

    @IBOutlet weak var actionButton: UIButton!
    @IBOutlet weak var timeLabel: UILabel!
    var timer:Timer?
    var timeLeft = 60

override func viewDidLoad() {
    super.viewDidLoad()
    setupTimer()
}

func setupTimer() {
    timer = Timer.scheduledTimer(timeInterval: 1.0, target: self, selector: #selector(onTimerFires), userInfo: nil, repeats: true)
}

@objc func onTimerFires() {
    timeLeft -= 1
    timeLabel.text = "\(timeLeft) seconds left"

    if timeLeft <= 0 {
        actionButton.isEnabled = true
        actionButton.setTitle("enabled", for: .normal)
        timer?.invalidate()
        timer = nil
    }
}

@IBAction func btnClicked(_ sender: UIButton) {
    print("API Fired")
}

回答9:

Make Countdown app Xcode 8.1, Swift 3

import UIKit
import Foundation

class ViewController: UIViewController, UITextFieldDelegate {

    var timerCount = 0
    var timerRunning = false

    @IBOutlet weak var timerLabel: UILabel! //ADD Label
    @IBOutlet weak var textField: UITextField! //Add TextField /Enter any number to Countdown

    override func viewDidLoad() {
        super.viewDidLoad()

        //Reset
        timerLabel.text = ""
        if timerCount == 0 {
            timerRunning = false
        }
}

       //Figure out Count method
    func Counting() {
        if timerCount > 0 {
        timerLabel.text = "\(timerCount)"
            timerCount -= 1
        } else {
            timerLabel.text = "GO!"

        }

    }

    //ADD Action Button
    @IBAction func startButton(sender: UIButton) {

        //Figure out timer
        if timerRunning == false {
         _ = Timer.scheduledTimer(timeInterval: 1.0, target: self, selector: #selector(ViewController.Counting), userInfo: nil, repeats: true)
            timerRunning = true
        }

        //unwrap textField and Display result
        if let countebleNumber = Int(textField.text!) {
            timerCount = countebleNumber
            textField.text = "" //Clean Up TextField
        } else {
            timerCount = 3 //Defoult Number to Countdown if TextField is nil
            textField.text = "" //Clean Up TextField
        }

    }

    //Dismiss keyboard
    func keyboardDismiss() {
        textField.resignFirstResponder()
    }

    //ADD Gesture Recignizer to Dismiss keyboard then view tapped
    @IBAction func viewTapped(_ sender: AnyObject) {
        keyboardDismiss()
    }

    //Dismiss keyboard using Return Key (Done) Button
    func textFieldShouldReturn(_ textField: UITextField) -> Bool {
        keyboardDismiss()

        return true
    }

}

https://github.com/nikae/CountDown-

回答10:

Swift 5 with Closure:

class ViewController: UIViewController {

var secondsRemaining = 30

@IBAction func startTimer(_ sender: UIButton) {

    Timer.scheduledTimer(withTimeInterval: 1.0, repeats: true) { (Timer) in
        if self.secondsRemaining > 0 {
            print ("\(self.secondsRemaining) seconds")
            self.secondsRemaining -= 1
        }
    }

}

回答11:

this for the now swift 5.0 and newst

var secondsRemaining = 60


Timer.scheduledTimer(timeInterval: 1.0, target: self, selector: #selector(updateCounter), userInfo: nil, repeats: true)
}
@objc func updateCounter(){
    if secondsRemaining > 0 {
    print("\(secondsRemaining) seconds.")
    secondsRemaining -= 1
            }
        }

来源：https://stackoverflow.com/questions/29374553/how-can-i-make-a-countdown-with-nstimer