ios - 如何为倒数计时器实现单独的分钟和秒标签

Question

好的，所以我正在开发一个倒数计时器功能，作为我正在开发的应用程序的一部分。我在如何实现计时器及其在屏幕上的显示方式方面遇到了一些问题。我的两个问题是，

1. 现在我只有计时器可以倒计时。计时器将始终有 10 分钟的固定倒计时时间。
2. 我有两个单独的计时器标签，因为我希望它们以不同的方式显示在屏幕上。是否可以将分钟和秒变量推送到显示屏上的单独标签？

如果有什么我没说清楚的，尽管问。

    import UIKit

    class ViewController: UIViewController {

    //MARK: - Countdown Timer Connections
    @IBOutlet weak var minuteLabel: UILabel!
    @IBOutlet weak var secondLabel: UILabel!

    //MARK: - Seed Connections
    @IBOutlet weak var seedSlot1: UIImageView!
    @IBOutlet weak var seedSlot2: UIImageView!
    @IBOutlet weak var seedSlot3: UIImageView!
    @IBOutlet weak var seedSlot4: UIImageView!

    //MARK: - Start/Pause Button Connection
    @IBOutlet weak var startButton: UIButton!
    @IBOutlet weak var stopButton: UIButton!
    @IBOutlet weak var pauseButton: UIButton!

    //MARK: - Variables
    var timer = Timer()

    var isTimerRunning : Bool = false
    var resumeTapped: Bool = false
    var minutes : Int = 24
    var seconds: Int = 10

    override func viewDidLoad() {
        super.viewDidLoad()
        // Do any additional setup after loading the view, typically from a nib.
        pauseButton.setImage(nil, for: .normal)
        stopButton.setImage(nil, for: .normal)
    }



    //MARK: Timer Control Functions
    //MARK: - Start Timer
    @IBAction func startTimer(_ sender: UIButton) {
        if isTimerRunning == false {
            isTimerRunning = true
            setButtons()

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

            print("The timer is currently running: \(isTimerRunning)")
        } else {
            isTimerRunning = false
            setButtons()
            print("The timer is currently running: \(isTimerRunning)")
        }
        print(secondLabel.text)
    }

    //MARK: - Stop Timer
    @IBAction func stopTimer(_ sender: UIButton) {
        timer.invalidate()
        isTimerRunning = false
        seconds = 60
        minuteLabel.text = "\(minutes)"
        secondLabel.text = "\(seconds)"
        setButtons()
    }

    //MARK: - Pause Timer
    @IBAction func pauseTimer(_ sender: UIButton) {
        if resumeTapped == false {
            timer.invalidate()
            isTimerRunning = false
            setButtons()
        } else {
            startTimer(startButton)
            isTimerRunning = true
            setButtons()
        }
    }

    func timeString (time:TimeInterval) -> String {
        let secondValue = Int(time) & 60
        let minuteValue = Int(time) / 60 % 60
        return String(format: "%02i", minuteValue, secondValue)
    }

    //MARK: - Update Timer
    @objc func updateTimer() {
        seconds -= 1     //This will decrement(count down)the seconds.
        secondLabel.text = timeString(time: TimeInterval(seconds)) //This will update the seconds text label
    }

Answer 1

如果您想通过递减seconds 变量的值来手动计算秒数，那可不是个好主意。因为 Timer 不保证它会在 1 秒间隔后触发。在我看来，如果您要计算计时器启动时间和当前时间之间的时间间隔，则首选方法。

class ViewController: UIViewController {

    @IBOutlet weak var minuteLabel: UILabel!
    @IBOutlet weak var secondLabel: UILabel!


    var timer: Timer?

    let countDownInterval: TimeInterval = 10*60 // minutes*seconds
    var finishTime: Date!
    var pauseStartTime: Date?    

    @IBAction func startTimer(_ sender: UIButton) {
        if let pause = pauseStartTime {
            let pauseInterval = Date().timeIntervalSince(pause)
            finishTime.addTimeInterval(pauseInterval)
        } else {
            finishTime = Date().addingTimeInterval(countDownInterval)
        }

        pauseStartTime = nil
        timer = Timer.scheduledTimer(withTimeInterval: 1, repeats: true, block: { [weak self] _ in self?.changeLabels() })
    }

    @IBAction func pauseTimer(_ sender: UIButton) {
        pauseStartTime = Date()
        timer?.invalidate()
    }

    func changeLabels() {
        let currentTime = Date()

        guard  currentTime < finishTime else {
            // Countdown finished
            timer?.invalidate()
            minuteLabel.text = String(format: "%02.f", 0)
            secondLabel.text = String(format: "%02.f", 0)
            return
        }

        let currentInterval = finishTime.timeIntervalSince(currentTime)
        let minutes = (currentInterval / 60).rounded(.down)
        let seconds = currentInterval.truncatingRemainder(dividingBy: 60).rounded()
        minuteLabel.text = String(format: "%02.f", minutes)
        secondLabel.text = String(format: "%02.f", seconds)
    }
}