swift - 在显示暂停计时器 Int 的标签上显示暂停和恢复的计时器

Question

下面我的 swift 代码应该有 2 个按钮，一个开始按钮和一个暂停按钮。现在，我的代码在文本字段上获取一个 int 并对其进行计数并显示在标签 lblTime 上。当点击暂停按钮时，标签计时器停止。当再次点击它时，计时器会减少 1 秒，并且应该像点击开始按钮时一样倒计时。计时器从标签上的时间开始倒计时。我希望它倒数到零，而不是只倒数一秒。查看函数暂停。

import UIKit

   class ViewController: UIViewController, UITextFieldDelegate {
let MAX_LENGTH_PHONENUMBER = 2
let ACCEPTABLE_NUMBERS     = "0123456789"
var enterTime = UITextField()
var lblTime = UILabel()
var startBTN = UIButton()
var timer = Timer()
var counter = 0

var pauseBTN = UIButton()
var jake = 0


override func viewDidLoad() {
    super.viewDidLoad()
    // Do any additional setup after loading the view.

    [enterTime,lblTime,startBTN,pauseBTN].forEach{
        $0.backgroundColor = .systemRed
        view.addSubview($0)
        $0.translatesAutoresizingMaskIntoConstraints = false
    }

    enterTime.frame = CGRect(x: view.center.x-115, y: view.center.y-200, width: 60, height: 50)
    lblTime.frame = CGRect(x: view.center.x-115, y: view.center.y, width: 60, height: 50)
    pauseBTN.frame = CGRect(x: view.center.x-115, y: view.center.y+90, width: 60, height: 50)
    startBTN.frame = CGRect(x: view.center.x-115, y: view.center.y+200, width: 60, height: 50)

    startBTN.addTarget(self, action: #selector(startHit), for: .touchDown)

    pauseBTN.addTarget(self, action: #selector(pause), for: .touchDown)

    enterTime.placeholder = String("MM:SS")

    enterTime.delegate = self
    enterTime.addTarget(self, action: #selector(self.textFieldDidChange), for: UIControl.Event.editingChanged)

    pauseBTN.setTitle("pause", for: .normal)
    startBTN.setTitle("Start", for: .normal)
}

@objc func pause() {


    if jake == 0 {
        timer.invalidate()
        pauseBTN.setTitle("go", for: .normal)


    }
    else {
        timer.fire()
        pauseBTN.setTitle("pause", for: .normal)
        counter -= 1
        lblTime.text = formatSeconds(counter)
        if ( counter == 0 ) {
            timer.invalidate()}
    }

    jake += 1

}

@objc func startHit() {
    timer.invalidate()
    counter = convertToSeconds(from: enterTime.text!)
    lblTime.text = formatSeconds(counter)
    timer = Timer.scheduledTimer(timeInterval: 1, target: self, selector: #selector(timerAction), userInfo: nil, repeats: true)
}

@objc func timerAction() {
    counter -= 1
    lblTime.text = formatSeconds(counter)
    if ( counter == 0 ) {
        timer.invalidate()
    }
}
func convertToSeconds(from timeString: String) -> Int {
    let components = timeString.components(separatedBy: ":")
    if components.count == 2 {
        let minutes = Int(components[0]) ?? 0
        let seconds = Int(components[1]) ?? 0
        return (minutes * 60) + seconds
    } else if components.count == 3 {
        let hours = Int(components[0]) ?? 0
        let minutes = Int(components[1]) ?? 0
        let seconds = Int(components[2]) ?? 0
        return (hours * 60 * 60) + (minutes * 60) + seconds
    } else {
        return 0
    }
}
func formatSeconds(_ totalSeconds: Int) -> String {
    let formatter = DateComponentsFormatter()
    formatter.unitsStyle = .positional
    formatter.allowedUnits = [.minute, .second]
    formatter.zeroFormattingBehavior = .pad
    return formatter.string(from: TimeInterval(totalSeconds))!
}
func textField(_ textField: UITextField, shouldChangeCharactersIn range: NSRange, replacementString string: String) -> Bool {

    let newLength: Int = textField.text!.count + string.count - range.length
    let numberOnly = NSCharacterSet.init(charactersIn: ACCEPTABLE_NUMBERS).inverted
    let strValid = string.rangeOfCharacter(from: numberOnly) == nil
    return (strValid && (newLength <= MAX_LENGTH_PHONENUMBER))
}



@objc func textFieldDidChange(_ textField: UITextField) {
    if  textField.text!.count == 2  {
        textField.text = textField.text! + ":00"
    }
}
 }

Answer 1

要暂停/停止计时器，请使用 timer.invalidate() 和 timer = nil 两者，因为在计时器启动时，它总是创建新实例。

class ViewController: UIViewController, UITextFieldDelegate {
    let MAX_LENGTH_PHONENUMBER = 2
    let ACCEPTABLE_NUMBERS     = "0123456789"
    var enterTime = UITextField()
    var lblTime = UILabel()
    var startBTN = UIButton()
    var timer:Timer? = Timer()
    var counter = 0

    var pauseBTN = UIButton()
    var isPaused = false

    override func viewDidLoad() {
        super.viewDidLoad()
        // Do any additional setup after loading the view.
        [enterTime,lblTime,startBTN,pauseBTN].forEach{
            $0.backgroundColor = .systemRed
            view.addSubview($0)
            $0.translatesAutoresizingMaskIntoConstraints = false
        }
        enterTime.frame = CGRect(x: view.center.x-115, y: view.center.y-200, width: 60, height: 50)
        lblTime.frame = CGRect(x: view.center.x-115, y: view.center.y, width: 60, height: 50)
        pauseBTN.frame = CGRect(x: view.center.x-115, y: view.center.y+90, width: 60, height: 50)
        startBTN.frame = CGRect(x: view.center.x-115, y: view.center.y+200, width: 60, height: 50)

        startBTN.addTarget(self, action: #selector(startHit), for: .touchDown)

        pauseBTN.addTarget(self, action: #selector(pause), for: .touchDown)

        enterTime.placeholder = String("MM:SS")

        enterTime.delegate = self
        enterTime.addTarget(self, action: #selector(self.textFieldDidChange), for: UIControl.Event.editingChanged)

        pauseBTN.setTitle("pause", for: .normal)
        startBTN.setTitle("Start", for: .normal)
    }

    @objc func pause() {

        if !isPaused {
            timer?.invalidate()
            timer = nil
            pauseBTN.setTitle("go", for: .normal)
        }
        else {
            timer = Timer.scheduledTimer(timeInterval: 1, target: self, selector: #selector(timerAction), userInfo: nil, repeats: true)
            pauseBTN.setTitle("pause", for: .normal)
        }
        isPaused = !isPaused
    }

    @objc func startHit() {
        isPaused = false
        timer?.invalidate()
        counter = convertToSeconds(from: enterTime.text ?? "")
        lblTime.text = formatSeconds(counter)
        timer = Timer.scheduledTimer(timeInterval: 1, target: self, selector: #selector(timerAction), userInfo: nil, repeats: true)
    }

    @objc func timerAction() {
        if ( counter == 0 ) {
            timer?.invalidate()
            timer = nil
            return
        }
        counter -= 1
        lblTime.text = formatSeconds(counter)
    }
    func convertToSeconds(from timeString: String) -> Int {
        let components = timeString.components(separatedBy: ":")
        if components.count == 1 {
            let minutes = Int(components[0]) ?? 0
            return minutes * 60
        } else if components.count == 2 {
            let minutes = Int(components[0]) ?? 0
            let seconds = Int(components[1]) ?? 0
            return (minutes * 60) + seconds
        } else if components.count == 3 {
            let hours = Int(components[0]) ?? 0
            let minutes = Int(components[1]) ?? 0
            let seconds = Int(components[2]) ?? 0
            return (hours * 60 * 60) + (minutes * 60) + seconds
        } else {
            return 0
        }
    }
    func formatSeconds(_ totalSeconds: Int) -> String {
        let formatter = DateComponentsFormatter()
        formatter.unitsStyle = .positional
        formatter.allowedUnits = [.minute, .second]
        formatter.zeroFormattingBehavior = .pad
        return formatter.string(from: TimeInterval(totalSeconds)) ?? ""
    }
    func textField(_ textField: UITextField, shouldChangeCharactersIn range: NSRange, replacementString string: String) -> Bool {

        let newLength: Int = (textField.text?.count ?? 0) + string.count - range.length
        let numberOnly = NSCharacterSet.init(charactersIn: ACCEPTABLE_NUMBERS).inverted
        let strValid = string.rangeOfCharacter(from: numberOnly) == nil
        return (strValid && (newLength <= MAX_LENGTH_PHONENUMBER))
    }



    @objc func textFieldDidChange(_ textField: UITextField) {
        if let text = textField.text, text.count == 2 {
            textField.text = text + ":00"
        }
    }
}