ios - 如何在 0 处停止倒计时？ - swift

Question

我是 Swift 和 iOS 开发的新手。我正在尝试为特定日期倒计时。 我的 iOS 倒计时应用程序在零后计数为负。我想停在零。我该如何解决？

let currentDate = Date()
let dateFormatter = DateFormatter()

let userCalendar = Calendar.current

 let requestedComponent: Set<Calendar.Component> = [.day,.hour,.minute,.second]


override func viewDidLoad() {
    super.viewDidLoad()
    // Do any additional setup after loading the view, typically from a nib.

    let timer = Timer.scheduledTimer(timeInterval: 1.0, target: self, selector: #selector(printTime), userInfo: nil, repeats: true)
    timer.fire()



}

func printTime()
{
    dateFormatter.dateFormat = "dd/MM/yy hh:mm:ss"
    let startTime = Date()
     let endTime = dateFormatter.date(from: "11/03/18 10:00:00")

    let time = userCalendar.dateComponents(requestedComponent, from: startTime, to: endTime!)


    dayLabel.text = "\(time.day!)"
    hourLabel.text = "\(time.hour!)"
    minuteLabel.text = "\(time.minute!)"
    secondLabel.text = "\(time.second!)"
}

override func didReceiveMemoryWarning() {
    super.didReceiveMemoryWarning()

}

Answer 1

尝试改变:

dayLabel.text = "\(time.day!)"
hourLabel.text = "\(time.hour!)"
minuteLabel.text = "\(time.minute!)"
secondLabel.text = "\(time.second!)"

到:

if startTime < endTime {
    dayLabel.text = "\(time.day!)"
    hourLabel.text = "\(time.hour!)"
    minuteLabel.text = "\(time.minute!)"
    secondLabel.text = "\(time.second!)"
} else {
    dayLabel.text = "0"
    hourLabel.text = "0"
    minuteLabel.text = "0"
    secondLabel.text = "0"
}

根据您的情况，您可能希望使用 timer.invalidate() 停止计时器，如下所示:

...

var timer: Timer?

override func viewDidLoad() {
    super.viewDidLoad()
    // Do any additional setup after loading the view, typically from a nib.

    timer = Timer.scheduledTimer(timeInterval: 1.0, target: self, selector: #selector(printTime), userInfo: nil, repeats: true)
    timer?.fire()

}

func printTime() {

     ...

     } else {
         ...
         timer?.invalidate()
     }
}