如何在0处停止倒数？ -迅捷

Question

I'm new at Swift and iOS development. I'm trying countdown for specific date. My iOS countdown app is counts negative after zero. I want stop at zero. How do I fix this?

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

Try changing:

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

to:

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"
}

And depending on your situation, you might want to stop the timer with timer.invalidate() like so:

...

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()
     }
}

Answer 2

let currentDate = Date()
let dateFormatter = DateFormatter()
var timer = Timer()
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.

    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!)

    if time.day! == 0 && time.hour! == 0 && time.minute! == 0 && time.second! == 0 {timer.invalidate()}

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