swift - 我无法在 Swift 3 中使用计时器更改 label.text

Question

@IBOutlet var timeLabel: UILabel!
var timer = Timer()

let now = Date()
let userCalendar = Calendar.current
let formatter = DateFormatter()

func printTime() {

    formatter.dateFormat = "MM/dd/yy hh/mm/ss a"
    let startTime = now
    let endTime = formatter.date(from: "01/01/17 00/00/00 a")

    let difference = userCalendar.dateComponents([.month, .day, .year, .hour, .minute, .second], from: startTime, to: endTime!)

    timeLabel.text = "Yılbaşına \(difference.month!) ay, \(difference.day!) gün, \(difference.hour!) saat, \(difference.minute!) dakika, \(difference.second!) saniye kaldı"

    print("hello world")

}


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

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

}



override func didReceiveMemoryWarning() {
    super.didReceiveMemoryWarning()
    // Dispose of any resources that can be recreated.
}

When it is running

我正在使用带有 Swift 3 的 Xcode 8。当我运行此代码时，它每秒都会写入控制台“hello world”，但在计时器运行时它不会更新标签。我想为每一秒的标签倒计时。

Answer 1

试试这个:

DispatchQueue.main.after(when: .now() + 1.0) { //after one second
    timeLabel.text = "Yılbaşına \(difference.month!) ay, \(difference.day!) gün, \(difference.hour!) saat, \(difference.minute!) dakika, \(difference.second!) saniye kaldı"
}