iOS Swift 1 秒后更新文本标签

Question

1 秒后尝试更新标签。我正在使用休眠功能，但应用程序正在加载并且不会动态更新文本字段。

代码是：

override func viewDidAppear(animated: Bool) {
    beginCountdown()
}

func beginCountdown() {

    for var i = 5; i >= 0; i-- {

        println("Time until launch \(i)")

        var county:String = "\(i)"

        countdownLabel.text = county
        sleep(1)
    }

}

插座是正确的，我知道我漏掉了什么。谢谢

Answer 1

您不应使用 sleep() 函数，因为这会暂停主线程并导致您的应用变得无响应。 NSTimer 是实现此目的的一种方法。它将在未来的指定时间派发一个函数。

例如-

var countdown=0
var myTimer: NSTimer? = nil

override func viewDidAppear(animated: Bool) {     
    countdown=5
    myTimer = NSTimer(timeInterval: 1.0, target: self, selector:"countDownTick", userInfo: nil, repeats: true)
    countdownLabel.text = "\(countdown)"
}

func countDownTick() {
    countdown--

    if (countdown == 0) {
       myTimer!.invalidate()
       myTimer=nil
    }

    countdownLabel.text = "\(countdown)"
}

Answer 2

你真的 不应该 使用 sleep 因为它会阻塞主线程并因此冻结 UI，这意味着你永远不会看到你的标签已更新（更糟糕的是）。

您可以使用 NSTimer 来实现您想要做的事情。

var timer: NSTimer!
var countdown: Int = 0

override func viewDidAppear(animated: Bool) {
    self.countdown = 5
    self.timer = NSTimer.scheduledTimerWithTimeInterval(1.0, target: self, selector: "updateCountdown", userInfo: nil, repeats: true)
}

func updateCountdown() {
    println("Time until launch \(self.countdown)")
    countdownLabel.text = "\(self.countdown)"

    self.countdown--

    if self.countdown == 0 {
        self.timer.invalidate()
        self.timer = nil
    }
}

Answer 3

在Swift3.0

var countdown=0
var myTimer: Timer? = nil

override func viewDidAppear(_ animated: Bool) {
     countdown=5
    myTimer = Timer.scheduledTimer(timeInterval: 5.0, target: self, selector:  #selector(Dashboard.countDownTick), userInfo: nil, repeats: true)
    lbl_CustomerName.text = "\(countdown)"
}

func countDownTick() {
    countdown = countdown - 1
    //For infinite time
    if (countdown == 0) {
        countdown = 5
      //till countdown value  
        /*myTimer!.invalidate()
        myTimer=nil*/
    }

    lbl_CustomerName.text = "\(countdown)"
}

iOS Swift 1 秒后更新文本标签

iOS Swift Update text label after 1 second

uilabel

ios

swift