如何获取日期和时间以在 UILabel 中显示时钟 [英] How to get date and time to show a clock in UILabel

问题描述

我是 swift 的新手(以及一般的编程)，现在我正在从事一个项目，我想在标签中显示一个时钟.

I'm new to swift (and programming in general) and right now I'm working on a project that I'd like to display a clock in a label.

现在我的模型中有这个:

right now I have this in my model:

class CurrentDateAndTime {

let currentTime = NSDateFormatter.localizedStringFromDate(NSDate(), dateStyle: .MediumStyle, timeStyle: .MediumStyle)
}

然后在我的视图控制器中使用此代码将其调用到标签中:

and then call it into the label with this code in my view controller:

@IBOutlet weak var currentTimeLabel: UILabel!

let currentTime = CurrentDateAndTime()



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

    currentTimeLabel.text = currentTime.currentTime
}

问题是这不会以第二个时间间隔更新以显示实际时间.最终我将需要获得两个时间戳之间的差异，以便我可以记录开始时间"和停止时间"之间的小时数.这甚至是最好/最简单的方法吗?任何关于我的目标的线索将不胜感激.

The problem is this doesn't update on a second interval to show the actual time. And eventually I will be needing to get a difference between two time stamps so that I can log hours between a "start time" and a "stop time". Is this even the best/simplest way of doing it? Any clues toward my objective will be much appreciated.

推荐答案

使用 NSTimer 以您想要的时间间隔安排回调——在这种情况下，

Use NSTimer to schedule the callbacks at your desired interval -- in this case,

• 每秒调用tick() self

• tick() 获取当前时间字符串并更新 UILabel

• call tick() on self every second

• tick() fetches the current time string and updates the UILabel

class MyViewController {
    @IBOutlet weak var currentTimeLabel: UILabel!

    var timer = NSTimer()

    override func viewDidLoad() {
        super.viewDidLoad()

        // Do any additional setup after loading the view, typically from a nib.

        timer = NSTimer.scheduledTimerWithTimeInterval(1.0
                                                            target: self,
                                                          selector: #selector(tick),    
                                                          userInfo: nil, 
                                                           repeats: true)
    }

    @objc func tick() {
        currentTimeLabel.text = NSDateFormatter.localizedStringFromDate(NSDate(),
                                                                        dateStyle: .MediumStyle,
                                                                        timeStyle: .MediumStyle)
    }
}

Swift 4.0 更新:

Swift 4.0 update:

class MyViewController : UIViewController {
    @IBOutlet weak var currentTimeLabel: UILabel!

    var timer = Timer()

    override func viewDidLoad() {
        super.viewDidLoad()
        timer = Timer.scheduledTimer(timeInterval: 1.0, target: self, selector:#selector(self.tick) , userInfo: nil, repeats: true)
    }

    @objc func tick() {
        currentTimeLabel.text = DateFormatter.localizedString(from: Date(),
                                                              dateStyle: .medium,
                                                              timeStyle: .medium)
    }
}

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