swift - 在标签中设置和动画化日期时间

Question

我很难完成某件事。我正在使用 Firebase 作为数据库。当用户创建新的投票帖子时，他们还必须设置到期日期。在应用程序本身中，我必须在 UILabel 中将到期日期显示为计时器(或倒计时？)，显示在投票应该被禁用之前剩余的时间。

这是我目前所拥有的:

extension Date {


func offsetFromNow() -> String {
       let formatter = DateComponentsFormatter()
       formatter.allowedUnits = [.day, .hour, .minute, .second]
       formatter.unitsStyle = .abbreviated
       return formatter.string(from: Date(), to: self)!
   }
}

class PostPollCVCell: UICollectionViewCell {
    var seconds = 60 
    var timer = Timer()
    var isTimerRunning = false
    func updateView() {
        if let expirationTimeInt = post?.pollExpirationTime {
            let expirationDate = Date(timeIntervalSince1970: Double(expirationTimeInt))
            self.pollExpirationDate.text = "poll ends in: " + expirationDate.offsetFromNow()
        }
    }

   func runTimer() {
   timer = Timer.scheduledTimer(timeInterval: 1, target: self, selector: #selector(self.updateTimer), userInfo: nil, repeats: true)
    }

    @objc func updateTimer() {
        seconds -= 1     //This will decrement(count down)the days, hours, min and seconds.
      // pollExpirationDate.text = Update the label with the total time left
    }
}

上面代码所做的唯一一件事就是简单地获取日期并将 pollExpirationDate.text 设置为基本上任何时间。输出格式是这样的:

3d 3h 34min 5s

我必须做什么但不知道怎么做(需要代码方面的帮助):

1. 我必须确保时间不是负数。现在，它只是显示时间，即使它是负数。如果时间为负，则意味着 pollExpirationDate UILabel 应该简单地说投票已经结束，禁用投票选项(即 UIButton)并显示一个包含结果的 block (现在，我不期望你会这样，此时甚至还没有设置，我只需要知道我应该在哪里运行这段代码，仅此而已)

   <

2. 我正在从 FirebaseDatabase 下载日期并设置 UILabel，但我不知道如何创建计时器(或倒计时)为 pollExpirationDate UILabel(剩余时间)制作动画

3. 当倒计时到0秒时，应该关闭投票(时间已过)

我从来没有做过这些，所以非常感谢帮助。

Answer 1

在类中全局创建两个变量来检查定时器的状态是工作还是暂停/停止。

fileprivate var timeWorking                     : Bool = false
var timer                                       : Timer?

然后，创建了一种方法来获取与您所描述的相同的每个日期组件。

func timeLeftExtended(date:Date) -> NSAttributedString {

    let cal = Calendar.current
    let now = Date()
    let calendarUnits : NSCalendar.Unit = [.day, .hour, .minute, .second]
    let components = (cal as NSCalendar).components(calendarUnits, from: now, to: date, options: [])

    let fullCountDownStr = ""

    if(components.day!.description == "0" || components.day!.description == "00") {

        // This will display hour, minute, and second
        fullCountDownStr = "\(components.hour!.description)h " + "\(components.minute!.description)m " + "\(components.second!.description)s "

    } else if (components.day!.description == "0" || components.day!.description == "00") && (components.hour!.description == "0" || components.hour!.description == "00") {

        // This will display minute and second
        fullCountDownStr = "\(components.minute!.description)m " + "\(components.second!.description)s "

    } else if (components.day!.description == "0" || components.day!.description == "00") && (components.hour!.description == "0" || components.hour!.description == "00") && (components.minute!.description == "0" || components.minute!.description == "00") {

        // This will display second only
        fullCountDownStr = "\(components.second!.description)s "

    } else {

        // This will display day, hour, minute, second
        fullCountDownStr = "\(components.day!.description)d " + "\(components.hour!.description)h " + "\(components.minute!.description)m " + "\(components.second!.description)s "

    }

    let mutableStr = NSMutableAttributedString(string: fullCountDownStr, attributes: [.foregroundColor: UIColor.white])

    for (index,char) in mutableStr.string.enumerated() {
        if(char == "d" || char == "h" || char == "m" || char == "s") {
            mutableStr.removeAttribute(NSAttributedStringKey.foregroundColor, range: NSMakeRange(index, 1))
            mutableStr.addAttributes([.foregroundColor : UIColor.white], range: NSMakeRange(index, 1))
            mutableStr.addAttributes([.font: UIFont.systemFont(ofSize: 12)], range: NSMakeRange(index, 1))
        }
    }

    return mutableStr
}

这将给我 3d 3h 34min 5s 格式的日期。

为 make Timer 的计数器设置动画并调用此方法。

func setupTimer() {

    if let expirationTimeInt = post?.pollExpirationTime {
        let expirationDate = Date(timeIntervalSince1970: Double(expirationTimeInt))

        if expirationDate == Date() {
            self.pollExpirationDate.text = "expirationDate is Today's date"
        } else if date! > Date() {
            if(!timeWorking) {
                timer = Timer.scheduledTimer(timeInterval: 1.0, target: self, selector: #selector(self.updateCountDown), userInfo: nil, repeats: true)
                self.timeWorking = true
            }
        } else if date! < Date() {
             self.pollExpirationDate.text = "expirationDate is gone"
        }
    }
}

更新计数器方法将为您的日期计时器倒计时。

@objc func updateCountDown() {
    if let expirationTimeInt = post?.pollExpirationTime {
        let expirationDate = Date(timeIntervalSince1970: Double(expirationTimeInt))

        self.pollExpirationDate.attributedText = self.timeLeftExtended(date: expirationDate)
    }
}

从 viewDidLoad 调用设置计时器方法。这是适合我的工作代码，希望对您有所帮助。