如何在 Swift 中有一个倒数计时器开始表单自定义时间？答案

【问题标题】：how can I have a countDown timer start form custom time in Swift?如何在 Swift 中有一个倒数计时器开始表单自定义时间？
【发布时间】：2017-05-08 09:51:03
【问题描述】：

使用这个倒数计时器，我可以从当前日期时间开始计数，但我如何才能从自定义日期时间开始倒数计时器。

let dateFormatter = DateFormatter()
let userCalendar = Calendar.current
let requestedComponent: Set<Calendar.Component> = [.month,.day,.hour,.minute,.second]

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

func printTime()
{
    dateFormatter.dateFormat = "yyyy/MM/dd HH:mm:ss"
    dateFormatter.calendar = Calendar(identifier: .gregorian)
    dateFormatter.locale = Locale.current
    let startTime = Date()
    let endTime = dateFormatter.date(from: "2017/10/18 14:02:00")
    let timeDifference = userCalendar.dateComponents(requestedComponent, from: startTime, to: endTime!)
    lableText.text = "\(timeDifference.month!):\(timeDifference.day!): \(timeDifference.hour!):\(timeDifference.minute!):\(timeDifference.second!)"}

【问题讨论】：

标签： ios swift3

【解决方案1】：

您需要按照以下方式进行更改

    var startTime = Date()

   override func viewDidLoad() {
          super.viewDidLoad()
           dateFormatter.dateFormat = "yyyy/MM/dd HH:mm:ss"
           dateFormatter.calendar = Calendar(identifier: .gregorian)
           dateFormatter.locale = Locale.current
           startTime = Date()
            let timer = Timer.scheduledTimer(timeInterval: 1.0, target: self, selector: #selector(printTime), userInfo: nil, repeats: true)
                    timer.fire()
         }

  func printTime()  {
          let endTime = dateFormatter.date(from: "2017/10/18 14:02:00")
          let timeDifference = userCalendar.dateComponents(requestedComponent, from: startTime, to: endTime!)
          lableText.text = "\(timeDifference.month!):\(timeDifference.day!): \(timeDifference.hour!):\(timeDifference.minute!):\(timeDifference.second!)"
                    }

【讨论】：

【解决方案2】：

你可以这样做：

let startTime = Date()

到这样的事情：

let calendar = NSCalendar.current
let components = NSDateComponents.init();
components.year = year
components.month = month
components.day = day
let startTime = calendar.date(from: components)

我设置了示例年、月和日，您也可以使用区域设置完整的日期时间。

希望对你有帮助！

【讨论】：