ios - 秒表超过 60 分钟

Question

抱歉，如果这听起来像是一个菜鸟问题。我正在为 iPhone 构建一个秒表应用程序。标签显示 hh:mm:ss。秒数在达到 60 时正确重置为 0，然后从 0 重新开始，但分钟超过 60。这是代码:

var elapsedTime = NSTimeInterval()

@IBAction func buttonAction(sender: AnyObject)
{
    timer = NSTimer.scheduledTimerWithTimeInterval(1, target: self, selector: "fireStopWatch", userInfo: nil, repeats: true)
    startTime = NSDate(timeIntervalSinceNow: 0)

}

func fireStopWatch()
   {
    var currentTime:NSDate = NSDate(timeIntervalSinceNow: 0)
    elapsedTime = currentTime.timeIntervalSinceDate(startTime)



    let minutes = UInt8(elapsedTime/60)
    elapsedTime -= (NSTimeInterval(minutes) * 60)
    let seconds = UInt8(elapsedTime)
    elapsedTime -= NSTimeInterval(seconds)
    let hours = UInt8(elapsedTime/3600.0)
    elapsedTime -= (NSTimeInterval(hours) * 3600)

    let strHours = hours > 9 ? String(hours):"0" + String(hours)
    let strMinutes = minutes > 9 ? String(minutes):"0" + String(minutes)
    let strSeconds = seconds > 9 ? String(seconds):"0" + String(seconds)


    displayTimeLabel.text = "\(strHours):\(strMinutes)"
    displaySecondsLabel.text = "\(strSeconds)"



}

秒发生了什么而分钟没有发生？

Answer 1

你的线路

let minutes = UInt8(elapsedTime/60)

计算总分钟数，而不是“一小时内”的分钟数。您可以稍后通过减去 60 * 小时 来解决这个问题。

但我发现从最低单位(秒)开始然后计算更高的单位更容易使用整数除法和余数运算符 % 的单位(分钟、小时...):

let totalSeconds = Int(elapsedTime)  // Total number of seconds as an integer
let seconds = totalSeconds % 60      // Seconds to display
let totalMinutes = totalSeconds / 60 // Total number of minutes
let minutes = totalMinutes % 60      // Minutes to display
let hours = totalMinutes / 60        // Hours to display

这也可以很容易地扩展到更多单位，例如天。

注意

let strHours = hours > 9 ? String(hours):"0" + String(hours)
let strMinutes = minutes > 9 ? String(minutes):"0" + String(minutes)
let strSeconds = seconds > 9 ? String(seconds):"0" + String(seconds)
displayTimeLabel.text = "\(strHours):\(strMinutes)"
displaySecondsLabel.text = "\(strSeconds)"

可以使用字符串格式化函数来简化:

displayTimeLabel.text = String(format: "%02d:%02d", hours, minutes)
displaySecondsLabel.text = String(format: "%02d", seconds)