如何为计时器增加5秒 [英] How to add 5 seconds to a timer

问题描述

我正在尝试使计时器显示以下内容-小时:分钟:秒:毫秒.这是我的代码:

I'm trying to make a timer showing the following - hours : minutes : seconds : milliseconds. Here is my code:

var timer = NSTimer()
var startTime = NSTimeInterval()

func updateTime()
{
    var currentTime = NSDate.timeIntervalSinceReferenceDate()
    var elapsedTime : NSTimeInterval = currentTime - startTime

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

    let minutes = UInt8(elapsedTime / 60.0)
    elapsedTime -= (NSTimeInterval(minutes) * 60)

    let seconds = UInt8(elapsedTime)
    elapsedTime -= NSTimeInterval(seconds)

    let fraction = UInt8(elapsedTime * 100)

    let strHours = String(format: "%02d", hours)
    let strMinutes = String(format: "%02d", minutes)
    let strSeconds = String(format: "%02d", seconds)
    let strFraction = String(format: "%02d", fraction)

    timeLabel.text = "\(strHours):\(strMinutes):\(strSeconds):\(strFraction)"
}

@IBAction func start(sender: AnyObject) {
    if !timer.valid {
        let aSelector : Selector = "updateTime"
        timer = NSTimer.scheduledTimerWithTimeInterval(0.01, target: self, selector: aSelector, userInfo: nil, repeats: true)
        startTime = NSDate.timeIntervalSinceReferenceDate()
    }
}

如何通过其他方法将5秒添加到计时器? (显然，我必须创建一个全局var，但我现在想使其保持简单，首先实际添加5秒，然后我们担心全局部分.)我尝试更改/添加以下内容:

How can I add 5 seconds to the timer in another method? (Obviously I will have to make a global var, but I'm trying to keep it simple for now and first actually add the 5 secs, then we'll worry about the global part.) I tried changing/adding the following:

var seconds = UInt8(elapsedTime)
seconds += 5 // Error here...
elapsedTime -= NSTimeInterval(seconds)

但我收到一条错误消息:

But I get an error saying:

致命错误:无法将浮点值转换为UInt8 因为它小于UInt8.min

fatal error: floating point value can not be converted to UInt8 because it is less than UInt8.min

向计时器添加5秒的正确方法是什么?

What's the correct way to add 5 seconds to the timer?

推荐答案

使计时器无效，然后创建一个新计时器.您无法修改计时器的时间间隔.

Invalidate the timer, then create a new one. You can't modify the time interval of a timer.

就您的错误而言，elapsedTime可能为负，从而产生错误. UInt8.min是0.

As far as your error, elapsedTime is probably negative, which yields the error. UInt8.min is 0.

计时器不是秒表. NSTimer在特定时间触发.

A timer is not a stop watch. An NSTimer fires off at a specific time.

对于秒表之类的东西，您只需设置开始日期即可.然后，您可以使用设置为一秒的计时器来每秒更新一次显示.您将显示当前时间和开始日期之间的时差.

For something like a stop watch, you should simply be setting a start date. Then, you could use a timer that's set to one second to update the display every second. You'd display the difference between the current time and the start date.

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