[英]Elapsed Timer not starting
I am building an elapsed timer and while the code gives no errors the timer does not start. 我正在建立一个经过的计时器,而代码没有给出错误,则计时器无法启动。
I am using two ViewControllers, one called Stopwatch which has the start stop function in it under the class Stopwatch() and then a regular ViewController with the rest in it. 我正在使用两个ViewController,一个叫做Stopwatch,它在Stopwatch()类下具有启动停止功能,然后是一个普通的ViewController,其中包含其余的控件。
View Controller Code: 查看控制器代码:
import UIKit
class ViewController: UIViewController {
let watch = Stopwatch()
@IBOutlet weak var elapsedTimeLabel: UILabel!
@IBAction func startButton(_ sender: Any) {
Timer.scheduledTimer(timeInterval: 0.1, target: self, selector: #selector(self.updateElapsedTimeLabel), userInfo: nil, repeats: true)
watch.start()
}
@IBAction func stopButton(_ sender: Any) {
watch.stop()
}
@objc func updateElapsedTimeLabel (timer : Timer) {
if watch.isRunning {
let minutes = Int (watch.elapsedTime/60)
let seconds = watch.elapsedTime.truncatingRemainder(dividingBy: 60)
let tenOfSeconds = (watch.elapsedTime * 10).truncatingRemainder(dividingBy: 10)
elapsedTimeLabel.text = String (format: "%02d:%02d:%02d", minutes, seconds, tenOfSeconds)
} else {
timer.invalidate()
}
}
override func viewDidLoad() {
super.viewDidLoad()
}
override func didReceiveMemoryWarning() {
super.didReceiveMemoryWarning()
}
override var prefersStatusBarHidden: Bool {
return true
}
}
The Stopwatch View Controller code: 秒表视图控制器代码:
import Foundation
class Stopwatch {
private var startTime : Date?
var elapsedTime: TimeInterval {
if let startTime = self.startTime {
return -startTime.timeIntervalSinceNow
} else {
return 0
}
}
var isRunning: Bool {
return startTime != nil
}
func start() {
startTime = Date()
}
func stop() {
startTime = nil
}
}
There is nothing at all coming in the debug window, so not sure what the issue is, I reconnected the buttons over and over so it's not that. 调试窗口中什么都没有,所以不确定是什么问题,我一遍又一遍地重新连接了按钮,事实并非如此。 I also get no other errors in the code as mentioned above.
如上所述,我在代码中也没有得到其他错误。
Can anyone shed some light on this. 任何人都可以阐明这一点。 Maybe I am using the wrong #selector or I am doing the updateElapsedTimeLabel minutes, seconds, tenOfSeconds calculations wrong.
也许我使用了错误的#selector或我在执行updateElapsedTimeLabel分钟,秒,tenOfSeconds计算错误。 Not sure.
不确定。 Thanks for having a look.
感谢您的浏览。
If you Option-click on seconds
and tenOfSeconds
you will find that one is of type TimeInterval
(ie Double
) and the other is of type Double
. 如果在Option上单击
seconds
和tenOfSeconds
您会发现一个类型为TimeInterval
(即Double
),另一个类型为Double
。 So your format specifier of %02d
was wrong. 因此,您的
%02d
格式说明符是错误的。 In C, a mismatch between the format specifier and the argument is undefined behavior. 在C语言中,格式说明符和参数之间的不匹配是未定义的行为。 Swift doesn't say how it handles that but I guess it will ignore the argument.
Swift并未说明如何处理,但我想它将忽略该参数。
To fix it, change your format specifier for the last 2 components to %02.f
: 要解决此问题,请将最后2个组件的格式说明符更改为
%02.f
:
let minutes = Int(watch.elapsedTime/60)
let seconds = watch.elapsedTime.truncatingRemainder(dividingBy: 60)
let tenOfSeconds = (watch.elapsedTime * 100).truncatingRemainder(dividingBy: 100) // fixed the math here
elapsedTimeLabel.text = String(format: "%02d:%02.f:%02.f", minutes, seconds, tenOfSeconds)
But why not use a DateFormatter
to make your life simpler: 但是,为什么不使用
DateFormatter
来简化您的生活:
class ViewController: UIViewController {
private let formatter: DateFormatter = {
let formatter = DateFormatter()
formatter.dateFormat = "mm:ss:SS"
return formatter
}()
@objc func updateElapsedTimeLabel (timer : Timer) {
if watch.isRunning {
elapsedTimeLabel.text = formatter.string(from: Date(timeIntervalSince1970: watch.elapsedTime))
} else {
timer.invalidate()
}
}
}
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