我想每毫秒更改一次计时器,但它不能按预期工作.
NSTimer.scheduledTimerWithTimeInterval(0.001,target: self,selector: Selector("advanceTimer:"),userInfo: nil,repeats: true);
func advanceTimer(timer: NSTimer){
self.time += 0.001;
let milliseconds = self.time * 100;
let remaingMilliseconds = Int((milliseconds % 1000) / 10);
let seconds = Int((milliseconds / 1000) % 60)
let strSeconds = String(format: "%02d",seconds)
let strFraction = String(format: "%02d",remaingMilliseconds)
timerText.text = "\(strSeconds):\(strFraction)";
}
结果是
计时器在毫秒部分(00：100)中更改为100,然后更改为01:00 = 40实际秒
邓肯方法：
var time: NSTimeInterval = 0;
var startTime: NSTimeInterval = 0;
//And your timer method...
func advanceTimer(timer: NSTimer){
//Total time since timer started,in seconds
self.time = NSDate.timeIntervalSinceReferenceDate() - startTime
println(self.time);
//The rest of your code goes here
}
override func didMoveToView(view: SKView) {
// Set anchor point
self.anchorPoint = CGPointMake(0.5,0.5);
var startTime: NSTimeInterval
//Sart the timer
startTime = NSDate.timeIntervalSinceReferenceDate()
NSTimer.scheduledTimerWithTimeInterval(0.02,repeats: true)
}
结果：456680125.54539第一次打印
解决方法
正如Martin在评论中所说,定时器的分辨率为50-100毫秒(0.05到0.1秒).尝试运行时间间隔短于此的计时器将无法提供可靠的结果.此外,计时器不是实时的.它们取决于它们所连接的运行循环,如果运行循环变忙,则计时器的触发会延迟.
不是每次计时器触发时都尝试递增计数器,而是在启动计时器时记录开始时间,然后进行一些数学计算以确定发生了多长时间：
var startTime: NSTimeInterval
//Sart the timer
startTime = NSDate.timeIntervalSinceReferenceDate()
NSTimer.scheduledTimerWithTimeInterval(0.02,repeats: true)
//And your timer method...
func advanceTimer(timer: NSTimer)
{
//Total time since timer started,in seconds
self.time = NSDate.timeIntervalSinceReferenceDate() - startTime
//The rest of your code goes here
}
编辑：
此代码的Swift 3版本如下所示：
(在测试项目中写为视图控制器)
class ViewController: UIViewController {
weak var timer: Timer?
var startTime: Double = 0
var time: Double = 0
@IBOutlet weak var timeValueLabel: UILabel!
/*
When the view controller first appears,record the time and start a timer
*/
override func viewDidAppear(_ animated: Bool) {
startTime = Date().timeIntervalSinceReferenceDate
timer = Timer.scheduledTimer(timeInterval: 0.05,selector: #selector(advanceTimer(timer:)),repeats: true)
}
//When the view controller is about to disappear,invalidate the timer
override func viewWillDisappear(_ animated: Bool) {
timer?.invalidate()
}
func advanceTimer(timer: Timer) {
//Total time since timer started,in seconds
time = Date().timeIntervalSinceReferenceDate - startTime
//The rest of your code goes here
//Convert the time to a string with 2 decimal places
let timeString = String(format: "%.2f",time)
//Display the time string to a label in our view controller
timeValueLabel.text = timeString
}
}
