C# -如何暂停应用程序直到计时器完成？
C# -如何暂停应用程序直到计时器完成？
提问于 2016-07-07 19:14:22
我有一个应用程序，我需要等待一个特定的时间，但我也需要能够取消当前的操作，如果需要。我有以下代码：
private void waitTimer(int days)
{
TimeSpan waitTime = TimeSpan.FromDays(days);
System.Timers.Timer timer = new System.Timers.Timer(waitTime.TotalMilliseconds); // Wait for some number of milliseconds
timer.Enabled = true;
timer.Start();
timer.Elapsed += new ElapsedEventHandler(OnTimedEvent); // Subscribe to event handler
while (!TimerSettings.TimerFinished && !quitToken.IsCancellationRequested); // Loop forever untill timer is finished or operation is cancled.
timer.Elapsed -= new ElapsedEventHandler(OnTimedEvent); // Unsubscribe
DoWork(); // Do work when timer finishes.......
}下面是计时器完成事件的事件处理程序：
private void OnTimedEvent(object obj, ElapsedEventArgs e)
{
TimerSettings.TimerFinished = true;
}while循环只是无限循环，直到计时器完成，或者直到一个取消请求被放入。我想保留这个功能，但我不想在等待计时器完成时永远循环。我的计时器可以设置为每隔几天运行一次，因此在这么长时间内循环是没有意义的。
还有别的办法吗？
我知道我能做到：
Thread.Sleep(runDuration.TotalMilliseconds);然而，这将是阻塞的，我将无法提出取消请求。
编辑:因此，为了详细说明我需要暂停的是什么/为什么需要暂停，这里有一个关于我的应用程序的更详细的解释。基本上，我希望有一个应用程序在一个固定的间隔上执行“工作”。因此，根据下面提供的一个答案，如果我做了这样的事情：
class Program
{
// Do something in this method forever on a regular interval
//(could be every 5min or maybe every 5days, it's up to the user)
static void Main(string[] args)
{
while(true)
{
if(args?.Length > 0)
waitTimer(args[0]);
else
wiatTimer(TimeSpan.FromDays(1).TotalSeconds); // Default to one day interval
}
}
private void waitTimer(int numIntervals)
{
this.ElapsedIntervals = 0;
this.IntervalsRequired = numIntervals;
this.timer = new System.Timers.Timer(1000); // raise the elapsed event every second
timer.Elapsed += new ElapsedEventHandler(OnTimedEvent); // Subscribe to event handler
//timer.Enabled = true; timer.Start() does this for you, don't do this
timer.Start();
//thats all here
}
private void OnTimedEvent(object obj, ElapsedEventArgs e)
{
this.ElapsedIntervals += 1;
if(this.CancelRequested)
{
this.ElapsedIntervals = 0;
this.timer.Stop();
return;
}
if(this.ElapsedIntervals >= this.IntervalsRequired)
{
this.ElapsedIntervals = 0;
this.timer.Stop();
DoWork(); // This is where my work gets done.......
return;
}
}
}然后，我的服务/控制台应用程序将启动并进入一个无限循环，只需整天设置定时器。以前，我实际上是在以下位置停止执行任何其他代码：
while (!TimerSettings.TimerFinished && !quitToken.IsCancellationRequested);这至少起作用了，但如前所述，这可能是暂停线程的资源密集型方法。基本上，我真正需要的是一种阻止线程直到计时器上升的方法。
EDIT2:这是我最后一个使用等待句柄工作的实现.
class TimerClass
{
/// <summary>
/// Initialize new timer. To set timer duration,
/// either set the "IntervalMinutes" app config
/// parameter, or pass in the duration timespan.
/// </summary>
/// <param name="time"></param>
internal bool StartTimer(CancellationToken quitToken, TimeSpan? duration = null)
{
TimeSpan runDuration = new TimeSpan();
runDuration = duration == null ? GetTimerSpan() : default(TimeSpan);
if (runDuration != default(TimeSpan))
{
WaitTimer(runDuration); // Waits for the runduration to pass
}
return true;
}
/// <summary>
/// Get duration to run the timer for.
/// </summary>
internal TimeSpan GetTimerSpan()
{
TimerSettings.Mode = App.Settings.Mode;
DateTime scheduledTime = new DateTime();
switch (TimerSettings.Mode)
{
case "Daily":
scheduledTime = DateTime.ParseExact(App.Settings.ScheduledTime, "HH:mm:ss", CultureInfo.InvariantCulture);
if (scheduledTime > DateTime.Now)
TimerSettings.TimerInterval = scheduledTime - DateTime.Now;
else
TimerSettings.TimerInterval = (scheduledTime + TimeSpan.FromDays(1)) - DateTime.Now;
break;
case "Interval":
double IntervalMin = double.TryParse(App.Settings.PollingIntervalMinutes, out IntervalMin) ? IntervalMin : 15.00;
int IntervalSec = Convert.ToInt32(Math.Round(60 * IntervalMin));
TimeSpan RunInterval = new TimeSpan(0, 0, IntervalSec);
TimerSettings.TimerInterval = RunInterval;
break;
case "Manual":
TimerSettings.TimerInterval = TimeSpan.FromMilliseconds(0);
break;
default:
TimerSettings.TimerInterval = (DateTime.Today + TimeSpan.FromDays(1)) - DateTime.Now;
break;
}
return TimerSettings.TimerInterval;
}
/// <summary>
/// Event handler for each timer tick.
/// </summary>
/// <param name="obj"></param>
/// <param name="e"></param>
private void OnTimedEvent(object obj, ElapsedEventArgs e)
{
ElapsedIntervals += 1;
if (CancelRequested.IsCancellationRequested) // If the application was cancled
{
ElapsedIntervals = 0;
timer.Stop();
WaitHandle.Set();
return;
}
if (ElapsedIntervals >= IntervalsRequired) // If time is up
{
ElapsedIntervals = 0;
timer.Stop();
WaitHandle.Set();
return;
}
}
/// <summary>
/// Timer method to wait for a
/// specified duration to pass.
/// </summary>
/// <param name="span"></param>
private void WaitTimer(TimeSpan span)
{
WaitHandle = new AutoResetEvent(false);
int tickDuration = 1000; // Number of milliseconds for each tick
IntervalsRequired = Convert.ToInt64(span.TotalMilliseconds / (tickDuration > 0 ? tickDuration : 0.01));
timer = new System.Timers.Timer(tickDuration); // Raise the elapsed event every tick
timer.Elapsed += new ElapsedEventHandler(OnTimedEvent); // Subscribe to event handler for when each tick is complete
timer.Start(); // Start ticking
WaitHandle.WaitOne(); // Halt the main thread untill span is reached
}
// Timer parameters:
private static long ElapsedIntervals { get; set; }
private static long IntervalsRequired { get; set; }
private static System.Timers.Timer timer { get; set; }
private static CancellationToken CancelRequested { get; set; }
private static string Mode { get; set; }
private static TimeSpan TimerInterval { get; set; }
private static EventWaitHandle WaitHandle { get; set; }
}
internal static class TimerSettings
{
internal static string Mode { get; set; }
internal static TimeSpan TimerInterval { get; set; }
}回答 2
Stack Overflow用户
回答已采纳
发布于 2016-07-07 19:43:59
您应该查看Timer.Elapsed事件文档。当AutoReset属性设置为true时，每次间隔过去时，都会重复引发此事件(这是默认的)。我会让您自己计算已经过了多少间隔，并将其与此事件处理程序中所需的运行间隔进行比较，以检查是否是停止计时器的时间。在这种情况下，您还可以处理取消。如果计时器完成了所需的间隔数，则可以从该事件处理程序调用您的doWork函数。
private void waitTimer(int numIntervals)
{
this.ElapsedIntervals = 0;
this.IntervalsRequired = numIntervals;
this.timer = new System.Timers.Timer(1000); // raise the elapsed event every second
timer.Elapsed += new ElapsedEventHandler(OnTimedEvent); // Subscribe to event handler
//timer.Enabled = true; timer.Start() does this for you, don't do this
timer.Start();
//thats all here
}
private void OnTimedEvent(object obj, ElapsedEventArgs e)
{
this.ElapsedIntervals += 1;
if(this.CancelRequested)
{
this.ElapsedIntervals = 0;
this.timer.Stop();
return;
}
if(this.ElapsedIntervals >= this.IntervalsRequired)
{
this.ElapsedIntervals = 0;
this.timer.Stop();
DoWork();
return;
}
}https://msdn.microsoft.com/en-us/library/system.timers.timer.elapsed(v=vs.110).aspx
在我看来，关于“暂停”，有两个理由要暂停，我不知道是你的原因：
- 您希望防止应用程序“完成”执行并正常终止。
- 您希望推迟执行其他代码，直到所需的间隔时间已经过去。
如果你的理由是#2，那么这个答案就完成了。
Stack Overflow用户
发布于 2016-07-07 19:19:56
首先：“你绝对不需要(！)想‘忙’--等待任何东西！”(坏狗！不要饼干！)
嗯哼..。
这个问题的一个实际解决方案是对信号量(或任何其他合适的互斥对象.)执行定时等待，而不是使用实际的计时器。如果你需要在等待完成之前摆脱它，只需在等待的东西上闪过。
您目前的“解决方案”的关键问题是，它将使进程100%的CPU利用率，完全浪费。从来没有那样做过！
页面原文内容由Stack Overflow提供。腾讯云小微IT领域专用引擎提供翻译支持
原文链接：
https://stackoverflow.com/questions/38253572
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