如何在 C# 中重置计时器？

Question

There are three Timer classes that I am aware of, System.Threading.Timer , System.Timers.Timer , and System.Windows.Forms.Timer , but none of these have a .Reset() function which would reset the current elapsed time to 0.

Is there a BCL class that has this functionality? Is there a non-hack way of doing it? (I thought perhaps changing the time limit on it might reset it) Thought on how hard it would be to reimplement a Timer class that had this functionality, or how to do it reliably with one of the BCL classes?

Answer 1

I always do ...

myTimer.Stop();
myTimer.Start();

... is that a hack? :)

Per comment, on Threading.Timer, it's the Change method ...

dueTime Type: System.Int32 The amount of time to delay before the invoking the callback method specified when the Timer was constructed, in milliseconds. Specify Timeout.Infinite to prevent the timer from restarting. Specify zero (0) to restart the timer immediately.

Answer 2

All the timers have the equivalent of Start() and Stop() methods, except System.Threading.Timer.

So an extension method such as...

public static void Reset(this Timer timer)
{
  timer.Stop();
  timer.Start();
}

...is one way to go about it.

Answer 3

For System.Timers.Timer , according to MSDN documentation, http://msdn.microsoft.com/en-us/library/system.timers.timer.enabled.aspx :

If the interval is set after the Timer has started, the count is reset. For example, if you set the interval to 5 seconds and then set the Enabled property to true, the count starts at the time Enabled is set. If you reset the interval to 10 seconds when count is 3 seconds, the Elapsed event is raised for the first time 13 seconds after Enabled was set to true.

So,

    const double TIMEOUT = 5000; // milliseconds

    aTimer = new System.Timers.Timer(TIMEOUT);
    aTimer.Start();     // timer start running

    :
    :

    aTimer.Interval = TIMEOUT;  // restart the timer

Answer 4

You could write an extension method called Reset(), which

• calls Stop()-Start() for Timers.Timer and Forms.Timer
• calls Change for Threading.Timer

Answer 5

For clarity since some other comments are incorrect, when using System.Timers setting Enabled to true will reset the elapsed time. I just tested the behavior with the below:

Timer countDown= new Timer(3000);

Main()
{
    TextBox.TextDidChange += TextBox_TextDidChange;
    countdown.Elapsed += CountDown_Elapsed;
}

void TextBox_TextDidChange(Object sender, EventArgs e)
{
    countdown.Enabled = true;
}

void CountDown_Elapsed(object sender, EventArgs e)
{
    System.Console.WriteLine("Elapsed");
}

I would input text to the text box repeatedly and the timer would only run 3 seconds after the last keystroke. It's hinted at in the docs as well, as you'll see: calling Timers.Start() simply sets Enabled to true.

And to be sure, which I should've just went straight to from the beginning, you'll see in the .NET reference source that if enabling an already Enabled timer it calls the private UpdateTimer() method, which internally calls Change() .

Answer 6

I just assigned a new value to the timer:

mytimer.Change(10000, 0); // reset to 10 seconds

It works fine for me.

at the top of the code define the timer: System.Threading.Timer myTimer;

if (!active)
    myTimer = new Timer(new TimerCallback(TimerProc));

myTimer.Change(10000, 0);
active = true;

private void TimerProc(object state)
{
    // The state object is the Timer object.
    var t = (Timer)state;

    t.Dispose();
    Console.WriteLine("The timer callback executes.");
    active = false;
    
    // Action to do when timer is back to zero
}

Answer 7

For a Timer (System.Windows.Forms.Timer).

The .Stop, then .Start methods worked as a reset.

Answer 8

你可以做timer.Interval = timer.Interval

Answer 9

Other alternative way to reset the windows.timer is using the counter, as follows:

int timerCtr = 0;
Timer mTimer;

private void ResetTimer() => timerCtr = 0;
private void mTimer_Tick()
{
    timerCtr++;
    // Perform task
}  

So if you intend to repeat every 1 second, you can set the timer interval at 100ms, and test the counter to 10 cycles.

This is suitable if the timer should wait for some processes those may be ended at the different time span.

Answer 10

i do this

//Restart the timer
queueTimer.Enabled = true;