c# - 为什么 Windows.Forms.Timer 的间隔会随着滴答声的增加而减少？

Question

我写了一个简单的程序，它使用定时器淡出标签。我发现定时器太不精确了，间隔越来越短。

下面的代码证明了我的想法:
(我也是用 StopWatch 实现的。刻度之间的间隔几乎相等。)

private void timer1_Tick(object sender, EventArgs e)
{
    elapsed += timer1.Interval;
    timerTest.AppendText(DateTime.UtcNow.Second.ToString() + "." + DateTime.UtcNow.Millisecond.ToString() + "\r\n");
    if (elapsed >= target)
        timer1.Stop();
}<br/>
int elapsed = 0;
int target = 4000;<br/>
private void button_Click(object sender, EventArgs e)
{
    labelFadeout.ForeColor = Color.Greed;
    elapsed = 0;
    timer1.Interval = 100;
    timer1.Tick += timer1_Tick;
    timer1.Start();
}

第 1 和第 5 输出导致大差异!

[1st]   [5th]
20.318  42.955
20.377  42.956
20.491  42.957
20.595  42.958
20.707  42.959
20.814  43.68
20.929  43.69
21.34   43.7
21.142  43.71
21.257  43.72
21.365  43.173
21.471  43.176
21.584  43.177
21.692  43.179
21.8    43.18
21.909  43.286
22.19   43.288
22.127  43.289
22.242  43.291
22.347  43.293
22.454  43.397
22.569  43.4
22.673  43.402
22.784  43.404
22.892  43.406
23.4    43.649
23.112  43.652
23.221  43.655
23.331  43.657
23.494  43.66
23.549  43.746
23.662  43.749
23.779  43.751
23.879  43.754
23.991  43.756
24.95   43.846
24.209  43.848
24.316  43.851
24.427  43.853
24.534  43.855

我检查过

• Comparing the Timer Classes in the .NET Framework Class Library
• 和Limitations of the Windows Forms Timer Component's Interval Property

并且仍然很好奇它怎么会如此不精确。谁能解释一下？？

Answer 1

您测试间隔的方法已关闭。您实际上只是每隔一段时间获取当前时间的一部分，并期望它与您上次获取的时间相当。

如果您想测试计时器以 100 为间隔真正花费多少时间。使用实际的秒表，并查看它的Elapsed 以了解过去了多少时间。

Stopwatch stopwatch = new Stopwatch();
int elapsed = 0;
int target = 4000;

private void timer1_Tick(object sender, EventArgs e)
{
    elapsed += timer1.Interval;
    timerTest.AppendText(stopwatch.Elapsed.TotalSeconds.ToString());
    stopwatch.Restart();

    if (elapsed >= target)
        timer1.Stop();
}

private void button1_Click(object sender, EventArgs e)
{
    elapsed = 0;
    timer1.Interval = 100;
    timer1.Tick += timer1_Tick;
    stopwatch.Start();
    timer1.Start();
}

我的结果:

0.1055445
0.0872668
0.1121169
0.1032453
0.1066107
0.1097218
0.103818
0.1079014
...