Question

我有一个使用System.Windows.Forms.Timer的应用，并且看到了定时器间隔的问题。当我使用1000的间隔持续180秒时，经过的时间始终为183秒左右。当我使用995的间隔时，经过的时间是准确的（即180秒）。我在3台不同的PC上尝试了这一点，每台PC上都有相同的结果。下面的代码使用2个文本框来显示开始和结束时间，使用标签作为倒数计时器。

任何人都可以解释这种行为吗？

Public Class Form1

Private WithEvents tmr As New System.Windows.Forms.Timer

Private Duration As Integer = 180

Private Sub Button1_Click(sender As Object, e As EventArgs) Handles Button1.Click
    RunTimer()
End Sub

Private Sub Form1_Load(sender As Object, e As EventArgs) Handles MyBase.Load

    lblActivityTimer.Text = FormatCounter(Duration)
    tmr.Interval = 1000

End Sub

Private Sub RunTimer()

    tmr.Start()
    TextBox1.Text = Now.ToString()

End Sub

Private Function FormatCounter(sec As Integer) As String

    Dim Hours, Minutes, Seconds As Integer

    Hours = sec \ 3600
    Seconds = sec Mod 3600
    Minutes = Seconds \ 60
    Seconds = sec Mod 60

    FormatCounter = Hours.ToString.PadLeft(2, "0"c) & ":" _
                                                    & Minutes.ToString.PadLeft(2, "0"c) _
                                                    & ":" _
                                                    & Seconds.ToString.PadLeft(2, "0"c)

End Function

Private Sub tmr_Tick(sender As Object, e As EventArgs) Handles tmr.Tick

    Duration -= 1
    lblActivityTimer.Text = FormatCounter(Duration)
    If Duration = 0 Then
        TextBox2.Text = Now.ToString()
        tmr.Stop()
    End If

End Sub

End Class

Answer 1

使用Stop Watch，它提供了一组方法和属性，可用于准确测量已用时间。

Shared Sub Main(ByVal args() As String)
    Dim stopWatch As New Stopwatch()
    stopWatch.Start()
    Thread.Sleep(10000)
    stopWatch.Stop()
    ' Get the elapsed time as a TimeSpan value.
    Dim ts As TimeSpan = stopWatch.Elapsed

    ' Format and display the TimeSpan value.
    Dim elapsedTime As String = String.Format("{0:00}:{1:00}:{2:00}.{3:00}", ts.Hours, ts.Minutes, ts.Seconds, ts.Milliseconds / 10)
    Console.WriteLine( "RunTime " + elapsedTime)

End Sub 'Main

Answer 2

有两种随时可用的Timer对象替代方案：

System.Threading.Timer（解释here，我的第一个选择）
System.Timers.Timer（解释here）

Winforms计时器不准确

2 个答案: