Question

我有一个案例需要生成数百万个唯一代码。为此我创建了一个生成函数，其中生成随机数。我从for循环中调用此函数，并在列表框中添加生成的数字。我的代码如下

  for i=1 to val(txtnumber.txt)
       mynum=generate()
  next

我在表单上创建了一个标签，我希望在处理循环时显示已经过的秒数。我使用计时器控制作为

     timer1.start()
     for i=1 to val(txtnumber.text)
        mynum=generate()
        listbox1.items.add(mynum)
     next
     timer1.stop

和timer1_tick函数

     Private Sub Timer1_Tick(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles Timer1.Tick
    Label1.Text = Val(Label1.Text) + 1
     End Sub

但是当我点击生成按钮时，会生成所有数字，但计时器不显示已过去的时间。

我可能错过了什么，所以请帮帮我

Answer 1

这可能最适合在BackgroundWorker中处理。在表单上放置一个并设置其WorkerReportsProgress=True。另外，在ListBox中放置一百万个数字可能不是一个好主意，所以我省略了它。

Private Sub Button1_Click(ByVal sender As Object, ByVal e As EventArgs) Handles Button1.Click
  Button1.Enabled = False
  BackgroundWorker1.RunWorkerAsync()
End Sub

Private Sub BackgroundWorker1_DoWork(ByVal sender As Object, ByVal e As DoWorkEventArgs) Handles BackgroundWorker1.DoWork
  Dim started As DateTime = Now
  For i As Integer = 1 To val(txtnumber.txt)
    mynum=generate()
    BackgroundWorker1.ReportProgress(i, Nothing)
  Next
  Dim ended As TimeSpan = Now.Subtract(started)
  BackgroundWorker1.ReportProgress(0, ended.TotalSeconds.ToString)
End Sub

Private Sub BackgroundWorker1_ProgressChanged(ByVal sender As Object, ByVal e As ProgressChangedEventArgs) Handles BackgroundWorker1.ProgressChanged
  If e.UserState IsNot Nothing Then
    Label1.Text = e.UserState.ToString()
  Else
    Label1.Text = e.ProgressPercentage.ToString
  End If
End Sub

Private Sub BackgroundWorker1_RunWorkerCompleted(ByVal sender As Object, ByVal e As RunWorkerCompletedEventArgs) Handles BackgroundWorker1.RunWorkerCompleted
  Button1.Enabled = True
End Sub

当工作人员报告ProgressChanged事件时，您的标签应该正确更新。

Answer 2

您遇到的是线程问题。您正在执行的生成数字的工作正在由UI线程执行，因此它永远不会有机会更新屏幕。看看这里：How to prevent UI from freezing during lengthy process?

这个可能也有适合您的信息：Updating UI from another thread

Answer 3

试试这个：

Private _Counter As Integer = 0
Private _StartTime As Date = Now

Private Sub Button1_Click(sender As System.Object, e As System.EventArgs) Handles Button1.Click
    _StartTime = Now
    _Counter = CInt(Val(txtnumber.Text))
    ListBox1.Items.Clear()
    Label1.Text = "0"
    Timer1.Interval = 50
    Timer1.Start()
End Sub

Private Sub Timer1_Tick(sender As System.Object, e As System.EventArgs) Handles Timer1.Tick
    ListBox1.Items.Add(generate())
    Label1.Text = New Date((Now - _StartTime).Ticks).ToString("HH:mm:ss.ff")
    _Counter -= 1
    If (_Counter <= 0) Then
        Timer1.Stop()
    End If
End Sub

或者您可以研究实际的Threading。

如何在visual basic 2008中使用计时器进行下一循环

3 个答案: