vb.net 更新进度条多线程

Question

长期读者，第一次海报。通常我能够找到答案并使其发挥作用。这次不是......我在 VS2013 中使用 VB.NET。我正在尝试使用在辅助线程中完成的工作来更新进度条。容易吧？不，我不得不让它变得更复杂。进度条 ( ToolStripProgressBar1 ) 位于项目的 MDI 主窗体 ( frmMain ) 上。辅助形式 ( frmShipping ) 有一个按钮，用于启动第二个线程以在类 ( cApex ) 中进行一些 COMM 端口通信。我可以在 上获取更新进度条frmMain 从主 UI 线程( frmShipping 按钮)。

这是 上按钮的代码frmShiping 和多线程过程:

 Private Sub btnreadScanner_Click(sender As Object, e As EventArgs) Handles btnreadScanner.Click

    Dim thrReadScanner As New System.Threading.Thread(AddressOf ReadScanner)
    thrReadScanner.IsBackground = True
    thrReadScanner.Start()

End Sub

    Private Sub ReadScanner()

    Dim strRowCount As String
    ShipmentMsg(2)
    strRowCount = objShipping.RecordsExisit.ToString()

    Try
        objApex.ImmediateMode()
        If objApex.FileDownload = False Then
            Throw New Exception(Err.Description)
        End If
    Catch ex As Exception
        ShipmentMsg(1)
        MessageBox.Show("No Data downloaded from Scanner.  Try Again.  Error#: " & Err.Number & " : " & Err.Description)
        Exit Sub
    End Try

    RecordCount()
    DataGridUpdate()
    btnProcessShipment.Enabled = True
    ShipmentMsg(5)
    ScanErrors()

End Sub

这一切都很好。正如预期的那样。调用 objApex.FileDownload 在类里面 顶点 是更新进度条的地方(实际上是在另一个从 FileDownload 调用的函数中)。所以这里是那里的代码。

Try
        GetHeaderRecord()
        If Count <> 0 Then intTicks = Math.Round((100 / Count), 1)
        For intcount As Integer = 1 To Count
            Dim intLength As Integer = Length
            Do While intLength > 0
                literal = Chr(_serialPort.ReadChar.ToString)
                If literal = ">" Then Exit Do
                strRecord = strRecord & literal
                intLength = intLength - 1
            Loop
            REF = strRecord.Substring(0, 16).TrimEnd
            SKID = strRecord.Substring(16, 16).TrimEnd
            REEL_BC = strRecord.Substring(32, 15).TrimEnd
            ScanDate = strRecord.Substring(47, 8).TrimEnd
            ScanDate = DateTime.ParseExact(ScanDate, "yyyyMMdd", Nothing).ToString("MM/dd/yyyy")
            ScanTime = strRecord.Substring(55, 6).TrimEnd
            ScanTime = DateTime.ParseExact(ScanTime, "HHmmss", Nothing).ToString("HH:mm:ss")
            strRecordTotal = strRecordTotal & strRecord & CRLF
            Dim strSQL As String
            strSQL = "INSERT INTO tblScanData (PONo,Barcode,SkidNo,ScanDate,ScanTime) " & _
            "VALUES (" & _
           Chr(39) & REF & Chr(39) & _
           "," & Chr(39) & REEL_BC & Chr(39) & _
           "," & Chr(39) & SKID & Chr(39) & _
           "," & Chr(39) & ScanDate & Chr(39) & _
           "," & Chr(39) & ScanTime & Chr(39) & ")"
            objData.Executecommand(strSQL)
            strRecord = ""
        Next

最后这就是我调用进度条更新的方式。

Dim f As frmMain = frmMain
System.Threading.Thread.Sleep(100)
DirectCast(f, frmMain).ToolStripProgressBar1.PerformStep()

我真的需要将 PerformStep 放在 For 循环中。每次循环都会步进进度条所需的步骤百分比，以使进度条相当准确(由循环前的数学代码完成)。我还在 上设置了进度条控件的属性。 frmMain .那么，我疯了，还是有办法做到这一点？我尝试使用委托(delegate)； Me.Invoke(新 MethodInvoker(AddressOf pbStep)) 使代码跨线程安全。我没有收到有关跨线程调用的错误，但进度条也没有更新。抱歉，这很长，但我迷路了，我的多动症不会让我放弃这个想法。

按要求编辑:

 Public Sub pbStep()

    Dim f As frmMain = frmMain
    If Me.InvokeRequired Then
        Me.Invoke(New MethodInvoker(AddressOf pbStep))
    Else
        DirectCast(f, frmMain).ToolStripProgressBar1.PerformStep()
        System.Threading.Thread.Sleep(100)
    End If

End Sub

Answer 1

两种回答都帮助我找到了我需要的正确答案。 James 提供的代码是一个很好的起点，Hans 有几篇文章解释了 BackgroundWorker。我想分享我想出的“答案”。我并不是说这是最好的方法，我确信我违反了一些常见的逻辑规则。此外，许多代码来自 MSDN 示例和 James 的代码。

让我们从我调用 bgw 的表单开始，frmShipping。我添加了这段代码:

Dim WithEvents bgw1 As New System.ComponentModel.BackgroundWorker

Private Sub bgw1_RunWorkerCompleted(ByVal sender As Object, ByVal e As System.ComponentModel.RunWorkerCompletedEventArgs) _
    Handles bgw1.RunWorkerCompleted

    If e.Error IsNot Nothing Then
        MessageBox.Show("Error: " & e.Error.Message)
    ElseIf e.Cancelled Then
        MessageBox.Show("Process Canceled.")
    Else
        MessageBox.Show("Finished Process.")
    End If

End Sub

Private Sub bgw1_ProgressChanged(ByVal sender As Object, ByVal e As System.ComponentModel.ProgressChangedEventArgs) _
    Handles bgw1.ProgressChanged
    DirectCast(Me.MdiParent, frmMain).ToolStripProgressBar1.Maximum = 1960
    DirectCast(Me.MdiParent, frmMain).ToolStripProgressBar1.Step = 2

    Dim state As cApex.CurrentState =
        CType(e.UserState, cApex.CurrentState)
    DirectCast(Me.MdiParent, frmMain).txtCount.Text = state.LinesCounted.ToString
    DirectCast(Me.MdiParent, frmMain).txtPercent.Text = e.ProgressPercentage.ToString
    DirectCast(Me.MdiParent, frmMain).ToolStripProgressBar1.PerformStep()

End Sub
Private Sub bgw1_DoWork(ByVal sender As Object, ByVal e As System.ComponentModel.DoWorkEventArgs) _
    Handles bgw1.DoWork

    Dim worker As System.ComponentModel.BackgroundWorker
    worker = CType(sender, System.ComponentModel.BackgroundWorker)

    Dim objApex As cApex = CType(e.Argument, cApex)
    objApex.CountLines(worker, e)

End Sub

Sub StartThread()

    Me.txtCount.Text = "0"
    Dim objApex As New cApex
    bgw1.WorkerReportsProgress = True
    bgw1.RunWorkerAsync(objApex)

End Sub

接下来，我在我的 cApex 类中添加了以下代码。

Public Class CurrentState
    Public LinesCounted
End Class

Private LinesCounted As Integer = 0


Public Sub CountLines(ByVal worker As System.ComponentModel.BackgroundWorker, _
                       ByVal e As System.ComponentModel.DoWorkEventArgs)
    Dim state As New CurrentState
    Dim line = ""
    Dim elaspedTime = 20
    Dim lastReportDateTime = Now
    Dim lineCount = File.ReadAllLines(My.Settings.strGenFilePath).Length
    Dim percent = Math.Round(100 / lineCount, 2)
    Dim totaldone As Double = 2

    Using myStream As New StreamReader(My.Settings.strGenFilePath)

        Do While Not myStream.EndOfStream
            If worker.CancellationPending Then
                e.Cancel = True
                Exit Do
            Else
                line = myStream.ReadLine
                LinesCounted += 1
                totaldone += percent

               If Now > lastReportDateTime.AddMilliseconds(elaspedTime) Then
                    state.LinesCounted = LinesCounted
                    worker.ReportProgress(totaldone, state)
                    lastReportDateTime = Now
                End If
                System.Threading.Thread.Sleep(2)
            End If
        Loop

        state.LinesCounted = LinesCounted
        worker.ReportProgress(totaldone, state)

    End Using

End Sub

我还在我的主窗体中添加了几个文本框，以显示正在读取的文件的当前行数以及以 100 的百分比表示的总体进度。然后在我的按钮的 Click 事件中，我只需调用 StartThread() .它不是 100% 准确的，但它足够接近，可以让用户很好地了解流程的位置。我还有一些工作要做，以将其添加到“ReadScanner”功能，我最初想在其中使用进度条。但这个功能是我在扫描仪上执行的两个功能中较长的一个，通过一个 COMM 端口编写了近 2,000 行代码。我对结果很满意。

谢谢各位帮忙!

附言我现在还添加了变量来设置 pbar.Maximum和 pbar.step因为如果扫描仪文件更改，这些可能会更改。