Question

我正在开发一个实用程序，它扫描用户定义的目录并提取所有文件扩展名在下面提到的按钮事件中，我正在启动线程，其中所有扫描都已完成，但我希望代码暂停或停在“点A”，直到该线程完成其工作，而现在它启动线程并继续'点一个'。如何停止代码继续？

Private Sub Btn_Extract_Click(sender As Object, e As EventArgs) Handles Btn_Extract.Click
    Dim eventobject As New EventsandFunctions
    eventobject.FilesCounter = 0
    eventobject.DirectoryCounter = 0
    AddHandler eventobject.FilesScanned, AddressOf eventobject.FilesScannedCounterIncrease
    AddHandler eventobject.DirectoryScanned, AddressOf eventobject.DirectoryScannedCounterIncrease
    If TxtB_SaveFilePath.Text = Nothing Or TxtBx_DirectoryToScan.Text = Nothing Then
        MessageBox.Show("Scan Path, Output File Path or Both Missing", "Error")
    Else

        ThreadFileScanning.Start(eventobject) 'Thread Starts here--<Point A>
        If ChckB_RemoveDot.Checked Then
            eventobject.WriteExtentionsToFileWithoutDot(TxtB_SaveFilePath.Text)
        Else
            eventobject.WriteExtentionsToFile(TxtB_SaveFilePath.Text)
        End If
        MessageBox.Show("Operation Completed Successfully." & vbCrLf & vbCrLf & "Total Directory Scanned: " & eventobject.DirectoryCounter & vbCrLf & "Total Files Scanned: " & eventobject.FilesCounter, "Completion Notification")
        Lbl_FileNames.Text = "Scanning & Writing Completed"
    End If
    Process.Start("notepad.exe", TxtB_SaveFilePath.Text)

End Sub

以下是在线程中调用的函数：

Public Sub RecursivelyScanFiles(ByVal Path As String, ByVal ObjectDb As DialogueBox)

    If Path <> Nothing Then
        For Each File In GetFiles(Path)
            If File.Length < 260 Then
                If System.IO.Path.HasExtension(File) = True Then
                    Extentions.Add(System.IO.Path.GetExtension(File).ToLower)
                End If
                ObjectDb.settext(File) 'Cross-Thread call Through a Delegate
                ObjectDb.Refreshlabel() 'Cross-Thread call Through a Delegate
                RaiseEvent FilesScanned(Me, EventArgs.Empty)
            End If
        Next
    End If
    If Path <> Nothing Then
        For Each SubDir In GetDirectories(Path)
            If SubDir.Length < 248 Then
                Try
                    RaiseEvent DirectoryScanned(Me, EventArgs.Empty)
                    RecursivelyWriteToFile(SubDir, ObjectDb)
                Catch ex As UnauthorizedAccessException
                    Continue For
                Catch ex As Exception
                    MessageBox.Show(ex.ToString)
                End Try
            End If
        Next
    End If
End Sub

Answer 1

创建一个全局布尔值（isBusy），并在线程启动时将其设置为True，然后在线程完成时将其设置为False，如下所示：

Private isBusy as Boolean = False

Private Sub Btn_Extract_Click(sender As Object, e As EventArgs) Handles Btn_Extract.Click

    ' Other code goes here

    ThreadFileScanning.Start(eventobject) 'Thread Starts here--<Point A>

    ' This will prevent the thread from continuing 
    ' while the ThreadFileScanning is busy
    While isBusy
        Threading.Thread.Sleep(200)
    End While

    If ChckB_RemoveDot.Checked Then
        eventobject.WriteExtentionsToFileWithoutDot(TxtB_SaveFilePath.Text)
    Else
        eventobject.WriteExtentionsToFile(TxtB_SaveFilePath.Text)
    End If

    ' rest of the code goes here

End Sub

Public Sub RecursivelyScanFiles(ByVal Path As String, ByVal ObjectDb As DialogueBox)
    isBusy = True

    ' Rest of code goes here

    isBusy = False
End Sub

这将阻止第一个帖子在RecursivelyScanFiles处于活动状态时继续。

线程启动Vb.Net时挂起其他线程

1 个答案: