循环内的VB.Net异步后台工作程序
我正在使用Vb.net visual studio 2008。我有一个进程(system.diagnostics.process)要在后台运行,它更新了Ui线程progressbar和一个标签,我使用backgroundworker.runworkerAsync进行了处理。现在的问题是,我必须用不同的输入在同一个过程中工作很多次 代码块是:循环内的VB.Net异步后台工作程序,vb.net,multithreading,loops,progress-bar,backgroundworker,Vb.net,Multithreading,Loops,Progress Bar,Backgroundworker,我正在使用Vb.net visual studio 2008。我有一个进程(system.diagnostics.process)要在后台运行,它更新了Ui线程progressbar和一个标签,我使用backgroundworker.runworkerAsync进行了处理。现在的问题是,我必须用不同的输入在同一个过程中工作很多次 代码块是: Private Sub fnStartEvent(ByVal sender As System.Object, ByVal e As System.Even
Private Sub fnStartEvent(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles btnStart.click
Dim inputFolder = Directory.GetFiles(textboxSourceFolder.text)
Dim currentNumberOfFile As Integer=1
For each Files in inputFolder
Dim arguments As Object = Files
updateProgressStatus(0, currentNumberOfFile)
BackgroundWorker1.WorkerReportsProgress = True
BackgroundWorker1.RunWorkerAsync(New Object() {arguments})
currentNumberOfFile += 1
Next
End Sub
Private Sub BackgroundWorker1_DoWork(ByVal sender As System.Object, ByVal e As System.ComponentModel.DoWorkEventArgs) Handles BackgroundWorker1.DoWork
'uses the arguments
Dim Bg_process As System.Diagnostics.Process = New System.Diagnostics.Process
With Bg_process.StartInfo
.Arguments = str_arguments
.FileName = ffmpegPath
.CreateNoWindow = True
.UseShellExecute = False
.RedirectStandardOutput = True
.RedirectStandardError = True
End With
Bg_process.Start()
Dim outputReader As StreamReader = Bg_process.StandardError
Dim output As String
While Not Bg_process.HasExited
output = outputReader.ReadLine()
BackgroundWorker1.ReportProgress(0, output)
Threading.Thread.Sleep(500)
End While
End Sub
Private Sub BackgroundWorker1_ProgressChanged(ByVal sender As Object, ByVal e As System.ComponentModel.ProgressChangedEventArgs) Handles BackgroundWorker1.ProgressChanged
' process args
updateProgressStatus(args(0), args(1) )
End Sub
Private Function BackgroundWorker1_RunWorkerCompleted(ByVal sender As Object, ByVal e As System.ComponentModel.RunWorkerCompletedEventArgs) Handles BackgroundWorker1.RunWorkerCompleted
Messagebox.Show(e.error.ToString)
End Try
Sub updateProgressStatus(ByVal progressValue As Integer, ByVal progressStatus As String)
progressBar.value = progressValue
lblprogressStatus.Text = progressStatus
End Sub
这里的问题是FNStarteEvent方法一旦启动,它调用BackgroundWorker1.runWorkerAsync进程,该进程在一个单独的线程中运行,不等待线程完成,它移动到下一行代码,即循环到下一项,并返回到同一BackgroundWorker1.runWorkerAsync行,并抛出已在运行的异常
尝试
1.
但这不会更新用于表示进度的Ui线程
2.将整个进程放在DoWork线程中,并对其中的每个文件进行循环,但这将返回进程条更新中的跨线程错误
backgroundworker执行循环以等待完成以及在不阻塞UI的情况下更新UI的标准过程是什么 无论何时使用Thread.Sleep,您实际上是在休眠连接到启动类(即表单)的当前线程。因此,如果您睡眠您的主线程,将不会发生UI更新 根据MSDN关于的文章,您需要抛出一个Application.DoEvents。下面的代码是从上面链接的文章中复制的
Private Sub downloadButton_Click( _
ByVal sender As Object, _
ByVal e As EventArgs) _
Handles downloadButton.Click
' Start the download operation in the background.
Me.backgroundWorker1.RunWorkerAsync()
' Disable the button for the duration of the download.
Me.downloadButton.Enabled = False
' Once you have started the background thread you
' can exit the handler and the application will
' wait until the RunWorkerCompleted event is raised.
' If you want to do something else in the main thread,
' such as update a progress bar, you can do so in a loop
' while checking IsBusy to see if the background task is
' still running.
While Me.backgroundWorker1.IsBusy
progressBar1.Increment(1)
' Keep UI messages moving, so the form remains
' responsive during the asynchronous operation.
Application.DoEvents()
End While
End Sub
感谢josaph,它可以工作了。但是有没有其他解决方案,bCoz这里出现了很多线程循环。
Private Sub downloadButton_Click( _
ByVal sender As Object, _
ByVal e As EventArgs) _
Handles downloadButton.Click
' Start the download operation in the background.
Me.backgroundWorker1.RunWorkerAsync()
' Disable the button for the duration of the download.
Me.downloadButton.Enabled = False
' Once you have started the background thread you
' can exit the handler and the application will
' wait until the RunWorkerCompleted event is raised.
' If you want to do something else in the main thread,
' such as update a progress bar, you can do so in a loop
' while checking IsBusy to see if the background task is
' still running.
While Me.backgroundWorker1.IsBusy
progressBar1.Increment(1)
' Keep UI messages moving, so the form remains
' responsive during the asynchronous operation.
Application.DoEvents()
End While
End Sub