我正在使用Vb.net visual studio 2008.我有一个进程(system.diagnostics.process)在后台运行,它更新了Ui线程进度条和一个标签,我使用backgroundworker.runworkerAsync进行了工作 . 现在问题是我必须使用不同的输入多次使用相同的过程 .
代码块是:
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fnStartEvent方法一旦启动,它调用BackgroundWorker1.runWorkerAsync进程并在一个单独的线程中运行,并且不等待线程完成并且它移动到下一行代码,即循环到下一个项目并且它返回到相同的BackgroundWorker1.runWorkerAsync行并抛出它已在运行的异常 .
试过1 .
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})
''
Do Until BackgroundWorker1.IsBusy
Thread.Sleep(500)
Loop
currentNumberOfFile += 1
Next
End Sub
但这并不会更新用于表示进度的Ui线程 .
2.将整个过程放在DoWork线程中并为其中的每个文件循环,但是返回进度条更新中的交叉线程错误 .
为后台工作者执行循环以等待完成以及更新UI而不阻塞它的标准过程是什么 .
1 回答
每当你使用Thread.Sleep时,你实际上正在睡觉挂钩到你的启动类的当前线程(即Form) . 因此,如果您睡眠主线程,则不会发生UI更新 .
根据有关BackgroundWorker.IsBusy的MSDN文章,您需要抛出Application.DoEvents . 以下代码是从上面链接的文章中复制的 .