Question

在VB.Net中，我创建了一个似乎有用的后台工作程序。它设置如下：

Private bw As BackgroundWorker = New BackgroundWorker

Public Sub construct_configure()
        bw.WorkerReportsProgress = True
        bw.WorkerSupportsCancellation = True
        AddHandler bw.DoWork, AddressOf bw_DoWork
        AddHandler bw.ProgressChanged, AddressOf bw_ProgressChanged
        AddHandler bw.RunWorkerCompleted, AddressOf bw_RunWorkerCompleted
end sub

然后我将doWork Sub设置为：

Private Sub bw_DoWork(ByVal sender As Object, ByVal e As DoWorkEventArgs)

        ' create the picture box
        pic_holder = New PictureBox()

        ' Show GIF and disable whatever you need to
        With pic_holder
            .Image = My.Resources.counter_gif
            .Size = New Size(200, 100)
            .Location = New Point(0, 0)
            .Visible = True
            .BackColor = Color.Red

        End With
        Main.Controls.Add(pic_holder)
        pic_holder.BringToFront()

        MessageBox.Show("worker started")

    End Sub

当我点击我的按钮来调用Sub时，会显示消息框，但动画gif从不这样做。我试图简单地设置一个指标，表明有一些背景工作正在进行中。当我在父子中设置它时，gif会出现。

另外，我想将gif放在已经存在的面板中，但每次尝试时，都会出现一个交叉线程错误，表明该面板是在另一个线程中创建的。我怎么能解决这个问题？

感谢。

Answer 1

如果要调用主表单，建议您在 ProgressChanged 事件中执行此操作。 bw_ProgressChanged在与主窗体相同的线程上调用。

Private Sub bw_DoWork(sender As Object, e As DoWorkEventArgs) Handles bw.DoWork

    'WORKER THREAD, do not invoke main form.

    Dim worker As BackgroundWorker = CType(sender, BackgroundWorker)

    'Report start
    worker.ReportProgress(0)

    'Do some work...
    Threading.Thread.Sleep(5000)

    'Report end.
    worker.ReportProgress(100)

End Sub

Private Sub bw_ProgressChanged(sender As Object, e As ProgressChangedEventArgs) Handles bw.ProgressChanged

    'MAIN THREAD, safe to invoke main form.

    If (e.ProgressPercentage = 0) Then
        'Started: Do something...
    ElseIf (e.ProgressPercentage = 100) Then
        'Stopped: Do something...
    End If

End Sub

vb.net - 我如何修复与后台工作者的crossthreading

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