Question

我使用vb.net 2008 express进行频谱分析应用程序，将频谱图像绘制到图片框中。我使用缓冲图形来提高速度并从绘图事件中调用绘图例程。在大多数情况下，这工作正常，但当另一个窗口移动到我的上方时，当我返回窗口时，被覆盖的部分是空白的。我已经确定在从picturebox.paint事件调用绘制例程之后发生了擦除。如果我再次调用绘图程序（在这种情况下由Spectra_MouseUp引起），则图像被完全重绘。

在我回到窗口后，我无法弄清楚如何保留（或重绘）整个图像。

我的代码的相关部分如下：

Private currentContext As BufferedGraphicsContext
Private spectraBuffer As BufferedGraphics

Private Sub DrawSpectra()
    Dim Gr As Graphics

    spectraBuffer = currentContext.Allocate(Spectra.CreateGraphics, Spectra.DisplayRectangle)
    Gr = spectraBuffer.Graphics
    '.
    '.
    '. Lots of drawing stuff here such as.... (yes, everything here is declared)
                If FillSpectra Then
                    Gr.DrawPolygon(BasePen, ptsSpec.ToArray)
                    Gr.FillPolygon(BaseBrush, ptsSpec.ToArray)
                Else
                    Gr.DrawLines(BasePen, ptsSpec.ToArray)
                End If
    '.
    '.
    ' Render the contents of the buffer to the Spectra window.
    spectraBuffer.Render()
End Sub

Private Sub frmMCAWindow_Activated(ByVal eventSender As System.Object, ByVal eventArgs As System.EventArgs) Handles MyBase.Activated
    Call DrawSpectra()
    ' DrawSpectra() works fine from here
End Sub

Private Sub Spectra_MouseUp(ByVal eventSender As System.Object, ByVal eventArgs As System.Windows.Forms.MouseEventArgs) Handles Spectra.MouseUp
    Call DrawSpectra()
End Sub

Private Sub Spectra_Paint(ByVal sender As Object, ByVal e As System.Windows.Forms.PaintEventArgs) Handles Spectra.Paint
    ' When dragging another window over mine, DrawSpectra() works fine here to keep the image in the picturebox 
    Debug.Print("Begin Spectra_Paint()")
    Call DrawSpectra()
    ' I put a 1 sec. sleep for testing, the image stayed complete while waiting
    ' The part that was covered was erased once the sleep completed.
    Debug.Print("End Spectra_Paint()")
End Sub

Answer 1

谢谢克里斯。结果是使用Spectra.CreateGraphics而不是PaintEventArgs（对于e.Graphics）是问题。我重写了以下＆amp;它现在完美无缺。

Private currentContext As BufferedGraphicsContext
Private spectraBuffer As BufferedGraphics

Private Sub frmMCAWindow_Activated(ByVal eventSender As System.Object, ByVal eventArgs As System.EventArgs) Handles MyBase.Activated
    Spectra.Invalidate()
End Sub

Private Sub Spectra_MouseUp(ByVal eventSender As System.Object, ByVal eventArgs As System.Windows.Forms.MouseEventArgs) Handles Spectra.MouseUp
    Spectra.Invalidate()
End Sub

Private Sub Spectra_Paint(ByVal sender As Object, ByVal e As System.Windows.Forms.PaintEventArgs) Handles Spectra.Paint
    Dim Gr As Graphics

    spectraBuffer = currentContext.Allocate(e.Graphics, Spectra.DisplayRectangle)
    Gr = spectraBuffer.Graphics
    '.
    '.
    '. Lots of drawing stuff here such as....
            If FillSpectra Then
                Gr.DrawPolygon(BasePen, ptsSpec.ToArray)
                Gr.FillPolygon(BaseBrush, ptsSpec.ToArray)
            Else
                Gr.DrawLines(BasePen, ptsSpec.ToArray)
            End If
    '.
    '.
    ' Render the contents of the buffer to the Spectra window.
    spectraBuffer.Render()
End Sub

另一个窗口下的PictureBox部分被删除

1 个答案: