Question

我试图在面板上绘图时似乎遇到了这个错误。我不是C＃的专家所以希望有人可以帮助我。提前谢谢。

堆栈跟踪显示，

在C：\ Users \ kasunt \ Microsoft Robotics Dev Studio 2008 R3 \ Marvin \ Teleoperation \中的Victoria.Robotics.Marvin.Teleoperation.MainForm.DrawXYAxis（Graphics g）中的System.Drawing.Graphics.set_Transform（Matrix值） MainForm.cs：维多利亚的线2173.Robotics.Marvin.Teleoperation.MainForm.envMap_Paint（对象发送者，PaintEventArgs e）在C：\ Users \ kasunt \ Microsoft Robotics Dev Studio 2008 R3 \ Marvin \ Teleoperation \ MainForm.cs：line 2143在System.Windows.Forms.Forms.Conm.Mm中的System.Windows.Forms.Control.OnPaint（PaintEventArgs e）处于System.Windows.Forms.Forms.Control.Wm（消息＆amp; m）的System.Windows.Forms.Control.PaintWithErrorHandling（PaintEventArgs e，Int16 layer，Boolean disposeEventArgs） System.Windows上System.Windows.Forms.Control.ControlNativeWindow.OnMessage（Message＆amp; m）的System.Windows.Forms.ScrollableControl.WndProc（Message＆amp; m）中的System.Windows.Forms.Control.WndProc（Message＆amp; m） System.Windows.Forms.NativeWindow.Callback中的.Forms.Control.ControlNativeWindow.WndProc（Message＆amp; m）（IntPtr hWnd，Int32 msg， IntPtr wparam，IntPtr lparam）

代码如下。设置转换时似乎发生错误，

    private void envMap_Paint(object sender, PaintEventArgs e)
    {
        DrawXYAxis(e.Graphics);
    }

    /// <summary>
    /// Helper to draw the XY axis and plot the map
    /// </summary>
    public void DrawXYAxis(Graphics g)
    {
        Rectangle rect = envMap.ClientRectangle;

        myPen = new Pen(Color.Black, 1);
        g.PageUnit = GraphicsUnit.Millimeter;
        g.PageScale = 0.1F;
        IntPtr hdc = g.GetHdc();
        int hMemDC = hdc.ToInt32();

        // Reverse the axis of the drawing surface
        Matrix mx = new Matrix(1, 0, 0, -1, 0, envMap.ClientSize.Height * 2);
        g.Transform = mx;
        g.TranslateTransform(50, 100, MatrixOrder.Append);

        // For drawing X - AXIS
        g.DrawLine(myPen, 0, 0, (2 * rect.Right - 60), 0);
        // For drawing Y - AXIS
        g.DrawLine(myPen, 0, 0, 0, 2 * rect.Bottom);

        // For drawing Arrow on X-AXIS
        g.DrawLine(myPen, (2 * rect.Right - 60) - 15, 8, (2 * rect.Right - 60), 0);
        g.DrawLine(myPen, (2 * rect.Right - 60), 0, (2 * rect.Right - 60) - 15, -8);

        // For drawing Arrow on Y-AXIS
        g.DrawLine(myPen, 8, 2 * rect.Bottom - 15, 0, 2 * rect.Bottom);
        g.DrawLine(myPen, 0, 2 * rect.Bottom, -8, 2 * rect.Bottom - 15);

        // Save the state to restore later
        GraphicsState state = g.Save();

        // Create a matrix to offset the text to the desired position and flip it the
        // right way up again
        Matrix mx2 = new Matrix(1, 0, 0, -1, 0, 0);
        Matrix mx1 = mx.Clone();
        mx1.Multiply(mx2);
        g.Transform = mx1;
        SolidBrush drawBrush = new SolidBrush(Color.Black);
        Font drawFont = new Font("Microsoft Sans Serif", 9, FontStyle.Bold);
        StringFormat sF = new StringFormat(StringFormatFlags.NoClip);
        sF.Alignment = StringAlignment.Center;
        g.DrawString("X", drawFont, drawBrush, (2 * rect.Right - 40), -2 * Font.Height, sF);
        g.DrawString("Y", drawFont, drawBrush, -40, -(2 * rect.Height + 2 * Font.Height), sF);

        // Restore state
        g.Restore(state);

        drawFont = new Font("Microsoft Sans Serif", 7);

        // Drawing Tick Marks and Labels
        // NOTE THE LABELS ON THE AXES WILL CHANGE TO REFFECT THE REAL POSITION OF THE ROBOT....
        myPen.Dispose();
   }

第＃2173行，

        g.Transform = mx;

第＃2143行，

        DrawXYAxis(e.Graphics);

Answer 1

这是一个异常，通常是由于在另一个线程中非法使用Graphics上下文引起的。我不得不猜测你的程序中还有其他代码也用图形处理。

如果您不知道该代码是什么，那么请使用Debug + Windows + Threads并查看其中列出的线程的调用堆栈。还要在源代码中查找对Control.CheckForIllegalCrossThreadCalls的任何分配。您将要删除该语句，以便在违反线程要求时获得更好的诊断。

Answer 2

原来是因为以下两行，

    IntPtr hdc = g.GetHdc();
    int hMemDC = hdc.ToInt32();

System.InvalidOperationException：Object目前正在其他地方使用

2 个答案: