RenderTargetBitmap问题

Question

我试图将用户控件的图像添加到视图框.我正在动态创建usercontrol.我正在使用下面的代码.

private static RenderTargetBitmap CaptureScreen(Visual target, double dpiX, double dpiY)
{
    if (target == null)
    {
        return null;
    }
    Rect bounds = VisualTreeHelper.GetDescendantBounds(target);
    //RenderTargetBitmap rtb = new RenderTargetBitmap((int)(bounds.Width * dpiX / 96.0),
    //                                                (int)(bounds.Height * dpiY / 96.0),
    //                                                dpiX,
    //                                                dpiY,
    //                                                PixelFormats.Pbgra32);
    RenderTargetBitmap rtb = new RenderTargetBitmap(596,596,dpiX,
                                                    dpiY,
                                                    PixelFormats.Pbgra32);
    DrawingVisual dv = new DrawingVisual();
    using (DrawingContext ctx = dv.RenderOpen())
    {
        VisualBrush vb = new VisualBrush(target);
        ctx.DrawRectangle(vb, null, new Rect(new Point(), bounds.Size));
    }
    rtb.Render(dv);
    return rtb;
}

我正在动态创建用户控件并将其传递给捕获屏幕方法.

UserControls.UserControl1 uc1 = new UserControls.UserControl1();
                        visualList.Add(uc1);
 for(int i = 0;i<=6;i++)
        {
            Image img = new Image();
            img.Source = CaptureScreen(visualList[i], 96, 96);
            img.Margin = new Thickness { Top = 2 };                   
            usingWorkaround.Children.Add(img);
        }

VisualTreeHelper.GetDescendantBounds(target)返回空边界.这就是为什么无法创建屏幕图像的原因.是否有其他方法来捕获动态创建的用户控件的屏幕？

Answer 1

您可以调用测量和排列如下

  private void ForceUpdate(FrameworkElement element, double width, double height)
  {
     Size size = new Size(width, height);

     element.Measure(size);

     element.Arrange(new Rect(0, 0, width, height));

     element.UpdateLayout();
  }