Adorner，无法设置不透明度，边框，背景WPF

Question

I have a custom adorner. (which shows an image while dragging an UIelement)

Now, this adorner is transparent, but i want it to be opaque. i also dont know how to set its background and other nice looking things like a border.

This is my custom adorner:

/// <summary>
/// Adorner, to show a picture of the listbox-item we are dragging.
/// </summary>
public class DraggedAdorner : Adorner
{
    private readonly ContentPresenter draggedItemPresenter;
    private readonly AdornerLayer draggedItemAdornerLayer;

    private double left;
    private double top;

    /// <summary>
    /// Initializes a new adorner, which will display the dragged listbox-item.
    /// </summary>
    /// <param name="listBoxItem">ListBoxItem, which we want to show while dragging.</param>
    /// <param name="listBox">ListBoxItem, which we want to show while dragging.</param>
    /// <param name="adornerLayer">Presentation layer for the adorner.</param>
    /// <param name="width"></param>
    public DraggedAdorner(ListBoxItem listBoxItem, ListBox listBox, AdornerLayer adornerLayer, double width, double height)
        : base(listBox)
    {
        draggedItemAdornerLayer = adornerLayer;            
        draggedItemPresenter = new ContentPresenter
        {
            Content = listBoxItem,
            Width = width,
            Height = height
        };
        draggedItemAdornerLayer.Add(this);
    }

    /// <summary>
    /// Sets the position of the dragged adorner.
    /// </summary>
    /// <param name="newLeft">new left position of the adorner</param>
    /// <param name="newTop">new top position of the adorner</param>
    public void SetPosition(double newLeft, double newTop)
    {
        // -1 and +13 align the dragged adorner with the dashed rectangle that shows up
        // near the mouse cursor when dragging.
        left = newLeft;
        top = newTop;
        if (draggedItemAdornerLayer != null)
        {
            draggedItemAdornerLayer.Update(AdornedElement);
        }
    }

    protected override Size MeasureOverride(Size constraint)
    {
        draggedItemPresenter.Measure(constraint);
        return draggedItemPresenter.DesiredSize;
    }

    protected override Size ArrangeOverride(Size finalSize)
    {
        draggedItemPresenter.Arrange(new Rect(finalSize));
        return finalSize;
    }

    protected override Visual GetVisualChild(int index)
    {
        return draggedItemPresenter;
    }

    protected override int VisualChildrenCount
    {
        get { return 1; }
    }

    public override GeneralTransform GetDesiredTransform(GeneralTransform transform)
    {
        GeneralTransformGroup result = new GeneralTransformGroup();
        result.Children.Add(base.GetDesiredTransform(transform));
        result.Children.Add(new TranslateTransform(left, top));

        return result;
    }

    /// <summary>
    /// Removes the this adorner form the adornerlayer.
    /// </summary>
    public void Detach()
    {
        draggedItemAdornerLayer.Remove(this);
    }
}

Can anyone help me?

Answer 1

I added now a background in a simply way: I just added a rectangle with property fill = backgroundcolor:

public class DraggedAdorner : Adorner
{
    private readonly Rectangle background;
    private readonly ContentPresenter draggedItemPresenter;
    private readonly AdornerLayer draggedItemAdornerLayer;

    private double left;
    private double top;

    /// <summary>
    /// Initializes a new adorner, which will display the dragged listbox-item.
    /// </summary>
    /// <param name="listBoxItem">ListBoxItem, which we want to show while dragging.</param>
    /// <param name="listBox">ListBoxItem, which we want to show while dragging.</param>
    /// <param name="adornerLayer">Presentation layer for the adorner.</param>
    /// <param name="width"></param>
    public DraggedAdorner(ListBoxItem listBoxItem, ListBox listBox, AdornerLayer adornerLayer, double width, double height)
        : base(listBox)
    {
        draggedItemAdornerLayer = adornerLayer;            
        draggedItemPresenter = new ContentPresenter
        {
            Content = listBoxItem,
            Width = width,
            Height = height
        };
        Rectangle rectangle = new Rectangle
            {
                Width = width,
                Height = height,
                Fill = new SolidColorBrush(Colors.SkyBlue)
            };
        background = rectangle;
        draggedItemAdornerLayer.Add(this);
    }

    /// <summary>
    /// Sets the position of the dragged adorner.
    /// </summary>
    /// <param name="newLeft">new left position of the adorner</param>
    /// <param name="newTop">new top position of the adorner</param>
    public void SetPosition(double newLeft, double newTop)
    {
        //only set the left property the first time, to not allow dragging the listboxitem
        //out of the listbox in the horizontal direction.
        if (Math.Abs(left) < 0.1)
        {
            left = newLeft + 20;
        }
        top = newTop;
        if (draggedItemAdornerLayer != null)
        {
            draggedItemAdornerLayer.Update(AdornedElement);
        }
    }

    protected override Size MeasureOverride(Size constraint)
    {
        draggedItemPresenter.Measure(constraint);
        background.Measure(constraint);
        return draggedItemPresenter.DesiredSize;
    }



    protected override Size ArrangeOverride(Size finalSize)
    {
        draggedItemPresenter.Arrange(new Rect(finalSize));
        background.Arrange(new Rect(finalSize));
        return finalSize;
    }

    protected override Visual GetVisualChild(int index)
    {
        return index == 0 ? (Visual) background : draggedItemPresenter;
    }

    protected override int VisualChildrenCount
    {
        get { return 2; }
    }

    public override GeneralTransform GetDesiredTransform(GeneralTransform transform)
    {
        GeneralTransformGroup result = new GeneralTransformGroup();
        result.Children.Add(base.GetDesiredTransform(transform));
        result.Children.Add(new TranslateTransform(left, top));

        return result;
    }

    /// <summary>
    /// Removes the this adorner form the adornerlayer.
    /// </summary>
    public void Detach()
    {
        draggedItemAdornerLayer.Remove(this);
    }
}