WPF – 使用 DrawingVisual 描繪圖形

在 WPF 中有很多種方式來描繪圖形, 其 DrawingVisual 是一個輕量級的 Class, 它需一個 container 來承接, 並不提供 Layout, Hit-Testing 及 Event-Handling.

那來實作一下如何使用 DrawingVisual 來描繪圖形.

建立一個 class, 它繼承 FrameworkElement Class, 並描繪一個 Rectangle .

    public class MyVisualHost : FrameworkElement
    {

        private VisualCollection childern;

        public MyVisualHost() {
            childern = new VisualCollection(this);
            childern.Add(CreateDrawingVisualRectangle());
        }

        protected override int VisualChildrenCount
        {
            get
            {
                return childern.Count;
            }
        }

        protected override Visual GetVisualChild(int index)
        {
            return childern[index];
        }

        private DrawingVisual CreateDrawingVisualRectangle()
        {
            DrawingVisual drawing = new DrawingVisual();
            using (DrawingContext content = drawing.RenderOpen())
            {
                content.DrawRectangle(Brushes.Red, new Pen(Brushes.Blue, 3), new Rect(new Point(100, 100), new Size(30, 30)));
                content.Close();
            }
            return drawing;
        }

    }

結果如下所示 :