WPF装饰器 安静点

  

顾名思义就是装饰用的，也就是说不改变原有的控件结构，但可以为控件添加一些新的功能，或是为控件的显示外观增加些东西。 我们以MSDN中的代码为例(装饰器概述)做延伸：

xaml：

<UserControl x:Class="MyWpf.MyAdorner"
             xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
             xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
             xmlns:mc="http://schemas.openxmlformats.org/markup-compatibility/2006" 
             xmlns:d="http://schemas.microsoft.com/expression/blend/2008" 
             xmlns:local="clr-namespace:MyWpf"
             mc:Ignorable="d" 
             d:DesignHeight="450" d:DesignWidth="800">
    <Grid>
        <Grid.RowDefinitions>
            <RowDefinition></RowDefinition>
            <RowDefinition Height="100"></RowDefinition>
        </Grid.RowDefinitions>
        
        <Button Grid.Row="0" HorizontalAlignment="Center" VerticalAlignment="Center"  x:Name="show" Width="200" Height="100"  ></Button>
        <StackPanel Grid.Row="1"  HorizontalAlignment="Center"  Orientation="Horizontal">
            <Button    Content="增加装饰器" x:Name="add" Width="77" Height="30"  HorizontalAlignment="Center"   Click="Add_Click"></Button>
            <Button    Content="移除装饰器" HorizontalAlignment="Center"
     x:Name="delete" Height="30"  Click="Delete_Click"  Margin="2,0,0,0"  Width="89"/> 
        </StackPanel>
    </Grid>
</UserControl>

后台代码：

namespace MyWpf
{
    /// <summary>
    /// MyAdorner.xaml 的交互逻辑
    /// </summary>
    public partial class MyAdorner : UserControl
    {
        public MyAdorner()
        {
            InitializeComponent();
        }

        private void Add_Click(object sender, RoutedEventArgs e)
        {
            //拿到被装饰的控件装饰层
            var layer = AdornerLayer.GetAdornerLayer(show);
            //将装饰的信息放到被装饰控件的装饰层中
            layer.Add(new TestAdorner(show));
        }

        private void Delete_Click(object sender, RoutedEventArgs e)
        {
            var layer = AdornerLayer.GetAdornerLayer(show);
            var arr = layer.GetAdorners(show);
            if (arr != null)
            {
                //不一定有多少装饰器，所以全部删除
                for (int i = arr.Length - 1; i >= 0; i--)
                {
                    layer.Remove(arr[i]);
                }
            }
        }
    }

    /// <summary>
    /// 自定义的装饰器类
    /// </summary>
    public class TestAdorner : Adorner
    {
        public TestAdorner(UIElement adornedElement) : base(adornedElement)
        {
        }

        // A common way to implement an adorner's rendering behavior is to override the OnRender
        // method, which is called by the layout system as part of a rendering pass.
        protected override void OnRender(DrawingContext drawingContext)
        {
            Rect adornedElementRect = new Rect(this.AdornedElement.DesiredSize);

            // Some arbitrary drawing implements.
            SolidColorBrush renderBrush = new SolidColorBrush(Colors.Green);
            renderBrush.Opacity = 0.2;
            Pen renderPen = new Pen(new SolidColorBrush(Colors.Navy), 1.5);
            double renderRadius = 5.0;

            // Draw a circle at each corner.
            drawingContext.DrawEllipse(renderBrush, renderPen, adornedElementRect.TopLeft, renderRadius, renderRadius);
            drawingContext.DrawEllipse(renderBrush, renderPen, adornedElementRect.TopRight, renderRadius, renderRadius);
            drawingContext.DrawEllipse(renderBrush, renderPen, adornedElementRect.BottomLeft, renderRadius, renderRadius);
            drawingContext.DrawEllipse(renderBrush, renderPen, adornedElementRect.BottomRight, renderRadius, renderRadius);
        }

    }

}

结果：