C#中wpf怎么利用附加属性实现界面上定义装饰器

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前言

装饰器是wpf中可以浮在控件上面的一种组件，我们通常可以用来实现一些诸如控件拖动点、提示框、自定义鼠标等界面功能。装饰器的用法其实还是比较复杂的，几乎需要完全再cs中编写所有代码，对于样式要求较高的情况下，完全在cs中些控件的样式是比较困难的。为了改变这种状况，我们可以使用附加属性将装饰器的逻辑封装，提供一个可以在界面上定义的属性。

一、如何实现

1、实现装饰器

由于Adorner是一个抽象类不能直接实现，所有我们需要定义一个子类实现并它。

class NormalAdorner : Adorner{    /// <summary>    /// 构造方法    /// </summary>    /// <param name="adornedElement">被添加装饰器的元素</param>    /// <param name="child">放到装饰器中的元素</param>    public NormalAdorner(UIElement adornedElement, UIElement child) : base(adornedElement);    protected override Visual GetVisualChild(int index);    protected override int VisualChildrenCount;    protected override Size ArrangeOverride(Size finalSize);}

2、定义附加属性

通过propa快捷定义一个名称为AdornerContent的附加属性其类型UIElement。

public static UIElementGetAdornerContent(DependencyObject obj){    return (UIElement)obj.GetValue(AdornerContent);}public static void SetAdornerContent(DependencyObject obj, Control value){    obj.SetValue(AdornerContent, value);}// Using a DependencyProperty as the backing store for MyProperty.  This enables animation, styling, binding, etc...public static readonly DependencyProperty AdornerContent =    DependencyProperty.RegisterAttached("AdornerContent", typeof(UIElement), typeof(AdornerHelper), new PropertyMetadata(null));

3、加入装饰层

在附加属性改变事件中，进行装饰层的添加。

public void PropertyChangedCallback(DependencyObject d, DependencyPropertyChangedEventArgs e){    var c = d as UIElement;    //获取装饰层    var layer = AdornerLayer.GetAdornerLayer(c);    //添加装饰器     layer.Add(new NormalAdorner(c, (UIElement)e.NewValue));}

二、完整代码

AdornerHelper.cs

using System;using System.Windows;using System.Windows.Documents;using System.Windows.Media;namespace AC{    internal class AdornerHelper    {        public static UIElement GetAdornerContent(DependencyObject obj)        {            return (UIElement)obj.GetValue(AdornerContent);        }        public static void SetAdornerContent(DependencyObject obj, UIElement value)        {            obj.SetValue(AdornerContent, value);        }        // Using a DependencyProperty as the backing store for MyProperty.  This enables animation, styling, binding, etc...        public static readonly DependencyProperty AdornerContent =            DependencyProperty.RegisterAttached("AdornerContent", typeof(UIElement), typeof(AdornerHelper), new PropertyMetadata(null, (d, e) =>            {                var c = d as FrameworkElement;                if (c == null)                    return;                var adronerContent = e.NewValue as UIElement;                if (!c.IsLoaded)                {                    if (adronerContent != null)                    {                        RoutedEventHandler l = null;                        l = (s, E) =>                        {                            var content = GetAdornerContent(c);                            if (content != null)                            {                                var layer = AdornerLayer.GetAdornerLayer(c);                                if (layer == null)                                    throw new Exception("获取控件装饰层失败，控件可能没有装饰层！");                                layer.Add(new NormalAdorner((UIElement)c, (UIElement)e.NewValue));                            }                            c.Loaded -= l;                        };                        c.Loaded += l;                    }                }                else                {                    var layer = AdornerLayer.GetAdornerLayer(d as Visual);                    if (layer == null)                        throw new Exception("获取控件装饰层失败，控件可能没有装饰层！");                    if (e.OldValue != null)                    {                        var adorners = layer.GetAdorners(c);                        foreach (var i in adorners)                        {                            if (i is NormalAdorner)                            {                                var na = i as NormalAdorner;                                if (na.Child == e.OldValue)                                {                                    layer.Remove(i);                                    break;                                }                            }                        }                    }                    if (adronerContent != null)                    {                        layer.Add(new NormalAdorner((UIElement)c, (UIElement)e.NewValue));                    }                }            }));        class NormalAdorner : Adorner        {            UIElement _child;            /// <summary>            /// 构造方法            /// </summary>            /// <param name="adornedElement">被添加装饰器的元素</param>            /// <param name="child">放到装饰器中的元素</param>            public NormalAdorner(UIElement adornedElement, UIElement child) : base(adornedElement)            {                _child = child;                AddVisualChild(child);            }            public UIElement Child { get { return _child; } }            protected override Visual GetVisualChild(int index)            {                return _child;            }            protected override int VisualChildrenCount            {                get                {                    return 1;                }            }            protected override Size ArrangeOverride(Size finalSize)            {                _child.Arrange(new Rect(new Point(0, 0), finalSize));                return finalSize;            }        }    }}

三、使用示例

<Window x:Class="WpfApp2.MainWindow"        xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"        xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"        xmlns:d="http://schemas.microsoft.com/expression/blend/2008"        xmlns:mc="http://schemas.openxmlformats.org/markup-compatibility/2006"        xmlns:local="clr-namespace:WpfApp2"        xmlns:ac="clr-namespace:AC"        mc:Ignorable="d"        Title="MainWindow" Height="450" Width="800"        >    <Grid>        <Border Background="RoyalBlue" Width="320" Height="180" CornerRadius="10">             <!--添加装饰器-->            <ac:AdornerHelper.AdornerContent>                <Grid >                    <Grid.Resources>                        <Style TargetType="Thumb">                            <Setter Property="Template">                                <Setter.Value>                                    <ControlTemplate TargetType="Thumb">                                        <Border BorderBrush="Gray" BorderThickness="2" CornerRadius="8"  Background="White"></Border>                                    </ControlTemplate>                                </Setter.Value>                            </Setter>                        </Style>                    </Grid.Resources>                    <!--左-->                    <Thumb  Margin="-8,0,0,0" Width="16" Height="16" HorizontalAlignment="Left" VerticalAlignment="Center" Cursor="SizeWE"/>                    <!--上-->                    <Thumb  Margin="0,-8,0,0" Width="16" Height="16" HorizontalAlignment="Center" VerticalAlignment="Top" Cursor="SizeNS"/>                    <!--右-->                    <Thumb  Margin="0,0,-8,0" Width="16" Height="16" HorizontalAlignment="Right" VerticalAlignment="Center" Cursor="SizeWE"/>                    <!--下-->                    <Thumb  Margin="0,0,0,-8" Width="16" Height="16" HorizontalAlignment="Center" VerticalAlignment="Bottom" Cursor="SizeNS"/>                    <!--左上-->                    <Thumb  Margin="-8,-8,0,0" Width="16" Height="16" HorizontalAlignment="Left" VerticalAlignment="Top" Cursor="SizeNWSE"/>                    <!--右上-->                    <Thumb  Margin="0,-8,-8,0" Width="16" Height="16" HorizontalAlignment="Right" VerticalAlignment="Top"  Cursor="SizeNESW"/>                    <!--右下-->                    <Thumb  Margin="0,0,-8,-8" Width="16" Height="16" HorizontalAlignment="Right" VerticalAlignment="Bottom"  Cursor="SizeNWSE"/>                    <!--左下-->                    <Thumb  Margin="-8,0,0,-8" Width="16" Height="16" HorizontalAlignment="Left" VerticalAlignment="Bottom" Cursor="SizeNESW"/>                </Grid>            </ac:AdornerHelper.AdornerContent>        </Border>    </Grid></Window>

效果预览

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