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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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