第17章 控件模版(8)——动态换肤

基本原理：在程序运行时加载新的资源字典，并使用新加载的资源字典代替当前的资源字典(不需要替换所有资源，只需要替换哪些用于皮肤的资源)。

有两种方式实现动态换肤：

①检索ResourceDictionary对象，并通过后台代码替换资源实现动态换肤。

②通过编写代码加载资源字典，然后通过后台代码替换资源实现动态换肤。

实例演示动态换肤：

假设有已创建用于定义同一个按钮控件模板的两个资源。一个保存在GradientButton.xaml文件中，另外一个保存在GradientButtonVariant.xaml文件中。为了更好的组织资源，将这两个文件都放在了Resources文件夹下。

GradientButton.xaml代码：

<ResourceDictionary xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"    xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml" x:Class="ControlTemplates.GradientButton"    >    <!-- Resources used by the template. -->    <RadialGradientBrush RadiusX="1" RadiusY="5" GradientOrigin="0.5,0.3"     x:Key="HighlightBackground">      <GradientStop Color="White" Offset="0" />      <GradientStop Color="Blue" Offset=".4" />    </RadialGradientBrush>    <RadialGradientBrush RadiusX="1" RadiusY="5" GradientOrigin="0.5,0.3"     x:Key="PressedBackground">      <GradientStop Color="White" Offset="0" />      <GradientStop Color="Blue" Offset="1" />    </RadialGradientBrush>    <SolidColorBrush Color="Blue" x:Key="DefaultBackground"></SolidColorBrush>    <SolidColorBrush Color="Gray" x:Key="DisabledBackground"></SolidColorBrush>    <RadialGradientBrush RadiusX="1" RadiusY="5" GradientOrigin="0.5,0.3"     x:Key="Border">      <GradientStop Color="White" Offset="0" />      <GradientStop Color="Blue" Offset="1" />    </RadialGradientBrush>    <!-- The button control template. -->    <ControlTemplate x:Key="GradientButtonTemplate" TargetType="{x:Type Button}">      <Border Name="Border" BorderBrush="{StaticResource Border}" BorderThickness="2"       CornerRadius="2" Background="{StaticResource DefaultBackground}"       TextBlock.Foreground="White">        <Grid>          <Rectangle Name="FocusCue" Visibility="Hidden" Stroke="Black"           StrokeThickness="1" StrokeDashArray="1 2" SnapsToDevicePixels="True">          </Rectangle>          <ContentPresenter Margin="{TemplateBinding Padding}"           RecognizesAccessKey="True"></ContentPresenter>        </Grid>      </Border>      <ControlTemplate.Triggers>        <Trigger Property="IsMouseOver" Value="True">          <Setter TargetName="Border" Property="Background"           Value="{StaticResource HighlightBackground}" />        </Trigger>        <Trigger Property="IsPressed" Value="True">          <Setter TargetName="Border" Property="Background"           Value="{StaticResource PressedBackground}" />        </Trigger>        <Trigger Property="IsKeyboardFocused" Value="True">          <Setter TargetName="FocusCue" Property="Visibility"            Value="Visible"></Setter>        </Trigger>        <Trigger Property="IsEnabled" Value="False">          <Setter TargetName="Border" Property="Background"           Value="{StaticResource DisabledBackground}"></Setter>        </Trigger>      </ControlTemplate.Triggers>    </ControlTemplate>    <!-- The style that applies the button control template. -->    <Style TargetType="{x:Type Button}">      <Setter Property="Control.Template"       Value="{StaticResource GradientButtonTemplate}"></Setter>    </Style>  </ResourceDictionary>

GradientButtonVariant.xaml代码：

<ResourceDictionary xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"    xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml" x:Class="ControlTemplates.GradientButtonVariant"    >       <RadialGradientBrush RadiusX="1" RadiusY="5" GradientOrigin="0.5,0.3" x:Key="HighlightBackground">      <GradientStop Color="White" Offset="0" />      <GradientStop Color="Green" Offset=".4" />    </RadialGradientBrush>  <RadialGradientBrush RadiusX="1" RadiusY="5" GradientOrigin="0.5,0.3" x:Key="PressedBackground">    <GradientStop Color="White" Offset="0" />    <GradientStop Color="Green" Offset="1" />  </RadialGradientBrush>    <SolidColorBrush Color="DarkGreen" x:Key="DefaultBackground"></SolidColorBrush>  <SolidColorBrush Color="Gray" x:Key="DisabledBackground"></SolidColorBrush>    <RadialGradientBrush RadiusX="1" RadiusY="5" GradientOrigin="0.5,0.3" x:Key="Border">    <GradientStop Color="White" Offset="0" />    <GradientStop Color="Green" Offset="1" />  </RadialGradientBrush>  <ControlTemplate x:Key="GradientButtonTemplate" TargetType="{x:Type Button}">    <Border Name="Border" BorderBrush="{StaticResource Border}" BorderThickness="2" CornerRadius="2"            Background="{StaticResource DefaultBackground}" TextBlock.Foreground="White">      <Grid>        <Rectangle Name="FocusCue" Visibility="Hidden" Stroke="Black" StrokeThickness="1" StrokeDashArray="1 2" SnapsToDevicePixels="True" ></Rectangle>        <ContentPresenter Margin="{TemplateBinding Padding}" RecognizesAccessKey="True"></ContentPresenter>      </Grid>    </Border>    <ControlTemplate.Triggers>      <Trigger Property="IsMouseOver" Value="True">        <Setter TargetName="Border" Property="Background" Value="{StaticResource HighlightBackground}" />      </Trigger>      <Trigger Property="IsPressed" Value="True">        <Setter TargetName="Border" Property="Background" Value="{StaticResource PressedBackground}" />              </Trigger>      <Trigger Property="IsKeyboardFocused" Value="True">        <Setter TargetName="FocusCue" Property="Visibility" Value="Visible"></Setter>      </Trigger>      <Trigger Property="IsEnabled" Value="False">                <Setter TargetName="Border" Property="Background" Value="{StaticResource DisabledBackground}"></Setter>      </Trigger>    </ControlTemplate.Triggers>  </ControlTemplate>    <Style  TargetType="{x:Type Button}">        <Setter Property="Control.Template" Value="{StaticResource GradientButtonTemplate}"></Setter>    </Style></ResourceDictionary>

方法一：

①项目目录结构

②MainWindow.xaml代码

<Window x:Class="AutoChangeTemplate.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:AutoChangeTemplate"        mc:Ignorable="d"        Title="MainWindow" Height="350" Width="525">    <Window.Resources>        <ResourceDictionary>            <ResourceDictionary.MergedDictionaries>                <ResourceDictionary Source="Resources/GradientButton.xaml"></ResourceDictionary>            </ResourceDictionary.MergedDictionaries>        </ResourceDictionary>    </Window.Resources>    <StackPanel>        <Button HorizontalAlignment="Center" Padding="5" Margin="0 30 0 0">GradientButton</Button>        <Button HorizontalAlignment="Center" Padding="5" Margin="5" Click="Button_Click">第一种方式动态换肤</Button>    </StackPanel></Window>

③MainWindow.xaml.cs代码

using System;using System.Collections.Generic;using System.Linq;using System.Text;using System.Threading.Tasks;using System.Windows;using System.Windows.Controls;using System.Windows.Data;using System.Windows.Documents;using System.Windows.Input;using System.Windows.Media;using System.Windows.Media.Imaging;using System.Windows.Navigation;using System.Windows.Shapes;namespace AutoChangeTemplate{    /// <summary>    /// MainWindow.xaml 的交互逻辑    /// </summary>    public partial class MainWindow : Window    {        public MainWindow()        {            InitializeComponent();        }        private void Button_Click(object sender, RoutedEventArgs e)        {            ResourceDictionary newDictionary = new ResourceDictionary();            newDictionary.Source = new Uri("Resources/GradientButtonVariant.xaml",UriKind.Relative);            this.Resources.MergedDictionaries[0] = newDictionary;        }    }}

④效果演示

当如果为整个应用程序改变皮肤，代码如下：

Application.Current.Resources.MergedDictionaries[0] = newDictionary;

通过pack URI语法加载在另外一个程序集中定义的资源字典：

ResourceDictionary newDictionary = new ResourceDictionary();newDictionary.Source = new Uri("ControlTemplateLibrary;component/Resources/GradientButtonVariant.xaml",UriKind.Relative);this.Resources.MergedDictionaries[0] = newDictionary;

注意：
上面的的例子两个资源文件都是通过类型样式自动改变的按钮。但如果是手动设置了Template或Style属性来选用新模板。必须用Dynamic Resource引用，而不能使用StaticResource。若用StaticResource，当切换皮肤时不会自动更新按钮模板。

方法二：

①为资源字典创建代码隐藏类

先将GradientButtonVariant.xaml文件从Resources文件夹下移到项目根目录，如下图：

然后再创建个GradientButtonVariant.xaml.cs类文件，此时的类文件会自动放到GradientButtonVariant.xaml下。

②将定义的类链接到GradientButtonVariant.xaml资源字典，即在资源字典的根元素添加Class特性，代码如下：

x:Class="AutoChangeTemplate.GradientButtonVariant"

③改造GradientButtonVariant.xaml.cs代码：

将这个类文件改为部分类，并在构造函数中调用InitializeComponent()方法。

using System;using System.Collections.Generic;using System.Linq;using System.Text;using System.Threading.Tasks;using System.Windows;namespace AutoChangeTemplate{    public partial class GradientButtonVariant : ResourceDictionary    {        public GradientButtonVariant()        {            InitializeComponent();        }    }}

④将GradientButtonVariant.xaml移回Resources文件夹下，此时GradientButtonVariant.xaml.cs会自动移过去。

⑤使用定义的类换肤，创建资源实例的时候直接new GradientButtonVariant即可，代码如下：

ResourceDictionary newDictionary = new GradientButtonVariant();this.Resources.MergedDictionaries[0] = newDictionary;

⑤效果如上面的GIF动画。