WPF入门（4）——资源

引用《深入浅出WPF》对资源的解读：

每个WPF的界面元素都具有一个名为Resources的属性，这个属性继承自FrameworkElement类，其类型为ResourceDictionary。ResourceDictionary能够以“键－值”对的形式存储资源（注：可以是实例，如一个类的实例；也可以是基本类型如字符串），当需要使用某个资源时，使用“键－值”对可以索引到资源对象。
——刘铁猛.深入浅出WPF(Kindle位置2580-2582).中国水利水电出版社.Kindle版本.

wpf的资源字典是FrameworkElement的一个字段，任何继承自FrameworkElement的类都拥有该属性。
我们可以把一些实例对象保存到资源字典中，为之设置一个key，当使用这些对象的时候直接在xaml中<Button Style="{StaticResource TransparentButton}">即可。TransparentButton就是保存在资源字典中的实例对象。

有一点要注意，public class Application : DispatcherObject, IHaveResources, IQueryAmbient，这个application类也有自己的资源字典属性，它并不是继承自FrameworkElement。

简单的资源使用

参考 https://www.cnblogs.com/zhili/p/WPFResourceAndStyle.html
下面的示例为window添加了资源字典。

<Window x:Class="ResourceDemo.ResourceUse"
        xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
        xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
        Title="REsource" Height="100" Width="350"
        xmlns:sys="clr-namespace:System;assembly=mscorlib">
    <Window.Resources>
        <!--定义一个字符串资源-->
        <sys:String x:Key="nameStr">
            LearningHard博客：http://www.cnblogs.com/zhili/
        </sys:String>
    </Window.Resources>
    <StackPanel>
        <!--通过资源key来对资源进行使用-->
        <TextBlock Text="{StaticResource nameStr}" Margin="10"/>
    </StackPanel>
</Window>

这样使用没什么难度，动态资源与静态资源这里也不赘述。

资源字典

下面的示例为Application类添加了资源字典，他是全局的，所有该应用下的类都能使用,如下面的示例

    <Application.Resources>
        <ResourceDictionary>
            <!--ResourceDictionary的MergedDictionaries属性是个集合，资源字典的集合，这里面的每一个元素都是一个资源字典-->
            <ResourceDictionary.MergedDictionaries>
                <!--这里就指定了一些资源字典添加到MergedDictionaries集合中，这些被添加的资源字典都作为Application对象的资源字典使用，可以直接用每个字典中的key引用字典中与之对应的实例-->
                <ResourceDictionary Source="/Resources/Str.xaml"/>
                <ResourceDictionary Source="/Themes/ControlStyle.xaml"/>
                <ResourceDictionary Source="/Resources/Colors.xaml"/>
            </ResourceDictionary.MergedDictionaries>          
        </ResourceDictionary>
    </Application.Resources>

msdn解释：
MergedDictionaries
获取 ResourceDictionary 字典的集合，这些字典构成了合并字典中的各种资源字典。

MergeDictionaries中每一个字典与字典之间的key可以重复。
典型应用是全球化。
https://docs.microsoft.com/zh-cn/dotnet/framework/wpf/advanced/wpf-globalization-and-localization-overview
https://www.bbsmax.com/A/gGdXAWPQz4/

以ScreenToGit项目为例，作者做国际化就是定义了n种语言实现的字符串：

切换语言的时候实际上是切换资源字典，代码则完全不用修改。

下面的代码是摘抄自ScreenToGif的StringResources.zh.xaml文件

<ResourceDictionary xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
                    xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
                    xmlns:s="clr-namespace:System;assembly=mscorlib"
                    xml:space="preserve">
    
    <!--To use a new line: &#x0d;-->
    <!--Or CarriageReturn + NewLine: &#x0d;&#x0a; or &#10;--> 
    <!--Special texts like {0}, are place holders for dynamic values, such as numbers.-->
    
    <!--General-->
    <s:String x:Key="Ok">确定</s:String>
    <s:String x:Key="Back">返回</s:String>
    <s:String x:Key="Cancel">取消</s:String>
    <s:String x:Key="Yes">是</s:String>
    <s:String x:Key="No">否</s:String>
    <s:String x:Key="Frame">帧</s:String>
    <s:String x:Key="Suppress">隐藏</s:String>
    <s:String x:Key="Preview">预览</s:String>
    <s:String x:Key="S.Add">添加</s:String>
    <s:String x:Key="S.Edit">编辑</s:String>
    <s:String x:Key="S.Id">标识</s:String>
    <s:String x:Key="S.Title">标题</s:String>
    <s:String x:Key="S.Description">描述</s:String>
    <s:String x:Key="S.SelectColor">单击此处选择颜色。</s:String>
</ResourceDictionary>

使用方式（同样摘自ScreenToGif）：

<!--Options-->
<StackPanel Grid.Row="0" Grid.Column="0" Grid.RowSpan="2" x:Name="OptionsStackPanel" Margin="0" MaxWidth="180">
	<n:ImageRadioButton x:Name="AppRadio" Text="{DynamicResource Application}" Content="{StaticResource Vector.Application}" TextWrapping="WrapWithOverflow" IsChecked="True"
						Padding="1,3,5,3" FontSize="17" FontFamily="Segoe UI Semilight" Cursor="Hand" MaxSize="24" HorizontalContentAlignment="Left"/>
	<n:ImageRadioButton x:Name="InterfaceRadio" Text="{DynamicResource Interface}" Content="{StaticResource Vector.Colors}" TextWrapping="WrapWithOverflow"
						Padding="1,3,5,3" FontSize="17" FontFamily="Segoe UI Semilight" Cursor="Hand" MaxSize="24" HorizontalContentAlignment="Left"/>
	<n:ImageRadioButton x:Name="AutomaticRadio" Text="{DynamicResource S.AutoTasks}" Content="{StaticResource Vector.Encoder}" TextWrapping="WrapWithOverflow"
						Padding="1,3,5,3" FontSize="17" FontFamily="Segoe UI Semilight" Cursor="Hand" MaxSize="24" HorizontalContentAlignment="Left"/>
	<n:ImageRadioButton x:Name="ShortcutsRadio" Text="{DynamicResource S.Shortcuts}" Content="{StaticResource Vector.Keyboard}" TextWrapping="Wrap"
						Padding="1,3,5,3" FontSize="17" FontFamily="Segoe UI Semilight" Cursor="Hand" MaxSize="24" HorizontalContentAlignment="Left"/>
	<n:ImageRadioButton x:Name="LanguageRadio" Text="{DynamicResource Language}" Content="{StaticResource Vector.Translate}"  TextWrapping="Wrap"
						Padding="1,3,5,3" FontSize="17" FontFamily="Segoe UI Semilight" Cursor="Hand" MaxSize="24" HorizontalContentAlignment="Left"/>
	<n:ImageRadioButton x:Name="TempRadio" Text="{DynamicResource TemporaryFiles}" Content="{StaticResource Vector.Temporary}" TextWrapping="Wrap"
						Padding="1,3,5,3" FontSize="17" FontFamily="Segoe UI Semilight" Cursor="Hand" MaxSize="24" HorizontalContentAlignment="Left"/>
	<n:ImageRadioButton x:Name="CloudRadioButton" Text="{DynamicResource Clouds}" Content="{StaticResource Vector.Web}" TextWrapping="Wrap"
						Padding="1,3,5,3" FontSize="17" FontFamily="Segoe UI Semilight" Cursor="Hand" MaxSize="24" HorizontalContentAlignment="Left"/>
	<n:ImageRadioButton x:Name="ExtrasRadioButton" Text="{DynamicResource Extras}" Content="{StaticResource Vector.Extras}" TextWrapping="Wrap"
						Padding="1,3,5,3" FontSize="17" FontFamily="Segoe UI Semilight" Cursor="Hand" MaxSize="24" HorizontalContentAlignment="Left"/>
	<n:ImageRadioButton x:Name="DonateRadio" Text="{DynamicResource Donate}" Content="{StaticResource Vector.Money}" TextWrapping="Wrap"
						Padding="1,3,5,3" FontSize="17" FontFamily="Segoe UI Semilight" Cursor="Hand" MaxSize="24" HorizontalContentAlignment="Left"/>
	<n:ImageRadioButton x:Name="AboutRadio" Text="{DynamicResource About}" Content="{StaticResource Vector.Info}"  TextWrapping="Wrap"
						Padding="1,3,5,3" FontSize="17" FontFamily="Segoe UI Semilight" Cursor="Hand" MaxSize="24" HorizontalContentAlignment="Left"/>
</StackPanel>

最后附上ScreenToGif切换字典的函数：

public static void SelectCulture(string culture)
{
	#region Validation

	//If none selected, fallback to english.
	if (string.IsNullOrEmpty(culture))
		culture = "en";

	if (culture.Equals("auto") || culture.Length < 2)
	{
		var ci = CultureInfo.InstalledUICulture;
		culture = ci.Name;
	}

	#endregion

	//Copy all MergedDictionarys into a auxiliar list.
	var dictionaryList = Application.Current.Resources.MergedDictionaries.ToList();

	#region Selected Culture

	//Search for the specified culture.
	var requestedCulture = $"/Resources/Localization/StringResources.{culture}.xaml";
	var requestedResource = dictionaryList.FirstOrDefault(d => d.Source?.OriginalString == requestedCulture);

	#endregion

	#region Generic Branch Fallback

	//Fallback to a more generic version of the language. Example: pt-BR to pt.
	while (requestedResource == null && !string.IsNullOrEmpty(culture))
	{
		culture = CultureInfo.GetCultureInfo(culture).Parent.Name;
		requestedCulture = $"/Resources/Localization/StringResources.{culture}.xaml";
		requestedResource = dictionaryList.FirstOrDefault(d => d.Source?.OriginalString == requestedCulture);
	}

	#endregion

	#region English Fallback

	//If not present, fall back to english.
	if (requestedResource == null)
	{
		culture = "en";
		requestedCulture = "/Resources/Localization/StringResources.en.xaml";
		requestedResource = dictionaryList.FirstOrDefault(d => d.Source?.OriginalString == requestedCulture);
	}

	#endregion

	//If we have the requested resource, remove it from the list and place at the end.
	//Then this language will be our current string table.
	Application.Current.Resources.MergedDictionaries.Remove(requestedResource);
	Application.Current.Resources.MergedDictionaries.Add(requestedResource);

	//Inform the threads of the new culture.
	Thread.CurrentThread.CurrentCulture = new CultureInfo(culture);
	Thread.CurrentThread.CurrentUICulture = new CultureInfo(culture);

	#region English Fallback of the Current Language

	//Only non-English resources need a fallback, because the English resource is evergreen. TODO
	if (culture.StartsWith("en"))
		return;

	var englishResource = dictionaryList.FirstOrDefault(d => d.Source?.OriginalString == "/Resources/Localization/StringResources.en.xaml");

	if (englishResource != null)
	{
		Application.Current.Resources.MergedDictionaries.Remove(englishResource);
		Application.Current.Resources.MergedDictionaries.Insert(Application.Current.Resources.MergedDictionaries.Count - 1, englishResource);
	}

	#endregion

	GC.Collect(0);

	if (!UserSettings.All.CheckForTranslationUpdates)
		return;

	//Async, fire and forget.
	Task.Factory.StartNew(() => CheckForUpdates(culture));
}

一个示例

工程上传到github ：https://github.com/feipeng8848/WPF-Demo