wpf - XAML 组合样式超越 BasedOn？

Question

有没有办法在 XAML 中组合多种样式来创建具有所有所需设置的新样式？

例如(伪代码)；

<Style x:key="A">
 ...
</Style>

<Style x:key="B">
 ...
</Style>

<Style x:key="Combined">
 <IncludeStyle Name="A"/>
 <IncludeStyle Name="B"/>
 ... other properties.
</Style>

我知道样式有一个 BasedOn 属性，但该功能只能带您到目前为止。我实际上只是在寻找一种简单的方法(在 XAML 中)来创建这些“组合”样式。但就像我之前说的，我怀疑它是否存在，除非有人听说过这样的事情？？

Answer 1

您可以创建自定义标记扩展，将样式属性和触发器合并为单个样式。您所需要做的就是将 MarkupExtension 派生类添加到您的命名空间，并定义了 MarkupExtensionReturnType 属性，然后就可以开始运行了。

这是一个扩展，允许您使用“类似 css”的语法合并样式。

MultiStyleExtension.cs

[MarkupExtensionReturnType(typeof(Style))]
public class MultiStyleExtension : MarkupExtension
{
    private string[] resourceKeys;

    /// <summary>
    /// Public constructor.
    /// </summary>
    /// <param name="inputResourceKeys">The constructor input should be a string consisting of one or more style names separated by spaces.</param>
    public MultiStyleExtension(string inputResourceKeys)
    {
        if (inputResourceKeys == null)
            throw new ArgumentNullException("inputResourceKeys");
        this.resourceKeys = inputResourceKeys.Split(new char[] { ' ' }, StringSplitOptions.RemoveEmptyEntries);
        if (this.resourceKeys.Length == 0)
            throw new ArgumentException("No input resource keys specified.");
    }

    /// <summary>
    /// Returns a style that merges all styles with the keys specified in the constructor.
    /// </summary>
    /// <param name="serviceProvider">The service provider for this markup extension.</param>
    /// <returns>A style that merges all styles with the keys specified in the constructor.</returns>
    public override object ProvideValue(IServiceProvider serviceProvider)
    {
        Style resultStyle = new Style();
        foreach (string currentResourceKey in resourceKeys)
        {
            object key = currentResourceKey;
            if (currentResourceKey == ".")
            {
                IProvideValueTarget service = (IProvideValueTarget)serviceProvider.GetService(typeof(IProvideValueTarget));
                key = service.TargetObject.GetType();
            }
            Style currentStyle = new StaticResourceExtension(key).ProvideValue(serviceProvider) as Style;
            if (currentStyle == null)
                throw new InvalidOperationException("Could not find style with resource key " + currentResourceKey + ".");
            resultStyle.Merge(currentStyle);
        }
        return resultStyle;
    }
}

public static class MultiStyleMethods
{
    /// <summary>
    /// Merges the two styles passed as parameters. The first style will be modified to include any 
    /// information present in the second. If there are collisions, the second style takes priority.
    /// </summary>
    /// <param name="style1">First style to merge, which will be modified to include information from the second one.</param>
    /// <param name="style2">Second style to merge.</param>
    public static void Merge(this Style style1, Style style2)
    {
        if(style1 == null)
            throw new ArgumentNullException("style1");
        if(style2 == null)
            throw new ArgumentNullException("style2");
        if(style1.TargetType.IsAssignableFrom(style2.TargetType))
            style1.TargetType = style2.TargetType;
        if(style2.BasedOn != null)
            Merge(style1, style2.BasedOn);
        foreach(SetterBase currentSetter in style2.Setters)
            style1.Setters.Add(currentSetter);
        foreach(TriggerBase currentTrigger in style2.Triggers)
            style1.Triggers.Add(currentTrigger);
        // This code is only needed when using DynamicResources.
        foreach(object key in style2.Resources.Keys)
            style1.Resources[key] = style2.Resources[key];
    }
}

您的示例将通过以下方式解决:

<Style x:key="Combined" BasedOn="{local:MultiStyle A B}">
      ... other properties.
</Style>

我们通过在内置 BasedOn 属性(用于样式继承)中合并其他两个样式“A”和“B”，定义了一个名为“Combined”的新样式。我们可以选择像往常一样将其他属性添加到新的“组合”样式中。

其他示例:

这里，我们定义了 4 种按钮样式，并且可以以各种组合方式使用它们，而无需重复:

<Window.Resources>
    <Style TargetType="Button" x:Key="ButtonStyle">
        <Setter Property="Width" Value="120" />
        <Setter Property="Height" Value="25" />
        <Setter Property="FontSize" Value="12" />
    </Style>
    <Style TargetType="Button" x:Key="GreenButtonStyle">
        <Setter Property="Foreground" Value="Green" />
    </Style>
    <Style TargetType="Button" x:Key="RedButtonStyle">
        <Setter Property="Foreground" Value="Red" />
    </Style>
    <Style TargetType="Button" x:Key="BoldButtonStyle">
        <Setter Property="FontWeight" Value="Bold" />
    </Style>
</Window.Resources>

<Button Style="{local:MultiStyle ButtonStyle GreenButtonStyle}" Content="Green Button" />
<Button Style="{local:MultiStyle ButtonStyle RedButtonStyle}" Content="Red Button" />
<Button Style="{local:MultiStyle ButtonStyle GreenButtonStyle BoldButtonStyle}" Content="green, bold button" />
<Button Style="{local:MultiStyle ButtonStyle RedButtonStyle BoldButtonStyle}" Content="red, bold button" />

您甚至可以使用“.”语法将类型的“当前”默认样式(依赖于上下文)与一些其他样式合并:

<Button Style="{local:MultiStyle . GreenButtonStyle BoldButtonStyle}"/>

上面的代码会将 TargetType="{x:Type Button}" 的默认样式与两个补充样式合并。

信用

我在 bea.stollnitz.com 找到了 MultiStyleExtension 的原始想法并将其修改为支持“.”表示法来引用当前样式。