在WPF中优雅地覆盖ComboBox的ToggleButton样式

Question

我有一个关于如何优雅地覆盖控件视觉树中任意元素的问题。我已经尝试过几种方法来解决它，但每种方法都遇到了一些问题。通常当我尝试三条不同的路径并在每一条路径上失败时，我会去楼下喝杯咖啡，问比我聪明的人。所以我来到这里。

具体而言：

我想要使组合框（ComboBox）的样式扁平化，使其不会引起注意。我希望它与Windows.Forms.ComboBox的FlatStyle类似，并且在Windows 7和XP上看起来相同。

主要是，我想改变ComboBox的ToggleButton的外观。

我可以使用Blend并拆开控件模板，然后手动更改它们。但那对我来说听起来并不吸引人。

我尝试使用样式来覆盖ToggleButton的背景，但事实证明整个ComboBox控件实际上是ToggleButton的前端。

<Window
xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
x:Class="ComboBoxExpiriment2.MainWindow"
x:Name="Window"
xmlns:Microsoft_Windows_Themes="clr-namespace:Microsoft.Windows.Themes;assembly=PresentationFramework.Classic" xmlns:d="http://schemas.microsoft.com/expression/blend/2008" xmlns:mc="http://schemas.openxmlformats.org/markup-compatibility/2006"
Title="MainWindow"
Width="204" Height="103">
<Grid x:Name="LayoutRoot">
    <ComboBox HorizontalAlignment="Left" Margin="32,26.723,0,0" Width="120" VerticalAlignment="Top" Height="21.277">
    <ComboBox.Style>
      <Style>
        <Setter Property="ToggleButton.Background" Value="Green" />
      </Style>
    </ComboBox.Style>
    </ComboBox>
</Grid>

所以我放弃了，改用Blend来提取它。我发现它实际上是一个名为ComboBoxTransparentButtonStyle的样式，其目标类型为ToggleButton。该样式设置了一个ControlTemplate，使用了一个DockPanel，其中“Microsoft_Windows_Themes:ClassicBorderDecorator”类型被设置到右侧，而这正是我们实际想要控制的东西。（到目前为止，你跟上我了吗？）
以下是图片：

<Style x:Key="ComboBoxTransparentButtonStyle" TargetType="{x:Type ToggleButton}">
                <Setter Property="MinWidth" Value="0"/>
                <Setter Property="MinHeight" Value="0"/>
                <Setter Property="Width" Value="Auto"/>
                <Setter Property="Height" Value="Auto"/>
                <Setter Property="Background" Value="Transparent"/>
                <Setter Property="BorderBrush" Value="{x:Static Microsoft_Windows_Themes:ClassicBorderDecorator.ClassicBorderBrush}"/>
                <Setter Property="BorderThickness" Value="2"/>
                <Setter Property="Template">
                    <Setter.Value>
                        <ControlTemplate TargetType="{x:Type ToggleButton}">
                            <DockPanel SnapsToDevicePixels="true" Background="{TemplateBinding Background}" LastChildFill="false">
                                <Microsoft_Windows_Themes:ClassicBorderDecorator x:Name="Border" Width="{DynamicResource {x:Static SystemParameters.VerticalScrollBarWidthKey}}" DockPanel.Dock="Right" Background="Green" BorderBrush="{TemplateBinding BorderBrush}" BorderStyle="None" BorderThickness="{TemplateBinding BorderThickness}">
                                    <Path Fill="{TemplateBinding Foreground}" HorizontalAlignment="Center" VerticalAlignment="Center" Data="{StaticResource DownArrowGeometry}"/>
                                </Microsoft_Windows_Themes:ClassicBorderDecorator>
                            </DockPanel>
                            <ControlTemplate.Triggers>
                                <Trigger Property="IsChecked" Value="true">
                                    <Setter Property="BorderStyle" TargetName="Border" Value="AltPressed"/>
                                </Trigger>
                            </ControlTemplate.Triggers>
                        </ControlTemplate>
                    </Setter.Value>
                </Setter>
                <Style.Triggers>
                    <Trigger Property="IsEnabled" Value="false">
                        <Setter Property="Foreground" Value="{DynamicResource {x:Static SystemColors.ControlDarkBrushKey}}"/>
                    </Trigger>
                </Style.Triggers>
            </Style>

哎呀。WPF不是很有趣吗？

我提取了样式ComboBoxTransparentButtonStyle，并将其放入另一个项目的application.resources中。问题是，我无法将该样式应用于ComboBox，因为我提取的样式的targetType是ToggleButton，所以TargetTypes不匹配。

总之，你们会怎么做呢？

- user218849

Answer 1

一个可行的解决方案

---

您好，这种风格可以满足您的需求，随意按照您的需要进行编辑：

    <SolidColorBrush x:Key="WindowBackgroundBrush" Color="White" />

<SolidColorBrush x:Key="MainColor" Color="DeepSkyBlue"/>
<SolidColorBrush x:Key="MainColorLight" Color="LightSkyBlue"/>
<SolidColorBrush x:Key="MainColorDark" Color="#00A7DF"/>

<SolidColorBrush x:Key="BorderMainBrush" Color="LightGray"/>
<SolidColorBrush x:Key="BorderDarkMainBrush" Color="#C0C0C0"/>

<SolidColorBrush x:Key="BackgroundGrayDark" Color="#FFEFEFEF"/>
<SolidColorBrush x:Key="BackgroundGrayLight" Color="#F5F5F5"/>

<SolidColorBrush x:Key="ForegroundDisabledBrush" Color="DimGray"/>
<SolidColorBrush x:Key="ForegroundBrush" Color="Black"/>


<LinearGradientBrush x:Key="FormBackgroundBrush"
                             EndPoint="0.5,1" StartPoint="0.5,0">
    <GradientStop Color="#FFFFFD" Offset="0.31" />
    <GradientStop Color="#FFF8F8F8" Offset="1" />
</LinearGradientBrush>


<ControlTemplate x:Key="ComboBoxToggleButton" TargetType="ToggleButton">
    <Grid>
        <Grid.ColumnDefinitions>
            <ColumnDefinition />
            <ColumnDefinition Width="20" />
        </Grid.ColumnDefinitions>
        <VisualStateManager.VisualStateGroups>
            <VisualStateGroup x:Name="CommonStates">
                <VisualState x:Name="Normal"/>
                <VisualState x:Name="MouseOver"/>
                <VisualState x:Name="Pressed"/>
                <VisualState x:Name="Disabled"/>
            </VisualStateGroup>
        </VisualStateManager.VisualStateGroups>
        <Border x:Name="Border" SnapsToDevicePixels="True" Grid.ColumnSpan="2" Background="{DynamicResource BackgroundGrayDark}" BorderBrush="{DynamicResource BorderDarkMainBrush}" BorderThickness="1"  />
        <Border x:Name="Border2" Grid.Column="0" SnapsToDevicePixels="True" Margin="1" Background="{StaticResource WindowBackgroundBrush}" BorderBrush="{DynamicResource BorderDarkMainBrush}" BorderThickness="0,0,1,0" />
        <Path x:Name="Arrow" Grid.Column="1" Data="M 0 0 L 4 4 L 8 0 Z" Fill="DimGray" HorizontalAlignment="Center" VerticalAlignment="Center" />
    </Grid>
    <ControlTemplate.Triggers>
        <Trigger Property="ToggleButton.IsMouseOver" Value="true">
            <Setter Property="Background" TargetName="Border" Value="{DynamicResource MainColor}" />
            <Setter Property="BorderBrush" TargetName="Border" Value="{DynamicResource MainColor}" />
            <Setter Property="BorderBrush" TargetName="Border2" Value="{DynamicResource MainColor}" />
            <Setter Property="Fill" TargetName="Arrow" Value="White" />
        </Trigger>
        <Trigger Property="ToggleButton.IsChecked" Value="true">
            <Setter Property="Background" TargetName="Border" Value="{DynamicResource MainColorDark}" />
            <Setter Property="BorderBrush" TargetName="Border" Value="{DynamicResource MainColorDark}" />
            <Setter Property="BorderBrush" TargetName="Border2" Value="{DynamicResource MainColorDark}" />
            <Setter Property="Fill" TargetName="Arrow" Value="White" />
        </Trigger>
        <Trigger Property="IsEnabled" Value="False">
            <Setter Property="Background" TargetName="Border" Value="{DynamicResource BackgroundGrayLight}" />
            <Setter Property="BorderBrush" TargetName="Border" Value="{StaticResource BorderMainBrush}" />
            <Setter Property="Foreground" Value="{StaticResource ForegroundDisabledBrush}" />
        </Trigger>
        <DataTrigger Binding="{Binding IsKeyboardFocusWithin, RelativeSource={RelativeSource Mode=TemplatedParent}, Mode=OneWay}" Value="True">
            <Setter Property="Background" TargetName="Border" Value="{DynamicResource MainColorLight}" />
            <Setter Property="BorderBrush" TargetName="Border" Value="{DynamicResource MainColorLight}" />
            <Setter Property="BorderBrush" TargetName="Border2" Value="{DynamicResource MainColorLight}" />
            <Setter Property="Fill" TargetName="Arrow" Value="White" />
        </DataTrigger >
    </ControlTemplate.Triggers>
</ControlTemplate>

<ControlTemplate x:Key="ComboBoxTextBox" TargetType="TextBox">
    <Border x:Name="PART_ContentHost" Background="{TemplateBinding Background}" Focusable="False" />
</ControlTemplate>

<Style TargetType="ComboBox">
    <Setter Property="Validation.ErrorTemplate" Value="{x:Null}" />
    <Setter Property="VerticalAlignment" Value="Center" />
    <Setter Property="OverridesDefaultStyle" Value="true" />
    <Setter Property="IsEditable" Value="True"/>
    <Setter Property="SnapsToDevicePixels" Value="true" />
    <Setter Property="ScrollViewer.HorizontalScrollBarVisibility" Value="Auto" />
    <Setter Property="ScrollViewer.VerticalScrollBarVisibility" Value="Auto" />
    <Setter Property="ScrollViewer.CanContentScroll" Value="true" />
    <Setter Property="Margin" Value="2" />
    <Setter Property="MinHeight" Value="20" />
    <Setter Property="Template">
        <Setter.Value>
            <ControlTemplate TargetType="ComboBox">
                <Grid>
                    <VisualStateManager.VisualStateGroups>
                        <VisualStateGroup x:Name="CommonStates">
                            <VisualState x:Name="Normal"/>
                            <VisualState x:Name="MouseOver"/>
                            <VisualState x:Name="Disabled"/>
                        </VisualStateGroup>
                    </VisualStateManager.VisualStateGroups>
                    <ToggleButton x:Name="ToggleButton" Grid.Column="2" ClickMode="Press" Focusable="false"
                        IsChecked="{Binding IsDropDownOpen, Mode=TwoWay, RelativeSource={RelativeSource TemplatedParent}}"
                        Template="{StaticResource ComboBoxToggleButton}"/>

                    <ContentPresenter Margin="3,3,23,3" Content="{TemplateBinding SelectionBoxItem}"
                        ContentTemplate="{TemplateBinding SelectionBoxItemTemplate}"
                        ContentTemplateSelector="{TemplateBinding ItemTemplateSelector}"
                        HorizontalAlignment="Left" IsHitTestVisible="False" x:Name="ContentSite"
                        VerticalAlignment="Center" />

                    <TextBox Style="{x:Null}" x:Name="PART_EditableTextBox" Margin="3,3,23,3" Background="Transparent"
                        Focusable="True" HorizontalAlignment="Left" IsReadOnly="{TemplateBinding IsReadOnly}"
                        Template="{StaticResource ComboBoxTextBox}" VerticalAlignment="Center" Visibility="Hidden" />

                    <Popup AllowsTransparency="True" Focusable="False" IsOpen="{TemplateBinding IsDropDownOpen}" x:Name="Popup" Placement="Bottom" PopupAnimation="Fade">
                        <Grid MaxHeight="{TemplateBinding MaxDropDownHeight}" MinWidth="{TemplateBinding ActualWidth}" x:Name="DropDown" SnapsToDevicePixels="True">
                            <Border x:Name="DropDownBorder" Background="White" BorderBrush="{StaticResource BorderDarkMainBrush}" BorderThickness="1" CornerRadius="0" />
                            <ScrollViewer Margin="2" SnapsToDevicePixels="True">
                                <StackPanel KeyboardNavigation.DirectionalNavigation="Contained" IsItemsHost="True" TextBlock.Foreground="Black" />
                            </ScrollViewer>
                        </Grid>
                    </Popup>
                </Grid>
                <ControlTemplate.Triggers>
                    <Trigger Property="HasItems" Value="false">
                        <Setter Property="MinHeight" TargetName="DropDownBorder" Value="95" />
                    </Trigger>
                    <Trigger Property="IsGrouping" Value="true">
                        <Setter Property="ScrollViewer.CanContentScroll" Value="false" />
                    </Trigger>
                    <Trigger Property="IsEditable" Value="true">
                        <Setter Property="IsTabStop" Value="false" />
                        <Setter Property="Visibility" TargetName="PART_EditableTextBox" Value="Visible" />
                        <Setter Property="Visibility" TargetName="ContentSite" Value="Hidden" />
                    </Trigger>
                </ControlTemplate.Triggers>
            </ControlTemplate>
        </Setter.Value>
    </Setter>
    <Style.Triggers>
    </Style.Triggers>
</Style>

注意在切换按钮样式内的DataTrigger，它连接到模板化父级的IsKeyboardFocusWithin属性而不是IsFocused属性，因为如果您在此样式中设置ComboBox.IsEditable为True，则后者将无法生效。

<DataTrigger Binding="{Binding IsKeyboardFocusWithin, RelativeSource={RelativeSource Mode=TemplatedParent}, Mode=OneWay}" Value="True">
    <Setter Property="Background" TargetName="Border" Value="{DynamicResource MainColorLight}" />
    <Setter Property="BorderBrush" TargetName="Border" Value="{DynamicResource MainColorLight}" />
    <Setter Property="BorderBrush" TargetName="Border2" Value="{DynamicResource MainColorLight}" />
    <Setter Property="Fill" TargetName="Arrow" Value="White" />
</DataTrigger >

- Mohammed A. Fadil

Answer 2

这个问题没有优雅的解决方案。最好的方法是覆盖整个ComboBox的样式，以便您可以更改它为ToggleButton设置的样式。

您可以使用Blend获取样式，但这可能不是最简单的方法。如果您已经安装了Blend，请转到“[程序文件或Blend安装位置]\SystemThemes\WPF\areo.normalcolor.xaml”。

- Steven