WPF 样式/模板仅应用于最后添加的元素

本文关键字：最后 添加 元素 应用于 样式 WPF | 更新日期: 2023-09-27 17:55:39

我有一个简单的控件，从ContentControl派生出以下代码：

public class HeaderFooterControl : ContentControl
{
    static HeaderFooterControl()
    {
        DefaultStyleKeyProperty.OverrideMetadata(typeof(HeaderFooterControl), new FrameworkPropertyMetadata(typeof(HeaderFooterControl)));
    }
    public object Header
    {
        get { return (object)GetValue(HeaderProperty); }
        set { SetValue(HeaderProperty, value); }
    }
    // Using a DependencyProperty as the backing store for Header.  This enables animation, styling, binding, etc...
    public static readonly DependencyProperty HeaderProperty =
        DependencyProperty.Register("Header", typeof(object), typeof(HeaderFooterControl));
    public object Footer
    {
        get { return (object)GetValue(FooterProperty); }
        set { SetValue(FooterProperty, value); }
    }
    // Using a DependencyProperty as the backing store for Footer.  This enables animation, styling, binding, etc...
    public static readonly DependencyProperty FooterProperty =
        DependencyProperty.Register("Footer", typeof(object), typeof(HeaderFooterControl));

    public string HeaderText
    {
        get { return (string)GetValue(HeaderTextProperty); }
        set { SetValue(HeaderTextProperty, value); }
    }
    // Using a DependencyProperty as the backing store for HeaderText.  This enables animation, styling, binding, etc...
    public static readonly DependencyProperty HeaderTextProperty =
        DependencyProperty.Register("HeaderText", typeof(string), typeof(HeaderFooterControl));

    public string FooterText
    {
        get { return (string)GetValue(FooterTextProperty); }
        set { SetValue(FooterTextProperty, value); }
    }
    // Using a DependencyProperty as the backing store for FooterText.  This enables animation, styling, binding, etc...
    public static readonly DependencyProperty FooterTextProperty =
        DependencyProperty.Register("FooterText", typeof(string), typeof(HeaderFooterControl));

}

它具有可自定义的页眉和页脚属性，因此用户可以在其中附加任何控件。

此应用程序中唯一定义的窗口如下所示：

<Window x:Class="CustomControlTest.MainWindow"
        xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
        xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
        xmlns:local="clr-namespace:CustomControlTest"
        Title="MainWindow" Height="350" Width="525">
    <Window.Resources>
        <Style TargetType="{x:Type local:HeaderFooterControl}" x:Key="DefaultHeaderFooterStyle">
            <Setter Property="Template">
                <Setter.Value>
                    <ControlTemplate TargetType="{x:Type local:HeaderFooterControl}">
                        <Grid Background="Pink">
                            <Grid.RowDefinitions>
                                <RowDefinition/>
                                <RowDefinition/>
                                <RowDefinition/>
                            </Grid.RowDefinitions>
                            <ContentPresenter Content="{Binding Header, RelativeSource={RelativeSource TemplatedParent}, Mode=TwoWay}"/>
                            <ContentPresenter Grid.Row="1"/>
                            <ContentPresenter Content="{Binding Footer, RelativeSource={RelativeSource TemplatedParent}, Mode=TwoWay}" Grid.Row="2"/>
                        </Grid>
                    </ControlTemplate>
                </Setter.Value>
            </Setter>
        </Style>
        <Style TargetType="{x:Type local:HeaderFooterControl}" BasedOn="{StaticResource DefaultHeaderFooterStyle}">
            <Style.Setters>
                <Setter Property="Header">
                    <Setter.Value>
                        <TextBlock Text="{Binding HeaderText, RelativeSource={RelativeSource FindAncestor, AncestorType={x:Type local:HeaderFooterControl}}}" Background="Yellow" HorizontalAlignment="Stretch" VerticalAlignment="Center"/>
                    </Setter.Value>
                </Setter>
                <Setter Property="Footer">
                    <Setter.Value>
                        <TextBlock Text="{Binding FooterText, RelativeSource={RelativeSource FindAncestor, AncestorType={x:Type local:HeaderFooterControl}}}" Background="Green" HorizontalAlignment="Stretch" VerticalAlignment="Center"/>
                    </Setter.Value>
                </Setter>
            </Style.Setters>
        </Style>
    </Window.Resources>
    <Grid>
        <Grid.RowDefinitions>
            <RowDefinition/>
            <RowDefinition/>
            <RowDefinition/>
        </Grid.RowDefinitions>
        <local:HeaderFooterControl HeaderText="H1" FooterText="F1" Margin="10"/>
        <local:HeaderFooterControl HeaderText="H2" FooterText="F2" Grid.Row="1" Margin="10"/>
        <local:HeaderFooterControl HeaderText="H3" FooterText="F3" Grid.Row="2" Margin="10"/>
    </Grid>
</Window>

此窗口的资源为我的自定义控件定义了 2 种样式。自定义控件显示页眉、主要内容和页脚。默认情况下，页眉/页脚TextBlock，其Text属性绑定到HeaderText或FooterText HeaderFooterControl的属性。问题是只有最后添加的HeaderFooterControl显示任何内容。为什么会这样？

WPF 样式/模板仅应用于最后添加的元素

到目前为止，我找到的唯一解决方案是将页眉和页脚部分的内容移动到资源中，然后使用StaticResource扩展从 xaml 代码中引用这些资源。所有内容都是UIElement的，因此每个实例都应该设置x:Shared="False"属性，以便每次在可视化树中需要时都会创建它。另请查看此答案，它暗示了 https://stackoverflow.com/a/8702180/371967 描述的相同行为

<Window x:Class="CustomControlTest.MainWindow"
        xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
        xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
        xmlns:local="clr-namespace:CustomControlTest"
        Title="MainWindow" Height="350" Width="525">
    <Window.Resources>
        <Style TargetType="{x:Type local:HeaderFooterControl}" x:Key="DefaultHeaderFooterStyle">
            <Setter Property="Template">
                <Setter.Value>
                    <ControlTemplate TargetType="{x:Type local:HeaderFooterControl}">
                        <Grid Background="Pink">
                            <Grid.RowDefinitions>
                                <RowDefinition/>
                                <RowDefinition/>
                                <RowDefinition/>
                            </Grid.RowDefinitions>
                            <ContentPresenter Content="{Binding Header, RelativeSource={RelativeSource TemplatedParent}, Mode=TwoWay}"/>
                            <ContentPresenter Grid.Row="1"/>
                            <ContentPresenter Content="{Binding Footer, RelativeSource={RelativeSource TemplatedParent}, Mode=TwoWay}" Grid.Row="2"/>
                        </Grid>
                    </ControlTemplate>
                </Setter.Value>
            </Setter>
        </Style>
        <TextBlock x:Key="DefaultHeaderContent" Text="{Binding HeaderText, RelativeSource={RelativeSource FindAncestor, AncestorType={x:Type local:HeaderFooterControl}}}" Background="Yellow" HorizontalAlignment="Stretch" VerticalAlignment="Center" x:Shared="False"/>
        <TextBlock x:Key="DefaultFooterContent" Text="{Binding FooterText, RelativeSource={RelativeSource FindAncestor, AncestorType={x:Type local:HeaderFooterControl}}}" Background="Green" HorizontalAlignment="Stretch" VerticalAlignment="Center" x:Shared="False"/>
        <Style TargetType="{x:Type local:HeaderFooterControl}" BasedOn="{StaticResource DefaultHeaderFooterStyle}">
            <Style.Setters>
                <Setter Property="Header" Value="{StaticResource DefaultHeaderContent}"/>
                <Setter Property="Footer" Value="{StaticResource DefaultFooterContent}"/>
            </Style.Setters>
        </Style>
    </Window.Resources>
    <Grid>
        <Grid.RowDefinitions>
            <RowDefinition/>
            <RowDefinition/>
            <RowDefinition/>
        </Grid.RowDefinitions>
        <local:HeaderFooterControl HeaderText="H1" FooterText="F1" Margin="10"/>
        <local:HeaderFooterControl HeaderText="H2" FooterText="F2" Grid.Row="1" Margin="10"/>
        <local:HeaderFooterControl HeaderText="H3" FooterText="F3" Grid.Row="2" Margin="10"/>
    </Grid>
</Window>
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