WPF - Group分组对ListBox等列表样式的约束 - 周金根

WPF - Group分组对ListBox等列表样式的约束

　　在做WPF主题支持时，出现一个分组引起的莫名错误，可是折腾了我一番。在没有使用样式时，列表分组很正常，使用了别人写的ListBox列表样式后，发现GroupItem分组区没有内容，是空的，本篇把这一问题的解决过程给大家说一下，做主题时可以注意分组对列表样式的限制了。

ListBox增加分组

　　WPF为ItemsControl提供很多的样式扩展,要想实现列表分组也很简单,只需要做以下几步就可以了:

给列表控件增加分组样式

代码

    <Style x:Key="GroupContainerStyle" TargetType="{x:Type GroupItem}">
        <Setter Property="Template">
            <Setter.Value>
                <ControlTemplate TargetType="{x:Type GroupItem}">
                    <Expander IsExpanded="True">
                        <Expander.Header>
                            <Grid>
                                <Grid.ColumnDefinitions>
                                    <ColumnDefinition Width="Auto"/>
                                    <ColumnDefinition />
                                </Grid.ColumnDefinitions>
                                <Grid.RowDefinitions>
                                    <RowDefinition/>
                                </Grid.RowDefinitions>
                                <StackPanel Orientation="Horizontal"  Margin="0,0,10,0">
                                    <TextBlock Text="{Binding Path=Name}" FontWeight="Bold" />
                                    <TextBlock FontWeight="Bold" Text="{Binding Path=ItemCount, StringFormat=(共{0}条)}"/>
                                </StackPanel>
                                <Line Grid.Column="1" SnapsToDevicePixels="true"  X1="0" X2="1" Stretch="Fill"  StrokeThickness="1"/>
                            </Grid>
                        </Expander.Header>
                        <ItemsPresenter />
                    </Expander>
                </ControlTemplate>
            </Setter.Value>
        </Setter>
    </Style>

GroupStyle gs = new GroupStyle();
gs.ContainerStyle = Application.Current.TryFindResource("GroupContainerStyle") as Style;
lbModule.GroupStyle.Add(gs);

给数据增加分组

代码

    <UserControl.Resources>
        <CollectionViewSource Source="{x:Static oea:ApplicationModel.DefaultBusinessObjectInfos}" x:Key="cvs">
            <CollectionViewSource.GroupDescriptions>
                <PropertyGroupDescription PropertyName="Catalog" />
            </CollectionViewSource.GroupDescriptions>
        </CollectionViewSource>
    </UserControl.Resources>

使用ListBox样式后

　　用了别人的一个ListBox样式文件,样式如下:

代码

    <Style TargetType="{x:Type ListBox}">
        <Setter Property="Background" Value="{DynamicResource {x:Static SystemColors.WindowBrushKey}}" />
        <Setter Property="BorderBrush">
            <Setter.Value>
                <LinearGradientBrush EndPoint="0.5,1" StartPoint="0.5,0">
                    <GradientStop Color="{DynamicResource PrimaryColor}" Offset="0" />
                    <GradientStop Color="{DynamicResource SecondaryColor}" Offset="1" />
                </LinearGradientBrush>
            </Setter.Value>
        </Setter>
        <Setter Property="BorderThickness" Value="1" />
        <Setter Property="Foreground" Value="{DynamicResource {x:Static SystemColors.ControlTextBrushKey}}" />
        <Setter Property="ScrollViewer.HorizontalScrollBarVisibility" Value="Auto" />
        <Setter Property="ScrollViewer.VerticalScrollBarVisibility" Value="Auto" />
        <Setter Property="ScrollViewer.CanContentScroll" Value="true" />
        <Setter Property="VerticalContentAlignment" Value="Center" />
        <Setter Property="Template">
            <Setter.Value>
                <ControlTemplate TargetType="{x:Type ListBox}">
                    <Border x:Name="Bd" SnapsToDevicePixels="true" Background="{TemplateBinding Background}" BorderBrush="{TemplateBinding BorderBrush}" BorderThickness="{TemplateBinding BorderThickness}" Padding="1" CornerRadius="4,4,4,4">
                        <Grid>
                            <ScrollViewer Padding="{TemplateBinding Padding}" Focusable="false" x:Name="scrollViewer">
                                <StackPanel Margin="2" IsItemsHost="true"/>

                                <!--<ItemsPresenter SnapsToDevicePixels="{TemplateBinding SnapsToDevicePixels}" />-->
                            </ScrollViewer>
                            <Border CornerRadius="4,4,4,4" Visibility="Collapsed" x:Name="border" Margin="-2,-2,-2,-2">
                                <Border.Background>
                                    <SolidColorBrush Color="{DynamicResource DisabledColor}"/>
                                </Border.Background>
                            </Border>
                        </Grid>
                    </Border>
                    <ControlTemplate.Triggers>
                        <Trigger Property="IsEnabled" Value="false">
                            <Setter Property="Visibility" TargetName="border" Value="Visible"/>
                        </Trigger>
                        <Trigger Property="IsGrouping" Value="true">
                            <Setter Property="ScrollViewer.CanContentScroll" Value="false" />
                        </Trigger>
                    </ControlTemplate.Triggers>
                </ControlTemplate>
            </Setter.Value>
        </Setter>
    </Style>

用完之后运行发现界面不对,点击分组标题后列表内容没有显示???

查找原因

　　自己想了一下，原因不明，无奈自己对WPF实现只了解一点，于是网上搜索ItemsPresenter empty，找到第一条网页ItemsPresenter + ItemsPanelTemplate vs Panel marked with IsItemsHost，进去后发现他提出了一个问题，就是在分组时如何取ItemsPresenter，发现Reflector工具可以看到以下代码：

代码internal static ItemsPresenter FromGroupItem(GroupItem groupItem)
{
    if (groupItem == null)
    {
        return null;
    }
    Visual parent = VisualTreeHelper.GetParent(groupItem) as Visual;
    if (parent == null)
    {
        return null;
    }
    return (VisualTreeHelper.GetParent(parent) as ItemsPresenter);
}