Question

我在wpf中有ListView，用于显示字段列表;基于属性值，某些字段可以在运行时折叠。它的工作正常，但ListVIew不会折叠为在运行时折叠的ListViewItem保留的空间。

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我能够在Snoop中看到额外的ListViewItems（可见性为折叠），ListView也会向上移动项目，但它不会调整其高度来移除空白区域！

我可以肯定地说，由于将ItemsPanel更改为StackPanel解决了问题，因此VirtualizedStackPanel发生了这种情况。以下是相关的ListView XAML：

<ListView
    x:Class="Wizards.FieldBinderModelListView"
    xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
    xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
    Margin="0"
    VerticalAlignment="Top"
    HorizontalContentAlignment="Stretch"
    VerticalContentAlignment="Top"
    Background="White"
    BorderThickness="0"
    Grid.IsSharedSizeScope="True"
    KeyboardNavigation.DirectionalNavigation="Continue"
    Padding="1"
    ScrollViewer.HorizontalScrollBarVisibility="Hidden"
    ScrollViewer.VerticalScrollBarVisibility="Hidden"
    SelectionChanged="ListViewSelectionChanged"
    SelectionMode="Single">
    <ListView.ItemsPanel>
       <ItemsPanelTemplate>
        <!--Works fine with StackPanel but not with VirtualizingStackPanel
          Explicitly added this PanelTemplate to show that it works with            
          StackPanel;ListView uses VirtualizingStackPanel as default panel 
          and causes same problem-->              
        <!--<StackPanel Orientation="Vertical" VerticalAlignment="Top"/>-->
          <VirtualizingStackPanel Orientation="Vertical" 
               VerticalAlignment="Top"/>
       </ItemsPanelTemplate>
    </ListView.ItemsPanel>
    <ListView.ItemContainerStyle>
      <Style TargetType="{x:Type ListViewItem}">
        <Style.Triggers>
            <Trigger Property="IsSelected" Value="True">
                <Setter Property="Foreground" Value="Black" />
            </Trigger>
            <DataTrigger Binding="{Binding Status}"
                         Value="{x:Static local:Status.NotExisting}">
                <!--Hide the fields which are in NotExisting state; 
                  Need a trigger here as Status can be different -->
                <Setter Property="Visibility" Value="Collapsed" />
            </DataTrigger>
        </Style.Triggers>
      </Style>
  </ListView.ItemContainerStyle>
  <ListView.ItemTemplate>
    <DataTemplate DataType="{x:Type View:FieldViewModel}">
       <local:FieldEditor
          Margin="0,2,0,0"
          HorizontalAlignment="Stretch"
          VerticalAlignment="Top"
          HorizontalContentAlignment="Stretch"
          VerticalContentAlignment="Top"
          Padding="0">
          <!--<local:FieldEditor.Style>
              <Style TargetType="{x:Type local:FieldEditor}">
                <Style.Triggers>
                  <DataTrigger
                    Binding="{Binding Status}"
                    Value="{x:Static local:Status.NotExisting}">
                      <Setter Property="Visibility" Value="Collapsed" />
                  </DataTrigger>
                </Style.Triggers>
              </Style>
            </local:FieldEditor.Style>-->
        </local:FieldEditor>
    </DataTemplate>
  </ListView.ItemTemplate>
</ListView>

这是VirtualizingStackPanel中的错误吗？其他人遇到过类似的问题？任何解决方法？

更新

在连接时向MS报告此错误 - https://connect.microsoft.com/VisualStudio/feedback/details/734113/virtualizingstackpanel-not-handling-collapsed-items-correctly

Answer 1

我设法重现了你的问题。它当然看起来像VirtualizingStackPanel中的一个错误。解决方法是将隐藏项目的高度设置为零而不是折叠它们：

<DataTrigger Binding="{Binding Status}" Value="False">
    <Setter Property="Height" Value="0" />
    <Setter Property="IsEnabled" Value="False"/>
    <!--<Setter Property="Visibility" Value="Collapsed" />-->
</DataTrigger>

Answer 2

对于其他寻求继续依赖可见性但又要删除多余间距的人，我通过删除ListBoxItem样式的填充来解决了该问题：

<ListBox.ItemContainerStyle>
    <Style TargetType="ListBoxItem">
        <Setter Property="Padding" Value="0"/>
    </Style>
</ListBox.ItemContainerStyle>

似乎ListBoxItem的默认填充为3。

VirtualizingStackPanel未正确处理折叠的项目

2 个答案: