flowdocumentscrollviewer不会滚动

我想找到最可行的方法来展示 FlowDocument 在窗户里-只是 流程文档 . 我有:

<FlowDocumentScrollViewer x:Name="message" HorizontalScrollBarVisibility="Disabled" VerticalScrollBarVisibility="Visible">

然后在窗口的构造函数中,我将查看器的文档设置为从xaml加载的文档(代码中)。xaml包含:

<FlowDocument xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
          xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml" Background="{x:Null}"
          FontSize="12" FontFamily="Segoe UI"  PagePadding="2">
<BlockUIContainer>
    <BlockUIContainer.Resources>
        <Style TargetType="{x:Type TextBlock}">
            <Setter Property="TextWrapping" Value="Wrap"/>
        </Style>
    </BlockUIContainer.Resources>
    <StackPanel MaxWidth="200">
        <TextBlock Text="{Binding DefinedWord}" FontWeight="Bold"  />
        <ListBox ItemsSource="{Binding Definitions}"
                 Style="{StaticResource InvisibleListBox}" Margin="0"
                 ScrollViewer.HorizontalScrollBarVisibility="Disabled" 
                 ScrollViewer.VerticalScrollBarVisibility="Disabled" 
                 ScrollViewer.CanContentScroll="false">
...

不管我怎么努力, FlowDocumentScrollViewer 不滚动,我看不到文档的截断部分。这和 BlockUIContainer ,还是我遗漏了什么?