如何在列表框中获得垂直滚动条？

在下面的示例中，我有一个包含几十个字体名称的 ListBox。

我本以为它会自动有一个垂直滚动条，这样你就可以选择任何字体，而不仅仅是列表中的第一个，但它没有。

So I added a "ScrollViewer" and that puts a "scrollbar area" on the right but there is no scrollbar in the scrollbar area so that you can scroll (!).

为什么一个滚动条不是自动的，我如何强制它有一个滚动条？

<StackPanel Name="stack1">
<Grid>
<Grid.RowDefinitions>
<RowDefinition Height="2*"></RowDefinition>
<RowDefinition Height="*"></RowDefinition>
</Grid.RowDefinitions>
<ScrollViewer>
<ListBox Grid.Row="0" Name="lstFonts" Margin="3"  ItemsSource="{x:Static Fonts.SystemFontFamilies}"/>
</ScrollViewer>
</Grid>
</StackPanel>
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最佳答案

The problem with your solution is you're putting a scrollbar around a ListBox where you probably want to put it inside the ListBox.

If you want to force a scrollbar in your ListBox, use the ScrollBar.VerticalScrollBarVisibility attached property.

<ListBox
ItemsSource="{Binding}"
ScrollViewer.VerticalScrollBarVisibility="Visible">
</ListBox>

Setting this value to Auto will popup the scrollbar on an as needed basis.

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I added a "Height" to my ListBox and it added the scrollbar nicely.

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Scroll Bar is added to the List box automatically unless its visibility is set to Hidden. Whenever the size of List Items exceeds the one, which can be shown inside a list box vertical or horizontal list box can be seen during the run time.

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ListBox already contains ScrollViewer. By default the ScrollBar will show up when there is more content than space. But some containers resize themselves to accommodate their contents (e.g. StackPanel), so there is never "more content than space". In such cases, the ListBox is always given as much space as is needed for the content.

In order to calculate the condition of having more content than space, the size should be known. Make sure your ListBox has a constrained size, either by setting the size explicitly on the ListBox element itself, or from the host panel.

In case the host panel is vertical StackPanel and you want VerticalScrollBar you must set the Height on ListBox itself. For other types of containers, e.g. Grid, the ListBox can be constrained by the container. For example, you can change your original code to look like this:

<Grid Name="grid1">
<Grid>
<Grid.RowDefinitions>
<RowDefinition Height="2*"></RowDefinition>
<RowDefinition Height="*"></RowDefinition>
</Grid.RowDefinitions>
<ListBox Grid.Row="0" Name="lstFonts" Margin="3"
ItemsSource="{x:Static Fonts.SystemFontFamilies}"/>
</Grid>
</Grid>

Note that it is not just the immediate container that is important. In your example, the immediate container is a Grid, but because that Grid is contained by a StackPanel, the outer StackPanel is expanded to accommodate its immediate child Grid, such that that child can expand to accommodate its child (the ListBox).

If you constrain the height at any point — by setting the height of the ListBox, by setting the height of the inner Grid, or simply by making the outer container a Grid — then a vertical scroll bar will appear automatically any time there are too many list items to fit in the control.

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In my case the number of items in the ListBox is dynamic so I didn't want to use the Height property. I used MaxHeight instead and it works nicely. The scrollbar appears when it fills the space I've allocated for it.

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I was having the same problem, I had a ComboBox followed by a ListBox in a StackPanel and the scroll bar for the ListBox was not showing up. I solved this by putting the two in a DockPanel instead. I set the ComboBox DockPanel.Dock="Top" and let the ListBox fill the remaining space.

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XAML ListBox Scroller - Windows 10(UWP)

<Style TargetType="ListBox">
<Setter Property="ScrollViewer.HorizontalScrollBarVisibility" Value="Visible"/>
<Setter Property="ScrollViewer.VerticalScrollBarVisibility" Value="Visible"/>
</Style>


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