WPF项控件不会自动显示垂直滚动条

这是意图,

当项目添加到ItemsControl时，如果内容超过可用大小，我希望在ItemsControl中看到滚动。我打赌这是任何ItemsControl类型的默认行为

所以我生成了一个复制我意图的样本。建议我需要修理什么

<StackPanel>
        <StackPanel.Resources>
            <Style TargetType="{x:Type ItemsControl}">
                <Setter Property="Template">
                    <Setter.Value>
                        <ControlTemplate TargetType="{x:Type ItemsControl}">
                            <Border SnapsToDevicePixels="true" Background="{TemplateBinding Background}" BorderBrush="{TemplateBinding BorderBrush}" BorderThickness="{TemplateBinding BorderThickness}" Padding="{TemplateBinding Padding}">
                                <ScrollViewer VerticalScrollBarVisibility="Visible">
                                    <ItemsPresenter SnapsToDevicePixels="{TemplateBinding SnapsToDevicePixels}"/>
                                </ScrollViewer>
                            </Border>
                        </ControlTemplate>
                    </Setter.Value>
                </Setter>
            </Style>
        </StackPanel.Resources>
        <ToggleButton Name="SomeToggle" Content="Show/Hide"/>
        <Button Content="Add Item" Click="ButtonBase_OnClick" />
        <TextBlock Text="Hide/Show on toggle" >
            <TextBlock.Style>
                <Style TargetType="TextBlock">
                    <Setter Property="Visibility" Value="Collapsed"/>
                    <Style.Triggers>
                        <DataTrigger Binding="{Binding Path=IsChecked,ElementName=SomeToggle}" Value="True">
                            <Setter Property="Visibility" Value="Visible" />
                        </DataTrigger>
                    </Style.Triggers>
                </Style>
            </TextBlock.Style>
        </TextBlock>

    <ItemsControl Name="ItemsCollection" >
    </ItemsControl>

</StackPanel>

和代码隐藏：

private int counter = 0;
    private ObservableCollection<string> coll; 
    public MainWindow()
    {
        coll= new ObservableCollection<string>();
        //ItemsCollection.ItemsSource = coll;
        InitializeComponent();
    }

    private void ButtonBase_OnClick(object sender, RoutedEventArgs e)
    {
        ItemsCollection.Items.Add(string.Format("Item {0}", ++counter));
    }

private int counter=0；
私人可观察收集公司；
公共主窗口（）
{
coll=新的可观察集合（）；
//ItemsCollection.ItemsSource=coll；
初始化组件（）；
}
private void按钮base_OnClick（对象发送方，RoutedEventTarget e）
{
ItemsCollection.Items.Add（string.Format（“Item{0}，++计数器））；
}

这基本上是每次您将

滚动查看器

放入

堆栈面板

时都会发生的，这是由于

堆栈面板

的工作方式造成的，请看一看

您可以将

堆栈面板

放在

滚动视图

中，或者最好将主面板更改为

网格

   <Grid >
    <Grid.RowDefinitions>
        <RowDefinition Height="Auto"/>
        <RowDefinition Height="Auto"/>
        <RowDefinition Height="Auto"/>            
        <RowDefinition Height="*"/>
    </Grid.RowDefinitions>
    <Grid.Resources>
        <Style TargetType="{x:Type ItemsControl}">
            <Setter Property="Template">
                <Setter.Value>
                    <ControlTemplate TargetType="{x:Type ItemsControl}">
                        <Border SnapsToDevicePixels="true" Background="{TemplateBinding Background}" BorderBrush="{TemplateBinding BorderBrush}" BorderThickness="{TemplateBinding BorderThickness}" Padding="{TemplateBinding Padding}">
                            <ScrollViewer VerticalScrollBarVisibility="Visible">
                                <ItemsPresenter SnapsToDevicePixels="{TemplateBinding SnapsToDevicePixels}"/>
                            </ScrollViewer>
                        </Border>
                    </ControlTemplate>
                </Setter.Value>
            </Setter>
        </Style>
    </Grid.Resources>
    <ToggleButton Name="SomeToggle" Content="Show/Hide" Grid.Row="0"/>
    <Button Content="Add Item" Click="ButtonBase_OnClick" Grid.Row="1"/>
    <TextBlock Text="Hide/Show on toggle" Grid.Row="2">
        <TextBlock.Style>
            <Style TargetType="TextBlock">
                <Setter Property="Visibility" Value="Collapsed"/>
                <Style.Triggers>
                    <DataTrigger Binding="{Binding Path=IsChecked,ElementName=SomeToggle}" Value="True">
                        <Setter Property="Visibility" Value="Visible" />
                    </DataTrigger>
                </Style.Triggers>
            </Style>
        </TextBlock.Style>
    </TextBlock>
    <ItemsControl Name="ItemsCollection" Grid.Row="3">
    </ItemsControl>
</Grid>

---

这基本上是每次您将

滚动查看器

放入

堆栈面板

时都会发生的，这是由于

堆栈面板

的工作方式造成的，请看一看

您可以将

堆栈面板

放在

滚动视图

中，或者最好将主面板更改为

网格

   <Grid >
    <Grid.RowDefinitions>
        <RowDefinition Height="Auto"/>
        <RowDefinition Height="Auto"/>
        <RowDefinition Height="Auto"/>            
        <RowDefinition Height="*"/>
    </Grid.RowDefinitions>
    <Grid.Resources>
        <Style TargetType="{x:Type ItemsControl}">
            <Setter Property="Template">
                <Setter.Value>
                    <ControlTemplate TargetType="{x:Type ItemsControl}">
                        <Border SnapsToDevicePixels="true" Background="{TemplateBinding Background}" BorderBrush="{TemplateBinding BorderBrush}" BorderThickness="{TemplateBinding BorderThickness}" Padding="{TemplateBinding Padding}">
                            <ScrollViewer VerticalScrollBarVisibility="Visible">
                                <ItemsPresenter SnapsToDevicePixels="{TemplateBinding SnapsToDevicePixels}"/>
                            </ScrollViewer>
                        </Border>
                    </ControlTemplate>
                </Setter.Value>
            </Setter>
        </Style>
    </Grid.Resources>
    <ToggleButton Name="SomeToggle" Content="Show/Hide" Grid.Row="0"/>
    <Button Content="Add Item" Click="ButtonBase_OnClick" Grid.Row="1"/>
    <TextBlock Text="Hide/Show on toggle" Grid.Row="2">
        <TextBlock.Style>
            <Style TargetType="TextBlock">
                <Setter Property="Visibility" Value="Collapsed"/>
                <Style.Triggers>
                    <DataTrigger Binding="{Binding Path=IsChecked,ElementName=SomeToggle}" Value="True">
                        <Setter Property="Visibility" Value="Visible" />
                    </DataTrigger>
                </Style.Triggers>
            </Style>
        </TextBlock.Style>
    </TextBlock>
    <ItemsControl Name="ItemsCollection" Grid.Row="3">
    </ItemsControl>
</Grid>

---

无法看到滚动条的唯一原因是您没有设置Items控件的高度。

每次添加项目时，它的高度将展开，StackPanel将随之展开以包含内容。您已经为ItemsControl模板定义了ScrollViewer，您还必须决定它在什么时候工作

<ItemsControl Name="ItemsCollection" Height="200" >
</ItemsControl>

然后，将其包含在StackPanel或任何其他控件中也无关紧要

初始滚动条

添加项目后

带有代码

而且仅仅从理解的角度来看。这也将起作用：

删除项目控件的样式并设置滚动查看器的高度。

处理所有元素的高度：

<ScrollViewer MaxHeight="{Binding RelativeSource={RelativeSource AncestorType={x:Type Border}},Path=ActualHeight,Mode=OneWay}">
    <StackPanel>
    <StackPanel.Resources>
        <Style TargetType="{x:Type ItemsControl}">
            <Setter Property="Template">
                <Setter.Value>
                    <ControlTemplate TargetType="{x:Type ItemsControl}">
                        <Border SnapsToDevicePixels="true" Background="{TemplateBinding Background}" BorderBrush="{TemplateBinding BorderBrush}" BorderThickness="{TemplateBinding BorderThickness}" Padding="{TemplateBinding Padding}">
                            <ScrollViewer VerticalScrollBarVisibility="Visible">
                                <ItemsPresenter SnapsToDevicePixels="{TemplateBinding SnapsToDevicePixels}"/>
                            </ScrollViewer>
                        </Border>
                    </ControlTemplate>
                </Setter.Value>
            </Setter>
        </Style>
    </StackPanel.Resources>
    <ToggleButton Name="SomeToggle" Content="Show/Hide"/>
    <Button Content="Add Item" Click="Button_Click" />
    <TextBlock Text="Hide/Show on toggle" >
        <TextBlock.Style>
            <Style TargetType="TextBlock">
                <Setter Property="Visibility" Value="Collapsed"/>
                <Style.Triggers>
                    <DataTrigger Binding="{Binding Path=IsChecked,ElementName=SomeToggle}" Value="True">
                        <Setter Property="Visibility" Value="Visible" />
                    </DataTrigger>
                </Style.Triggers>
            </Style>
        </TextBlock.Style>
    </TextBlock>

    <ItemsControl Name="ItemsCollection" ItemsSource="{Binding list}" 
                  MaxHeight="{Binding RelativeSource={RelativeSource AncestorType={x:Type Border}},Path=ActualHeight,Mode=OneWay}">
    </ItemsControl>

</StackPanel>
</ScrollViewer>

---

无法看到滚动条的唯一原因是您没有设置Items控件的高度。

每次添加项目时，它的高度将展开，StackPanel将随之展开以包含内容。您已经为ItemsControl模板定义了ScrollViewer，您还必须决定它在什么时候工作

<ItemsControl Name="ItemsCollection" Height="200" >
</ItemsControl>

然后，将其包含在StackPanel或任何其他控件中也无关紧要

初始滚动条

添加项目后

带有代码

而且仅仅从理解的角度来看。这也将起作用：

删除项目控件的样式并设置滚动查看器的高度。

处理所有元素的高度：

<ScrollViewer MaxHeight="{Binding RelativeSource={RelativeSource AncestorType={x:Type Border}},Path=ActualHeight,Mode=OneWay}">
    <StackPanel>
    <StackPanel.Resources>
        <Style TargetType="{x:Type ItemsControl}">
            <Setter Property="Template">
                <Setter.Value>
                    <ControlTemplate TargetType="{x:Type ItemsControl}">
                        <Border SnapsToDevicePixels="true" Background="{TemplateBinding Background}" BorderBrush="{TemplateBinding BorderBrush}" BorderThickness="{TemplateBinding BorderThickness}" Padding="{TemplateBinding Padding}">
                            <ScrollViewer VerticalScrollBarVisibility="Visible">
                                <ItemsPresenter SnapsToDevicePixels="{TemplateBinding SnapsToDevicePixels}"/>
                            </ScrollViewer>
                        </Border>
                    </ControlTemplate>
                </Setter.Value>
            </Setter>
        </Style>
    </StackPanel.Resources>
    <ToggleButton Name="SomeToggle" Content="Show/Hide"/>
    <Button Content="Add Item" Click="Button_Click" />
    <TextBlock Text="Hide/Show on toggle" >
        <TextBlock.Style>
            <Style TargetType="TextBlock">
                <Setter Property="Visibility" Value="Collapsed"/>
                <Style.Triggers>
                    <DataTrigger Binding="{Binding Path=IsChecked,ElementName=SomeToggle}" Value="True">
                        <Setter Property="Visibility" Value="Visible" />
                    </DataTrigger>
                </Style.Triggers>
            </Style>
        </TextBlock.Style>
    </TextBlock>

    <ItemsControl Name="ItemsCollection" ItemsSource="{Binding list}" 
                  MaxHeight="{Binding RelativeSource={RelativeSource AncestorType={x:Type Border}},Path=ActualHeight,Mode=OneWay}">
    </ItemsControl>

</StackPanel>
</ScrollViewer>

这样不行。只有当它工作时，它才能被封闭在一个网格中。@user841612为什么不呢？请查看带有屏幕截图的更新答案。场景u发布：当窗口大小很小，仅适合内容时，我显示或