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我有一个 WPF UserControl（在一个内部ElementHost），其中一个ScrollViewer包含一个ItemsControl. HorizontalScrollbarVisibility设置为，因此Auto如果不需要滚动，则会ScrollBar隐藏 。

我的要求是，如果ScrollBar显示/隐藏，ElementHost确实会相应地调整它的高度。为了实现这一点，我正在听SizeChanged事件，我得到了DesiredSize中ScrollViewer的EventHandler，然后我传递DesiredSize.Height给ElementHost.

  1. 可见的 2. 隐 3.不正确的，重叠的

一种方法，这是可行的：在ScrollBar可见的情况下（情况 1），我放大我的窗口，直到所有项目ItemsControl都可见，ScrollBar消失，ElementHost调整到降低的高度（情况 2）。实际上在隐藏DesiredSize的那一刻变小了。ScrollBar

但是，另一种方式不起作用：在ScrollBar不可见的情况下（情况 2），我减小了窗口大小，直到 aScrollBar是必要的并出现。DesiredSize保持不变，并且ElementHost不调整（情况3）。

有任何想法吗？

这是 的 xaml Scrollviewer，有一些 MVVM 的东西，但不要挂断这个，关键是，为什么出现DesiredSize时不增加ScrollBar？为什么只是缩水？

<ScrollViewer HorizontalScrollBarVisibility="Auto" VerticalScrollBarVisibility="Hidden" >
    <i:Interaction.Behaviors>
        <beh:HeightChangedBehavior HeightChangedCommand="{Binding HeightChangedCommand}" />
    </i:Interaction.Behaviors>
    <ItemsControl ItemsSource="{Binding TabHeaders}" >
        <ItemsControl.ItemsPanel>
            <ItemsPanelTemplate>
                <StackPanel IsItemsHost="True" Orientation="Horizontal"/>
            </ItemsPanelTemplate>
        </ItemsControl.ItemsPanel>
        <ItemsControl.ItemTemplate>
            <DataTemplate DataType="models:TabHeaderButtonModel">
                <RadioButton Content="{Binding Caption}" IsChecked="{Binding IsChecked, Mode=TwoWay}" GroupName="Tabs" 
                            Command="{Binding SelectionChangedCommand}" CommandParameter="{Binding}"
                            Style="{StaticResource TabHeaderToggleButtonStyle}">
                </RadioButton>
            </DataTemplate>
        </ItemsControl.ItemTemplate>
    </ItemsControl>
</ScrollViewer>

ScrollViewer 样式（基本上是默认的 WPF）：

<Style x:Key="ScrollViewerStyle1" TargetType="{x:Type ScrollViewer}">
    <Setter Property="Template" >
        <Setter.Value>
            <ControlTemplate TargetType="{x:Type ScrollViewer}">
                <Grid x:Name="Grid" Background="{TemplateBinding Background}">
                    <Grid.ColumnDefinitions>
                        <ColumnDefinition Width="*"/>
                        <ColumnDefinition Width="Auto"/>
                    </Grid.ColumnDefinitions>
                    <Grid.RowDefinitions>
                        <RowDefinition Height="*"/>
                        <RowDefinition Height="Auto"/>
                    </Grid.RowDefinitions>
                    <Rectangle x:Name="Corner" Grid.Column="1" Fill="{DynamicResource {x:Static SystemColors.ControlBrushKey}}" Grid.Row="1"/>
                    <ScrollContentPresenter x:Name="PART_ScrollContentPresenter" CanContentScroll="{TemplateBinding CanContentScroll}" CanHorizontallyScroll="False" CanVerticallyScroll="False" ContentTemplate="{TemplateBinding ContentTemplate}" Content="{TemplateBinding Content}" Grid.Column="0" Margin="{TemplateBinding Padding}" Grid.Row="0"/>
                    <ScrollBar x:Name="PART_VerticalScrollBar" AutomationProperties.AutomationId="VerticalScrollBar" Cursor="Arrow" Grid.Column="1" Maximum="{TemplateBinding ScrollableHeight}" Minimum="0" Grid.Row="0" Visibility="{TemplateBinding ComputedVerticalScrollBarVisibility}" Value="{Binding VerticalOffset, Mode=OneWay, RelativeSource={RelativeSource TemplatedParent}}" ViewportSize="{TemplateBinding ViewportHeight}"/>
                    <ScrollBar x:Name="PART_HorizontalScrollBar" AutomationProperties.AutomationId="HorizontalScrollBar" Cursor="Arrow" Grid.Column="0" Maximum="{TemplateBinding ScrollableWidth}" Minimum="0" Orientation="Horizontal" Grid.Row="1" Visibility="{TemplateBinding ComputedHorizontalScrollBarVisibility}" Value="{Binding HorizontalOffset, Mode=OneWay, RelativeSource={RelativeSource TemplatedParent}}" ViewportSize="{TemplateBinding ViewportWidth}" Style="{DynamicResource ScrollBarStyle1}"/>
                </Grid>
            </ControlTemplate>
        </Setter.Value>
    </Setter>
    <Style.Triggers>
        <Trigger Property="IsEnabled" Value="false">
            <Setter Property="Foreground" Value="White"/>
        </Trigger>
    </Style.Triggers>
</Style>
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1 回答 1

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我必须通过获取 ScrollViewer 的内容所需的高度并添加 ScrollBar 高度（如果可见）来计算所需的高度。

这对我来说仍然有点尴尬，所以如果你有更好的解决方案，我很乐意改变接受的答案。

public class HeightChangedBehavior : Behavior<ScrollViewer>
{
    public ICommand HeightChangedCommand { get { return (ICommand)GetValue(HeightChangedCommandProperty); } set { SetValue(HeightChangedCommandProperty, value); } }
    public static readonly DependencyProperty HeightChangedCommandProperty = DependencyProperty.Register("HeightChangedCommand", typeof(ICommand), typeof(HeightChangedBehavior), new PropertyMetadata(null));


    protected override void OnAttached()
    {
        this.AssociatedObject.ScrollChanged += AssociatedObject_ScrollChanged;
        base.OnAttached();
    }

    /// <summary>
    /// Calculates the desired height for the scrollviewer, as the sum of its content
    /// desired height and, if visible, the horizontal scrollbar height.
    /// </summary>
    void AssociatedObject_ScrollChanged(object sender, ScrollChangedEventArgs e)
    {
        ScrollViewer sv = (ScrollViewer)sender;

        // get content height
        double height = ((FrameworkElement)sv.Content).DesiredSize.Height;

        if (sv.ComputedHorizontalScrollBarVisibility == Visibility.Visible)
        {
            // add scrollbar height
            height += (double)sv.FindResource(SystemParameters.HorizontalScrollBarHeightKey); // template of scrollbar should use this key
        }

        int intHeight = (int)Math.Ceiling(height); // whole pixels

        // execute the command
        ICommand cmd = this.HeightChangedCommand;
        if (cmd != null && intHeight != sv.ActualHeight)
            cmd.Execute(intHeight);
    }
}
于 2013-03-03T14:40:34.417 回答