WPF ListBox WrapPanel剪辑长组 [英] WPF ListBox WrapPanel clips long groups

问题描述

我创建了一个ListBox来显示组中的项目，当这些组不再适合ListBox面板的高度时，将这些组从右向左包裹.因此，这些组在列表框中的显示类似于此，其中每个组的高度是任意的(例如，组1的高度是组2的两倍):

I've created a ListBox to display items in groups, where the groups are wrapped right to left when they can no longer fit within the height of the ListBox's panel. So, the groups would appear similar to this in the listbox, where each group's height is arbitrary (group 1, for instance, is twice as tall as group 2):

[ 1 ][ 3 ][ 5 ]
[   ][ 4 ][ 6 ]
[ 2 ][   ]

以下XAML可以正常工作，因为它可以执行换行，并且当项目从ListBox的右侧运行时，允许水平滚动条出现.

The following XAML works correctly in that it performs the wrapping, and allows the horizontal scroll bar to appear when the items run off the right side of the ListBox.

<ListBox> 
  <ListBox.ItemsPanel> 
    <ItemsPanelTemplate> 
      <StackPanel Orientation="Vertical"/> 
    </ItemsPanelTemplate> 
  </ListBox.ItemsPanel> 

  <ListBox.GroupStyle> 
    <ItemsPanelTemplate> 
      <WrapPanel Orientation="Vertical" 
                 Height="{Binding Path=ActualHeight, 
                          RelativeSource={RelativeSource 
                            FindAncestor, 
                            AncestorLevel=1, 
                            AncestorType={x:Type ScrollContentPresenter}}}"/> 
    </ItemsPanelTemplate> 
  </ListBox.GroupStyle> 
</ListBox>

当一组项目的长度大于WrapPanel的高度时，会发生此问题.除了允许垂直滚动条显示以查看截止项目组之外，还可以仅剪切该组中的项目.我假设这是WrapPanel中Height绑定的副作用-滚动条认为不必启用它.

The problem occurs when a group of items is longer than the height of the WrapPanel. Instead of allowing the vertical scroll bar to appear to view the cutoff item group, the items in that group are simply clipped. I'm assuming that this is a side effect of the Height binding in the WrapPanel - the scrollbar thinks it does not have to enabled.

有什么方法可以启用滚动条，或者有其他方法可以解决我没有看到的问题?

Is there any way to enable the scrollbar, or another way around this issue that I'm not seeing?

推荐答案

以下是稍作修改的代码-先前张贴此代码的Abe Heidebrecht均获此功劳-允许水平和垂直滚动.唯一的变化是MeasureOverride的返回值必须为base.MeasureOverride(new Size(ret.width，h)).

Here is the slightly modified code - all credit given to Abe Heidebrecht, who previously posted it - that allows both horizontal and vertical scrolling. The only change is that the return value of MeasureOverride needs to be base.MeasureOverride(new Size(ret.width, h)).

// Original code : Abe Heidebrecht
public class SmartWrapPanel : WrapPanel
{
  /// <summary>
  /// Identifies the DesiredHeight dependency property
  /// </summary>
  public static readonly DependencyProperty DesiredHeightProperty = DependencyProperty.Register(
    "DesiredHeight",
    typeof(double),
    typeof(SmartWrapPanel),
    new FrameworkPropertyMetadata(Double.NaN, 
            FrameworkPropertyMetadataOptions.AffectsArrange |
            FrameworkPropertyMetadataOptions.AffectsMeasure));

  /// <summary>
  /// Gets or sets the height to attempt to be.  If any child is taller than this, will use the child's height.
  /// </summary>
  public double DesiredHeight
  {
    get { return (double)GetValue(DesiredHeightProperty); }
    set { SetValue(DesiredHeightProperty, value); }
  }

  protected override Size MeasureOverride(Size constraint)
  {
    Size ret = base.MeasureOverride(constraint);
    double h = ret.Height;

    if (!Double.IsNaN(DesiredHeight))
    {
      h = DesiredHeight;
      foreach (UIElement child in Children)
      {
        if (child.DesiredSize.Height > h)
          h = child.DesiredSize.Height;
      }
    }

    return base.MeasureOverride(new Size(ret.Width, h));
  }

  protected override System.Windows.Size ArrangeOverride(Size finalSize)
  {
    double h = finalSize.Height;

    if (!Double.IsNaN(DesiredHeight))
    {
      h = DesiredHeight;
      foreach (UIElement child in Children)
      {
        if (child.DesiredSize.Height > h)
          h = child.DesiredSize.Height;
      }
    }

    return base.ArrangeOverride(new Size(finalSize.Width, h));
  }
}

这篇关于WPF ListBox WrapPanel剪辑长组的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持IT屋！