ItemsControl 调整大小时边框消失（使用“stretchpanel”）

昨天我问如何让 ItemsControl 使其子项均匀分布在可用空间中；在愉快地阅读答案后，我写了（实际上是复制并调整了它）我自己的“stretchpanel”，它正是我想要的。然而，我的孩子应该在右侧有一个边框，只要孩子比其内容大，它就可以工作。一旦它变小，边框就会消失，我不知道为什么（因此，不修复它）。下面您可以找到我的视图和拉伸面板中覆盖方法的简化版本，使用this样品作为基础。预先非常感谢。

<Grid Background="Red" HorizontalAlignment="Stretch" VerticalAlignment="Stretch">
<Grid.ColumnDefinitions>
  <ColumnDefinition Width="*"/>
</Grid.ColumnDefinitions>
<ItemsControl x:Name="HorizontalListBox" Background="Blue" HorizontalAlignment="Left" HorizontalContentAlignment="Left" >
  <ItemsControl.Items>
    <System:String>Test</System:String>
    <System:String>Test</System:String>
    <System:String>This demonstrates the problem exceptionally well</System:String>
    <System:String>Test</System:String>
    <System:String>Test</System:String>
  </ItemsControl.Items>
  <ItemsControl.ItemsPanel>
    <ItemsPanelTemplate>
      <Controls:StretchPanel Orientation="Horizontal" HorizontalAlignment="Stretch"/>
    </ItemsPanelTemplate>
  </ItemsControl.ItemsPanel>
  <ItemsControl.ItemTemplate>
    <DataTemplate>
      <Grid Background="Yellow" HorizontalAlignment="Stretch">
        <TextBlock Text="{Binding}" HorizontalAlignment="Stretch"/>
        <Border BorderBrush="Black" BorderThickness="0,0,1,0"/>
      </Grid>
    </DataTemplate>
  </ItemsControl.ItemTemplate>
</ItemsControl>

protected override Size MeasureOverride(Size availableSize)
{
  var size = new Size();
  SetSide(ref size, GetSide(availableSize));
  foreach (UIElement child in Children)
  {
    child.Measure(availableSize);
    SetOtherSide(ref size, Math.Max(GetOtherSide(size), GetOtherSide(child.DesiredSize)));
  }
  _measureSize = size;
  return size;
}

protected override Size ArrangeOverride(Size finalSize)
{
  double offset = 0;
  var Side = GetSide(_measureSize) / Children.Count;
  var Rest = GetSide(_measureSize) % Children.Count;
  foreach (UIElement child in Children)
  {
    double side = Math.Floor(GetSide(_measureSize) / Children.Count);
    if (Rest > 0)
    {
      side++;
      Rest--;
    }
    var final = new Size();
    SetSide(ref final, side);
    SetOtherSide(ref final, GetOtherSide(finalSize));
    child.Arrange(new Rect(GetOffsetPoint(offset), final));
    offset += side;
  }
  return finalSize;
}

如果您像这样编写 StretchPanel ，它会工作，它以零宽度和高度测量其子元素：

public class StretchPanel : Panel
{
    protected override Size MeasureOverride(Size availableSize)
    {
        foreach (UIElement element in Children)
        {
            element.Measure(new Size());
        }

        return new Size();
    }

    protected override Size ArrangeOverride(Size finalSize)
    {
        for (int i = 0; i < Children.Count; i++)
        {
            int x1 = (int)(finalSize.Width / Children.Count * i);
            int x2 = (int)(finalSize.Width / Children.Count * (i + 1));
            Children[i].Arrange(new Rect(x1, 0, x2 - x1, finalSize.Height));
        }

        return finalSize;
    }
}

然后设置HorizontalAlignment="Stretch"（或者根本不设置它，因为这是默认值）在 ItemsControl 上。