WPF - 如何在 WrapPanel 中居中所有項目？

我正在使用 aWrapPanel作為aItemsPanel的ItemsControl。現在，控制項中的項目如下所示：

|1234567  |
|890      |

我希望他們像這樣包裝：

| 1234567 |
|   890   |

從概念上講，佈局過程應該對齊每行項目，使其在WrapPanel’ 範圍內居中。

有人可以解釋一下這是怎麼可能的嗎？

內置WrapPanel將不允許您對齊其內容 - 只有它自己。這是一種允許您設置的技術HorizontalContentAlignment：

using System;
using System.Windows;
using System.Windows.Controls;

public class AlignableWrapPanel : Panel
{
   public HorizontalAlignment HorizontalContentAlignment
   {
       get { return (HorizontalAlignment)GetValue(HorizontalContentAlignmentProperty); }
       set { SetValue(HorizontalContentAlignmentProperty, value); }
   }

   public static readonly DependencyProperty HorizontalContentAlignmentProperty =
       DependencyProperty.Register("HorizontalContentAlignment", typeof(HorizontalAlignment), typeof(AlignableWrapPanel), new FrameworkPropertyMetadata(HorizontalAlignment.Left, FrameworkPropertyMetadataOptions.AffectsArrange));

   protected override Size MeasureOverride(Size constraint)
   {
       Size curLineSize = new Size();
       Size panelSize = new Size();

       UIElementCollection children = base.InternalChildren;

       for (int i = 0; i < children.Count; i++)
       {
           UIElement child = children[i] as UIElement;

           // Flow passes its own constraint to children
           child.Measure(constraint);
           Size sz = child.DesiredSize;

           if (curLineSize.Width + sz.Width > constraint.Width) //need to switch to another line
           {
               panelSize.Width = Math.Max(curLineSize.Width, panelSize.Width);
               panelSize.Height += curLineSize.Height;
               curLineSize = sz;

               if (sz.Width > constraint.Width) // if the element is wider then the constraint - give it a separate line                    
               {
                   panelSize.Width = Math.Max(sz.Width, panelSize.Width);
                   panelSize.Height += sz.Height;
                   curLineSize = new Size();
               }
           }
           else //continue to accumulate a line
           {
               curLineSize.Width += sz.Width;
               curLineSize.Height = Math.Max(sz.Height, curLineSize.Height);
           }
       }

       // the last line size, if any need to be added
       panelSize.Width = Math.Max(curLineSize.Width, panelSize.Width);
       panelSize.Height += curLineSize.Height;

       return panelSize;
   }

   protected override Size ArrangeOverride(Size arrangeBounds)
   {
       int firstInLine = 0;
       Size curLineSize = new Size();
       double accumulatedHeight = 0;
       UIElementCollection children = this.InternalChildren;

       for (int i = 0; i < children.Count; i++)
       {
           Size sz = children[i].DesiredSize;

           if (curLineSize.Width + sz.Width > arrangeBounds.Width) //need to switch to another line
           {
               ArrangeLine(accumulatedHeight, curLineSize, arrangeBounds.Width, firstInLine, i);

               accumulatedHeight += curLineSize.Height;
               curLineSize = sz;

               if (sz.Width > arrangeBounds.Width) //the element is wider then the constraint - give it a separate line                    
               {
                   ArrangeLine(accumulatedHeight, sz, arrangeBounds.Width, i, ++i);
                   accumulatedHeight += sz.Height;
                   curLineSize = new Size();
               }
               firstInLine = i;
           }
           else //continue to accumulate a line
           {
               curLineSize.Width += sz.Width;
               curLineSize.Height = Math.Max(sz.Height, curLineSize.Height);
           }
       }

       if (firstInLine < children.Count)
           ArrangeLine(accumulatedHeight, curLineSize, arrangeBounds.Width, firstInLine, children.Count);

       return arrangeBounds;
   }

   private void ArrangeLine(double y, Size lineSize, double boundsWidth, int start, int end)
   {
       double x = 0;
       if (this.HorizontalContentAlignment == HorizontalAlignment.Center)
       {
           x = (boundsWidth - lineSize.Width) / 2;
       }
       else if (this.HorizontalContentAlignment == HorizontalAlignment.Right)
       {
           x = (boundsWidth - lineSize.Width);
       }

       UIElementCollection children = InternalChildren;
       for (int i = start; i < end; i++)
       {
           UIElement child = children[i];
           child.Arrange(new Rect(x, y, child.DesiredSize.Width, lineSize.Height));
           x += child.DesiredSize.Width;
       }
   }
}

引用自：https://stackoverflow.com/questions/806777