如何:创建自定义 Panel 元素

示例

此示例演示如何替代 Panel 元素的默认布局行为,并创建派生自 Panel 的自定义布局元素。

示例定义了一个名为 PlotPanel 的简单自定义 Panel 元素,该元素根据两个硬编码的 x 坐标和 y 坐标定位子元素。 在此示例中,xy 均设置为 50;因此,所有子元素都位于 x 和 y 轴上的该位置。

为了实现自定义 Panel 行为,该示例使用 MeasureOverrideArrangeOverride 方法。 每个方法都返回 Size 定位和呈现子元素所需的数据。

public: 
   ref class PlotPanel : Panel {

   public: 
      PlotPanel () {};

   protected: 
      // Override the default Measure method of Panel
      virtual Size MeasureOverride(Size availableSize) override
      {
          Size^ panelDesiredSize = gcnew Size();

          // In our example, we just have one child. 
          // Report that our panel requires just the size of its only child.
          for each (UIElement^ child in InternalChildren)
          {
              child->Measure(availableSize);
              panelDesiredSize = child->DesiredSize;
          }
          return *panelDesiredSize ;
      }

   protected: 
      virtual System::Windows::Size ArrangeOverride (Size finalSize) override 
      {
         for each (UIElement^ child in InternalChildren)
         {
            double x = 50;
            double y = 50;
            child->Arrange(Rect(Point(x, y), child->DesiredSize));
         }
         return finalSize;
      };
   };
public class PlotPanel : Panel
{
    // Default public constructor
    public PlotPanel()
        : base()
    {
    }

    // Override the default Measure method of Panel
    protected override Size MeasureOverride(Size availableSize)
    {
        Size panelDesiredSize = new Size();

        // In our example, we just have one child.
        // Report that our panel requires just the size of its only child.
        foreach (UIElement child in InternalChildren)
        {
            child.Measure(availableSize);
            panelDesiredSize = child.DesiredSize;
        }

        return panelDesiredSize ;
    }
    protected override Size ArrangeOverride(Size finalSize)
    {
        foreach (UIElement child in InternalChildren)
        {
            double x = 50;
            double y = 50;

            child.Arrange(new Rect(new Point(x, y), child.DesiredSize));
        }
        return finalSize; // Returns the final Arranged size
    }
}
Public Class PlotPanel
    Inherits Panel
    'Override the default Measure method of Panel.

    Protected Overrides Function MeasureOverride(ByVal availableSize As System.Windows.Size) As System.Windows.Size
        Dim panelDesiredSize As Size = New Size()
        ' In our example, we just have one child. 
        ' Report that our panel requires just the size of its only child.
        For Each child As UIElement In InternalChildren
            child.Measure(availableSize)
            panelDesiredSize = child.DesiredSize
        Next
        Return panelDesiredSize
    End Function
    Protected Overrides Function ArrangeOverride(ByVal finalSize As System.Windows.Size) As System.Windows.Size
        For Each child As UIElement In InternalChildren
            Dim x As Double = 50
            Dim y As Double = 50
            child.Arrange(New Rect(New System.Windows.Point(x, y), child.DesiredSize))
        Next
        Return finalSize
    End Function
End Class

另请参阅