为什么自定义面板不自动刷新

Question

我编写了一个自定义面板。代码如下：

public class GameBoardPanel:Panel
{
    public GameBoardPanel() { }

    public static readonly DependencyProperty SquareSideLengthProperty =
        DependencyProperty.Register("SquareSideLength", typeof(int), typeof(GameBoardPanel), new PropertyMetadata(0));

    public int SquareSideLength
    {
        get { return (int)GetValue(SquareSideLengthProperty); }
        private set { SetValue(SquareSideLengthProperty, value); }
    }

    public static readonly DependencyProperty RowsProperty =
        DependencyProperty.Register("Rows", typeof(int), typeof(GameBoardPanel), new PropertyMetadata(0));

    public int Rows
    {
        get { return (int)GetValue(RowsProperty); }
        set { SetValue(RowsProperty, value); }
    }

    public int Columns
    {
        get { return (int)GetValue(ColumnsProperty); }
        set { SetValue(ColumnsProperty, value); }
    }

    public static readonly DependencyProperty ColumnsProperty =
        DependencyProperty.Register("Columns", typeof(int), typeof(GameBoardPanel), new PropertyMetadata(0));

    public static readonly DependencyProperty RowProperty =
        DependencyProperty.RegisterAttached("Row", typeof(int), typeof(GameBoardPanel));

    public static readonly DependencyProperty ColumnProperty =
        DependencyProperty.RegisterAttached("Column", typeof(int), typeof(GameBoardPanel));

    public static void SetRow(DependencyObject control, int value)
    {
        control.SetValue(RowProperty, value);
    }
    public static int GetRow(DependencyObject control)
    {
        return (int)control.GetValue(RowProperty);
    }
    public static void SetColumn(DependencyObject control, int value)
    {
        control.SetValue(ColumnProperty, value);
    }
    public static int GetColumn(DependencyObject control)
    {
        return (int)control.GetValue(ColumnProperty);
    }
    protected override Size MeasureOverride(Size availableSize)
    {
        double min=Math.Min(availableSize.Width/Columns,availableSize.Height/Rows );
        SquareSideLength=(int)min;
        return new Size(SquareSideLength*Columns, SquareSideLength*Rows);
    }
    protected override Size ArrangeOverride(Size finalSize)
    {
        double min=Math.Min(finalSize.Width/Columns,finalSize.Height/Rows );
        SquareSideLength=(int)min;
        Size destinationSize = new Size(SquareSideLength * Columns, SquareSideLength * Rows);
        foreach (UIElement element in base.InternalChildren)
        {
            int row = GameBoardPanel.GetRow(element);
            int column = GameBoardPanel.GetColumn(element);
            element.Arrange(new Rect(column * SquareSideLength, row * SquareSideLength,SquareSideLength, SquareSideLength));
        }
        return destinationSize;
    }
}

很简单的想法，类似于 wpf Grid 面板。我有一个控件，它通过设置子GameBoardPanel.Row 和GameBoardPanel.Column 附加属性在这样的面板上排列它的子。假设我还有一个GameObject 类，它是一个CustomControl，我将它添加到面板中。例如，我想将其移动到左侧。所以我按照以下方式进行：

GameObject movable=new GameObject();
//setting properties such as GameBoardPanel.Row and GameBoardPanel.Column
panel.Children.Add(movable);
GameBoardPanel.SetColumn(GameBoardPanel.GetColumn(movable)-1);

让我们跳过movable 对象可以移出面板的问题。这不是一个大问题。但是，如果我以这种方式进行运动，我看不到任何效果。仅在添加附加行后：

panel.InvalidateArrange(); 

我观察到物体向左移动。我很确定，如果我对 wpf Grid 做同样的事情，就没有必要调用 InvalidateArrange 方法。所以，我很好奇为什么会发生这种情况？ :D

Answer 1

您可以设置适当的属性元数据选项来告诉框架Row 和Column 附加属性会影响您的自定义面板的布局：

public static readonly DependencyProperty RowProperty =
    DependencyProperty.RegisterAttached("Row", typeof(int), typeof(GameBoardPanel),
        new FrameworkPropertyMetadata(0,
            FrameworkPropertyMetadataOptions.AffectsParentArrange));

public static readonly DependencyProperty ColumnProperty =
    DependencyProperty.RegisterAttached("Column", typeof(int), typeof(GameBoardPanel),
        new FrameworkPropertyMetadata(0,
            FrameworkPropertyMetadataOptions.AffectsParentArrange));

---

也就是说，您通常还应该在 MeasureOverride 方法中测量子元素：

protected override Size MeasureOverride(Size availableSize)
{
    double min = Math.Min(availableSize.Width / Columns, availableSize.Height / Rows);
    SquareSideLength = (int)min;

    foreach (UIElement element in InternalChildren)
    {
        element.Measure(new Size(SquareSideLength, SquareSideLength));
    }

    return new Size(SquareSideLength * Columns, SquareSideLength * Rows);
}

此外，SquareSideLength 似乎也不是依赖属性。它也可以是一个普通的 CLR 属性（或者可能只是一个私有字段）。它的类型也最好是double 而不是int。

最后，您的 MeasureOverride 实现还应该为无限的availableSize 参数值做好准备。来自MSDN：

这个可以使用的尺寸 element 可以赋予子元素。无穷大可以指定为 值来指示元素的大小将适应任何内容 可用。