为什么不启动 MeasureOverride？

Question

我有两个用于显示评论和签名集合的自定义控件。这些控件中的每一个都有一个用于更改显示样式的按钮 - 显示整个集合或仅显示前 4 个元素。

当我将这些控件放在默认的 WrapPanel 中时 - 它们工作正常：根据用户的操作展开或折叠。在我自己的带有新 ArrangeOverride 函数的自定义 WrapPanel 中，它们也可以正常工作。

现在我需要带选项 "LastChildFill" 的 WrapPanel（我在此处找到示例）和自定义 "WrapDirection"（类似于 FlowDirection）。当 WrapPanel 中的第一个或最后一个元素超过元素的 MinWidth 时，必须填充所有剩余的 space。所以我用自定义 MeasureOverride 和 ArrangeOverride 创建了第三个 WrapPanel。它按我的意愿工作，但是当我更改控件显示样式时，控件内的集合会更改，但我的 WrapPanel 中的 MeasureOverride 不会启动，直到我更改 window 大小。

更新：MeasureOverride 不会开始扩展填充剩余 space 的第一个或最后一个元素。折叠此元素效果很好。

我不明白自定义 MeasureOverride 破坏了什么？

更新 2：我发现我的问题与此类似：MeasureOverride not always called on children's property changes.

并附上 MeasureOverride 代码。

public class WrapPanelFlowDirection : WrapPanel
{
    public bool LastChildFill
    {
        get { return (bool)GetValue(LastChildFillProperty); }
        set { SetValue(LastChildFillProperty, value); }
    }

    public static readonly DependencyProperty LastChildFillProperty =
        DependencyProperty.Register("LastChildFill", typeof(bool), typeof(WrapPanelFlowDirection), new FrameworkPropertyMetadata(true, FrameworkPropertyMetadataOptions.AffectsMeasure));

    public WrapDirection WrapDirection
    {
        get { return (WrapDirection)GetValue(WrapDirectionProperty); }
        set { SetValue(WrapDirectionProperty, value); }
    }

    public static readonly DependencyProperty WrapDirectionProperty =
        DependencyProperty.Register("WrapDirection", typeof(WrapDirection), typeof(WrapPanelFlowDirection), new FrameworkPropertyMetadata(WrapDirection.LeftToRight, FrameworkPropertyMetadataOptions.AffectsMeasure));

    #region Measure Override

    protected override Size MeasureOverride(Size availableSize)
    {
        var panelSize = new Size(availableSize.Width, 0);
        double minWidth = 0;

        foreach (FrameworkElement child in this.InternalChildren)
        {
            child.Measure(availableSize);
            minWidth += child.DesiredSize.Width;
        }

        int firstChildInLine = 0;
        double currLineHeight = 0;
        double currLineWidth = 0;
        UIElementCollection children = this.InternalChildren;

        for (int i = 0; i < children.Count; i++)
        {
            FrameworkElement child = children[i] as FrameworkElement;
            if (child == null)
                continue;

            double w = 0;
            if (child.MinWidth == 0)
                w = child.DesiredSize.Width;
            else
                w = child.MinWidth;

            if (currLineWidth + w <= availableSize.Width)
            {
                currLineWidth += w;
                currLineHeight = Math.Max(currLineHeight, child.DesiredSize.Height);
            }
            else
            {
                MeasureOneLine(firstChildInLine, i - 1, ref currLineHeight, availableSize.Width);
                panelSize.Height += currLineHeight;
                currLineWidth = w;
                currLineHeight = child.DesiredSize.Height;
                if (w > availableSize.Width)
                {
                    MeasureOneLine(i, i, ref currLineHeight, availableSize.Width);
                    panelSize.Height += currLineHeight;
                    currLineHeight = currLineWidth = 0;
                    firstChildInLine = i + 1;
                }
                else
                {
                    firstChildInLine = i;
                }
            }

        }

        if (firstChildInLine < children.Count)
        {
            MeasureOneLine(firstChildInLine, children.Count - 1, ref currLineHeight, availableSize.Width);
            panelSize.Height += currLineHeight;
        }

        if (double.IsInfinity(panelSize.Width))
            panelSize.Width = minWidth;
        return panelSize;
    }

    private void MeasureOneLine(int start, int end, ref double height, double totalWidth)
    {
        UIElementCollection children = this.InternalChildren;

        if (WrapDirection == WrapDirection.LeftToRight)
        {
            for (int i = start; i < end; i++)
            {
                FrameworkElement child = children[i] as FrameworkElement;
                if (child == null)
                    continue;

                double w = 0;
                if (child.MinWidth == 0)
                    w = child.DesiredSize.Width;
                else
                    w = child.MinWidth;
                if (i < end)
                {
                    child.Measure(new Size(w, height));
                    totalWidth -= w;
                }
                else
                {
                    child.Measure(new Size(totalWidth, double.PositiveInfinity));
                    height = Math.Max(height, child.DesiredSize.Height);
                }
            }
        }
        else
        {
            for (int i = end; i >= start; i--)
            {
                FrameworkElement child = children[i] as FrameworkElement;
                if (child == null)
                    continue;

                double w = 0;
                if (child.MinWidth == 0)
                    w = child.DesiredSize.Width;
                else
                    w = child.MinWidth;
                if (i > start)
                {
                    child.Measure(new Size(w, height));
                    totalWidth -= w;
                }
                else
                {
                    child.Measure(new Size(totalWidth, double.PositiveInfinity));
                    height = Math.Max(height, child.DesiredSize.Height);
                }
            }
        }
    }

    #endregion

Answer 1

我在这里找到了解决方案：How does a container know when a child has called InvalidateArrange?

它对我有用。

    public static void OnPropertyChanged(DependencyObject source, DependencyPropertyChangedEventArgs e)
    {
        UIElement panel= VisualTreeHelper.GetParent(source) as UIElement;
        if(panel != null)       
            {
                panel.InvalidateMeasure();
                panel.InvalidateArrange();
            }
    }

为什么不启动 MeasureOverride？

Why doesn't start MeasureOverride?

wpf

wrappanel

custom-controls

measureoverride