检测WPF焦点到达焦点范围的末尾

public UIElement GetLastFocusedElement(DependencyObject parent)
{
    UIElement lastFocusedElement = null;

    int childCount = VisualTreeHelper.GetChildrenCount(parent);
    for (int i = 0; i < childCount; i++)
    {
        DependencyObject child = VisualTreeHelper.GetChild(parent, i);
        if (child is UIElement)
        {
            if ((child as UIElement).IsKeyboardFocused)
            {
                lastFocusedElement = child as UIElement;
                // 继续检查子元素的子元素
                lastFocusedElement = GetLastFocusedElement(child);
            }
        }
    }

    return lastFocusedElement;
}