从itemsControl设置ItemsPanel的属性

Question

我正在使用我的自定义项目控件(从列表框派生的DisplayPanelControl )的自定义面板，样式类似于下面的XAML

<Style x:Key="ContainerStyle" TargetType="{x:Type local:DisplayPanelControl}">
    <Setter Property="Template">
        <Setter.Value>
            <ControlTemplate>
                <Grid>                   
                    <local:CustomePanel Background="AliceBlue" IsItemsHost="True">
                    </local:CustomePanel>
                </Grid>
            </ControlTemplate>
        </Setter.Value>
    </Setter>
</Style>

CustomePanel有一个属性Edgblending。我想通过我的Items控件来设置这个属性，所以我重写了OnApplyTemplate()方法，并使用VisualTreeHelper来查找设置了所需属性的customPanel。

我想问一下，有没有更好的解决方案来通过Itemscontrol来设置ItemsPanel的属性？

Answer 1

这是一种可能的变通方法，它将在2种情况下工作，已经使用了项目控件上的方法OnApplyTemplate()方法。

1. 当我们在itemsControls模板中通过设置面板
2. 上的IsItemsHost属性来指定面板时，当我们通过"ItemsPanelTemplate“标记设置项目面板时。

已经通过Ian Griffiths Find Control Inside ListBox? answer给出的解释解决了这个问题。

private T GetItemsPanel<T>(ItemsControl itemsControl) where T : Panel
    {
        T _Panel = UIHelper.FindVisualChild<T>(itemsControl);
        if (_Panel == null)
        {
            ItemsPresenter itemsPresenter = UIHelper.FindVisualChild<ItemsPresenter>(itemsControl);
            if (itemsPresenter != null)
            {
                itemsPresenter.ApplyTemplate();
                _Panel = VisualTreeHelper.GetChild(itemsPresenter, 0) as T;
            }
        }
        return _Panel;
    }  

UiHelper类的实现只是在可视化树中查找对象，实现如下(我也从一些博客文章中复制了这一点，但不记得找到链接)

public static class UIHelper
{
    /// <summary>
    /// Finds a parent of a given item on the visual tree.
    /// </summary>
    /// <typeparam name="T">The type of the queried item.</typeparam>
    /// <param name="child">A direct or indirect child of the queried item.</param>
    /// <returns>The first parent item that matches the submitted type parameter. 
    /// If not matching item can be found, a null reference is being returned.</returns>
    public static T FindVisualParent<T>(DependencyObject child)
      where T : DependencyObject
    {
        // get parent item
        DependencyObject parentObject = VisualTreeHelper.GetParent(child);

        // we’ve reached the end of the tree
        if (parentObject == null) return null;

        // check if the parent matches the type we’re looking for
        T parent = parentObject as T;
        if (parent != null)
        {
            return parent;
        }
        else
        {
            // use recursion to proceed with next level
            return FindVisualParent<T>(parentObject);
        }
    }
    public static T FindVisualChild<T>(DependencyObject parent) where T : DependencyObject
    {
        T child = default(T);

        int numVisuals = VisualTreeHelper.GetChildrenCount(parent);
        for (int i = 0; i < numVisuals; i++)
        {
            Visual v = (Visual)VisualTreeHelper.GetChild(parent, i);
            child = v as T;
            if (child == null)
            {
                child = FindVisualChild<T>(v);
            }
            if (child != null)
            {
                break;
            }
        }
        return child;
    }

}