从 codeBehind UWP 的 GridView 中获取 gridViewItem

Question

我正在开发一个 UWP 应用程序，尝试使用 GridView 而不是 HubSection 从平台示例中实现 Transform3DAnimations。除了获取GridViewItem 之外，我已经弄清楚了。下面的代码是从上下文中的示例到 hubsection。

private void UpdateRandomSection()
    {
        // Updating the section triggers a cool animation!
        // See SectionView.xaml and SectionView.xaml.cs

        var sectionsInView = HeadlinesHub.SectionsInView;
        var sectionsCount = sectionsInView.Count;

        if (sectionsCount > 0)
        {
            var sectionToUpdate = sectionsInView[_random.Next(sectionsCount)];
            sectionToUpdate.DataContext = new HeroArticlesViewModel();
        }
    }

我正在尝试获取GridViewItem，但我无法获取GridViewItem，它总是返回GridViewItem 的数据模型。如何从GridView 获取GridViewItem？我的代码如下：

private Random InAppLiveTileRandomTileNumberGenerator;
private void UpdateRandomSection()
    {
        var sectionsInView = AllDevicesGridView.Items;
        var sectionsCount = sectionsInView.Count;

        if (sectionsCount > 0)
        {
            var sectionToUpdate = (GridViewItem)AllDevicesGridView.Items[InAppLiveTileRandomTileNumberGenerator.Next(sectionsCount)]; //Invalid Cast exception here
            sectionToUpdate.DataContext = new InappLiveTileViewModelModel();
        }
    }

---

Link to the sample

Solution I tried from stack answers

Answer 1

对于您的代码行var sectionToUpdate = (GridViewItem)AllDevicesGridView.Items[InAppLiveTileRandomTileNumberGenerator.Next(sectionsCount)];，它将返回您所看到的GridViewItem 的数据模型。要获得GridViewItem，您可能需要使用ContainerFromItem 方法。例如，如果要从选中的项目中获取GridViewItem对象，代码可能如下：

 private void listViewDirectory_SelectionChanged(object sender, SelectionChangedEventArgs e)
 {        
     var container = AllDevicesGridView.ContainerFromItem(AllDevicesGridView.SelectedItem);
     GridViewItem item = container as GridViewItem;
     System.Diagnostics.Debug.WriteLine(item.ActualHeight);
 }

您似乎想要获得一个分配了项目索引的特殊项目：

var container = AllDevicesGridView.ContainerFromItem(AllDevicesGridView.Items[1]);
GridViewItem item = container as GridViewItem;

如果要获取GridViewItem 的数据上下文，可能需要从GridViewItem 获取ListViewItemPresenter。这里我使用VisualTreeHelper 来获取ListViewItemPresenter。对了，VisualTreeHelper不建议使用，除非你没有其他办法。

private void listViewDirectory_SelectionChanged(object sender, SelectionChangedEventArgs e)
{
    var container = AllDevicesGridView.ContainerFromItem(AllDevicesGridView.Items[1]);
    GridViewItem item = container as GridViewItem;
    ListViewItemPresenter itempresenter;
    IEnumerable<ListViewItemPresenter> items = FindVisualChildren<ListViewItemPresenter>(item);
    int count = items.Count();
    itempresenter = items.ElementAt<ListViewItemPresenter>(0);           
    itempresenter.DataContext = new Person() { Name = "update", Contact = "update" };
}
private static IEnumerable<T> FindVisualChildren<T>(DependencyObject depObj) where T : DependencyObject
{
    if (depObj != null)
    {
        for (int i = 0; i < VisualTreeHelper.GetChildrenCount(depObj); i++)
        {
            DependencyObject child = VisualTreeHelper.GetChild(depObj, i);
            if (child != null && child is T)
            {
                yield return (T)child;
            }

            foreach (T childOfChild in FindVisualChildren<T>(child))
            {
                yield return childOfChild;
            }
        }
    }
}