在TreeViewItem_OnExpanded事件中,我有以下代码。
var expandedTreeViewItem = e.OriginalSource as TreeViewItem;
var child = expandedTreeViewItem.ItemContainerGenerator.ContainerFromItem(item) as TreeViewItem;
expandedTreeViewItem.ItemsSource = // Update ItemsSource
var child = expandedTreeViewItem.ItemContainerGenerator.ContainerFromItem(item) as TreeViewItem;
在更改扩展树视图项的ItemSource之前获取子项时没有问题,但在更改ItemSource之后,child将为null。
ContainerFromItem(item)中的项目相同,并且在更改ItemSource之前和之后存在。代码的其他部分正常工作。在ItemSource更改后,我该怎么做才能获取元素?
TreeViewItem_OnExpanded事件代码
private void TreeViewItem_OnExpanded(object sender, RoutedEventArgs e)
{
var expandedTreeViewItem = e.OriginalSource as TreeViewItem;
var directoryInfo = expandedTreeViewItem?.Items[0] as DirectoryInfoModel;
if (expandedTreeViewItem == null || directoryInfo?.HasChild == false) return;
_folderExplorerViewModel.GetDirectories(directoryInfo?.DirectoryInfo, directoryInfo?.SubDirectoriesCollection);
expandedTreeViewItem.ItemsSource = directoryInfo?.SubDirectoriesCollection;
var expandedItemHeader = expandedTreeViewItem?.Template.FindName("PART_Header", expandedTreeViewItem) as ContentPresenter;
var expandedItemCheckBox = expandedItemHeader?.ContentTemplate.FindName("CheckBoxFolderItem", expandedItemHeader) as CheckBox;
foreach (var item in expandedTreeViewItem.Items)
{
var childItem = expandedTreeViewItem.ItemContainerGenerator.ContainerFromItem(item) as TreeViewItem;
var childHeader = childItem?.Template.FindName("PART_Header", childItem) as ContentPresenter;
var childCheckBox = childHeader?.ContentTemplate.FindName("CheckBoxFolderItem", childHeader) as CheckBox;
if (childCheckBox != null && expandedItemCheckBox != null)
{
childCheckBox.IsChecked = expandedItemCheckBox.IsChecked;
}
}
}
在ItemesSource更改后使用它时,childItem始终为null。但在此之前,它确实有效。
非常感谢。
答案 0 :(得分:0)
我找到了答案here。在TreeViewItem_OnExpanded事件未完成其作业之前,尚未在UI中创建新项目,因此ItemContainerGenerator返回null。我在其类中创建了expandedTreeViewItem,并为每个展开的树视图项添加了LayoutUpdated事件处理程序,然后在LayoutUpdated事件中,我可以访问由ItemSource添加的新项。我不知道它是否是一种标准方式,但现在它的工作没有任何返回null。
private TreeViewItem _expandedTreeViewItem;
private void TreeViewItem_OnExpanded(object sender, RoutedEventArgs e)
{
_expandedTreeViewItem = e.OriginalSource as TreeViewItem;
var directoryInfo = _expandedTreeViewItem?.Items[0] as DirectoryInfoModel;
if (_expandedTreeViewItem == null || directoryInfo?.HasChild == false) return;
_folderExplorerViewModel.GetDirectories(directoryInfo?.DirectoryInfo, directoryInfo?.SubDirectoriesCollection);
_expandedTreeViewItem.ItemsSource = directoryInfo?.SubDirectoriesCollection;
_expandedTreeViewItem.LayoutUpdated += ExpandedTreeViewItem_OnLayoutUpdated;
}
private void ExpandedTreeViewItem_OnLayoutUpdated(object sender, EventArgs e)
{
var expandedItemHeader = _expandedTreeViewItem?.Template.FindName("PART_Header", _expandedTreeViewItem) as ContentPresenter;
var expandedItemCheckBox = header?.ContentTemplate.FindName("CheckBoxFolderItem", header) as CheckBox;
foreach (var item in _expandedTreeViewItem.Items)
{
var childItem = _expandedTreeViewItem.ItemContainerGenerator.ContainerFromItem(item) as TreeViewItem;
var childHeader = childItem?.Template.FindName("PART_Header", childItem) as ContentPresenter;
var childCheckBox = childHeader?.ContentTemplate.FindName("CheckBoxFolderItem", childHeader) as CheckBox;
if (childCheckBox != null && expandedItemCheckBox != null)
{
childCheckBox.IsChecked = expandedItemCheckBox.IsChecked;
}
}
}