private void SetFocusOnFirstButton()
{
var firstButton = VisualTreeHelpers.FindVisualChild <Button>(AnswerButtons.ItemContainerGenerator.ContainerFromIndex(0));
if (firstButton != null)
{
FocusManager.SetFocusedElement(AnswerButtons, firstButton);
firstButton.Dispatcher.BeginInvoke((Action) delegate
{
firstButton.Focus();
Keyboard.Focus(firstButton);
}, DispatcherPriority.Input);
}
}
/// <summary>
/// Recursively search for an item in this subtree.
/// </summary>
/// <param name="container">
/// The parent ItemsControl. This can be a TreeView or a TreeViewItem.
/// </param>
/// <param name="item">
/// The item to search for.
/// </param>
/// <returns>
/// The TreeViewItem that contains the specified item.
/// </returns>
public static TreeViewItem?GetTreeViewItem(ItemsControl container, object item)
{
if (container == null)
{
return(null);
}
if (container.DataContext == item)
{
return(container as TreeViewItem);
}
// Expand the current container
if (container is TreeViewItem tvi && !tvi.IsExpanded)
{
container.SetValue(TreeViewItem.IsExpandedProperty, true);
}
// Try to generate the ItemsPresenter and the ItemsPanel.
// by calling ApplyTemplate. Note that in the
// virtualizing case even if the item is marked
// expanded we still need to do this step in order to
// regenerate the visuals because they may have been virtualized away.
container.ApplyTemplate();
ItemsPresenter?itemsPresenter = (ItemsPresenter)container.Template.FindName("ItemsHost", container);
if (itemsPresenter != null)
{
itemsPresenter.ApplyTemplate();
}
else
{
// The Tree template has not named the ItemsPresenter,
// so walk the descendents and find the child.
itemsPresenter = VisualTreeHelpers.FindVisualChild <ItemsPresenter>(container);
if (itemsPresenter == null)
{
container.UpdateLayout();
itemsPresenter = VisualTreeHelpers.FindVisualChild <ItemsPresenter>(container);
}
}
Panel itemsHostPanel = (Panel)VisualTreeHelper.GetChild(itemsPresenter, 0);
for (int i = 0, count = container.Items.Count; i < count; i++)
{
TreeViewItem subContainer;
if (itemsHostPanel is MyVirtualizingStackPanel virtualizingPanel)
{
// Bring the item into view so
// that the container will be generated.
virtualizingPanel.BringIntoView(i);
subContainer = (TreeViewItem)container.ItemContainerGenerator.ContainerFromIndex(i);
}
else
{
subContainer = (TreeViewItem)container.ItemContainerGenerator.ContainerFromIndex(i);
// Bring the item into view to maintain the
// same behavior as with a virtualizing panel.
subContainer.BringIntoView();
}
if (subContainer != null)
{
// Search the next level for the object.
TreeViewItem?resultContainer = GetTreeViewItem(subContainer, item);
if (resultContainer != null)
{
return(resultContainer);
}
// The object is not under this TreeViewItem
// so collapse it.
subContainer.IsExpanded = false;
}
}
return(null);
}
