protected override void RecycleElementCore(ElementFactoryRecycleArgs args)
{
var element = args.Element;
var key = RecyclePool.GetReuseKey(element);
m_recyclePool.PutElement(element, key, args.Parent);
}
public ViewManager(ItemsRepeater owner)
{
// ItemsRepeater is not fully constructed yet. Don't interact with it.
m_owner = owner;
m_resetPool = new UniqueIdElementPool(owner);
m_lastFocusedElement = owner;
m_phaser = new Phaser(owner);
m_ElementFactoryGetArgs = new ElementFactoryGetArgs();
m_ElementFactoryRecycleArgs = new ElementFactoryRecycleArgs();
}
public void ClearElementToElementFactory(UIElement element)
{
m_owner.OnElementClearing(element);
if (m_owner.ItemTemplateShim != null)
{
if (m_ElementFactoryRecycleArgs == null)
{
// Create one.
m_ElementFactoryRecycleArgs = new ElementFactoryRecycleArgs();
}
var context = m_ElementFactoryRecycleArgs;
context.Element = element;
context.Parent = m_owner;
m_owner.ItemTemplateShim.RecycleElement(context);
context.Element = null;
context.Parent = null;
}
else
{
// No ItemTemplate to recycle to, remove the element from the children collection.
var children = m_owner.Children;
int childIndex = 0;
childIndex = children.IndexOf(element);
if (childIndex < 0)
{
throw new InvalidOperationException("ItemsRepeater's child not found in its Children collection.");
}
children.RemoveAt(childIndex);
}
var virtInfo = ItemsRepeater.GetVirtualizationInfo(element);
virtInfo.MoveOwnershipToElementFactory();
m_phaser.StopPhasing(element, virtInfo);
if (m_lastFocusedElement == element)
{
// Focused element is going away. Remove the tracked last focused element
// and pick a reasonable next focus if we can find one within the layout
// realized elements.
int clearedIndex = virtInfo.Index;
MoveFocusFromClearedIndex(clearedIndex);
}
REPEATER_TRACE_PERF("ElementCleared");
}
private void UnlinkElementFromParent(ElementFactoryRecycleArgs args)
{
// We want to unlink the containers from the parent repeater
// in case we are required to move it to a different repeater.
if (args.Parent is Panel panel)
{
var children = panel.Children;
var childIndex = children.IndexOf(args.Element);
if (childIndex >= 0)
{
children.RemoveAt(childIndex);
}
}
}
protected override void RecycleElementCore(ElementFactoryRecycleArgs args)
{
var element = args.Element;
if (element != null)
{
if (element is NavigationViewItem nvi)
{
var nviImpl = nvi;
// Check whether we wrapped the element in a NavigationViewItem ourselves.
// If yes, we are responsible for recycling it.
if (nviImpl.CreatedByNavigationViewItemsFactory)
{
nviImpl.CreatedByNavigationViewItemsFactory = false;
UnlinkElementFromParent(args);
args.Element = null;
// Retain the NVI that we created for future re-use
navigationViewItemPool.Add(nvi);
// Retrieve the proper element that requires recycling for a user defined item template
// and update the args correspondingly
if (m_itemTemplateWrapper != null)
{
// TODO: Retrieve the element and add to the args
}
}
}
// Do not recycle SettingsItem
bool isSettingsItem = m_settingsItem != null && m_settingsItem == args.Element;
if (m_itemTemplateWrapper != null && !isSettingsItem)
{
m_itemTemplateWrapper.RecycleElement(args);
}
else
{
UnlinkElementFromParent(args);
}
}
}
protected override void RecycleElementCore(Microsoft.UI.Xaml.Controls.ElementFactoryRecycleArgs args)
{
}
protected override void RecycleElementCore(ElementFactoryRecycleArgs args)
{
}
// Retrieve the element that will be displayed for a specific data item.
// If the resolved element is not derived from NavigationViewItemBase, wrap in a NavigationViewItem before returning.
protected override UIElement GetElementCore(ElementFactoryGetArgs args)
{
object GetNewContent(IElementFactoryShim itemTemplateWrapper, NavigationViewItemBase settingsItem)
{
// Do not template SettingsItem
if (settingsItem != null && settingsItem == args.Data)
{
return(args.Data);
}
if (itemTemplateWrapper != null)
{
return(itemTemplateWrapper.GetElement(args));
}
return(args.Data);
}
var newContent = GetNewContent(m_itemTemplateWrapper, m_settingsItem);
// Element is already of expected type, just return it
if (newContent is NavigationViewItemBase newItem)
{
return(newItem);
}
#if !HAS_UNO_WINUI
// Accidentally adding a OS XAML NavigationViewItem to WinUI's NavigationView can cause unnecessary confusion for developers
// due to unexpected rendering, potentially without an easy way to understand what went wrong here. To help out developers,
// we are explicitly checking for this scenario here and throw a helpful error message so that they can quickly fix their app.
if (newContent is Windows.UI.Xaml.Controls.NavigationViewItemBase)
{
throw new InvalidOperationException("A NavigationView instance contains a Windows.UI.Xaml.Controls.NavigationViewItem. This control requires that its NavigationViewItems be of type Microsoft.UI.Xaml.Controls.NavigationViewItem.");
}
#endif
// Get or create a wrapping container for the data
NavigationViewItem GetNavigationViewItem()
{
if (navigationViewItemPool.Count > 0)
{
var nvi = navigationViewItemPool[navigationViewItemPool.Count - 1];
navigationViewItemPool.RemoveAt(navigationViewItemPool.Count - 1);
return(nvi);
}
return(new NavigationViewItem());
}
var nvi = GetNavigationViewItem();
var nviImpl = nvi;
nviImpl.CreatedByNavigationViewItemsFactory = true;
// If a user provided item template exists, just pass the template and data down to the ContentPresenter of the NavigationViewItem
if (m_itemTemplateWrapper != null)
{
if (m_itemTemplateWrapper is ItemTemplateWrapper itemTemplateWrapper)
{
// Recycle newContent
var tempArgs = new ElementFactoryRecycleArgs();
tempArgs.Element = newContent as UIElement;
m_itemTemplateWrapper.RecycleElement(tempArgs);
nviImpl.Content = args.Data;
nviImpl.ContentTemplate = itemTemplateWrapper.Template;
nviImpl.ContentTemplateSelector = itemTemplateWrapper.TemplateSelector;
return(nviImpl);
}
}
nviImpl.Content = newContent;
return(nviImpl);
}
protected virtual void RecycleElementCore(ElementFactoryRecycleArgs args) => throw new NotImplementedException();
public void RecycleElement(ElementFactoryRecycleArgs args) => RecycleElementCore(args);