protected void UpdateSubview(object view, DataTemplate viewTemplate, ref UIView uiView, ref VisualElement formsElement)
{
if (uiView != null)
{
CollectionView.Subviews.Remove(uiView);
}
if (formsElement != null)
{
ItemsView.RemoveLogicalChild(formsElement);
formsElement.MeasureInvalidated -= OnFormsElementMeasureInvalidated;
}
UpdateView(view, viewTemplate, ref uiView, ref formsElement);
if (uiView != null)
{
CollectionView.AddSubview(uiView);
}
if (formsElement != null)
{
ItemsView.AddLogicalChild(formsElement);
}
if (formsElement != null)
{
RemeasureLayout(formsElement);
formsElement.MeasureInvalidated += OnFormsElementMeasureInvalidated;
}
else if (uiView != null)
{
uiView.SizeToFit();
}
}
internal void UpdateSubview(object view, DataTemplate viewTemplate, nint viewTag, ref UIView uiView, ref VisualElement formsElement)
{
uiView?.RemoveFromSuperview();
if (formsElement != null)
{
ItemsView.RemoveLogicalChild(formsElement);
formsElement.MeasureInvalidated -= OnFormsElementMeasureInvalidated;
}
UpdateView(view, viewTemplate, ref uiView, ref formsElement);
if (uiView != null)
{
uiView.Tag = viewTag;
CollectionView.AddSubview(uiView);
}
if (formsElement != null)
{
ItemsView.AddLogicalChild(formsElement);
}
if (formsElement != null)
{
RemeasureLayout(formsElement);
formsElement.MeasureInvalidated += OnFormsElementMeasureInvalidated;
}
else if (uiView != null)
{
uiView.SizeToFit();
}
}
public void Recycle(ItemsView itemsView)
{
if (_itemView is SizedItemContentView _sizedItemContentView)
{
_sizedItemContentView.Recycle();
}
itemsView.RemoveLogicalChild(View);
}
public override void OnViewRecycled(Object holder)
{
if (holder is TemplatedItemViewHolder templatedItemViewHolder)
{
ItemsView.RemoveLogicalChild(templatedItemViewHolder.View);
}
base.OnViewRecycled(holder);
}
void ResetBindedView(View view)
{
if (view.BindingContext != null && _dataBindedViewTable.ContainsKey(view.BindingContext))
{
_dataBindedViewTable[view.BindingContext] = null;
_itemsView.RemoveLogicalChild(view);
view.BindingContext = null;
}
}
public void Bind(DataTemplate template, object bindingContext, ItemsView itemsView)
{
var oldElement = VisualElementRenderer?.Element;
// Run this through the extension method in case it's really a DataTemplateSelector
var itemTemplate = template.SelectDataTemplate(bindingContext, itemsView);
if (itemTemplate != _currentTemplate)
{
// Remove the old view, if it exists
if (oldElement != null)
{
oldElement.MeasureInvalidated -= MeasureInvalidated;
itemsView.RemoveLogicalChild(oldElement);
ClearSubviews();
_size = Size.Zero;
}
// Create the content and renderer for the view
var view = itemTemplate.CreateContent() as View;
// Prevents the use of default color when there are VisualStateManager with Selected state setting the background color
// First we check whether the cell has the default selected background color; if it does, then we should check
// to see if the cell content is the VSM to set a selected color
if (SelectedBackgroundView.BackgroundColor == ColorExtensions.Gray && IsUsingVSMForSelectionColor(view))
{
SelectedBackgroundView = new UIView
{
BackgroundColor = UIColor.Clear
};
}
// Set the binding context _before_ we create the renderer; that way, it's available during OnElementChanged
view.BindingContext = bindingContext;
var renderer = TemplateHelpers.CreateRenderer(view);
SetRenderer(renderer);
// And make the new Element a "child" of the ItemsView
// We deliberately do this _after_ setting the binding context for the new element;
// if we do it before, the element briefly inherits the ItemsView's bindingcontext and we
// emit a bunch of needless binding errors
itemsView.AddLogicalChild(view);
}
else
{
// Same template, different data
var currentElement = VisualElementRenderer?.Element;
if (currentElement != null)
{
currentElement.BindingContext = bindingContext;
}
}
_currentTemplate = itemTemplate;
}
void TearDownEmptyView()
{
HideEmptyView();
// RemoveLogicalChild will trigger a disposal of the native view and its content
ItemsView.RemoveLogicalChild(_emptyViewFormsElement);
_emptyUIView = null;
_emptyViewFormsElement = null;
}
public void Recycle(ItemsView itemsView)
{
if (View == null)
{
return;
}
itemsView.RemoveLogicalChild(View);
View.BindingContext = null;
}
internal void RemoveLogicalChild(UICollectionViewCell cell)
{
if (cell is TemplatedCell templatedCell)
{
var oldView = templatedCell.VisualElementRenderer?.Element;
if (oldView != null)
{
_itemsView.RemoveLogicalChild(oldView);
}
}
}
internal void PrepareCellForRemoval(UICollectionViewCell cell)
{
if (cell is TemplatedCell templatedCell)
{
templatedCell.ContentSizeChanged -= CellContentSizeChanged;
var oldView = templatedCell.VisualElementRenderer?.Element;
if (oldView != null)
{
oldView.BindingContext = null;
ItemsView.RemoveLogicalChild(oldView);
}
templatedCell.PrepareForRemoval();
}
}
protected virtual void UpdateEmptyViewVisibility()
{
bool isEmpty = (CollectionViewSource?.View?.Count ?? 0) == 0;
if (isEmpty)
{
if (_formsEmptyView != null)
{
if (_emptyViewDisplayed)
{
ItemsView.RemoveLogicalChild(_formsEmptyView);
}
if (ItemsView.EmptyViewTemplate == null)
{
ItemsView.AddLogicalChild(_formsEmptyView);
}
}
if (_emptyView != null && ListViewBase is IEmptyView emptyView)
{
emptyView.EmptyViewVisibility = WVisibility.Visible;
if (ActualWidth >= 0 && ActualHeight >= 0)
{
_formsEmptyView?.Layout(new Rect(0, 0, ActualWidth, ActualHeight));
}
}
_emptyViewDisplayed = true;
}
else
{
if (_emptyViewDisplayed)
{
if (_emptyView != null && ListViewBase is IEmptyView emptyView)
{
emptyView.EmptyViewVisibility = WVisibility.Collapsed;
}
ItemsView.RemoveLogicalChild(_formsEmptyView);
}
_emptyViewDisplayed = false;
}
}
public void Bind(DataTemplate template, object bindingContext, ItemsView itemsView)
{
var oldElement = VisualElementRenderer?.Element;
// Run this through the extension method in case it's really a DataTemplateSelector
var itemTemplate = template.SelectDataTemplate(bindingContext, itemsView);
if (itemTemplate != _currentTemplate)
{
// Remove the old view, if it exists
if (oldElement != null)
{
oldElement.MeasureInvalidated -= MeasureInvalidated;
itemsView.RemoveLogicalChild(oldElement);
ClearSubviews();
_size = Size.Zero;
}
// Create the content and renderer for the view
var view = itemTemplate.CreateContent() as View;
// Set the binding context _before_ we create the renderer; that way, it's available during OnElementChanged
view.BindingContext = bindingContext;
var renderer = TemplateHelpers.CreateRenderer(view);
SetRenderer(renderer);
// And make the new Element a "child" of the ItemsView
// We deliberately do this _after_ setting the binding context for the new element;
// if we do it before, the element briefly inherits the ItemsView's bindingcontext and we
// emit a bunch of needless binding errors
itemsView.AddLogicalChild(view);
}
else
{
// Same template, different data
var currentElement = VisualElementRenderer?.Element;
if (currentElement != null)
{
currentElement.BindingContext = bindingContext;
}
}
_currentTemplate = itemTemplate;
}
void UpdateEmptyViewVisibility(bool isEmpty)
{
if (isEmpty && _emptyUIView != null)
{
var emptyView = CollectionView.ViewWithTag(EmptyTag);
if (emptyView != null)
{
emptyView.RemoveFromSuperview();
ItemsView.RemoveLogicalChild(_emptyViewFormsElement);
}
_emptyUIView.Tag = EmptyTag;
CollectionView.AddSubview(_emptyUIView);
LayoutEmptyView();
if (_emptyViewFormsElement != null)
{
if (ItemsView.EmptyViewTemplate == null)
{
ItemsView.AddLogicalChild(_emptyViewFormsElement);
}
// Now that the native empty view's frame is sized to the UICollectionView, we need to handle
// the Forms layout for its content
_emptyViewFormsElement.Layout(_emptyUIView.Frame.ToRectangle());
}
_emptyViewDisplayed = true;
}
else
{
// Is the empty view currently in the background? Swap back to the default.
if (_emptyViewDisplayed)
{
_emptyUIView.RemoveFromSuperview();
_emptyUIView.Dispose();
_emptyUIView = null;
ItemsView.RemoveLogicalChild(_emptyViewFormsElement);
}
_emptyViewDisplayed = false;
}
}
void UpdateEmptyViewVisibility(bool isEmpty)
{
if (isEmpty && _emptyUIView != null)
{
if (!_currentBackgroundIsEmptyView)
{
// Cache any existing background view so we can restore it later
_backgroundUIView = CollectionView.BackgroundView;
}
// Replace any current background with the EmptyView. This will also set the native empty view's frame
// to match the UICollectionView's frame
CollectionView.BackgroundView = _emptyUIView;
if (_emptyViewFormsElement != null)
{
if (ItemsView.EmptyViewTemplate == null)
{
ItemsView.AddLogicalChild(_emptyViewFormsElement);
}
// Now that the native empty view's frame is sized to the UICollectionView, we need to handle
// the Forms layout for its content
_emptyViewFormsElement.Layout(_emptyUIView.Frame.ToRectangle());
}
_currentBackgroundIsEmptyView = true;
}
else
{
// Is the empty view currently in the background? Swap back to the default.
if (_currentBackgroundIsEmptyView)
{
CollectionView.BackgroundView = _backgroundUIView;
ItemsView.RemoveLogicalChild(_emptyViewFormsElement);
}
_currentBackgroundIsEmptyView = false;
}
}
public void Bind(DataTemplate template, object bindingContext, ItemsView itemsView)
{
var oldElement = VisualElementRenderer?.Element;
if (template != _currentTemplate)
{
// Remove the old view, if it exists
if (oldElement != null)
{
oldElement.MeasureInvalidated -= MeasureInvalidated;
itemsView.RemoveLogicalChild(oldElement);
ClearSubviews();
_size = Size.Zero;
}
// Create the content and renderer for the view
var view = template.CreateContent() as View;
var renderer = TemplateHelpers.CreateRenderer(view);
SetRenderer(renderer);
}
var currentElement = VisualElementRenderer?.Element;
// Bind the view to the data item
if (currentElement != null)
{
currentElement.BindingContext = bindingContext;
}
if (template != _currentTemplate)
{
// And make the Element a "child" of the ItemsView
// We deliberately do this _after_ setting the binding context for the new element;
// if we do it before, the element briefly inherits the ItemsView's bindingcontext and we
// emit a bunch of needless binding errors
itemsView.AddLogicalChild(currentElement);
}
_currentTemplate = template;
}
internal void UpdateSubview(object view, DataTemplate viewTemplate, ref UIView uiView, ref VisualElement formsElement)
{
if (uiView != null)
{
CollectionView.Subviews.Remove(uiView);
}
if (formsElement != null)
{
ItemsView.RemoveLogicalChild(formsElement);
formsElement.MeasureInvalidated -= OnFormsElementMeasureInvalidated;
}
UpdateView(view, viewTemplate, ref uiView, ref formsElement);
if (uiView != null)
{
CollectionView.AddSubview(uiView);
}
if (formsElement != null)
{
ItemsView.AddLogicalChild(formsElement);
}
if (formsElement != null)
{
var request = formsElement.Measure(CollectionView.Frame.Width, double.PositiveInfinity, MeasureFlags.IncludeMargins);
Xamarin.Forms.Layout.LayoutChildIntoBoundingRegion(formsElement, new Rectangle(0, -request.Request.Height, CollectionView.Frame.Width, request.Request.Height));
formsElement.MeasureInvalidated += OnFormsElementMeasureInvalidated;
}
else if (uiView != null)
{
uiView.SizeToFit();
}
}
public void Recycle(ItemsView itemsView)
{
itemsView.RemoveLogicalChild(View);
}
public void Recycle(ItemsView itemsView)
{
View.BindingContext = null;
itemsView.RemoveLogicalChild(View);
_itemContentView.Recycle();
}
