public UICollectionViewCell CreateMeasurementCell(NSIndexPath indexPath)
{
if (ItemsView.ItemTemplate == null)
{
var frame = new CGRect(0, 0, ItemsViewLayout.EstimatedItemSize.Width, ItemsViewLayout.EstimatedItemSize.Height);
DefaultCell cell;
if (ItemsViewLayout.ScrollDirection == UICollectionViewScrollDirection.Horizontal)
{
cell = new HorizontalDefaultCell(frame);
}
else
{
cell = new VerticalDefaultCell(frame);
}
UpdateDefaultCell(cell, indexPath);
return(cell);
}
TemplatedCell templatedCell = CreateAppropriateCellForLayout();
UpdateTemplatedCell(templatedCell, indexPath);
// Keep this cell around, we can transfer the contents to the actual cell when the UICollectionView creates it
_measurementCells[ItemsSource[indexPath]] = templatedCell;
return(templatedCell);
}
protected virtual void UpdateTemplatedCell(TemplatedCell cell, NSIndexPath indexPath)
{
cell.ContentSizeChanged -= CellContentSizeChanged;
cell.LayoutAttributesChanged -= CellLayoutAttributesChanged;
var bindingContext = ItemsSource[indexPath];
// If we've already created a cell for this index path (for measurement), re-use the content
if (_measurementCells.TryGetValue(bindingContext, out TemplatedCell measurementCell))
{
_measurementCells.Remove(bindingContext);
measurementCell.ContentSizeChanged -= CellContentSizeChanged;
measurementCell.LayoutAttributesChanged -= CellLayoutAttributesChanged;
cell.UseContent(measurementCell);
}
else
{
cell.Bind(ItemsView.ItemTemplate, ItemsSource[indexPath], ItemsView);
}
cell.ContentSizeChanged += CellContentSizeChanged;
cell.LayoutAttributesChanged += CellLayoutAttributesChanged;
ItemsViewLayout.PrepareCellForLayout(cell);
}
protected virtual void UpdateTemplatedCell(TemplatedCell cell, NSIndexPath indexPath)
{
ApplyTemplateAndDataContext(cell, indexPath);
if (cell is ItemsViewCell constrainedCell)
{
_layout.PrepareCellForLayout(constrainedCell);
}
}
void UpdateTemplatedSupplementaryView(TemplatedCell cell, NSString elementKind, NSIndexPath indexPath)
{
ApplyTemplateAndDataContext(cell, elementKind, indexPath);
if (cell is ItemsViewCell constrainedCell)
{
cell.ConstrainTo(ItemsViewLayout.ConstrainedDimension);
}
}
internal void UseContent(TemplatedCell measurementCell)
{
// Copy all the content and values from the measurement cell
ConstrainedDimension = measurementCell.ConstrainedDimension;
ConstrainedSize = measurementCell.ConstrainedSize;
CurrentTemplate = measurementCell.CurrentTemplate;
_size = measurementCell._size;
SetRenderer(measurementCell.VisualElementRenderer);
}
protected virtual void UpdateTemplatedCell(TemplatedCell cell, NSIndexPath indexPath)
{
cell.ContentSizeChanged -= CellContentSizeChanged;
cell.Bind(ItemsView, ItemsSource[indexPath]);
cell.ContentSizeChanged += CellContentSizeChanged;
ItemsViewLayout.PrepareCellForLayout(cell);
}
void ApplyTemplateAndDataContext(TemplatedCell cell, NSIndexPath indexPath)
{
// We need to create a renderer, which means we need a template
var view = _itemsView.ItemTemplate.CreateContent() as View;
_itemsView.AddLogicalChild(view);
var renderer = CreateRenderer(view);
BindableObject.SetInheritedBindingContext(view, _itemsSource[indexPath.Row]);
cell.SetRenderer(renderer);
}
void ApplyTemplateAndDataContext(TemplatedCell cell, NSIndexPath indexPath)
{
// We need to create a renderer, which means we need a template
var templateElement = _itemsView.ItemTemplate.CreateContent() as View;
IVisualElementRenderer renderer = CreateRenderer(templateElement);
if (renderer != null)
{
BindableObject.SetInheritedBindingContext(renderer.Element, _itemsSource[indexPath.Row]);
cell.SetRenderer(renderer);
}
}
void UpdateTemplatedSupplementaryView(TemplatedCell cell, NSString elementKind, NSIndexPath indexPath)
{
DataTemplate template = elementKind == UICollectionElementKindSectionKey.Header
? ItemsView.GroupHeaderTemplate
: ItemsView.GroupFooterTemplate;
var bindingContext = ItemsSource.Group(indexPath);
cell.Bind(template, bindingContext, ItemsView);
if (cell is ItemsViewCell)
{
cell.ConstrainTo(ItemsViewLayout.ConstrainedDimension);
}
}
public TemplatedCell CreateMeasurementCell(NSIndexPath indexPath)
{
if (ItemsView.ItemTemplate == null)
{
return(null);
}
TemplatedCell templatedCell = CreateAppropriateCellForLayout();
UpdateTemplatedCell(templatedCell, indexPath);
// Keep this cell around, we can transfer the contents to the actual cell when the UICollectionView creates it
_measurementCells[indexPath] = templatedCell;
return(templatedCell);
}
void ApplyTemplateAndDataContext(TemplatedCell cell, NSString elementKind, NSIndexPath indexPath)
{
DataTemplate template;
if (elementKind == UICollectionElementKindSectionKey.Header)
{
template = GroupableItemsView.GroupHeaderTemplate;
}
else
{
template = GroupableItemsView.GroupFooterTemplate;
}
var templateElement = template.CreateContent() as View;
var renderer = CreateRenderer(templateElement);
BindableObject.SetInheritedBindingContext(renderer.Element, ItemsSource.Group(indexPath));
cell.SetRenderer(renderer);
}
void ApplyTemplateAndDataContext(TemplatedCell cell, NSIndexPath indexPath)
{
var template = _itemsView.ItemTemplate;
var item = _itemsSource[indexPath.Row];
// Run this through the extension method in case it's really a DataTemplateSelector
template = template.SelectDataTemplate(item, _itemsView);
// Create the content and renderer for the view and
var view = template.CreateContent() as View;
var renderer = CreateRenderer(view);
cell.SetRenderer(renderer);
// Bind the view to the data item
view.BindingContext = _itemsSource[indexPath.Row];
// And make sure it's a "child" of the ItemsView
_itemsView.AddLogicalChild(view);
}
// These measurement methods are only necessary for iOS 10 and lower
CGSize MeasureTemplatedSupplementaryCell(NSString elementKind, nint section, NSString reuseId)
{
if (_measurementCellTemplated == null)
{
if (reuseId == HorizontalSupplementaryView.ReuseId)
{
_measurementCellTemplated = new HorizontalSupplementaryView(CGRect.Empty);
}
else if (reuseId == VerticalSupplementaryView.ReuseId)
{
_measurementCellTemplated = new VerticalSupplementaryView(CGRect.Empty);
}
}
if (_measurementCellTemplated == null)
{
return(CGSize.Empty);
}
UpdateTemplatedSupplementaryView(_measurementCellTemplated, elementKind, NSIndexPath.FromItemSection(0, section));
return(_measurementCellTemplated.Measure());
}
