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);
}
internal UIEdgeInsets GetInsetForSection(ItemsViewLayout itemsViewLayout,
UICollectionView collectionView, nint section)
{
var uIEdgeInsets = ItemsViewLayout.GetInsetForSection(collectionView, itemsViewLayout, section);
if (!ItemsView.IsGrouped)
{
return(uIEdgeInsets);
}
// If we're grouping, we'll need to inset the sections to maintain the spacing between the
// groups and their group headers/footers
nfloat spacing = itemsViewLayout.GetMinimumLineSpacingForSection(collectionView, itemsViewLayout, section);
var top = uIEdgeInsets.Top;
var left = uIEdgeInsets.Left;
if (itemsViewLayout.ScrollDirection == UICollectionViewScrollDirection.Horizontal)
{
left += spacing;
}
else
{
top += spacing;
}
return(new UIEdgeInsets(top, left,
uIEdgeInsets.Bottom, uIEdgeInsets.Right));
}
protected override void Dispose(bool disposing)
{
if (_disposed)
{
return;
}
_disposed = true;
if (disposing)
{
ItemsSource?.Dispose();
CollectionView.Delegate = null;
Delegator?.Dispose();
_emptyUIView?.Dispose();
_emptyUIView = null;
_emptyViewFormsElement = null;
ItemsViewLayout?.Dispose();
CollectionView?.Dispose();
}
base.Dispose(disposing);
}
void CheckForEmptySource()
{
var wasEmpty = _isEmpty;
_isEmpty = ItemsSource.ItemCount == 0;
if (_isEmpty)
{
_measurementCells.Clear();
ItemsViewLayout?.ClearCellSizeCache();
}
if (wasEmpty != _isEmpty)
{
UpdateEmptyViewVisibility(_isEmpty);
}
if (wasEmpty && !_isEmpty)
{
// If we're going from empty to having stuff, it's possible that we've never actually measured
// a prototype cell and our itemSize or estimatedItemSize are wrong/unset
// So trigger a constraint update; if we need a measurement, that will make it happen
ItemsViewLayout.ConstrainTo(CollectionView.Bounds.Size);
}
}
public CarouselViewController(CarouselView itemsView, ItemsViewLayout layout) : base(itemsView, layout)
{
Carousel = itemsView;
CollectionView.AllowsSelection = false;
CollectionView.AllowsMultipleSelection = false;
Carousel.Scrolled += CarouselViewScrolled;
_oldViews = new List <View>();
}
public ReorderableItemsViewController(TItemsView reorderableItemsView, ItemsViewLayout layout)
: base(reorderableItemsView, layout)
{
// The UICollectionViewController has built-in recognizer for reorder that can be installed by setting "InstallsStandardGestureForInteractiveMovement".
// For some reason it only seemed to work when the CollectionView was inside the Flyout section of a FlyoutPage.
// The UILongPressGestureRecognizer is simple enough to set up so let's just add our own.
InstallsStandardGestureForInteractiveMovement = false;
}
public virtual void UpdateItemsSource()
{
_measurementCells.Clear();
ItemsViewLayout?.ClearCellSizeCache();
ItemsSource = CreateItemsViewSource();
CollectionView.ReloadData();
CollectionView.CollectionViewLayout.InvalidateLayout();
}
protected virtual void UpdateDefaultCell(DefaultCell cell, NSIndexPath indexPath)
{
cell.Label.Text = ItemsSource[indexPath].ToString();
if (cell is ItemsViewCell constrainedCell)
{
ItemsViewLayout.PrepareCellForLayout(constrainedCell);
}
}
void ConstrainToItemsView()
{
var itemsViewWidth = ItemsView.Width;
var itemsViewHeight = ItemsView.Height;
if (itemsViewHeight < 0 || itemsViewWidth < 0)
{
ItemsViewLayout.UpdateConstraints(CollectionView.Bounds.Size);
return;
}
ItemsViewLayout.UpdateConstraints(new CGSize(itemsViewWidth, itemsViewHeight));
}
protected virtual void CacheCellAttributes(NSIndexPath indexPath, CGSize size)
{
if (!ItemsSource.IsIndexPathValid(indexPath))
{
// The upate might be coming from a cell that's being removed; don't cache it.
return;
}
var item = ItemsSource[indexPath];
if (item != null)
{
ItemsViewLayout.CacheCellSize(item, size);
}
}
internal CGSize GetSizeForItem(NSIndexPath indexPath)
{
if (ItemsViewLayout.EstimatedItemSize.IsEmpty)
{
return(ItemsViewLayout.ItemSize);
}
if (ItemsSource.IsIndexPathValid(indexPath))
{
var item = ItemsSource[indexPath];
if (item != null && ItemsViewLayout.TryGetCachedCellSize(item, out CGSize size))
{
return(size);
}
}
return(ItemsViewLayout.EstimatedItemSize);
}
public void UpdateLayout(ItemsViewLayout newLayout)
{
// Ignore calls to this method if the new layout is the same as the old one
if (CollectionView.CollectionViewLayout == newLayout)
{
return;
}
ItemsViewLayout = newLayout;
_initialized = false;
EnsureLayoutInitialized();
if (_initialized)
{
// Reload the data so the currently visible cells get laid out according to the new layout
CollectionView.ReloadData();
}
}
void EnsureLayoutInitialized()
{
if (_initialized)
{
return;
}
_initialized = true;
ItemsViewLayout.GetPrototype = GetPrototype;
Delegator = CreateDelegator();
CollectionView.Delegate = Delegator;
ItemsViewLayout.SetInitialConstraints(CollectionView.Bounds.Size);
CollectionView.SetCollectionViewLayout(ItemsViewLayout, false);
UpdateEmptyView();
}
protected ItemsViewController(TItemsView itemsView, ItemsViewLayout layout) : base(layout)
{
ItemsView = itemsView;
ItemsViewLayout = layout;
}
protected override ItemsViewController <TItemsView> CreateController(TItemsView itemsView, ItemsViewLayout layout) => new ReorderableItemsViewController <TItemsView>(itemsView, layout);
public StructuredItemsViewController(TItemsView structuredItemsView, ItemsViewLayout layout)
: base(structuredItemsView, layout)
{
}
protected override ItemsViewController <TItemsView> CreateController(TItemsView itemsView, ItemsViewLayout layout) => new StructuredItemsViewController <TItemsView>(itemsView, layout);
protected virtual void UpdateLayout()
{
_layout = SelectLayout();
Controller?.UpdateLayout(_layout);
}
public CarouselViewDelegator(ItemsViewLayout itemsViewLayout, CarouselViewController itemsViewController)
: base(itemsViewLayout, itemsViewController)
{
}
public SelectableItemsViewController(TItemsView selectableItemsView, ItemsViewLayout layout)
: base(selectableItemsView, layout)
{
}
protected override CarouselViewController CreateController(CarouselView newElement, ItemsViewLayout layout) => new CarouselViewController(newElement, layout);
protected abstract ItemsViewController <TItemsView> CreateController(TItemsView newElement, ItemsViewLayout layout);
public GroupableItemsViewController(TItemsView groupableItemsView, ItemsViewLayout layout)
: base(groupableItemsView, layout)
{
_isGrouped = ItemsView.IsGrouped;
}
public GroupableItemsViewDelegator(ItemsViewLayout itemsViewLayout, TViewController itemsViewController)
: base(itemsViewLayout, itemsViewController)
{
}
public ItemsViewDelegator(ItemsViewLayout itemsViewLayout, TViewController itemsViewController)
{
ItemsViewLayout = itemsViewLayout;
ViewController = itemsViewController;
}