NSIndexPath GetIndexPathForCenteredItem(UICollectionView collectionView)
{
var centerPoint = new CGPoint(collectionView.Center.X + collectionView.ContentOffset.X, collectionView.Center.Y + collectionView.ContentOffset.Y);
var centerIndexPath = collectionView.IndexPathForItemAtPoint(centerPoint);
return(centerIndexPath);
}
private void SnapToCenter(UICollectionView collectionView)
{
if (collectionView == null || !_weakElement.TryGetTarget(out var element))
{
return;
}
var firstIndex = NSIndexPath.FromItemSection(0, 0);
if (IsCellFullyVisible(collectionView, firstIndex))
{
// Check if first item is fully visible, if true don't snap.
collectionView.ScrollToItem(firstIndex, UICollectionViewScrollPosition.CenteredHorizontally, true);
return;
}
var lastIndex = NSIndexPath.FromItemSection(collectionView.NumberOfItemsInSection(0) - 1, 0);
if (IsCellFullyVisible(collectionView, lastIndex))
{
// Check if last item is fully visible, if true don't snap.
collectionView.ScrollToItem(lastIndex, UICollectionViewScrollPosition.CenteredHorizontally, true);
return;
}
var collectionViewCenter = collectionView.Center;
var contentOffset = collectionView.ContentOffset;
var center = new CGPoint(
collectionViewCenter.X
+ contentOffset.X
+ (nfloat)element.CollectionPadding.Left
- (nfloat)element.CollectionPadding.Right,
collectionViewCenter.Y
+ contentOffset.Y
+ (nfloat)element.CollectionPadding.Top
- (nfloat)element.CollectionPadding.Bottom);
var indexPath = collectionView.IndexPathForItemAtPoint(center);
if (indexPath == null)
{
// Point is right between two cells: picking one
var indexes = collectionView.IndexPathsForVisibleItems.OrderBy(i => i.Item).ToArray();
if (indexes.Length > 0)
{
int middleIndex = (indexes.Count() - 1) / 2;
var candidateIndexPath = indexes[middleIndex];
if (candidateIndexPath.Row < element.CurrentIndex)
{
indexPath = candidateIndexPath;
}
else
{
indexPath = indexes[middleIndex + 1 > indexes.Length ? middleIndex : middleIndex + 1];
}
}
}
collectionView.ScrollToItem(indexPath, UICollectionViewScrollPosition.CenteredHorizontally, true);
}
public CalendarItem?CalendarItemAtPoint(CGPoint point)
{
var indexPath = collectionView.IndexPathForItemAtPoint(point);
if (indexPath != null && indexPath.Item < calendarItems.Count)
{
return(calendarItems[(int)indexPath.Item]);
}
return(null);
}
private NSIndexPath IndexPathForCenterCellFromCollectionView(UICollectionView collectionView)
{
var point = collectionView.ConvertPointFromView(collectionView.Center, collectionView.Superview);
var indexPath = collectionView.IndexPathForItemAtPoint(point);
if (indexPath != null)
{
return(indexPath);
}
else
{
return(collectionView.IndexPathsForVisibleItems.First());
}
}
private void GestureAction(UITapGestureRecognizer tap)
{
try
{
var touchLocation = tap.LocationOfTouch(0, CollectionResult);
var indexP = CollectionResult.IndexPathForItemAtPoint(touchLocation);
var index = (int)indexP.Item;
if (index >= 0 && index < ResultItems.Count)
{
RemoveItem(index);
}
}
catch (Exception ex)
{
Console.WriteLine(ex.StackTrace);
}
}
public static int GetCenteredIndex(this UICollectionView collectionView)
{
var centerItemIndex = -1;
var indexPathsForVisibleItems = collectionView.IndexPathsForVisibleItems.OrderBy(x => x.Row).ToList();
if (indexPathsForVisibleItems.Count == 0)
{
return(-1);
}
var firstVisibleItemIndex = (int)indexPathsForVisibleItems.First().Item;
var centerPoint = new CGPoint(collectionView.Center.X + collectionView.ContentOffset.X, collectionView.Center.Y + collectionView.ContentOffset.Y);
var centerIndexPath = collectionView.IndexPathForItemAtPoint(centerPoint);
centerItemIndex = centerIndexPath?.Row ?? firstVisibleItemIndex;
return(centerItemIndex);
}
public override void ViewDidLoad()
{
base.ViewDidLoad();
//Calculate Cell Size for screen resolution
CGSize CellSize = GetSize();
/*
* Initialize the collectionview layout
*/
UICollectionViewFlowLayout layout = new UICollectionViewFlowLayout
{
SectionInset = new UIEdgeInsets(20, 20, 20, 20),
MinimumInteritemSpacing = 1,
MinimumLineSpacing = 10,
ItemSize = CellSize //new SizeF(110, 110)
};
/*
* Initialize the CollectionViewSource and UICollectionView
*/
CollectionViewSource = new CollectionViewImageStackSource();
CollectionViewSource.ImageViewSize = new SizeF((float)CellSize.Width, (float)CellSize.Height);
CollectionView = new UICollectionView(UIScreen.MainScreen.Bounds, layout);
CollectionView.BackgroundColor = AppColors.LIGHT_TEAL;
var longPressGesture = new UILongPressGestureRecognizer(gesture =>
{
// Take action based on state
switch (gesture.State)
{
case UIGestureRecognizerState.Began:
var selectedIndexPath = CollectionView.IndexPathForItemAtPoint(gesture.LocationInView(View));
if (selectedIndexPath != null)
{
CollectionView.BeginInteractiveMovementForItem(selectedIndexPath);
}
break;
case UIGestureRecognizerState.Changed:
CollectionView.UpdateInteractiveMovement(gesture.LocationInView(View));
break;
case UIGestureRecognizerState.Ended:
CollectionView.EndInteractiveMovement();
break;
default:
CollectionView.CancelInteractiveMovement();
break;
}
});
// Add the custom recognizer to the collection view
CollectionView.AddGestureRecognizer(longPressGesture);
CollectionView.ShowsHorizontalScrollIndicator = true;
CollectionView.RegisterClassForCell(typeof(UserCell2), UserCell2.CellID);
CollectionView.ShowsHorizontalScrollIndicator = true;
CollectionView.Source = CollectionViewSource;
}
private void UpdateCurrentIndex(UICollectionView collectionView)
{
if (collectionView == null || !_weakElement.TryGetTarget(out var element))
{
return;
}
nint newIndex;
if (element.SnapStyle == SnapStyle.Center)
{
var lastIndex = NSIndexPath.FromItemSection(collectionView.NumberOfItemsInSection(0) - 1, 0);
if (IsCellFullyVisible(collectionView, lastIndex))
{
newIndex = lastIndex.Item;
}
else if (IsFirstCellFullyVisible(collectionView))
{
newIndex = 0;
}
else
{
var collectionViewCenter = collectionView.Center;
var contentOffset = collectionView.ContentOffset;
var center = new CGPoint(
collectionViewCenter.X
+ contentOffset.X
+ (nfloat)element.CollectionPadding.Left
- (nfloat)element.CollectionPadding.Right,
collectionViewCenter.Y
+ contentOffset.Y
+ (nfloat)element.CollectionPadding.Top
- (nfloat)element.CollectionPadding.Bottom);
var centerPath = collectionView.IndexPathForItemAtPoint(center);
if (centerPath == null)
{
InternalLogger.Warn(
"Failed to find a NSIndexPath in SnapStyle center context: UpdateCurrentIndex returns nothing");
return;
}
newIndex = centerPath.Item;
}
}
else
{
var firstCellBounds = new CGRect
{
X = collectionView.ContentOffset.X,
Y = collectionView.ContentOffset.Y,
Size = new CGSize(element.ItemWidth, element.ItemHeight),
};
var firstCellCenter = new CGPoint(firstCellBounds.GetMidX(), firstCellBounds.GetMidY());
var indexPath = collectionView.IndexPathForItemAtPoint(firstCellCenter);
if (indexPath == null)
{
return;
}
newIndex = indexPath.Row;
}
InternalLogger.Info($"UpdateCurrentIndex => {newIndex}");
element.CurrentIndex = (int)newIndex;
}
