iOS Swift 3: UICollectionView horizontal center and bigger cell - ios

Question

I want to build an collection view like this one:
Collection View
which has bigger cell at the center and cell is snapped to center of container view, but with Swift 3. I don't want to use library since I want to learn how to build a custom Collection View like this.
I've searched over SO but not found any appropriate solution yet

Answer 1

write that function
func collectionView(_ collectionView: UICollectionView, layout collectionViewLayout: UICollectionViewLayout, sizeForItemAt indexPath: IndexPath) -> CGSize {
return CGSize(width: collectionView.frame.size.width, height: collectionView.frame.size.height)
}
make collection view [scroll Direction] Horizontal
and [scrolling] tick scrolling enable and paging enable
make cell biger
override func viewWillTransition(to size: CGSize, with coordinator: UIViewControllerTransitionCoordinator) {
let offSet = self.collectionView.contentOffset
let width = self.collectionView.bounds.size.width
let index = round(offSet.x / width)
let newPoint = CGPoint(x: index * size.width, y: offSet.y)
coordinator.animate(alongsideTransition: { (UIViewControllerTransitionCoordinatorContext) in
},completion: {(UIVIewTransitionCoordinatorContext) in
self.collectionView.reloadData()
self.collectionView.setContentOffset(newPoint, animated: true)
})
}

Answer 2

To achieve this you will need to subclass UICollectionViewFlowLayout and override:
- (UICollectionViewLayoutAttributes *)layoutAttributesForItemAtIndexPath:(NSIndexPath *)indexPath
then call super.layoutAt... and alter the cell it returns via its .transform attribute and return your altered attributes
Here is an example I made previously.
override func layoutAttributesForElements(in rect: CGRect) -> [UICollectionViewLayoutAttributes]? {
var att = super.layoutAttributesForElements(in: rect)!
if !(delegate?.reelPlayerFlowIsPreviewMode() ?? true) {
return att
}
let region = CGRect(x: (self.collectionView?.contentOffset.x)!,
y: (self.collectionView?.contentOffset.y)!,
width: (self.collectionView?.bounds.size.width)!,
height: (self.collectionView?.bounds.size.height)!)
let center = CGPoint(x: region.midX, y: region.midY)
for theCell in att {
print("\(theCell.indexPath.item)\n\(theCell)\n")
let cell = theCell.copy() as! UICollectionViewLayoutAttributes
var f = cell.frame
let cellCenter = CGPoint(x: f.midX, y: f.midY)
let realDistance = min(center.x - cellCenter.x, region.width)
let distance = abs(realDistance)
let d = (region.width - distance) / region.width
let p = (max(d, ReelPlayerFlowLayout.minPercent) * ReelPlayerFlowLayout.maxPercent)
f.origin.x += (realDistance * ((1 - ReelPlayerFlowLayout.maxPercent) + (ReelPlayerFlowLayout.maxPercent - ReelPlayerFlowLayout.minPercent)))
cell.frame = f
cell.size = CGSize (width: f.width * p, height: f.height * p)
let index = att.index(of: theCell)!
att[index] = cell
}
return att
}