I have a horizontal collectionView and i would like to manage that when scrolling it, the centre cell becomes larger. So, each time a cell is the center cell it will be larger than the others. Check the image beneath.
Can anyone help me with the best way to do this? Thanks in advance!
My code so far:
import UIKit
class ViewController: UIViewController, UICollectionViewDataSource, UICollectionViewDelegate {
@IBOutlet var horizontalCollectionView: UICollectionView!
@IBOutlet var verticalCollectionView: UICollectionView!
var horizontal = ["1","2","3","4","5","6","7","8","9","10","1","2","3","4","5","6","7","8","9","10"]
var horizontalCellSize = CGSize(width: 50, height: 50)
var horizontalLargeCellSize = CGSize(width: 80, height: 80)
var centerCell = UICollectionViewCell()
var cellIsInCenter = false
var myIndexPath = IndexPath()
override func viewDidLoad() {
super.viewDidLoad()
}
// When the main view's dimensions change this will re-layout the collection view
override func viewWillLayoutSubviews() {
verticalCollectionView.collectionViewLayout.invalidateLayout()
}
func collectionView(_ collectionView: UICollectionView, numberOfItemsInSection section: Int) -> Int {
return horizontal.count
}
func collectionView(_ collectionView: UICollectionView, cellForItemAt indexPath: IndexPath) -> UICollectionViewCell {
if collectionView == horizontalCollectionView {
let horizontalCell = collectionView.dequeueReusableCell(withReuseIdentifier: "HorizontalCell", for: indexPath) as! HorizontalCell
horizontalCell.backgroundColor = UIColor.blue
horizontalCell.textLabel.text = horizontal[indexPath.row]
return horizontalCell
}
else {
let verticalCell = collectionView.dequeueReusableCell(withReuseIdentifier: "VerticalCell", for: indexPath) as! VerticalCell
verticalCell.backgroundColor = UIColor.red
verticalCell.textLabel.text = horizontal[indexPath.row]
return verticalCell
}
}
// MARK: UIScrollViewDelegate
func scrollViewDidScroll(_ scrollView: UIScrollView) {
if scrollView == self.horizontalCollectionView {
let horizontalScrollPosition = scrollView.contentOffset.x * 35
self.verticalCollectionView.delegate = nil
self.verticalCollectionView.contentOffset = CGPoint(x: 0, y: horizontalScrollPosition)
self.verticalCollectionView.delegate = self
}
if scrollView == self.verticalCollectionView {
let verticalScrollPosition = scrollView.contentOffset.y
self.horizontalCollectionView.delegate = nil
self.horizontalCollectionView.contentOffset = CGPoint(x: verticalScrollPosition, y: 0)
self.horizontalCollectionView.delegate = self
}
}
// MARK: CollectionViewLayout
func collectionView(_ collectionView: UICollectionView,
layout collectionViewLayout: UICollectionViewLayout,
sizeForItemAtIndexPath indexPath: NSIndexPath) -> CGSize {
if collectionView == verticalCollectionView {
let size = CGSize(width: collectionView.bounds.width, height: collectionView.bounds.height)
return size
}
if indexPath.item == 3 {
return CGSize(width: 70, height: 70)
}
return CGSize(width: 50, height: 50)
}
func collectionView(_ collectionView: UICollectionView, didSelectItemAt indexPath: IndexPath) {
self.verticalCollectionView.scrollToItem(at: indexPath, at: .centeredVertically, animated: true)
print("\(indexPath)")
}
func scrollViewDidEndDecelerating(_ scrollView: UIScrollView) {
var closestCell: UICollectionViewCell = self.horizontalCollectionView.visibleCells[0]
for cell in self.horizontalCollectionView.visibleCells as [UICollectionViewCell] {
let closestCellDelta = abs(closestCell.center.x - self.horizontalCollectionView.bounds.size.width / 2.0 - self.horizontalCollectionView.contentOffset.x)
let cellDelta = abs(cell.center.x - self.horizontalCollectionView.bounds.size.width/2.0 - self.horizontalCollectionView.contentOffset.x)
if (cellDelta < closestCellDelta){
closestCell = cell
self.centerCell = cell
self.cellIsInCenter = true
horizontalCellSize = CGSize(width: 80, height: 50)
}
}
let indexPath = self.horizontalCollectionView.indexPath(for: closestCell)
self.horizontalCollectionView.scrollToItem(at: indexPath!, at: .centeredHorizontally , animated: true)
if closestCell.backgroundColor == UIColor.black {
closestCell.backgroundColor = UIColor.blue
}
horizontalCollectionView.reloadItems(at: [self.horizontalCollectionView.indexPath(for: closestCell)!])
closestCell.backgroundColor = UIColor.black
}
}
Try this out:
func collectionView(_ collectionView: UICollectionView,layout collectionViewLayout: UICollectionViewLayout,
sizeForItemAtIndexPath indexPath: NSIndexPath) -> CGSize {
if collectionView == verticalCollectionView {
let size = CGSize(width: collectionView.bounds.width, height: collectionView.bounds.height)
return size
}
let point = CGPoint(x: self.view.frame.size.width/2.0, y:35 )
//or you can try this code also
//let point = CGPoint(x: UIScreen.main.bounds.width/2, y:35 )
print(point)
let centerIndex = self.collectionView.indexPathForItemAtPoint(point)
if indexPath.item == centerIndex {
return CGSize(width: 70, height: 70)
}
return CGSize(width: 50, height: 50)
}
This code gives you the index of the item at the center of the collection View. Hope this helps
来源：https://stackoverflow.com/questions/40741161/swift-how-to-get-the-centre-cell-in-a-collectionview-and-resize-it-when-scrollin