I'm having an issue in my cellForItemAtIndexPath where I am setting an image to my cell's UIButton but every time I scroll the collectionView's cells, it's placing the image on top of the already set image again and again. I can tell because the shadow of the image is getting thicker and thicker. I'm pulling the images from an array that I created of image literals in that swift file and the correct images are loading so there's no problem there. I'm sure this is a simple fix for most but I can't seem to find an answer anywhere.
Image of my cellForItemAtIndexPath function
My app running before I scroll
App after scrolling a bit
override func collectionView(_ collectionView: UICollectionView, cellForItemAt indexPath: IndexPath) -> UICollectionViewCell {
let cell = collectionView.dequeueReusableCell(withReuseIdentifier: "cellId", for: indexPath) as! HomeViewCell
collectionView.bounces = false
let imageNumber = indexPath.item
let collectionImage: UIButton = {
let image = UIButton()
image.setImage(collectionImageArray[imageNumber].withRenderingMode(.alwaysOriginal), for: .normal)
image.contentMode = .scaleAspectFit
image.addTarget(self, action: #selector(handleCollectionTap), for: .touchUpInside)
return image
}()
collectionImage.imageView?.image = collectionImageArray[imageNumber]
cell.addSubview(collectionImage)
collectionImage.anchor(top: nil, left: nil, bottom: nil, right: nil, paddingTop: 0, paddingLeft: 0, paddingBottom: 0, paddingRight: 0, width: 0, height: 0)
collectionImage.centerXAnchor.constraint(equalTo: cell.centerXAnchor).isActive = true
collectionImage.centerYAnchor.constraint(equalTo: cell.centerYAnchor).isActive = true
print(imageNumber)
return cell
}
If anyone else comes across this issue (or maybe I'm the only dumb one), the problem was that I should have created my UIButton, added the subview, and constrained it inside of the cell class and from the cellForItem AtindexPath method set the image and target handler like this.
class HomeViewCell: UICollectionViewCell {
let collectionImage: UIButton = {
let image = UIButton(type: .custom)
image.contentMode = .scaleAspectFit
return image
}()
override init(frame: CGRect) {
super.init(frame: frame)
addSubview(collectionImage)
collectionImage.anchor(top: nil, left: nil, bottom: nil, right: nil, paddingTop: 0, paddingLeft: 0, paddingBottom: 0, paddingRight: 0, width: 0, height: 0)
collectionImage.centerXAnchor.constraint(equalTo: centerXAnchor).isActive = true
collectionImage.centerYAnchor.constraint(equalTo: centerYAnchor).isActive = true
}
required init?(coder aDecoder: NSCoder) {
fatalError("init(coder:) has not been implemented")
}
}
override func collectionView(_ collectionView: UICollectionView, cellForItemAt indexPath: IndexPath) -> UICollectionViewCell {
let cell = collectionView.dequeueReusableCell(withReuseIdentifier: "cellId", for: indexPath) as! HomeViewCell
collectionView.bounces = false
let imageNumber = indexPath.item
let image = collectionImageArray[imageNumber].withRenderingMode(.alwaysOriginal)
cell.collectionImage.setImage(image, for: .normal)
cell.collectionImage.addTarget(self, action: #selector(handleCollectionTap), for: .touchUpInside)
print(imageNumber)
return cell
}
func collectionView(_ collectionView: UICollectionView, layout collectionViewLayout: UICollectionViewLayout, sizeForItemAt indexPath: IndexPath) -> CGSize {
return CGSize(width: view.frame.width, height: view.frame.height)
}
#objc func handleCollectionTap() {
let layout = UICollectionViewFlowLayout()
let cardViewer = CardViewerController(collectionViewLayout: layout)
present(cardViewer, animated: true, completion: nil)
}
Everything is running smoothly now! :)
Related
I have an issue where a custom UICollectionViewCell will not appear in the UICollectionView. Anyone know what I am missing? I appreciate it in advance.
Below is my UICollectionViewController:
private let reuseIdentifier = "FeedCell"
class FeedViewController: UICollectionViewController, UICollectionViewDelegateFlowLayout {
// MARK: Properties
override func viewDidLoad() {
super.viewDidLoad()
// Register cell classes
self.collectionView!.register(FeedCell.self, forCellWithReuseIdentifier: reuseIdentifier)
}
//MARK: - UICollectionViewFlowLayout
func collectionView(_ collectionView: UICollectionView, layout collectionViewLayout: UICollectionViewLayout, sizeForItemAt indexPath: IndexPath) -> CGSize {
let width = view.frame.width
return CGSize(width: width, height: width)
}
//MARK: - UICollectionViewDataSource
override func numberOfSections(in collectionView: UICollectionView) -> Int {
return 1
}
override func collectionView(_ collectionView: UICollectionView, numberOfItemsInSection section: Int) -> Int {
return 5
}
override func collectionView(_ collectionView: UICollectionView, cellForItemAt indexPath: IndexPath) -> UICollectionViewCell {
let cell = collectionView.dequeueReusableCell(withReuseIdentifier: reuseIdentifier, for: indexPath) as! FeedCell
print("CELL")
cell.backgroundColor = .black
return cell
}
//FEED CELL
class FeedCell: UICollectionViewCell {
//MARK: - Properties
let profileImageView: CustomeImageView = {
let imageView = CustomeImageView()
imageView.contentMode = .scaleAspectFill
imageView.clipsToBounds = true
imageView.backgroundColor = .lightGray
return imageView
}()
override init(frame: CGRect) {
super.init(frame: frame)
self.backgroundColor = .red
print("feedcell1")
addSubview(profileImageView)
profileImageView.anchor(top: topAnchor, bottom: nil, left: leftAnchor, right: nil, paddingTop: 8, paddingBottom: 0, paddingLeft: 8, paddingRight: 0, width: 40, height: 40)
profileImageView.layer.cornerRadius = 40/2
}
required init?(coder: NSCoder) {
fatalError("init(coder:) has not been implemented")
}
}
THANKS :)
The issue was I had previously instantiated FeedViewController with
FeedViewController(collectionViewLayout: UICollectionViewLayout())
instead of `FeedViewController(collectionViewLayout:
UICollectionViewFlowLayout()))` since FeedViewController has
UICollectionViewDelegateFlowLayout protocol.
I'm trying to select the first Item in CollectionView when the Collectionview loads. I found many solutions for Swift 3 but nothing of that worked for me in Swift4. What I tried(viewDidAppear):
import UIKit
import SDWebImage
class PostsTab_Details: UIViewController, UICollectionViewDelegate, UICollectionViewDataSource, UICollectionViewDelegateFlowLayout {
#IBOutlet weak var PostsSelectRarityCollectionView: UICollectionView!
#IBOutlet weak var RarityTypeLbl: UILabel!
//Center my Collectionview Horizontal
func collectionView(_ collectionView: UICollectionView, layout collectionViewLayout: UICollectionViewLayout, insetForSectionAt section: Int) -> UIEdgeInsets {
let totalCellWidth = 100 * (selectedPosts?.rarity.count)!
let totalSpacingWidth = 10 * (3 - 1)
let leftInset = (PostsSelectRarityCollectionView.frame.width - CGFloat(totalCellWidth + totalSpacingWidth)) / 2
let rightInset = leftInset
return UIEdgeInsetsMake(0, leftInset, 0, rightInset)
}
func collectionView(_ collectionView: UICollectionView, numberOfItemsInSection section: Int) -> Int {
return (selectedPosts?.rarity.count)!
}
func collectionView(_ collectionView: UICollectionView, cellForItemAt indexPath: IndexPath) -> UICollectionViewCell {
let cell = PostsSelectRarityCollectionView.dequeueReusableCell(withReuseIdentifier: "PostssTab_DetailCollectionCell", for: indexPath) as! PostsTab_DetailsCollectionViewCell
cell.PostssTab_DetailCollectionImage.sd_setImage(with: URL(string: (selectedPosts?.PostsImageURL)!))
return cell
}
func collectionView(_ collectionView: UICollectionView, didSelectItemAt indexPath: IndexPath) {
RarityTypeLbl.text = selectedPosts?.rarity[indexPath.row].rarity
}
//Tried this also with IndexPath(item: 0, section: 0)
override func viewDidAppear(_ animated: Bool) {
let selectedIndexPath = IndexPath(row: 0, section: 0)
PostsSelectRarityCollectionView.selectItem(at: selectedIndexPath, animated: true, scrollPosition: .right)
}
var selectedPosts: Posts?
override func viewDidLoad() {
PostsSelectRarityCollectionView.delegate = self
PostsSelectRarityCollectionView.dataSource = self
}
}
But this is not working... I hope someone knows what I'm doing wrong..
Thanks in advance
Update:
This worked for me now, thanks to Razib's answer:
override func viewWillAppear(_ animated: Bool) {
self.collectionView(PostsSelectRarityCollectionView, didSelectItemAt: IndexPath(row: 0, section: 0))
}
Your code seems okay to me. If you like to trigger the didSelectItemAt method, use the following code.
override func viewDidAppear(_ animated: Bool) {
self.PostsSelectRarityCollectionView(self.PostsSelectRarityCollectionView, didSelectItemAt: IndexPath(row: 0, section: 0))
}
To programmatically select the first Item in CollectionViewCell when the Collectionview loads you should code in viewDidAppear:
override func viewDidAppear(_ animated: Bool) {
let indexPath:IndexPath = IndexPath(row: 0, section: 0)
collectionView?.selectItem(at: indexPath, animated: false, scrollPosition: .top)
}
Try this (Swift 5):
let indexPath:IndexPath = IndexPath(row: 0, section: 0)
collectionView?.selectItem(at: indexPath, animated: false, scrollPosition: .top)
I want to get a deleteButton that is a delete image to sit on the outside of a collectionViewCell (it can be partially inside).
I looked at other SO answers and they said just play with the button's frame's Rect's x & y values which I did. When I set the x & y values to 0,0 I get:
class CustomCell: UICollectionViewCell {
#IBOutlet weak var imageView: UIImageView!
var deleteButton: UIButton!
var deleteButtonImg: UIImage!
override func awakeFromNib() {
super.awakeFromNib()
deleteButton = UIButton(frame: CGRect(x: 0, y: 0, width: frame.size.width/4, height: frame.size.width/4))
deleteButtonImg = UIImage(named: "delete-icon")!.withRenderingMode(.alwaysTemplate)
deleteButton.setImage(deleteButtonImg, for: .normal)
deleteButton.tintColor = UIColor.red
contentView.addSubview(deleteButton)
}
When I try to set the the Rect's x & y to -10,-10 the deleteButton gets clipped inside the cell's imageView. I don't have clipsToBounds set.
deleteButton = UIButton(frame: CGRect(x: -10, y: -10, width: frame.size.width/4, height: frame.size.width/4))
I even tried setting clipToBounds to false but I get the same effect as pic # 3.
func collectionView(_ collectionView: UICollectionView, cellForItemAt indexPath: IndexPath) -> UICollectionViewCell {
let cell = collectionView.dequeueReusableCell(withReuseIdentifier: "CustomCell", for: indexPath) as! CustomCell
cell.imageView.image = myImageArray[indexPath.row]
cell.imageView.clipsToBounds = false
return cell
}
Where am I going wrong?
The problem was inside storyboard I had a:
CollectionView
-CustomCell (type collectionViewCell)
-imageView
Under the Attributes Inspector, in the Drawing section, all 3 of these have the property clipsToBounds.
I overlooked the fact that I had clipsToBounds set to false (unchecked) on the imageView but set to true (checked) on the CustomCell and the CollectionView.
If anyone else has this problem make sure you uncheck clipsToBounds on the collectionView, collectionViewCell, and the imageView.
okay u can do like below, first create a xib file and replace default view with collection view cell and set up like below,
in the above image set the class name to CustomCell (In my case) and place image view (green ) and button (blue).
and in View controller,
override func viewDidLoad() {
super.viewDidLoad()
// Do any additional setup after loading the view, typically from a nib.
//register the nib to collectionview
self.aColectionView.register(UINib(nibName: "CustomCell", bundle: nil), forCellWithReuseIdentifier: "CUSTOM_CELL")
}
override func didReceiveMemoryWarning() {
super.didReceiveMemoryWarning()
// Dispose of any resources that can be recreated.
}
func numberOfSections(in collectionView: UICollectionView) -> Int {
return 1
}
func collectionView(_ collectionView: UICollectionView, numberOfItemsInSection section: Int) -> Int {
return 40
}
//cell creation as u are doing
func collectionView(_ collectionView: UICollectionView, cellForItemAt indexPath: IndexPath) -> UICollectionViewCell {
let cell:CustomCell = collectionView.dequeueReusableCell(withReuseIdentifier: "CUSTOM_CELL", for: indexPath) as! CustomCell
//set the image for custom cell
return cell
}
//return the required size
func collectionView(_ collectionView: UICollectionView, layout collectionViewLayout: UICollectionViewLayout, sizeForItemAt indexPath: IndexPath) -> CGSize {
return CGSize(width: 200, height: 150)
}
and output like below,
and in custom cell class, u add any other features like action for a button and other views related code
class CustomCell:UICollectionViewCell {
#IBOutlet weak var deleteButton: UIButton!
#IBOutlet weak var imageView: UIImageView!
//other view related code
}
I have a simple collection view test (based on an online tutorial) which works fine stand alone. But when I embed it in a navigation controller it stops working. I built the screen in code by (1) creating a headerView (64 pixel high) and added it to the view at the top. (2) I built a collection view and added it to the headerView.
Here is the code:
import UIKit
class ViewController: UIViewController,
UICollectionViewDelegate, UICollectionViewDataSource,
UINavigationControllerDelegate
{
var collectionView : UICollectionView!
var topView: UIView!
override func viewDidLoad() {
super.viewDidLoad()
var frame = CGRect(x:0,y:128, width:view.frame.width, height:64)
topView = UIView(frame:frame)
self.view.addSubview(topView)
// CollectionView
let layout: UICollectionViewFlowLayout = UICollectionViewFlowLayout()
layout.scrollDirection = .horizontal
layout.sectionInset = UIEdgeInsets(top: 0, left: 10, bottom: 0, right: 10)
layout.itemSize = CGSize(width: 50, height: 50)
frame = CGRect(x: 0, y: 0, width: Int(self.topView.frame.width), height: Int(self.topView.frame.height))
collectionView = UICollectionView (frame: frame, collectionViewLayout: layout)
collectionView.dataSource = self
collectionView.delegate = self
collectionView.register(UICollectionViewCell.self, forCellWithReuseIdentifier: "collectionCell")
collectionView.backgroundColor = UIColor.green
self.topView.addSubview(collectionView)
}
//MARK: - CollectionView
func collectionView(_ collectionView: UICollectionView, numberOfItemsInSection section: Int) -> Int {
return 14
}
func collectionView(_ collectionView: UICollectionView, cellForItemAt indexPath: IndexPath) -> UICollectionViewCell {
let cell = collectionView.dequeueReusableCell(withReuseIdentifier: "collectionCell", for: indexPath as IndexPath)
for v in cell.subviews {
v.removeFromSuperview()
}
cell.backgroundColor = UIColor.orange
let label = UILabel(frame: CGRect(x:0 , y:0 , width:50 , height:50))
label.text = "\(indexPath.item)"
label.textAlignment = .center
label.textColor = UIColor.white
cell.addSubview(label)
return cell
}
func numberOfSections(in collectionView: UICollectionView) -> Int {
return 1
}
override func didReceiveMemoryWarning() {
super.didReceiveMemoryWarning()
// Dispose of any resources that can be recreated.
}
}
I couldn't make Kaushal's suggestion work as stated. It did give me a clue that my positioning of the view in which I had embedded the collection view was being misplaced in viewDidLoad for reasons that I have not understood. However by putting the collection view configuration in viewDidAppear (rather than viewDidLoad) it worked well. I offset the y position by 64 to clear the navbar, and I reduced the row height to 64. I also, put code to execute the code only once so that navigating from pages does not add multiple views of top of each other. BTW, my original objective was to have horizontally scrolling cells. In my program I have tableview with corresponding sections and the idea is to use the row with horizontally scrolling cells to move to a corresponding section.
The code is shown below:
//
// CustomViewController.swift
// DSM Tracker
//
// Created by Syed Tariq on 1/7/17.
// Copyright © 2017 com.syedtariq. All rights reserved.
//
import UIKit
class ViewController: UIViewController,
UICollectionViewDelegate,
UICollectionViewDataSource,
UINavigationControllerDelegate
{
var executeOnce = true
var cellDimensions = [String:Int]()
var cellHeight = 50
var cellWidth = 120
var collectionContainerView: UICollectionView!
var navBar: UINavigationBar = UINavigationBar()
// view constants
var viewY = CGFloat()
var viewX = CGFloat()
var viewWidth = CGFloat()
var viewHeight = CGFloat()
// gaps from view edge
let leftGap = CGFloat(20)
let rightGap = CGFloat(20)
// navbar constants
let navBarHeight = CGFloat(64)
var headerLabels = ["Cell 01","Cell 02","Cell 03","Cell 04","Cell 05","Cell 06","Cell 07","Cell 08","Cell 09","Cell 10","Cell 11","Cell 12","Cell 13","Cell 14","Cell 15","Cell 16"]
override func viewDidLoad() {
super.viewDidLoad()
navBar.backgroundColor = UIColor.green
executeOnce = true
viewY = view.frame.origin.y
viewX = view.frame.origin.x
viewWidth = view.frame.width
viewHeight = view.frame.height
}
func configureCollectionView () {
if executeOnce {
executeOnce = false
let layout: UICollectionViewFlowLayout = UICollectionViewFlowLayout()
layout.scrollDirection = .horizontal
layout.sectionInset = UIEdgeInsets(top: 0, left: 0, bottom: 0, right: 10)
layout.itemSize = CGSize(width: cellWidth, height: cellHeight)
let colWidth = viewWidth - leftGap - rightGap
let colX = viewX + leftGap
let colY = viewY + navBarHeight
let colHeight = CGFloat(64)
let frame = CGRect(x:colX, y:colY, width: colWidth, height: colHeight)
//let frame = CGRect.zero
collectionContainerView = UICollectionView (frame: frame, collectionViewLayout: layout)
collectionContainerView.dataSource = self
collectionContainerView.delegate = self
collectionContainerView.autoresizingMask = [.flexibleLeftMargin,.flexibleLeftMargin,.flexibleBottomMargin,.flexibleRightMargin, .flexibleHeight, .flexibleWidth]
collectionContainerView.register(UICollectionViewCell.self, forCellWithReuseIdentifier: "collectionCell")
collectionContainerView.backgroundColor = UIColor.blue
collectionContainerView.allowsSelection = true
collectionContainerView.isScrollEnabled = true
collectionContainerView.setNeedsDisplay()
print("collectionContainerView.frame \(collectionContainerView.frame)")
view.addSubview(collectionContainerView)
}
}
override func viewDidAppear(_ animated: Bool) {
configureCollectionView()
}
func numberOfSections(in collectionView: UICollectionView) -> Int {
return 1
}
func collectionView(_ collectionView: UICollectionView, numberOfItemsInSection section: Int) -> Int {
print("headerLabels.count \(headerLabels.count)")
return headerLabels.count
}
func collectionView(_ collectionView: UICollectionView, cellForItemAt indexPath: IndexPath) -> UICollectionViewCell {
let cell = collectionView.dequeueReusableCell(withReuseIdentifier: "collectionCell", for: indexPath as IndexPath)
for v in cell.subviews {
v.removeFromSuperview()
}
let cellTitle = headerLabels[indexPath.row]
let cellTitleLines = cellTitle.components(separatedBy: " ")
let nLabels = cellTitleLines.count
cell.layer.borderWidth = 1
cell.layer.cornerRadius = 8
let labelHeight = cellHeight / cellTitleLines.count
for i in (0 ..< nLabels) {
let frame = CGRect(x: 0, y: labelHeight * i, width: cellWidth, height: labelHeight)
let label1 = UILabel(frame: frame)
cell.backgroundColor = UIColor.lightGray
label1.numberOfLines = 1
label1.text = headerLabels[indexPath.row]
label1.textAlignment = .center
label1.textColor = UIColor.black
label1.clipsToBounds = true
label1.adjustsFontSizeToFitWidth = true
label1.text = cellTitleLines[i]
cell.addSubview(label1)
}
return cell
}
func collectionView(_ collectionView: UICollectionView, shouldSelectItemAt indexPath: IndexPath) -> Bool {
collectionContainerView.scrollToItem(at:IndexPath(item: indexPath.item, section: 0), at: .centeredHorizontally, animated: false)
return true
}
func collectionView(_ collectionView: UICollectionView, didSelectItemAt indexPath: IndexPath) {
let cell = collectionContainerView.cellForItem(at: indexPath)
print("cell = \(cell)")
collectionContainerView.scrollToItem(at:IndexPath(item: indexPath.item, section: 0), at: .centeredHorizontally, animated: false)
}
func collectionView(_ collectionView: UICollectionView, shouldHighlightItemAt indexPath: IndexPath) -> Bool {
return true
}
func collectionView(_ collectionView: UICollectionView, didHighlightItemAt indexPath: IndexPath) {
}
override func prepare(for segue: UIStoryboardSegue, sender: Any?) {
}
}
On iOS 10.0, UICollectionView pre-fetches cells by default. This leads to cells that are prepared for being shown on screen, but are hidden. This question describes it really well.
The following code will successfully deselect an index path when its cell is either visible or does not exist at all. If the cell exists and is hidden, the index path will be deselected, but the cell becomes stuck in the selected state until it is reused.
collectionView!.deselectItem(at: indexPath, animated: false)
This problem does not exits on iOS 9 or when pre-fetching is disabled with isPrefetchingEnabled = false on iOS 10.0.
Is this a bug in UICollectionView or am I misunderstanding how deselectItem is supposed to work?
Here is the full code of a UICollectionViewController subclass that demonstrates this behaviour with the following steps:
Tap on a cell, so that it becomes selected (red)
Scroll the cell slightly off-screen
Tap the "Deselect Cell" button
Scroll the cell back on screen
Observe how it still looks selected
Tap on another cell
Observe how both cells look selected
Scroll the first cell far off-screen and back again
Observe how the first cell finally does not look selected
import UIKit
private let reuseIdentifier = "Cell"
class CollectionViewController: UICollectionViewController {
override func viewDidLoad() {
super.viewDidLoad()
self.collectionView!.register(UICollectionViewCell.self, forCellWithReuseIdentifier: reuseIdentifier)
let button = UIButton(frame: CGRect(x: 10, y: 30, width: 360, height: 44))
button.backgroundColor = #colorLiteral(red: 0.9686274529, green: 0.78039217, blue: 0.3450980484, alpha: 1)
button.setTitleColor(#colorLiteral(red: 1, green: 1, blue: 1, alpha: 1), for: .normal)
button.setTitleColor(#colorLiteral(red: 0.05882352963, green: 0.180392161, blue: 0.2470588237, alpha: 1), for: .highlighted)
button.setTitle("Deselect Cell", for: .normal)
button.addTarget(self, action: #selector(CollectionViewController.buttonPress), for: .touchUpInside)
view.addSubview(button)
}
func buttonPress() {
for indexPath in collectionView!.indexPathsForSelectedItems ?? [IndexPath]() {
let cell = collectionView!.cellForItem(at: indexPath)
NSLog("Deselecting indexPath: %#, cell: %#", indexPath.description, cell?.frame.debugDescription ?? "not visible")
collectionView!.deselectItem(at: indexPath, animated: false)
}
}
override func numberOfSections(in collectionView: UICollectionView) -> Int {
return 1
}
override func collectionView(_ collectionView: UICollectionView, numberOfItemsInSection section: Int) -> Int {
return 300
}
override func collectionView(_ collectionView: UICollectionView, cellForItemAt indexPath: IndexPath) -> UICollectionViewCell {
let cell = collectionView.dequeueReusableCell(withReuseIdentifier: reuseIdentifier, for: indexPath)
cell.backgroundColor = #colorLiteral(red: 1, green: 1, blue: 1, alpha: 1)
cell.selectedBackgroundView = UIView(frame: cell.bounds)
cell.selectedBackgroundView!.backgroundColor = #colorLiteral(red: 0.9254902005, green: 0.2352941185, blue: 0.1019607857, alpha: 1)
return cell
}
}
As far as I can tell this is a bug in UICollectionView, and I've opened a Radar myself. You might want to do so as well to apply more pressure.
Even before prefetching, collection view didn't bother deselecting cells that weren't visible. Even cellForItemAtIndexPath: states that it returns nil for cells that are not visible.
But before prefetching, as soon as a cell left the content view it was added to the reuse pool, and when you scrolled back you got a reused cell that had its selected state reset.
Now, that cell remains loaded and wont reset until it's reused, by scrolling further away, beyond the prefetching area.
To fix this you can either set prefetchingEnabled to NO and lose its benefits, or update selection state whenever a cell appears -
- (void)collectionView:(UICollectionView *)collectionView
willDisplayCell:(UICollectionViewCell *)cell forItemAtIndexPath:(NSIndexPath *)indexPath {
if (!cell.isSelected) {
return;
}
if ([[collectionView indexPathsForSelectedItems] containsObject:indexPath]) {
return;
}
cell.selected = NO;
}
This doesn't seem to diminish performance.