CollectionView Auto Scroll - ios

Question

So I have some code that I am using to auto scroll a collectionView and it is giving me lots of problems. It works based off of a timer that calls a certain function every 3.5 seconds to scroll to a certain item in the collectionView. The code is included belwo
import UIKit
class HomeFeedCell: UICollectionViewCell, UICollectionViewDataSource, UICollectionViewDelegate, UICollectionViewDelegateFlowLayout, UIScrollViewDelegate {
var homeFeedController: HomeFeedController?
let emptyView = UIView()
//Timer user for call autoscroller of top collection view
private var timer:Timer?
var scrollTimer = Timer()
private let cellId = "cellId"
var featuredEvents: [Event]?{
didSet {
homeFeedCollectionView.reloadData()
}
}
var titles: String? {
didSet {
guard let titles = titles else {
return
}
// let attributedText = NSMutableAttributedString(string: titles, attributes: [NSAttributedStringKey.font: UIFont.boldSystemFont(ofSize: 100)])
sectionNameLabel.text = titles
// sectionNameLabel.attributedText = attributedText
}
}
override init(frame: CGRect) {
super.init(frame: frame)
self.setTimer()
setupViews()
}
func setTimer(){
//auto scroll method to call every 2.5 seconds interval
self.timer = Timer.scheduledTimer(timeInterval: 5, target: self, selector: #selector(self.startTimer(theTimer:)), userInfo: nil, repeats: true)
}
required init?(coder aDecoder: NSCoder) {
fatalError("init(coder:) has not been implemented")
}
let sectionNameLabel : UILabel = {
let sectionNameLabel = UILabel()
sectionNameLabel.font = UIFont(name:"HelveticaNeue-CondensedBlack", size: 36.0)
return sectionNameLabel
}()
lazy var emptyLabel: UILabel = {
let emptyLabel = UILabel()
emptyLabel.text = "Sorry We Currently Have No Events, \n In This Category Near You"
emptyLabel.font = UIFont(name: "Avenir", size: 14)
emptyLabel.numberOfLines = 0
emptyLabel.textAlignment = .center
return emptyLabel
}()
lazy var iconImageView: UIImageView = {
let imageView = UIImageView()
imageView.contentMode = .scaleAspectFit
return imageView
}()
let homeFeedCollectionView: UICollectionView = {
let layout = UICollectionViewFlowLayout()
layout.scrollDirection = .horizontal
let cv = UICollectionView(frame: .zero, collectionViewLayout: layout)
cv.backgroundColor = .clear
return cv
}()
#objc func setupViews(){
backgroundColor = .clear
addSubview(homeFeedCollectionView)
addSubview(sectionNameLabel)
sectionNameLabel.anchor(top: topAnchor, left: leftAnchor, bottom: nil, right: nil, paddingTop: 2, paddingLeft: 4, paddingBottom: 0, paddingRight: 0, width: 0, height: 0)
homeFeedCollectionView.anchor(top: sectionNameLabel.bottomAnchor, left: leftAnchor, bottom: bottomAnchor, right: rightAnchor, paddingTop: 4, paddingLeft: 0, paddingBottom: 0, paddingRight: 0, width: 0, height: 0)
homeFeedCollectionView.delegate = self
homeFeedCollectionView.dataSource = self
homeFeedCollectionView.showsHorizontalScrollIndicator = false
homeFeedCollectionView.register(HomeFeedEventCell.self, forCellWithReuseIdentifier: cellId)
}
func collectionView(_ collectionView: UICollectionView, numberOfItemsInSection section: Int) -> Int {
guard let currentEventCount = featuredEvents?.count else{
return 0
}
if currentEventCount == 0 {
print("no events")
setupEmptyDataSet()
}else{
emptyView.removeFromSuperview()
}
return currentEventCount
}
#objc func setupEmptyDataSet(){
self.addSubview(emptyView)
emptyView.backgroundColor = .clear
emptyView.snp.makeConstraints { (make) in
make.edges.equalTo(self)
}
emptyView.addSubview(iconImageView)
iconImageView.image = UIImage(named: "icons8-face-100")
iconImageView.snp.makeConstraints { (make) in
make.center.equalTo(emptyView)
}
emptyView.addSubview(emptyLabel)
emptyLabel.snp.makeConstraints { (make) in
make.bottom.equalTo(iconImageView.snp.bottom).offset(30)
make.left.right.equalTo(emptyView)
}
}
func collectionView(_ collectionView: UICollectionView, layout collectionViewLayout: UICollectionViewLayout, insetForSectionAt section: Int) -> UIEdgeInsets {
return UIEdgeInsets(top: 20, left: 5, bottom: 20, right: 5)
}
func collectionView(_ collectionView: UICollectionView, layout collectionViewLayout: UICollectionViewLayout, sizeForItemAt indexPath: IndexPath) -> CGSize {
return CGSize(width: frame.width - 40, height: frame.height - 40)
}
func collectionView(_ collectionView: UICollectionView, didSelectItemAt indexPath: IndexPath) {
let eventDetails = EventDetailViewController()
eventDetails.currentEvent = featuredEvents?[indexPath.item]
homeFeedController?.navigationController?.pushViewController(eventDetails, animated: true)
}
func collectionView(_ collectionView: UICollectionView, cellForItemAt indexPath: IndexPath) -> UICollectionViewCell {
let cell = collectionView.dequeueReusableCell(withReuseIdentifier: cellId, for: indexPath) as! HomeFeedEventCell
cell.event = featuredEvents?[indexPath.item]
var rowIndex = indexPath.row
let numberOfRecords = (featuredEvents?.count)! - 1
if rowIndex < numberOfRecords {
rowIndex = rowIndex + 1
}else{
rowIndex = 0
}
scrollTimer = Timer.scheduledTimer(timeInterval: 3.5, target: self, selector: #selector(self.startTimer(theTimer:)), userInfo: rowIndex, repeats: true)
return cell
}
#objc func startTimer(theTimer: Timer){
UIView.animate(withDuration: 1.0, delay: 0, options: .curveEaseOut, animations: {
if let currentIndexPath = self.homeFeedCollectionView.indexPathsForVisibleItems.last{
//Check visible cell is last cell of top collection view then set first index as visible
if currentIndexPath.item == self.homeFeedCollectionView.numberOfItems(inSection: 0)-1{
let nextIndexPath = NSIndexPath(item: 0, section: 0)
//top collection view scroller in first item
self.homeFeedCollectionView.scrollToItem(at: nextIndexPath as IndexPath, at: .right, animated: false)
}else{
//create next index path from current index path of the top collection view
let nextIndexPath = NSIndexPath(item: currentIndexPath.item + 1, section: 0)
//top collection view scroller to next item
self.homeFeedCollectionView.scrollToItem(at: nextIndexPath as IndexPath, at: .left, animated: true)
}
}
}) { (finished) in
if finished {
print("done")
}
}
}
func scrollViewDidEndDecelerating(_ scrollView: UIScrollView) {
self.homeFeedCollectionView.scrollToNearestVisibleCollectionViewCell()
}
func scrollViewDidEndDragging(_ scrollView: UIScrollView, willDecelerate decelerate: Bool) {
if !decelerate {
self.homeFeedCollectionView.scrollToNearestVisibleCollectionViewCell()
}
}
}
Im not really sure what I am doing wrong, to be honest. But my problems with this approach are
When you I first enter the collectionView it goes straight to the third item
It sometimes scrolls to a certain item may be the first or the third and then it just gets stuck there and stops moving. It tried to move but it just keeps getting stuck.

Answer 1

You have a viewController for the view that shows up what you want and contains collectionView. This class should implement UICollectionViewDataSource and UICollectionViewDelegate:
class viewController: UIViewController, UICollectionViewDelegate, UICollectionViewDataSource
in this class you should implement the numberOfItemsInSection and cellForItemAt methods.
and you need another class for cells in the collectionView:
class customCell: UICollectionViewCell
in this class you could define IBOutlets or what ever you want related to each cell NOT collectionView
and in last you should fire the timer in viewDidLoad (or viewDidAppear) instead of cellForItemAt delegate,
that func calls for each row then you start timers as number of cells that your collectionView has.
override func viewDidAppear(_ animated: Bool) {
super.viewDidAppear(true)
scrollTimer = Timer.scheduledTimer(timeInterval: 3.5, target: self, selector: #selector(self.startTimer(theTimer:)), userInfo: rowIndex, repeats: true)
}

Answer 2

You can use this pod https://cocoapods.org/pods/AutoScrollCollectionView
https://github.com/mohankrishnameruva/AutoScrollCollectionView
Subclass your collection view from 'AutoScrollCollectionView' in storyboard and
whenever you want to start scroll call this method
on collectionView startAutoScrolling(withTimeInterval: TimeInterval(exactly: 2.0)!)