CollectionView FlowLayout overlapping when scrolling not working - ios

Question

I hope you all working fine
Here I have created a collection view flow layouts some scenarios not working, please share your references.
here is the collection view
import UIKit
class ViewController: UIViewController {
#IBOutlet weak var collection: UICollectionView!
private let kCellHeight: CGFloat = UIScreen.main.bounds.width/2+38
private let kItemSpace: CGFloat = UIScreen.main.bounds.width/2.08
lazy var expand_click = false
lazy var index_value = [String]()
override func viewDidLoad() {
super.viewDidLoad()
collection.delegate = self
collection.dataSource = self
let layout = StickyCollectionViewFlowLayout2()
layout.minimumLineSpacing = -kItemSpace
collection.collectionViewLayout = layout
collection.reloadData()
}
}
extension ViewController: UICollectionViewDelegate, UICollectionViewDataSource, UICollectionViewDelegateFlowLayout {
func collectionView(_ collectionView: UICollectionView, numberOfItemsInSection section: Int) -> Int {
return 15
}
func collectionView(_ collectionView: UICollectionView, cellForItemAt indexPath: IndexPath) -> UICollectionViewCell {
let cell = collectionView.dequeueReusableCell(withReuseIdentifier: "CollectionViewCell", for: indexPath) as! CollectionViewCell
print("Index",indexPath.row)
return cell
}
func collectionView(_ collectionView: UICollectionView, layout collectionViewLayout: UICollectionViewLayout, sizeForItemAt indexPath: IndexPath) -> CGSize {
return CGSize(width: view.frame.width-40, height: kCellHeight)
}
func collectionView(_ collectionView: UICollectionView, didSelectItemAt indexPath: IndexPath) {
if (15)-1 == indexPath.row {
self.showAlert(alertText: "", alertMessage: "last Cell")
}else{
if index_value.contains("\(indexPath.row)") {
self.showAlert(alertText: "", alertMessage: "Redirect")
expand_click = true
}else{
index_value.removeAll()
index_value.append("\(indexPath.row)")
expand_click = true
cellData = indexPath.row
collectionView.performBatchUpdates({
}, completion: nil)
}
}
}
}
collection view cells
class CollectionViewCell: UICollectionViewCell {
#IBOutlet weak var container: UIView!
override func layoutSubviews() {
container.backgroundColor = .white
container.layer.cornerRadius = 13
container.layer.shadowRadius = 2
container.layer.shadowOpacity = 0.7
container.layer.shadowOffset = CGSize(width: 0, height: 1)
container.layer.shadowColor = UIColor.black.withAlphaComponent(0.45).cgColor
}
}
When clicked cell it will be expanding the cell and moved to be under the other the cells
> * Expanded cell again click it will be redirected to another page forEx (I showed alert)
> * the last cell click it's should also redirect These are all I have done my self if we have 15 cards it working fine more than 50 cards
> not smooth scrolling and we have a problem for contending size maybe I
> could not solve the issue
**Collection view FlowLayout**
class StickyCollectionViewFlowLayout2: UICollectionViewFlowLayout {
var firstItemTransform: CGFloat?
override func layoutAttributesForElements(in rect: CGRect) -> [UICollectionViewLayoutAttributes]? {
let items = NSArray (array: super.layoutAttributesForElements(in: rect)!, copyItems: true)
print("------------------------------------------------------------------------------------------------------------------------")
print("Count-------->",items.count,"<--------Count")
print("------------------------------------------------------------------------------------------------------------------------")
var headerAttributes: UICollectionViewLayoutAttributes?
self.firstItemTransform = nil
if cellData != nil {
let min = cellData!
print(min)
var b = [UICollectionViewLayoutAttributes?]()
var a = false
items.forEach({ (object) in
let object = object as! UICollectionViewLayoutAttributes
if min == object.indexPath.row {
a = true
}else{
if a == true {
b.append(object)
}
}
})
for attributes in b {
if attributes?.representedElementKind == UICollectionView.elementKindSectionHeader {
headerAttributes = attributes
}
else {
self.atributeLayout(attributes!, headerAttributes: headerAttributes)
}
}
cellData = nil
}else{
items.enumerateObjects(using: { (object, idex, stop) -> Void in
let attributes = object as! UICollectionViewLayoutAttributes
if attributes.representedElementKind == UICollectionView.elementKindSectionHeader {
headerAttributes = attributes
}
else {
self.atributeLayoutReset(attributes, headerAttributes: headerAttributes)
}
})
}
return items as? [UICollectionViewLayoutAttributes]
}
func atributeLayout(_ attributes: UICollectionViewLayoutAttributes, headerAttributes: UICollectionViewLayoutAttributes?){
let minY = self.collectionView!.bounds.minY + self.collectionView!.contentInset.top
var maxY = attributes.frame.origin.y+attributes.frame.height/2+80
if let headerAttributes = headerAttributes {
maxY -= headerAttributes.bounds.height
}
let finalY = max(minY, maxY)
var origin = attributes.frame.origin
let deltaY = (finalY - origin.y) / attributes.frame.height + 100
if let itemTransform = self.firstItemTransform {
let scale = 1 - deltaY * itemTransform
attributes.transform = CGAffineTransform(scaleX: scale, y: scale)
}
origin.y = finalY
attributes.frame = CGRect(origin: origin, size: attributes.frame.size)
attributes.zIndex = attributes.indexPath.row
}
func atributeLayoutReset(_ attributes: UICollectionViewLayoutAttributes, headerAttributes: UICollectionViewLayoutAttributes?){
cellIndex = nil
if isExpandCell != true {
let minY = self.collectionView!.bounds.minY + self.collectionView!.contentInset.top
var maxY = attributes.frame.origin.y
if let headerAttributes = headerAttributes {
maxY -= headerAttributes.bounds.height
}
let finalY = max(minY, maxY)
var origin = attributes.frame.origin
let deltaY = (finalY - origin.y) / attributes.frame.height + 100
if let itemTransform = self.firstItemTransform {
let scale = 1 - deltaY * itemTransform
attributes.transform = CGAffineTransform(scaleX: scale, y: scale)
}
origin.y = finalY
attributes.frame = CGRect(origin: origin, size: attributes.frame.size)
attributes.zIndex = attributes.indexPath.row
// })
}else{
print(collectionView!.contentInset.top,collectionView!.bounds.minY)
let minY = 0.0 + collectionView!.contentInset.top
var maxY = attributes.frame.origin.y
if let headerAttributes = headerAttributes {
maxY -= headerAttributes.bounds.height
}
let finalY = max(minY, maxY)
var origin = attributes.frame.origin
let deltaY = (finalY - origin.y) / attributes.frame.height + 100
if let itemTransform = firstItemTransform {
let scale = 1 - deltaY * itemTransform
attributes.transform = CGAffineTransform(scaleX: scale, y: scale)
}
origin.y = finalY
attributes.frame = CGRect(origin: origin, size: attributes.frame.size)
attributes.zIndex = attributes.indexPath.row
}
}
override func shouldInvalidateLayout(forBoundsChange newBounds: CGRect) -> Bool {
return false
}
}
if anyone experienced collection view please share me your references
Thank you

Answer 1

Hello please try my code. I have tested on an iPhone simulator and it works great.
import SwiftUI
struct CardView: View {
static let CARD_HEIGHT: CGFloat = 200
static let CARD_WIDTH: CGFloat = 300
static let TAB_HEIGHT: CGFloat = 30
#State var selected: Int? = nil
let cards: Int
var body: some View {
ScrollView {
ZStack(alignment: .top) {
ForEach(0 ..< cards) { card_i in
Button {
withAnimation {
self.selected = self.selected == card_i ? nil : card_i
}
print("A card was tapped. Do something with card_i here")
} label: { self.card }
.buttonStyle(PlainButtonStyle())
.frame(width: Self.CARD_WIDTH, height: Self.CARD_HEIGHT, alignment: .top)
.offset(x: .zero, y: CGFloat(card_i) * Self.TAB_HEIGHT + ((selected ?? cards + 1) < card_i ? Self.CARD_HEIGHT - Self.TAB_HEIGHT / 2 : 0))
}
}
.frame(height: Self.CARD_HEIGHT + Self.TAB_HEIGHT * CGFloat(cards), alignment: .top)
.padding()
}
}
var card: some View {
RoundedRectangle(cornerRadius: 17, style: .continuous)
.fill(Color.gray)
.overlay(RoundedRectangle(cornerRadius: 17, style: .continuous).stroke(Color.black, lineWidth: 5))
}
}
Edit
Use it like this
let swiftUIview = CardView(cards: 10, onCardTapped: { card in
print("card number \(card) tapped")
})
let uiViewController = UIHostingController(rootView: swiftUIview)
Gif removed because outdated.