I have a horizontally scrollable UICollectionView with three cells each of which are different subclasses of UICollectionViewCell. Each one of these cells contains a UITableView.
Inside of the first two cells, my table view cells are the same subclasses of UITableViewCell and have just a UIImageView. I use it to set its backgroundColor. Inside of the third cell, my table view's cells are different subclasses of UITableViewCell than in the previous two. They have both a UILabel and a UIImageView. The label has some dummy text, and I set imageView's backgroundColor to some color, again.
In order to follow MVC pattern, I use my UIViewController as a data source and a delegate for both collection view, and table view. Here is the code of UIViewController:
class ViewController: UIViewController, UITableViewDelegate, UITableViewDataSource {
let collectionViewCellId = "collectionViewCell"
let tableViewCellId = "tableViewCell"
let collectionViewCellId2 = "collectionViewCellId2"
let collectionViewCellId3 = "collectionViewCellId3"
let tableViewCellDif = "tableViewCellDif"
var collectionViewIndex: Int?
@IBOutlet weak var collectionView: UICollectionView! {
didSet {
collectionView.delegate = self
collectionView.dataSource = self
collectionView.isPagingEnabled = true
}
}
//MARK: UITableViewDataSource
public func tableView(_ tableView: UITableView, numberOfRowsInSection section: Int) -> Int {
return 5
}
public func tableView(_ tableView: UITableView, cellForRowAt indexPath: IndexPath) -> UITableViewCell {
let colors: [UIColor] = [.red, .green, .purple, .orange, .blue]
let colors2: [UIColor] = [.blue, .brown, .yellow, .magenta, .cyan]
if collectionViewIndex == 0 {
let cell = tableView.dequeueReusableCell(withIdentifier: tableViewCellId, for: indexPath) as! TableViewCell
cell.colorForImageView = colors[indexPath.row]
return cell
} else
if collectionViewIndex == 1 {
let cell = tableView.dequeueReusableCell(withIdentifier: tableViewCellId, for: indexPath) as! TableViewCell
cell.colorForImageView = colors2[indexPath.row]
return cell
} else
if collectionViewIndex == 2 {
let cell = tableView.dequeueReusableCell(withIdentifier: tableViewCellDif, for: indexPath) as! TableViewCellDifferent
cell.colorForImageView = colors2[indexPath.row]
return cell
} else {
return UITableViewCell()
}
}
}
//MARK: UICollectionViewDataSource
extension ViewController: UICollectionViewDataSource {
func collectionView(_ collectionView: UICollectionView, numberOfItemsInSection section: Int) -> Int {
return 3
}
func collectionView(_ collectionView: UICollectionView, cellForItemAt indexPath: IndexPath) -> UICollectionViewCell {
let identifier: String
if indexPath.item == 0 {
identifier = collectionViewCellId
} else if indexPath.item == 1 {
identifier = collectionViewCellId2
} else if indexPath.item == 2 {
identifier = collectionViewCellId3
} else {
identifier = ""
}
let cell = collectionView.dequeueReusableCell(withReuseIdentifier: identifier, for: indexPath)
return cell
}
}
//MARK: UICollectionViewDelegate
extension ViewController: UICollectionViewDelegate {
func collectionView(_ collectionView: UICollectionView, willDisplay cell: UICollectionViewCell, forItemAt indexPath: IndexPath) {
if indexPath.item == 0 {
let cell = cell as! CollectionViewCell
cell.tableView.dataSource = self
cell.tableView.delegate = self
collectionViewIndex = 0
}
if indexPath.item == 1 {
let cell = cell as! CollectionViewCell2
cell.tableView.dataSource = self
cell.tableView.delegate = self
collectionViewIndex = 1
}
if indexPath.item == 2 {
let cell = cell as! CollectionViewCell3
cell.tableView.dataSource = self
cell.tableView.delegate = self
collectionViewIndex = 2
print (collectionViewIndex)
}
}
}
//MARK: UICollectionViewDelegateFlowLayout
extension ViewController: UICollectionViewDelegateFlowLayout {
func collectionView(_ collectionView: UICollectionView, layout collectionViewLayout: UICollectionViewLayout, sizeForItemAt indexPath: IndexPath) -> CGSize {
let layout = collectionViewLayout as! UICollectionViewFlowLayout
layout.minimumInteritemSpacing = 0
layout.minimumLineSpacing = 0
return CGSize(width: collectionView.frame.width, height: collectionView.frame.height)
}
}
As I stated in a title of the question, nothing happens on a background thread. I, basically, only set the backgroundColor of table view's cells.
The problem is that inside the collection view's third cell (and only inside of there), my table view dequeues its cells only after a minor scroll or tap happens. Here is how it looks like:
I can't figure out why this happens. Maybe, this happens because inside of the third cell of the collection view, my table view's cells are instances of different subclass than inside of the first two?
EDITED
I could solve the problem by reloading the table view before before showing the collection view's each cell but I'm not sure that this is the most efficient solution. Here is the code:
//MARK: UICollectionViewDelegate
extension ViewController: UICollectionViewDelegate {
func collectionView(_ collectionView: UICollectionView, willDisplay cell: UICollectionViewCell, forItemAt indexPath: IndexPath) {
if indexPath.item == 0 {
let cell = cell as! CollectionViewCell
cell.tableView.dataSource = self
cell.tableView.delegate = self
cell.tableView.reloadData()
collectionViewIndex = 0
}
if indexPath.item == 1 {
let cell = cell as! CollectionViewCell2
cell.tableView.dataSource = self
cell.tableView.delegate = self
cell.tableView.reloadData()
collectionViewIndex = 1
}
if indexPath.item == 2 {
let cell = cell as! CollectionViewCell3
cell.tableView.dataSource = self
cell.tableView.delegate = self
cell.tableView.reloadData()
collectionViewIndex = 2
}
}
}
If you know a better way, I would appreciate your help.
