Why are my tableVeiws Rows so Jumpy while scrolling? - ios

Question

Below is the code of my tableView controller which takes an image from a UIImage array resizes it to aspect ratio and displays it on screen. While I scroll the images are very choppy? Is there anyway to reduce the choppiness?
import UIKit
class TableViewController: UITableViewController {
var images = imagePost.defaultimages //An array of a class containing images
var indexPathPass = IndexPath(row: 0, section: 0)
override func viewDidLoad() {
super.viewDidLoad()
tableView.rowHeight = UITableViewAutomaticDimension
tableView.estimatedRowHeight = 100
tableView.backgroundColor = colors.backgroundColor
DispatchQueue.main.async {
self.tableView.scrollToRow(at: self.indexPathPass, at: .top, animated: false)
}
}
override func tableView(_ tableView: UITableView, cellForRowAt indexPath: IndexPath) -> UITableViewCell {
let cell = tableView.dequeueReusableCell(withIdentifier: "Cell", for: indexPath) as! TableViewCell
// Configure the cell...
cell.cellImageView.image = self.images[indexPath.row].image
cell.cellImageView.image = cell.cellImageView.image?.resizeImageWith()
cell.backgroundColor = UIColor(displayP3Red: 0, green: 20, blue: 1, alpha: 0.99)
cell.layer.shouldRasterize = true
return cell
}
override func tableView(_ tableView: UITableView, estimatedHeightForRowAt indexPath: IndexPath) -> CGFloat {
return 100
}
}

Answer 1

Check for the difference in your estimatedRowHeight and the actualRowHeight, the more is the difference the more it will jump while scrolling.

Answer 2

Solution 1.
If possible, try to implement 'heightForItem at indexPath' method. And return calculated height
Solution 2.
You can implement height caching mechanism. Like below code.
class TableViewController: UITableViewController {
var images = imagePost.defaultimages //An array of a class containing images
var indexPathPass = IndexPath(row: 0, section: 0)
fileprivate var cachedHeight = [IndexPath: CGFloat]()
override func viewDidLoad() {
super.viewDidLoad()
tableView.rowHeight = UITableViewAutomaticDimension
tableView.estimatedRowHeight = 100
tableView.backgroundColor = colors.backgroundColor
DispatchQueue.main.async {
self.tableView.scrollToRow(at: self.indexPathPass, at: .top, animated: false)
}
}
override func tableView(_ tableView: UITableView, cellForRowAt indexPath: IndexPath) -> UITableViewCell {
let cell = tableView.dequeueReusableCell(withIdentifier: "Cell", for: indexPath) as! TableViewCell
// Configure the cell...
cell.cellImageView.image = self.images[indexPath.row].image
cell.cellImageView.image = cell.cellImageView.image?.resizeImageWith()
cell.backgroundColor = UIColor(displayP3Red: 0, green: 20, blue: 1, alpha: 0.99)
cell.layer.shouldRasterize = true
return cell
}
override func tableView(_ tableView: UITableView, estimatedHeightForRowAt indexPath: IndexPath) -> CGFloat {
return cachedHeight[indexPath] ?? 100
}
override func tableView(_ tableView: UITableView, willDisplay cell: UITableViewCell, forRowAt indexPath: IndexPath) {
cachedHeight[indexPath] = cell.frame.height
}
}