In my tableview I have a few custom cells. When I scroll in the tableview it lags in the same spot but only for the first time the app is open. if I go back to the root view then open the tableview again it doesn't seem to lag. I've traced the lag to one cell. In that cell I have an embedded collection view and each of those cells has image view with is showing a MKMapSnapshot and also a few labels etc. If run with 0 collectionView cells (numberOfCellsInSection) the tableview scrolls smoothly but lags when I have 1 or more CollectionViewCell cells.
I initially loaded the image in the collectionView cell class in layoutSubviews which worked but I then learned that this is called numerous times so code like that shouldn't be there. if I put it in awakeFromNib the Branch struct doesn't seem to have been passed to the cell as yet (from cellForRowAt) so it doesn't work there. I then moved setting the image in cellForItemAt but I'm still not sure if it is correct there.
// Table View cellForRowAt
case .branchesCell:
let cell = tableView.dequeueReusableCell(withIdentifier: "branchesCell", for: indexPath) as! BranchesCell
cell.branches = restaurant?.branches // This is the info the embedded collectionView cell should display. Text for labels and coordinates for the MKMapSnapshot.
return cell
// TableView Cell Class
class BranchesCell: UITableViewCell, UICollectionViewDelegate, UICollectionViewDataSource {
@IBOutlet var collectionView: UICollectionView!
var branches: [Branch]?
var restaurantName = String()
override func awakeFromNib() {
super.awakeFromNib()
collectionView.delegate = self
collectionView.dataSource = self
collectionView.backgroundColor = .clear
collectionView.delaysContentTouches = false
}
// MARK: UICollectionView
func numberOfSections(in collectionView: UICollectionView) -> Int { return 1 }
func collectionView(_ collectionView: UICollectionView, numberOfItemsInSection section: Int) -> Int {
if let branches = branches {
return branches.count
} else { return 0 }
}
func collectionView(_ collectionView: UICollectionView, cellForItemAt indexPath: IndexPath) -> UICollectionViewCell {
let cell = collectionView.dequeueReusableCell(withReuseIdentifier: "cell", for: indexPath) as! NestledBranchCell
cell.layer.masksToBounds = false
cell.backgroundColor = .clear
let imageView = cell.viewWithTag(1) as! UIImageView
if let branches = branches {
cell.branch = branches[indexPath.row]
cell.restaurantName = restaurantName
// Tried to run this in a different thread to see if it would make a difference.
DispatchQueue.main.async() { [self] in
let size = CGSize(width: 314, height: 195)
// Set the image here
getMapImage(branch: branches[indexPath.row], size: size) { mapImage in
imageView.image = mapImage
}
}
}
return cell
}
func getMapImage(branch: Branch, size: CGSize, completion: @escaping (UIImage?) -> ()) {
var mapImage = UIImage()
let mapSnapshotOptions = MKMapSnapshotter.Options()
let location = branch.coordinates.coordinate
let region = MKCoordinateRegion(center: location, latitudinalMeters: 300, longitudinalMeters: 300)
mapSnapshotOptions.region = region
mapSnapshotOptions.scale = UIScreen.main.scale
mapSnapshotOptions.size = size
mapSnapshotOptions.showsBuildings = true
mapSnapshotOptions.pointOfInterestFilter = .none
let snapShotter = MKMapSnapshotter(options: mapSnapshotOptions)
snapShotter.start { snapshot, error in
let image = snapshot?.image
mapImage = image!
completion(mapImage)
}
}
}
