How to hide tableview until images are completely loaded iOS Swift? - ios

My images take a second to load before they appear, which looks bad. On apps such as instagram, the tableview is hidden until the tableview is loaded... how do they do this? I have a loader that I want to display but don't know when to stop it and show tableview and detect the images have first finished loading? Where do I put stopTimer() ?
func tableView(_ tableView: UITableView, cellForRowAt indexPath: IndexPath) -> UITableViewCell {
let cell = tableView.dequeueReusableCell(withIdentifier: "MainTableViewCell",
for: indexPath) as! MainTableViewCell
let payment = self.payments[indexPath.row]
cell.profilePicture.layer.cornerRadius = cell.profilePicture.frame.size.width / 2
cell.profilePicture.clipsToBounds = true
if let profileImageUrl = payment.picture {
cell.profilePicture.loadImageUsingCacheWithUrlString(profileImageUrl)
}
if payment.message == "none" {
cell.detailsLabel.text = "No Message"
} else {
cell.detailsLabel.text = "\"\(payment.message ?? "")\""
}
}
MY CODE TO FETCH IMAGE IN TABLEVIEW:
let imageCache = NSCache<NSString, AnyObject>()
extension UIImageView {
func loadImageUsingCacheWithUrlString(_ urlString: String) {
self.image = nil
//check cache for image first
if let cachedImage = imageCache.object(forKey: urlString as NSString) as? UIImage {
self.image = cachedImage
return
}
//otherwise fire off a new download
guard let url = URL(string: urlString) else { return }
URLSession.shared.dataTask(with: url, completionHandler: { (data, response, error) in
//download hit an error so lets return out
if let error = error {
print(error)
return
}
DispatchQueue.main.async(execute: {
if let downloadedImage = UIImage(data: data!) {
imageCache.setObject(downloadedImage, forKey: urlString as NSString)
self.image = downloadedImage
}
})
}).resume()
}
}

You can simple use SDWebImage with cocoaPods and use it for async image downloader with cache support. Your cell will look like after ad SDWebImage.
import SDWebImage
func tableView(_ tableView: UITableView, cellForRowAt indexPath: IndexPath) -> UITableViewCell {
let cell = tableView.dequeueReusableCell(withIdentifier: "MainTableViewCell",
for: indexPath) as! MainTableViewCell
let payment = self.payments[indexPath.row]
cell.profilePicture.layer.cornerRadius = cell.profilePicture.frame.size.width / 2
cell.profilePicture.clipsToBounds = true
if let profileImageUrl = payment.picture {
cell.profilePicture.sd_setImage(with: profileImageUrl, placeholderImage: UIImage(named: "yourPlaceholderImage.png"))
}
if payment.message == "none" {
cell.detailsLabel.text = "No Message"
} else {
cell.detailsLabel.text = "\"\(payment.message ?? "")\""
}
}
There is no need to hide tableView for downloading image.

Related

How to stop tableview cells from glitching and flickering image when scrolling in swift?

I have a tableview that displays data from Firebase. It displays fine in the tableview but when scrolling begins, the table starts glitching or having the cells image and text reload and flicker which is very ugly. Help! Here's my code:
func tableView(_ tableView: UITableView, cellForRowAt indexPath: IndexPath) -> UITableViewCell {
let cell = tableView.dequeueReusableCell(withIdentifier: "MainTableViewCell", for: indexPath) as! MainTableViewCell
func downloadPicture(finished: () -> Void) {
cell.profilePicture.image = nil
if let imageUrlString = self.payments[indexPath.row].picture,
let imageUrl = URL(string: imageUrlString) {
do {
let imageData = try Data(contentsOf: imageUrl)
cell.profilePicture.image = UIImage(data: imageData)
cell.profilePicture.layer.cornerRadius = cell.profilePicture.frame.size.width / 2
cell.profilePicture.clipsToBounds = true
cell.profilePicture.alpha = 1
}
catch {
print("Error fetching image - \(error)")
}
}
finished()
}
downloadPicture {
print("success")
}
cell.amountLabel.text = "$\(self.payments[indexPath.row].amount ?? "")"
cell.detailsLabel.text = self.payments[indexPath.row].amount ?? ""
return cell
}
You can simply go with SDWebImage An asynchronous image downloader with cache management and efficient to use.
i.e. :
import SDWebImage
yourImageView.sd_setImage(with: URL(string: "yourImageURLFromFirebase.jpg"), placeholderImage: UIImage(named: "placeholder.png"))
#Lukeksaunders just go to GitHub Kinfisher. This library contains all functionality you want.
import Kingfisher
let url = URL(string: "https://example.com/image.png")
imageView.kf.setImage(with: url)
This library cache your images
func tableView(_ tableView: UITableView, cellForRowAt indexPath: IndexPath) -> UITableViewCell {
let cell = tableView.dequeueReusableCell(withIdentifier: "MainTableViewCell", for: indexPath) as! MainTableViewCell
if let imageUrlString = self.payments[indexPath.row].picture,
let imageUrl = URL(string: imageUrlString) {
cell.profilePicture.kf.setImage(with: imageUrl)
}
cell.amountLabel.text = "$\(self.payments[indexPath.row].amount ?? "")"
cell.detailsLabel.text = self.payments[indexPath.row].amount ?? ""
return cell
}

Set a default image in TableViewCell

I have tried several different approaches and nothing has yet to work. I am pulling in album artwork for a recently played tableview for my radio station app. I get blank images when there is no album artwork to pull into the cell. I just want to have my station logo "WhiteLogo.png" as a placeholder whenever there is no album artwork pulled into the tableview cell. Any help in the right direction is much appreciated. Thanks
import UIKit
//----------
//MARK: JSON
//----------
//The Initial Response From The JSON
struct Response: Codable {
var playHistory: Album
}
//The Album Received Which Is An Array Of Song Data
struct Album: Codable {
var song: [SongData]
}
//The SongData From The PlayHistory Album
struct SongData: Codable{
var album: String
var artist: String
var cover: String
var duration: String
var programStartTS: String
var title: String
}
class TableViewController: UITableViewController {
//1. Create An Array To Store The SongData
var songs = [SongData]()
var currentStation: RadioStation!
var downloadTask: URLSessionDownloadTask?
override func viewDidLoad() { super.viewDidLoad()
self.tableView.delegate = self
self.tableView.dataSource = self
//2. Load The JSON From The Main Bundle
guard let urlText = URL (string: "http://streamdb3web.securenetsystems.net/player_status_update/JACKSON1_history.txt")
else { return }
do{
//a. Get The Data From The From The File
let data = try Data(contentsOf: urlText)
//b. Decode The Data To Our Structs
let albumData = try JSONDecoder().decode(Response.self, from: data)
//c. Append The Songs Array With The PlayHistory
albumData.playHistory.song.forEach { songs.append($0) }
//d. Test Some Data
print("""
**The First Album Details**
Album = \(songs[0].album)
Artist = \(songs[0].artist)
Cover = \(songs[0].cover)
Duration = \(songs[0].duration)
Start = \(songs[0].programStartTS)
Title = \(songs[0].title)
""")
//3. Load The Data
DispatchQueue.main.async {
self.tableView.reloadData()
}
}catch{
print(error)
}
}
//-----------------
//MARK: UITableView
//-----------------
override func numberOfSections(in tableView: UITableView) -> Int {
return 1
}
override func tableView(_ tableView: UITableView, numberOfRowsInSection section: Int) -> Int {
return songs.count
}
override func tableView(_ tableView: UITableView, cellForRowAt indexPath: IndexPath) -> UITableViewCell {
//1. Create A Cell
let cell = tableView.dequeueReusableCell(withIdentifier: "cell", for: indexPath) as! TableViewCell
//2. Set It's Text
cell.songTitle.text = songs[indexPath.row].title
cell.artistLabel.text = songs[indexPath.row].artist
//3. Get The Image
if let imageURL = URL(string: songs[indexPath.row].cover){
let request = URLSession.shared.dataTask(with: imageURL) { (imageData, response, error) in
if let error = error{
print(error)
}else{
guard let image = imageData else { return }
DispatchQueue.main.async {
cell.songCover.image = UIImage(data: image)
cell.setNeedsLayout()
cell.layoutIfNeeded()
}
}
}
request.resume()
}
return cell
}
override func tableView(_ tableView: UITableView, didSelectRowAt indexPath: IndexPath) {
print("""
**Album \(indexPath.row) Selected**
Album = \(songs[indexPath.row].album)
Artist = \(songs[indexPath.row].artist)
Cover = \(songs[indexPath.row].cover)
Duration = \(songs[indexPath.row].duration)
Start = \(songs[indexPath.row].programStartTS)
Title = \(songs[indexPath.row].title)
""")
}
}
Just the right case handling is required.
I would set the placeholder image first and then proceed to download an image from a URL.
override func tableView(_ tableView: UITableView, cellForRowAt indexPath: IndexPath) -> UITableViewCell {
//...
/*
Start with placeholder image so it shows until the image download completes.
And if the next `if let imageURL` condition fails, the placeholder image will stay
*/
cell.songCover.image = UIImage(named: "WhiteLogo")
//Continue with your logic, no change really but could be shortened to:
if let imageURL = URL(string: songs[indexPath.row].cover) {
let request = URLSession.shared.dataTask(with: imageURL) { (imageData, response, error) in
guard let imageData = imageData else { return }
DispatchQueue.main.async {
cell.songCover.image = UIImage(data: imageData)
}
}
request.resume()
}
//...
}
However, since the image download logic is async, it will misbehave if the cell is reused before the download completes.
i.e. Image download for the first song starts but you scroll fast enough to reuse the first cell for, lets say, the third song.
Now, when the download completes, the first image could show on the third cell.
If you face this issue then let me know and I shall update my answer.
Set "WhiteLogo.png" on above your code which download image for album or set logo image if album image data is nil like guard let image = imageData else { var image : UIImage = UIImage(named:"WhiteLogo.png")!
cell.songCover.image = UIImageView(image: image) }
override func tableView(_ tableView: UITableView, cellForRowAt indexPath: IndexPath) -> UITableViewCell {
//1. Create A Cell
let cell = tableView.dequeueReusableCell(withIdentifier: "cell", for: indexPath) as! TableViewCell
//2. Set It's Text
cell.songTitle.text = songs[indexPath.row].title
cell.artistLabel.text = songs[indexPath.row].artist
//set image
var image : UIImage = UIImage(named:"WhiteLogo.png")!
cell.songCover.image = UIImageView(image: image)
//3. Get The Image
if let imageURL = URL(string: songs[indexPath.row].cover){
let request = URLSession.shared.dataTask(with: imageURL) { (imageData, response, error) in
if let error = error{
print(error)
}else{
guard let image = imageData else { return }
DispatchQueue.main.async {
cell.songCover.image = UIImage(data: image)
cell.setNeedsLayout()
cell.layoutIfNeeded()
}
}
}
request.resume()
}
return cell
}
guard let image = imageData else { cell.songCover.image = UIImage(named : "your_image_name"); return }
Please use the Kingfisher library it will download image from url and set placeholder image.Library URL:- https://github.com/onevcat/Kingfisher

Image in table view [duplicate]

This question already has an answer here:
Asynchronously load image in uitableviewcell
(1 answer)
Closed 5 years ago.
I have a problem with the image in table view cell
The images are downloaded form the Google Firebase and in every cell there is one of that
But when I scroll up or down the images change automatically the index
Here is my code, someone can help me? thanks a lot!
func tableView(_ tableView: UITableView, cellForRowAt indexPath: IndexPath) -> UITableViewCell {
if postsArray[indexPath.row].imageNoImage == true{
let cell = tableView.dequeueReusableCell(withIdentifier: "imageLook", for: indexPath) as! imageLookTableViewCell
cell.authorLabel.text = self.postsArray[indexPath.row].author
cell.likesCountLabel.text = "\(self.postsArray[indexPath.row].likes!)"
cell.postID = postsArray[indexPath.row].postId
cell.textViewPost.text = self.postsArray[indexPath.row].textPost
let url = URL(string: postsArray[indexPath.row].pathToImage as! String)
if url != nil {
DispatchQueue.global().async {
let data = try? Data(contentsOf: url!)
DispatchQueue.main.async {
if data != nil {
cell.imagePost.image = UIImage(data:data!)
}else{
}
}
}
}
for person in self.postsArray[indexPath.row].peopleWhoLike {
if person == FIRAuth.auth()!.currentUser!.uid {
cell.likesBtn.isHidden = false
break
}
}
return cell
}
Your question is not very descriptive/well written, but I think your problem is that you are not caching your images.
Try this:
let imageCache = NSCache()
let cell = tableView.dequeueReusableCell(withIdentifier: "imageLook", for: indexPath) as! imageLookTableViewCell
cell.authorLabel.text = self.postsArray[indexPath.row].author
cell.likesCountLabel.text = "\(self.postsArray[indexPath.row].likes!)"
cell.postID = postsArray[indexPath.row].postId
cell.textViewPost.text = self.postsArray[indexPath.row].textPost
let url = URL(string: postsArray[indexPath.row].pathToImage as! String)
if url != nil {
if let cachedImage = imageCache.objectForKey(url) as? UIImage {
cell.imagePost.image = cachedImage
return
}
DispatchQueue.global().async {
let data = try? Data(contentsOf: url!)
DispatchQueue.main.async {
if data != nil {
if let myImageName = UIImage(data:data!){
imageCache.setObject(myImageName, forKey: url)
}
cell.imagePost.image = UIImage(data:data!)
}else{
}
}
}
}
for person in self.postsArray[indexPath.row].peopleWhoLike {
if person == FIRAuth.auth()!.currentUser!.uid {
cell.likesBtn.isHidden = false
break
}
}
return cell
}

TableView assigning image to cell in TVC

Having a problem with this code. Basically i'm trying to populate a table cell using an image im pulling from twitter. The url field here has the value http://pbs.twimg.com/profile_images/796924570150301696/35nSG5nN_normal.jpg but for some reason the print("REACHED") is never printed. Any help/suggestions appreciated!
code snippet:
override func tableView(_ tableView: UITableView, cellForRowAt indexPath: IndexPath) -> UITableViewCell {
let cell = tableView.dequeueReusableCell(withIdentifier: tIdentifier, for: indexPath) as! TweetCell
let tweet = tweets[indexPath.section][indexPath.row]
let url = tweet.user.profileImageURL!
print(url.absoluteString)
let data = try? Data(contentsOf: url)
if (data == nil){
} else {
print("REACHED")
cell.avatarImage = UIImage(data: data!)
}
cell.tweet = tweets[indexPath.section][indexPath.row]
return cell
}
This worked for me:
func example() {
let cell = UITableViewCell()
let url = URL(string: "http://pbs.twimg.com/profile_images/796924570150301696/35nSG5nN_normal.jpg")
do {
let data = try Data(contentsOf: url!)
print("REACHED")
cell.imageView?.image = UIImage(data: data)
} catch {
print("received this error:\n\(error.localizedDescription)")
}
}
If it doesn't work right away, at least you'll have an error message to help you figure it out. Good luck!
Edit:
You should make sure you have updated your Info.plist to include an entry for:
App Transport Security Settings
Without this you will not have access to other sites.
Transport security has blocked a cleartext HTTP
Some tips for an easy life…
Don't force unwrap
Don't download on the main queue
Don't expose your cell's IBOutlets
let imageQueue = DispatchQueue(label: "imageQueue", qos: DispatchQoS.background)
class TweetCell: UITableViewCell {
#IBOutlet fileprivate var avatarImage: UIImageView!
var tweet: Tweet {
didSet {
guard let url = tweet.user.profileImageURL else { return }
loadImage(url: url)
}
}
fileprivate func loadImage(url: URL) {
imageQueue.async {
do {
let data = try Data(contentsOf: url)
DispatchQueue.main.async {
self.avatarImage.image = UIImage(data: data)
}
} catch {
// Handle error
}
}
}
}
override func tableView(_ tableView: UITableView, cellForRowAt indexPath: IndexPath) -> UITableViewCell {
let cell = tableView.dequeueReusableCell(withIdentifier: tIdentifier, for: indexPath) as! TweetCell
cell.tweet = tweets[indexPath.section][indexPath.row]
return cell
}

Swift Images change to wrong images while scrolling after async image loading to a UITableViewCell

I'm trying to async load pictures inside my FriendsTableView (UITableView) cell. The images load fine but when I'll scroll the table the images will change a few times and wrong images are getting assigned to wrong cells.
I've tried all methods I could find in StackOverflow including adding a tag to the raw and then checking it but that didn't work. I'm also verifying the cell that should update with indexPath and check if the cell exists. So I have no idea why this is happening.
Here is my code:
func tableView(tableView: UITableView, cellForRowAtIndexPath indexPath: NSIndexPath) -> UITableViewCell {
let cell = tableView.dequeueReusableCellWithIdentifier("friendCell", forIndexPath: indexPath) as! FriendTableViewCell
var avatar_url: NSURL
let friend = sortedFriends[indexPath.row]
//Style the cell image to be round
cell.friendAvatar.layer.cornerRadius = 36
cell.friendAvatar.layer.masksToBounds = true
//Load friend photo asyncronisly
avatar_url = NSURL(string: String(friend["friend_photo_url"]))!
if avatar_url != "" {
getDataFromUrl(avatar_url) { (data, response, error) in
dispatch_async(dispatch_get_main_queue()) { () -> Void in
guard let data = data where error == nil else { return }
let thisCell = tableView.cellForRowAtIndexPath(indexPath)
if (thisCell) != nil {
let updateCell = thisCell as! FriendTableViewCell
updateCell.friendAvatar.image = UIImage(data: data)
}
}
}
}
cell.friendNameLabel.text = friend["friend_name"].string
cell.friendHealthPoints.text = String(friend["friend_health_points"])
return cell
}
On cellForRowAtIndexPath:
1) Assign an index value to your custom cell. For instance,
cell.tag = indexPath.row
2) On main thread, before assigning the image, check if the image belongs the corresponding cell by matching it with the tag.
dispatch_async(dispatch_get_main_queue(), ^{
if(cell.tag == indexPath.row) {
UIImage *tmpImage = [[UIImage alloc] initWithData:imgData];
thumbnailImageView.image = tmpImage;
}});
});
This is because UITableView reuses cells. Loading them in this way causes the async requests to return at different time and mess up the order.
I suggest that you use some library which would make your life easier like Kingfisher. It will download and cache images for you. Also you wouldn't have to worry about async calls.
https://github.com/onevcat/Kingfisher
Your code with it would look something like this:
func tableView(tableView: UITableView, cellForRowAtIndexPath indexPath: NSIndexPath) -> UITableViewCell {
let cell = tableView.dequeueReusableCellWithIdentifier("friendCell", forIndexPath: indexPath) as! FriendTableViewCell
var avatar_url: NSURL
let friend = sortedFriends[indexPath.row]
//Style the cell image to be round
cell.friendAvatar.layer.cornerRadius = 36
cell.friendAvatar.layer.masksToBounds = true
//Load friend photo asyncronisly
avatar_url = NSURL(string: String(friend["friend_photo_url"]))!
if avatar_url != "" {
cell.friendAvatar.kf_setImageWithURL(avatar_url)
}
cell.friendNameLabel.text = friend["friend_name"].string
cell.friendHealthPoints.text = String(friend["friend_health_points"])
return cell
}
UPDATE
There are some great open source libraries for image caching such as KingFisher and SDWebImage. I would recommend that you try one of them rather than writing your own implementation.
END UPDATE
So there are several things you need to do in order for this to work. First let's look at the caching code.
// Global variable or stored in a singleton / top level object (Ex: AppCoordinator, AppDelegate)
let imageCache = NSCache<NSString, UIImage>()
extension UIImageView {
func downloadImage(from imgURL: String) -> URLSessionDataTask? {
guard let url = URL(string: imgURL) else { return nil }
// set initial image to nil so it doesn't use the image from a reused cell
image = nil
// check if the image is already in the cache
if let imageToCache = imageCache.object(forKey: imgURL as NSString) {
self.image = imageToCache
return nil
}
// download the image asynchronously
let task = URLSession.shared.dataTask(with: url) { (data, response, error) in
if let err = error {
print(err)
return
}
DispatchQueue.main.async {
// create UIImage
let imageToCache = UIImage(data: data!)
// add image to cache
imageCache.setObject(imageToCache!, forKey: imgURL as NSString)
self.image = imageToCache
}
}
task.resume()
return task
}
}
You can use this outside of a TableView or CollectionView cell like this
let imageView = UIImageView()
let imageTask = imageView.downloadImage(from: "https://unsplash.com/photos/cssvEZacHvQ")
To use this in a TableView or CollectionView cell you'll need to reset the image to nil in prepareForReuse and cancel the download task. (Thanks for pointing that out #rob
final class ImageCell: UICollectionViewCell {
#IBOutlet weak var imageView: UIImageView!
private var task: URLSessionDataTask?
override func prepareForReuse() {
super.prepareForReuse()
task?.cancel()
task = nil
imageView.image = nil
}
// Called in cellForRowAt / cellForItemAt
func configureWith(urlString: String) {
if task == nil {
// Ignore calls when reloading
task = imageView.downloadImage(from: urlString)
}
}
}
func collectionView(_ collectionView: UICollectionView, cellForItemAt indexPath: IndexPath) -> UICollectionViewCell {
let cell = collectionView.dequeueReusableCell(withReuseIdentifier: "imageCell", for: indexPath) as! ImageCell
cell.configureWith(urlString: "https://unsplash.com/photos/cssvEZacHvQ") // Url for indexPath
return cell
}
Keep in mind that even if you use a 3rd party library you'll still want to nil out the image and cancel the task in prepareForReuse
If targeting iOS 13 or later, you can use Combine and dataTaskPublisher(for:). See WWDC 2019 video Advances in Networking, Part 1.
The idea is to let the cell keep track of the “publisher”, and have prepareForReuse:
cancel the prior image request;
set the image property of the image view to nil (or a placeholder); and then
start another image request.
For example:
extension ViewController: UITableViewDataSource {
func tableView(_ tableView: UITableView, numberOfRowsInSection section: Int) -> Int {
return objects.count
}
func tableView(_ tableView: UITableView, cellForRowAt indexPath: IndexPath) -> UITableViewCell {
let cell = tableView.dequeueReusableCell(withIdentifier: "CustomCell", for: indexPath) as! CustomCell
let url = ...
cell.setImage(to: url)
return cell
}
}
class CustomCell: UITableViewCell {
#IBOutlet weak var customImageView: UIImageView!
private var subscriber: AnyCancellable?
override func prepareForReuse() {
super.prepareForReuse()
subscriber?.cancel()
customImageView?.image = nil
}
func setImage(to url: URL) {
subscriber = ImageManager.shared.imagePublisher(for: url, errorImage: UIImage(systemName: "xmark.octagon"))
.assign(to: \.customImageView.image, on: self)
}
}
Where:
class ImageManager {
static let shared = ImageManager()
private init() { }
private let session: URLSession = {
let configuration = URLSessionConfiguration.default
configuration.requestCachePolicy = .returnCacheDataElseLoad
let session = URLSession(configuration: configuration)
return session
}()
enum ImageManagerError: Error {
case invalidResponse
}
func imagePublisher(for url: URL, errorImage: UIImage? = nil) -> AnyPublisher<UIImage?, Never> {
session.dataTaskPublisher(for: url)
.tryMap { data, response in
guard
let httpResponse = response as? HTTPURLResponse,
200..<300 ~= httpResponse.statusCode,
let image = UIImage(data: data)
else {
throw ImageManagerError.invalidResponse
}
return image
}
.replaceError(with: errorImage)
.receive(on: DispatchQueue.main)
.eraseToAnyPublisher()
}
}
If targeting earlier iOS versions, rather than using Combine, you can use URLSession, with the same idea of canceling the prior request in prepareForReuse:
class CustomCell: UITableViewCell {
#IBOutlet weak var customImageView: UIImageView!
private weak var task: URLSessionTask?
override func prepareForReuse() {
super.prepareForReuse()
task?.cancel()
customImageView?.image = nil
}
func setImage(to url: URL) {
task = ImageManager.shared.imageTask(for: url) { result in
switch result {
case .failure(let error): print(error)
case .success(let image): self.customImageView.image = image
}
}
}
}
Where:
class ImageManager {
static let shared = ImageManager()
private init() { }
private let session: URLSession = {
let configuration = URLSessionConfiguration.default
configuration.requestCachePolicy = .returnCacheDataElseLoad
let session = URLSession(configuration: configuration)
return session
}()
enum ImageManagerError: Error {
case invalidResponse
}
#discardableResult
func imageTask(for url: URL, completion: #escaping (Result<UIImage, Error>) -> Void) -> URLSessionTask {
let task = session.dataTask(with: url) { data, response, error in
guard let data = data else {
DispatchQueue.main.async { completion(.failure(error!)) }
return
}
guard
let httpResponse = response as? HTTPURLResponse,
200..<300 ~= httpResponse.statusCode,
let image = UIImage(data: data)
else {
DispatchQueue.main.async { completion(.failure(ImageManagerError.invalidResponse)) }
return
}
DispatchQueue.main.async { completion(.success(image)) }
}
task.resume()
return task
}
}
Depending on the implementation there can be many things that will cause all of the answers here to not work (including mine). Checking the tag did not work for me, checking the cache neither, i have a custom Photo class that carries the full image, thumbnail and more data, so i have to take care of that too and not just prevent the image from being reused improperly. Since you will probably be assigning the images to the cell imageView after they're done downloading, you will need to cancel the download and reset anything you need on prepareForReuse()
Example if you're using something like SDWebImage
override func prepareForReuse() {
super.prepareForReuse()
self.imageView.sd_cancelCurrentImageLoad()
self.imageView = nil
//Stop or reset anything else that is needed here
}
If you have subclassed the imageview and handle the download yourself make sure you setup a way to cancel the download before the completion is called and call the cancel on prepareForReuse()
e.g.
imageView.cancelDownload()
You can cancel this from the UIViewController too. This on itself or combined with some of the answers will most likely solve this issue.
I solve the problem just implementing a custom UIImage class and I did a String condition as the code below:
let imageCache = NSCache<NSString, UIImage>()
class CustomImageView: UIImageView {
var imageUrlString: String?
func downloadImageFrom(withUrl urlString : String) {
imageUrlString = urlString
let url = URL(string: urlString)
self.image = nil
if let cachedImage = imageCache.object(forKey: urlString as NSString) {
self.image = cachedImage
return
}
URLSession.shared.dataTask(with: url!, completionHandler: { (data, response, error) in
if error != nil {
print(error!)
return
}
DispatchQueue.main.async {
if let image = UIImage(data: data!) {
imageCache.setObject(image, forKey: NSString(string: urlString))
if self.imageUrlString == urlString {
self.image = image
}
}
}
}).resume()
}
}
It works for me.
TableView reuses cells. Try this:
import UIKit
class CustomViewCell: UITableViewCell {
#IBOutlet weak var imageView: UIImageView!
private var task: URLSessionDataTask?
override func prepareForReuse() {
super.prepareForReuse()
task?.cancel()
imageView.image = nil
}
func configureWith(url string: String) {
guard let url = URL(string: string) else { return }
task = URLSession.shared.dataTask(with: url) { (data, response, error) in
if let data = data, let image = UIImage(data: data) {
DispatchQueue.main.async {
self.imageView.image = image
}
}
}
task?.resume()
}
}
Because TableView reuses cells. In your cell class try this code:
class CustomViewCell: UITableViewCell {
#IBOutlet weak var catImageView: UIImageView!
private var task: URLSessionDataTask?
override func prepareForReuse() {
super.prepareForReuse()
task?.cancel()
catImageView.image = nil
}
func configureWith(url string: String) {
guard let url = URL(string: string) else { return }
task = URLSession.shared.dataTask(with: url) { (data, response, error) in
if let data = data, let image = UIImage(data: data) {
DispatchQueue.main.async {
self.catImageView.image = image
}
}
}
task?.resume()
}
}
the Best Solution for This Problem i have is for Swift 3 or Swift 4
Simply write these two lines
cell.videoImage.image = nil
cell.thumbnailimage.setImageWith(imageurl!)
Swift 3
DispatchQueue.main.async(execute: {() -> Void in
if cell.tag == indexPath.row {
var tmpImage = UIImage(data: imgData)
thumbnailImageView.image = tmpImage
}
})
I created a new UIImage variable in my model and load the image/placeholder from there when creating a new model instance. It worked perfectly fine.
It is an example that using Kingfisher caching at memory and disk after downloaded.
It replace UrlSession downloading traditional and avoid re-download UIImageView after scroll down TableViewCell
https://gist.github.com/andreconghau/4c3b04205195f452800d2892e91a079a
Example Output
sucess
Image Size:
(460.0, 460.0)
Cache:
disk
Source:
network(Kingfisher.ImageResource(cacheKey: "https://avatars0.githubusercontent.com/u/5936?v=4", downloadURL: https://avatars0.githubusercontent.com/u/5936?v=4))
Original source:
network(Kingfisher.ImageResource(cacheKey: "https://avatars0.githubusercontent.com/u/5936?v=4", downloadURL: https://avatars0.githubusercontent.com/u/5936?v=4))

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