For now i download the image, story it in a mutable dictionary and then verify if the image was already downloaded and if not, download it and store it. As a key i use the indexPath.
This code kinda works, but from the tests i did if i scroll too fast the cell image will load the wrong one and after a split of a second it will load the right one (replacing the wrong image).
Im always clearing my thumbnail (imageView) after i call the method so i don't know why im getting this bug.
I though that maybe the if(self.imageCache.object(forKey: cacheKey) != nil) statement was true and thats why i would get multiple images, but the breakpoint didn't stop at once when i was scrolling down.
Any ideas?
func tableView(_ tableView: UITableView, cellForRowAt indexPath: IndexPath) -> UITableViewCell
{
let cell = tableView.dequeueReusableCell(withIdentifier: "cell", for: indexPath) as! MovieCellController
cell.thumbnail.image = UIImage()
let cacheKey = indexPath.row
if(self.imageCache.object(forKey: cacheKey) != nil)
{
cell.thumbnail.image = self.imageCache.object(forKey: cacheKey) as? UIImage
}
else
{
DispatchQueue.global(qos: DispatchQoS.QoSClass.default).async {
if let url = NSURL(string: self.moviesCollection[indexPath.row].imageLink) {
if let data = NSData(contentsOf: url as URL) {
let image: UIImage = UIImage(data: data as Data)!
self.imageCache.setObject(image, forKey: cacheKey as NSCopying)
DispatchQueue.main.async(execute: {
cell.thumbnail.image = image
})
}
}
}
}
cell.name.text = moviesCollection[indexPath.row].name
return cell
}
It is happening because the cells are reused due to which when scrolling fast the image of another cell seems to be assigned, but if fact it is the previous cell's image which is reused.
In cell's prepareForReuse method set your imageView's image to nil. Like, imageView.image = nil
Because the cell is reused.
The reused-cell keeps its old data.
The new image downloading will cost few seconds so that the reused -cell cannot change the image immediately.
You can use a placeholder-image when downloading the new image.
Or you can use the 3rd part library - SDWebImage.
Related
The problem is that I don't know how to refresh images loaded asynchronously from url with SDWebImage.
override func tableView(_ tableView: UITableView, cellForRowAt indexPath: IndexPath) -> UITableViewCell {
let cell = tableView.dequeueReusableCell(withIdentifier: "Cell", for: indexPath)
let item = items[indexPath.row]
if let url = URL(string: item.stringUrl) {
let placeholderImage = UIImage(named: "noPhoto.png")
itemImage.sd_setImage(with: url, placeholderImage: placeholderImage)
}
cell.imageView?.image = itemImage.image
cell.textLabel?.text = item.title
cell.detailTextLabel?.text = "item id: \(item.id)"
return cell
}
The images will only refresh after scrolling through the table. Until then the table only shows placeHolder image which is expected as it only reloads images when cells are reused. I tried to use the completion handler to refresh images when loaded using tableview.reload() as shown below:
itemImage.sd_setImage(with: url, placeholderImage: placeholderImage, completed: {image,error,cache,url in
if image != nil {
DispatchQueue.main.async {
self.tableView.reloadData()
}
}
})
This solution results in tableView loading all the images in a second which is what I want but it reloads the whole table basically every time I try to scroll through it so it "pushes" the whole table to the top position instantly.
The last solution I tries is this:
itemImage.sd_setImage(with: url, placeholderImage: placeholderImage, completed: {image,error,cache,url in
if image != nil {
DispatchQueue.main.async {
self.tableView.reloadRows(at: [indexPath], with: .none)
}
}
})
This also doesn't and makes tableview randomly showing and hiding images.
I suppose the problem is that I try to reload images in a function that creates cells but I can't find a solution to how resolve this issue. I will be very grateful for any help.
I'm trying to load images extracted from the web URL into the image view of each cell.
However, when i scroll the table the screen will freeze as I believe it is attempting to grab the images for each cell 1 by 1.
Is there a way i can make it asynchronous? The resources available out there currently is outdated or incompatible(running obj c) as I'm running on Swift 2
The relevant code I'm using within the table view controller is below :
override func tableView(newsFeedTableView: UITableView, cellForRowAtIndexPath indexPath: NSIndexPath) -> UITableViewCell {
let cell = tableView.dequeueReusableCellWithIdentifier("Cell", forIndexPath: indexPath)
let blogPost: BlogPost = blogPosts[indexPath.row]
cell.textLabel?.text = blogPost.postTitle
let unformattedDate = blogPost.postDate
//FORMATTING: Splitting of raw data into arrays based on delimiter '+" to print only useful information
let postDateArr = unformattedDate.characters.split{$0 == "+"}.map(String.init)
cell.detailTextLabel?.text = postDateArr[0]
let url = NSURL(string: blogPost.postImageUrl)
let data = NSData(contentsOfURL: url!)
cell.imageView!.image = UIImage(data: data!)//WHY SO SLOW!?
print(blogPost.postImageUrl)
return cell
}
Try this
var image: UIImage
dispatch_async(dispatch_get_global_queue(DISPATCH_QUEUE_PRIORITY_DEFAULT, 0), {() -> Void in
// Background thread stuff.
let url = NSURL(string: blogPost.postImageUrl)
let data = NSData(contentsOfURL: url!)
image = UIImage(data:data)
dispatch_async(dispatch_get_main_queue(), {() -> Void in
// Main thread stuff.
cell.imageView.image = image
})
})
Lets clean your code a bit. First of all, you are trying to declear ALL your cells in your viewController. That means your app is not trying to load every image one byt one, but more like everything all together.
You need to create a separate file called PostCell what is going to be a type of UITableViewCell.
Then you need to go to your prototype cell and connect those view elements to that PostCell just like you would add those to any other ViewController.
Now, here is new code to your cellForRowAtIndexPath function:
override func tableView(newsFeedTableView: UITableView, cellForRowAtIndexPath indexPath: NSIndexPath) -> UITableViewCell {
let blogPost = blogPosts[indexPath.row]
if let cell = tableView.dequeueReusableCellWithIdentifier("Cell") as? PostCell {
cell.configureCell(blogPost)
return cell
}
return UITableViewCell() // You need to do this because of if let
}
And declear this on that PostCell:
func configureCell(post: BlogPost) {
this.textLabel.text = post.postTitle
let postDateArr = unformattedDate.characters.split{$0 == "+"}.map(String.init)
this.detailTextLabel.text = postDateArr[0]
// I would add few if let declarations here too, but if you are sure all these forced ! variables do exciest, then its ok
let url = NSURL(string: blogPost.postImageUrl)
let data = NSData(contentsOfURL: url!)
this.imageView.image = UIImage(data: data!)
}
Or something along those lines. When you connect those elements to your cell, you will get proper variable names for those.
That SHOULD help. There are plenty of tutorials how to make a custom tableviewcell. Some of them advice to put all the declarations inside that cellForRowAtIndexPath, but I have found that it get's problematic very fast.
So...my advice in a nutscell...create a custom tableviewcell.
Hope this helps! :)
To load the image on every cell use SDWebImage third party library. You can add it using pods as put pod 'SDWebImage' It provides various methods to load the image with caching or without caching asynchronously. With caching you don't really need to worry about loading image data every time cell appears on the screen. Try this
override func tableView(newsFeedTableView: UITableView, cellForRowAtIndexPath indexPath: NSIndexPath) -> UITableViewCell {
if let cell = tableView.dequeueReusableCellWithIdentifier("Cell") as? PostCell {
--reset your cell here--
// cell.imageView.image = nil
}
cell.imageView.sd_setImageWithURL(YOUR_URL, placeholderImage: UIImage(named: "")) {
(UIImage img, NSError err, SDImageCacheType cacheType, NSURL imgUrl) -> Void in
// Do awesome things
}
-- configure your cell here --
}
I am loading a tableview of images that are being fetched from a public CloudKit database as CKAssets. However, the images are loading out of order about two seconds until the correct image is loaded into the UIImageView of a custom UITableview cell. I know that the issue is that since the cell is reusable the image is still downloaded from CloudKit and displayed in any visible cell while a user is scrolling through the TableView before the correct image is shown in the image view. I am wondering if there is a fix to this in swift so that the image downloaded is only for that of a visible cell and not any previous cells.
Here is the code for cellForRowAtIndexPath:
func tableView(tableView: UITableView, cellForRowAtIndexPath indexPath: NSIndexPath) -> UITableViewCell {
let cell = tableView.dequeueReusableCellWithIdentifier("Cell", forIndexPath: indexPath) as! PostsTableViewCell
cell.userInteractionEnabled = false
photoRecord = sharedRecords.fetchedRecords[indexPath.row]
cell.photoTitle.text = photoRecord.objectForKey("photoTitle") as? String
cell.photoImage.backgroundColor = UIColor.blackColor()
cell.photoImage.image = UIImage(named: "stock_image.png")
if let imageFileURL = imageCache.objectForKey(self.photoRecord.recordID) as? NSURL {
cell.photoImage.image = UIImage(data: NSData(contentsOfURL: imageFileURL)!)
cell.userInteractionEnabled = true
print("Image Cached: \(indexPath.row)")
} else {
let container = CKContainer.defaultContainer()
let publicDatabase = container.publicCloudDatabase
let fetchRecordsImageOperation = CKFetchRecordsOperation(recordIDs:[self.photoRecord.recordID])
fetchRecordsImageOperation.desiredKeys = ["photoImage"]
fetchRecordsImageOperation.queuePriority = .VeryHigh
fetchRecordsImageOperation.perRecordCompletionBlock = {(record:CKRecord?, recordID:CKRecordID?, error:NSError?) -> Void in
if let imageRecord = record {
NSOperationQueue.mainQueue().addOperationWithBlock() {
if let imageAsset = imageRecord.objectForKey("photoImage") as? CKAsset{
cell.photoImage.image = UIImage(data: NSData(contentsOfURL: imageAsset.fileURL)!)
self.imageCache.setObject(imageAsset.fileURL, forKey:self.photoRecord.recordID)
cell.userInteractionEnabled = true
}
}
}
}
publicDatabase.addOperation(fetchRecordsImageOperation)
}
return cell
}
Thanks in advance!
There is latency between when your table view appears and when fetchRecordsImageOperation.perRecordCompletionBlock is called. Within that time the user may scroll the table view causing the table view cell to dequeue and requeue with a different indexPath and different data associated with it, if you do not check that the cell's index path is the same as when you constructed fetchRecordsImageOperation.perRecordCompletionBlock, this line: cell.photoImage.image = UIImage(data: NSData(contentsOfURL: imageAsset.fileURL)!) will cause the image to be placed in the cell that is already displaying different data. You can modify your completion block like so to avoid this.
if let imageRecord = record {
NSOperationQueue.mainQueue().addOperationWithBlock() {
if let imageAsset = imageRecord.objectForKey("photoImage") as? CKAsset{
if indexPath == tableView.indexPathForCell(cell){
cell.photoImage.image = UIImage(data: NSData(contentsOfURL: imageAsset.fileURL)!)
}
self.imageCache.setObject(imageAsset.fileURL, forKey:self.photoRecord.recordID)
cell.userInteractionEnabled = true
}
}
}
You find the answer in here I believe, I bias of course cause I wrote it.
How to determine when all images have been downloaded from a set in Swift?
You should setup an image to display while its loading an image and show that so that the user understands what is happening?
Good day! I have 2 problems and I hope you will help me.
1) I have news feed in my application, that contains images.
I am using Autolayout for dynamic cells:
and I want the image to keep its ratio and to completely fill the width of the cell (with margins = 12).
I set constrains, cell is autoresizable, but image didn't save its ratio:
.
What I am doing wrong?
2) The second problem, i load images asynchronously, here is my code:
override func tableView(tableView: UITableView, cellForRowAtIndexPath indexPath: NSIndexPath) -> UITableViewCell {
var cell: EventCell = tableView.dequeueReusableCellWithIdentifier("Cell", forIndexPath: indexPath) as EventCell
var rowData: NSDictionary = tableData[indexPath.row] as NSDictionary
cell.titleButton.setTitle(rowData["title"] as? String, forState: UIControlState.Normal)
cell.titleButton.addTarget(self, action: "openWebSite:", forControlEvents: UIControlEvents.TouchUpInside)
cell.titleButton.tag = indexPath.row
cell.descriprionLabel.text = rowData["description"] as? String
var urlString = rowData["image"] as String
var image = imageCache[urlString]
if( image == nil ) {
var imgURL = NSURL(string: urlString)
// Download an NSData representation of the image at the URL
var request: NSURLRequest = NSURLRequest(URL: imgURL!)
NSURLConnection.sendAsynchronousRequest(request, queue: NSOperationQueue.mainQueue(), completionHandler: {(response: NSURLResponse!,data: NSData!,error: NSError!) -> Void in
if error == nil {
image = UIImage(data: data) // data -> image
// Store the image in to our cache
self.imageCache[urlString] = image // save in our dictionary
if let cellToUpdate : EventCell = tableView.cellForRowAtIndexPath(indexPath) as? EventCell {
self.table.reloadRowsAtIndexPaths([indexPath], withRowAnimation: UITableViewRowAnimation.Automatic)
}
}
else {
println("Error: \(error.localizedDescription)")
}
})
} else {
dispatch_async(dispatch_get_main_queue(), {
if let cellToUpdate : EventCell = tableView.cellForRowAtIndexPath(indexPath) as? EventCell {
cellToUpdate.img.image = image
}
})
}
cell.selectionStyle = UITableViewCellSelectionStyle.None;
cell.contentView.setNeedsLayout(); // autolayout bug solution
cell.contentView.layoutIfNeeded(); // autolayout bug solution
return cell
}
All seems okay, but UITableViewCell don't resize when image is loaded and I am trying to reload cell at index path.
Interesting moment, that it will work if I scroll down and then come back to cell.
I have similar error before and I fixed it reading this article UITableView layout messing up on push segue and return. (iOS 8, Xcode beta 5, Swift) , third answer. But it didn't help me now. Looks like I need to call some method to recalculate UITableViewCell, but I don't understand what.
First question : Change UIImageView view mode from Scale to Fill to Aspect Fit (in storyboad)
Second question : Remove dispatch async if image is not nil and make you code look similar like this:
if( image == nil ) {
...
}
else {
cell.img.image = image
}
For first one in the storyboard select the image view and click on the pin icon for setting auto layout constraint and check width and height.
it will remain the width and height constant.
I'm trying to create an RSS app for practice. So my tableView cell has both textLabel and image. My textLabel's text and image data come from a dictionary stored in Core Data. Some cells have images, and some don't. The initial load of tableView looks fine to me. But when I scroll down and up, cell's images seem to change. The cells' textLabel text doesn't change though.
override func tableView(tableView: UITableView, cellForRowAtIndexPath indexPath: NSIndexPath) -> UITableViewCell {
let cell = tableView.dequeueReusableCellWithIdentifier("Cell", forIndexPath: indexPath) as UITableViewCell
self.configureCell(cell, atIndexPath: indexPath)
return cell
}
func configureCell(cell: UITableViewCell, atIndexPath indexPath: NSIndexPath) {
let object = self.fetchedResultsController.objectAtIndexPath(indexPath) as NSManagedObject
cell.accessoryType = UITableViewCellAccessoryType.DisclosureIndicator
cell.textLabel!.text = object.valueForKey("title")!.description
var image: UIImage?
if let imageData = object.valueForKey("imageData") as? NSData {
image = UIImage(data: imageData)
let itemSize = CGSizeMake(80, 80)
UIGraphicsBeginImageContext(itemSize)
let imageRect = CGRectMake(0.0, 0.0, itemSize.width, itemSize.height)
image?.drawInRect(imageRect)
cell.imageView?.image = UIGraphicsGetImageFromCurrentImageContext()
UIGraphicsEndImageContext()
}
}
If the initial tableView loads correctly, that means my Core Data stores my data's mapping correctly. But when scrolling down and up, configureCell is being called again since it needs to redraw the cell. cell.textLabel!.text = object.valueForKey("title")!.description is set correctly again, but not image here. Don't know why it behaves like this. Please give some pointer.
I had this same problem once and I think it has something to do with the reused cell not being in the default state so sometimes the image you set is being reused. To fix it, I just did an else condition on imageData and set the image to a default image if no image was found. I'm sure you could set it to nil here as well.
if let image = UIImage(contentsOfFile: imagePath) {
cell.imageView.image = image
} else {
// Default image or nil
cell.imageView.image = UIImage(named: "Calendar")
}
And I wouldn't suggest storing images as raw data in core data, as this can be very inefficient. Instead, download them to your documents directory and store a file name in core data.
What i did was remove the image from imageView and set image again. It works for me.
cell.imageView.image = nil
cell.imageView.image = UIImage(named:"Calendar")