here is my issue :
I have a UITableView containing custom UITableViewCells. Each of those UITableViewCell (called HomePicCell) is associated to a Pic object which has a property pointing to an image URL.
As soon as my cell is displayed, I start downloading this image using SDWebImage manager.
Everything is working smoothly, but after 20 to 80 seconds, some threads start hogging the CPU. The device then become a perfect hand heater for those cold winter nights, but I'd rather skip this feature for now !
I can't really put my finger on what would cause this issue. I don't think a retain loop would be the problem as it would only hog the memory. An experimented opinion would really help.
Here is my code :
UITableView Datasource
- (UITableViewCell*)tableView:(UITableView *)tableView cellForRowAtIndexPath:(NSIndexPath *)indexPath
{
NSString* cellIdentifier = [#"HomePicCell" stringByAppendingString:[Theme sharedTheme].currentTheme];
HomePicCell* cell = [tableView dequeueReusableCellWithIdentifier:cellIdentifier];
if (!cell) {
cell = [[HomePicCell alloc] initWithStyle:UITableViewCellStyleSubtitle reuseIdentifier:cellIdentifier];
}
if(self.pics.count>0){
Pic* pic = self.pics[indexPath.section];
[cell configureWithPic:pic];
}
return cell;
}
HomePicCell (configureWithPic:)
- (void)configureWithPic:(Pic*)pic
{
self.pic = pic;
// Reinit UI
[self.progressView setHidden:NO];
[self.errorLabel setHidden:YES];
[self.photoImageView setAlpha:0];
[self.progressView setProgress:0];
[self.pic downloadWithDelegate:self];
}
Pic
- (void) downloadWithDelegate:(id<PicDownloadDelegate>)delegate
{
SDWebImageManager *manager = [SDWebImageManager sharedManager];
[manager downloadWithURL:self.url options:0 progress:^(NSUInteger receivedSize, long long expectedSize) {
if(expectedSize>0){
float progress = [#(receivedSize) floatValue]/[#(expectedSize) floatValue];
[delegate pic:self DownloadDidProgress:progress];
}
} completed:^(UIImage *image, NSError *error, SDImageCacheType cacheType, BOOL finished) {
self.isGif = #(image.images.count>1);
if(image){
if(cacheType == SDImageCacheTypeNone){
[delegate pic:self DownloadDidFinish:image fromCache:NO];
}else{
[delegate pic:self DownloadDidFinish:image fromCache:YES];
}
}else{
[delegate pic:self DownloadFailWithError:error];
}
}];
}
HomePicCell (delegate methods)
- (void)pic:(Pic*)pic DownloadDidFinish:(UIImage *)image fromCache:(BOOL)fromCache
{
if(![pic isEqual:self.pic]){
return;
}
[self.progressView setHidden:YES];
self.photoImageView.image = image;
[self updateUI];
}
- (void)pic:(Pic*)pic DownloadFailWithError:(NSError *)error
{
if(![pic isEqual:self.pic]){
return;
}
[self.errorLabel setHidden:NO];
[self.progressView setHidden:YES];
}
- (void)pic:(Pic*)pic DownloadDidProgress:(float)progress
{
if(![pic isEqual:self.pic]){
return;
}
[self.progressView setProgress:progress+.01f];
}
Thanks !
The issue is apparently fixed by switching to SDWebImage 3.0 (instead of 3.3).
I'll go ahead and declare an issue on the project github page to see if some people have had the same problem.
Related
I am using SDWebImage for fetching images from server to my table view app in IOS.
But the problem is that when I scroll down in table view instead of waiting for the images to load it put the images downloaded in the first few rows of table view and repeat those images till the end row and when it downloads the images it changes those repeated images to the actual image for that row.
NSURL * url = [NSURL URLWithString:string];
SDWebImageManager *manager = [SDWebImageManager sharedManager];
[manager downloadImageWithURL:url
options:0
progress:^(NSInteger receivedSize, NSInteger expectedSize)
{
// progression tracking code
}
completed:^(UIImage *image, NSError *error, SDImageCacheType cacheType, BOOL finished,NSURL * url)
{
if (finished && image )
{
NSArray *visibleIndexPaths = [tableView indexPathsForVisibleRows];
if ([visibleIndexPaths containsObject:indexPath]) {
cell.myImage.image = image;
}
}
}];
Actually, it is not a bug with SDWebImage, but rather it's the nature of how UITableView works. downloadImageWithURL, is an async process,so when your tableView delegate/datasource methods are called, the image isn't downloaded yet, therefore cellForRow doesn't have an image to display.
To overcome this issue you should first check image from cache as
[[SDWebImageManager sharedManager] diskImageExistsForURL:[NSURL URLWithString:ImageUrl]]
if yes then set image to UIImageView otherwise use downloadImageWithURL to download image and add cell tag(To display image to correct row) as
cell.tag = indexPath.row;
on successfull download first check correct row as
if(cell.tag == indexPath.row){
and set image to UIImageView.Here is setImage method.
-(void)setImage:(SLFirstTableViewCell *)cell atIndexPath:(NSIndexPath *)indexPath{
SLFirstTableViewCellItem * slFirstTableViewCellItem = [self.categories objectAtIndex:indexPath.row]; // categories is array of items,replace with yours.
NSString *ImageUrl = slFirstTableViewCellItem.imageUrl; //assume image url is in slFirstTableViewCellItem object.
cell.tag = indexPath.row;
if([[SDWebImageManager sharedManager] diskImageExistsForURL:[NSURL URLWithString:ImageUrl]]){
[cell.imgItem setImage: [[SDImageCache sharedImageCache] imageFromDiskCacheForKey:ImageUrl]];
[self hideProgressView:cell];
}else{
[self showProgressView:cell];
[SDWebImageDownloader.sharedDownloader downloadImageWithURL:[NSURL URLWithString:ImageUrl]
options:0
progress:^(NSInteger receivedSize, NSInteger expectedSize)
{
// progression tracking code
}
completed:^(UIImage *image, NSData *data, NSError *error, BOOL finished)
{
if (image && finished)
{
[[SDImageCache sharedImageCache] storeImage:image forKey:ImageUrl]; // cache image
if(cell.tag == indexPath.row){ // check if correct row
[cell.imgItem setImage:image];
[self hideProgressView:cell];
}
}else{
cell.imgItem.hidden = YES;
cell.progressBar.hidden = YES;
}
}];
}
}
And define showProgressView and hideProgressView methods as
-(void)showProgressView:(SLFirstTableViewCell *)cell {
cell.progressText.hidden = NO;
cell.progressBar.hidden = NO;
cell.imgItem.hidden = YES;
[cell.progressBar startAnimating];
[cell.progressText setText:#"Loading Image..."];
}
-(void)hideProgressView:(SLFirstTableViewCell *)cell{
cell.progressBar.hidden = YES;
cell.progressText.hidden = YES;
cell.imgItem.hidden = NO;
[cell.progressBar stopAnimating];
}
finally call setImage from cellForRowAtIndexPath method(before returning cell) as
[self setImage:cell atIndexPath:indexPath];
I have a UITableView that uses paging. All the delegates, and datasource are set.
My table view fetches a list of ten cars over the network and displays them by sending a page number (currentPage). During this fetch request I also get the pageCount which is the number of pages that contains cars on the server. Each page contains 10 cars.
I create a loading cell on the row that equals self.allCars.count which is my car array. This cell then fetches the next ten, and adds them to the self.allCars.count array. A loading cell is then created again for self.allCars.count + 1 etc. (I hope you get the picture, if not please ask).
On first launch the list contains All Cars which is the default request. However, the user can change it from a drop down. For example, they can select Blue Cars. This is passed into the fetchCars methods as the params parameter.
There is an unwanted behaviour in my code however: When I scroll down through the list, with the default paramter selected, and I scroll down three pages (three network calls to fetchCars...) and the array now contains 30 cars displayed in the tableView. However I now want to start a different search from scratch, so I go to the drop down, and select to filter by only blue cars (donePickerBlue). This method removes all the car objects, sets the currentPage back to 1, calls the network for the blue cars, and reloads the data. The unwanted behaviour occurs here. Because there had been 30 cells/indexPath.rows, the network call is called 3 times. This is because the indexPath.row < self.allCars.count is not true. This is where I am stuck, I can't seem to figure out how to fix it, so that if the search parameter is change (blue in this case) that it should treat it as new, I thought the [tableView reloadData] would handle this, but unfortunately it remembers how many index paths there are.
Its something i've been stuck on for a while. I've a feeling im missing something very simple to fix it.
Header file
#property (nonatomic) NSInteger currentPage;
#property (nonatomic) NSInteger pageCount;
Implementation
-(void)viewDidLoad{
...
self.currentPage = 1;
...
}
- (NSInteger)numberOfSectionsInTableView:(UITableView *)tableView
{
return 1;
}
- (NSInteger)tableView:(UITableView *)tableView numberOfRowsInSection:(NSInteger)section{
if (self.allCars.count ==0) {
return 0;
}
else{
if (self.currentPage<self.pageCount)
return self.allCars.count+1;
}
return 0;
}
- (UITableViewCell *)tableView:(UITableView *)tableView cellForRowAtIndexPath:(NSIndexPath *)indexPath{
UITableViewCell * cell = nil;
if (self.allCars.count!=0) {
if(indexPath.row <self.allCars.count){//here is where the problem occurs
cell=[self customCellForIndexPath:indexPath tableView:tableView];
}
else {
cell=[self loadingCell];
}
}
else{
// Disable user interaction for this cell.
cell = [[UITableViewCell alloc] init];
cell.selectionStyle = UITableViewCellSelectionStyleNone;
}
return cell;
}
-(UITableViewCell *)loadingCell{
UITableViewCell * cell = [[UITableViewCell alloc] initWithStyle:UITableViewCellStyleDefault reuseIdentifier:nil];
UIActivityIndicatorView * activityIndicator = [[UIActivityIndicatorView alloc] initWithActivityIndicatorStyle:UIActivityIndicatorViewStyleWhiteLarge];
activityIndicator.center = cell.center;
cell.backgroundColor = [UIColor lightGrayColor];
[cell addSubview:activityIndicator];
cell.tag=kLoadingCellTag;
[activityIndicator startAnimating];
return cell;
}
-(void)tableView:(UITableView *)tableView willDisplayCell:(UITableViewCell *)cell forRowAtIndexPath:(NSIndexPath *)indexPath{
if (cell.tag==kLoadingCellTag) {
self.currentPage++;
[self performSelector:#selector(getCars:withParams) withObject:nil afterDelay:1.5f];
}
}
-(void)getCars{
[self getCars:url withParams:params];
}
-(void)getCars: (NSURL *)url withParams: (NSString *)params{
NSMutableURLRequest * request = [[NSMutableURLRequest alloc] initWithURL:url cachePolicy:0 timeoutInterval:80];
[request setHTTPBody:[params dataUsingEncoding:NSUTF8StringEncoding]];
[request setHTTPMethod:#"POST"];
NSURLSessionConfiguration *sessionConfig = [NSURLSessionConfiguration defaultSessionConfiguration];
sessionConfig.timeoutIntervalForResource=1;
NSURLSession * session = [NSURLSession sessionWithConfiguration:sessionConfig];
NSURLSessionDataTask * task = [session dataTaskWithRequest:request completionHandler:^(NSData *data, NSURLResponse *response, NSError *error) {
NSHTTPURLResponse * httpResp = (NSHTTPURLResponse *)response;
NSDictionary * dataDict = [NSJSONSerialization JSONObjectWithData:data options:kNilOptions error:nil];
if (data) {
switch (httpResp.statusCode) {
case 200:{
dispatch_async(dispatch_get_main_queue(), ^{
self.pageCount = [dataDict[#"message"][#"total_pages"] intValue];
NSArray * carsArray = dataDict[#"message"][#"results"];
for (NSDictionary *cDict in carsArray) {
Car *car = [Car carWithID:[cDict[#"car_id"] stringValue] ];
car.car_name=cDict[#"car_name"];
car.car_description = cDict[#"car_description"];
[self.allCars addObject:car];
}
[self.tableView reloadData];
});
break;
}
default:
dispatch_async(dispatch_get_main_queue(), ^{
NSLog(#"Error");
});
break;
}
}
else{
dispatch_async(dispatch_get_main_queue(), ^{
NSLog(#"Error");
});
}
}];
[task resume];
}
//reset list to start new search
-(void)donePickingBlue{
[self.tableView scrollToRowAtIndexPath:[NSIndexPath indexPathForRow:0 inSection:0] atScrollPosition:UITableViewScrollPositionTop animated:YES];
self.currentPage=1;
[self.allCars removeAllObjects];
[self getCars:url withParams:blue];
}
Edit
I seem to have resolved the the problem by doing the following;
//reset list to start new search
-(void)donePickingBlue{
self.currentPage=1;
[self.allCars removeAllObjects];
[self.tableView reloadData];//after removing all the cars, now we call reload, as there are no cars. I was calling reload in `[self getCars:....]` just below, and thought this was enough.
[self getCars:url withParams:blue];
}
I was able to answer my own problem. The answer can be seen in the Edit above incase anybody else has the same problem.
It should have been;
//reset list to start new search
-(void)donePickingBlue{
self.currentPage=1;
[self.allCars removeAllObjects];
[self.tableView reloadData];//after removing all the cars, now we call reload, as there are no cars. I was calling reload in `[self getCars:....]` just below, and thought this was enough.
[self getCars:url withParams:blue];
}
If you want to download cars page by page, willDisplayCell: is pretty good choice. But you must change the condition a little, to prevent downloading the same data multiple times. Also, I recommend you to change data model and provide ability to determine a page for particular cars. That's what I mean:
-(void)tableView:(UITableView *)tableView
willDisplayCell:(UITableViewCell *)cell
forRowAtIndexPath:(NSIndexPath *)indexPath{
// 10 cells on page
NSUInteger currentPage = indexPath.row / 10;
// Check, if cars for the current page are downloaded
if (carsOnPagesDict[#(currentPage)] != nil) {
// Add a stub to indicate that downloading started
// You can use this later to display correct cell
// Also it prevents getCars: from calling multiple times for the current page
carsOnPagesDict[#(currentPage)] = #"downloading";
// I removed delay for simplicity
[self getCars:url withParams:params forPage:currentPage];
}
}
Also, change getCars method:
-(void)getCars:(NSURL *)url withParams:(NSString *)params forPage:(NSUInteger)page{
// Creating request...
// ...
// Processing response...
// ...
// Array obtained:
NSArray *carsArray = dataDict[#"message"][#"results"];
// Storing required data to the array
NSMutableArray *cars = [NSMutableArray arrayWithCapacity:carsArray.count];
for (NSDictionary *cDict in carsArray) {
Car *car = [Car carWithID:[cDict[#"car_id"] stringValue] ];
car.car_name=cDict[#"car_name"];
car.car_description = cDict[#"car_description"];
[cars addObject:car];
}
// Save cars to the dictionary for the page given
carsOnPagesDict[#(page)] = cars;
// ...
// Resuming tasks...
}
You may consider using CoreData to store that cars.
I have a View Controller with a property galleryCache and when an image is downloaded using GCD and imageWithData: the image is added to the cache successfully with a key. However, when the view controller is dismissed it keeps strong pointers to those downloaded images causing them not to be removed from memory. Even if I use the removeAllObjects method on the cache in viewDidDisappear: memory does not clear up.
Does anyone know why this might be?
Here is the code for the method which downloads the images.
- (void)imageForFootageSize:(FootageSize)footageSize withCompletionHandler:(void (^)(UIImage *image))completionBlock
{
if (completionBlock) {
__block UIImage *image;
// Try getting local image from disk.
//
__block NSURL *imageURL = [self localURLForFootageSize:footageSize];
dispatch_async(dispatch_get_global_queue(DISPATCH_QUEUE_PRIORITY_DEFAULT, 0), ^{
image = [UIImage imageWithData:[NSData dataWithContentsOfURL:imageURL]];
dispatch_async(dispatch_get_main_queue(), ^{
if (image) {
completionBlock(image);
} else {
//
// Otherwise try getting remote image.
//
imageURL = [self remoteURLForFootageSize:footageSize];
dispatch_async(dispatch_get_global_queue(DISPATCH_QUEUE_PRIORITY_DEFAULT, 0), ^{
NSData *imageData = [NSData dataWithContentsOfURL:imageURL];
dispatch_async(dispatch_get_main_queue(), ^{
image = [UIImage imageWithData:imageData];
if (image) {
//
// Save remote image to disk
//
NSURL *photoDirectoryURL = [Footage localURLForDirectory];
// Create the folder(s) where the photos are stored.
//
[[NSFileManager defaultManager] createDirectoryAtPath:[photoDirectoryURL path] withIntermediateDirectories:YES attributes:nil error:nil];
// Save photo
//
NSString *localPath = [[self localURLForFootageSize:footageSize] path];
[imageData writeToFile:localPath atomically:YES];
}
completionBlock(image);
});
});
}
});
});
}
}
Methods which use the above class method to fetch and process the UIImage in the completionHandler.
Method inside UICollectionViewCell subclass.
- (void)setPhoto:(Photo *)photo withImage:(UIImage *)image
{
[self setBackgroundColor:[UIColor blackColor]];
[self.imageView setBackgroundColor:[UIColor clearColor]];
if (photo && !image) {
[photo imageForFootageSize:[Footage footageSizeThatBestFitsRect:self.bounds]
withCompletionHandler:^(UIImage *image) {
if ([self.delegate respondsToSelector:#selector(galleryPhotoCollectionViewCell:didLoadImage:)]) {
[self.delegate galleryPhotoCollectionViewCell:self didLoadImage:image];
}
image = nil;
}];
}
[self.imageView setImage:image];
BOOL isPhotoAvailable = (BOOL)(image);
[self.imageView setHidden:!isPhotoAvailable];
[self.activityIndicatorView setHidden:isPhotoAvailable];
}
Method in UICollectionView data source delegate
- (UICollectionViewCell *)collectionView:(UICollectionView *)collectionView cellForItemAtIndexPath:(NSIndexPath *)indexPath
{
DIGalleryPhotoCollectionViewCell *photoCell = [collectionView dequeueReusableCellWithReuseIdentifier:photoCellIdentifier forIndexPath:indexPath];
[photoCell setDelegate:self];
Footage *footage = [self footageForIndexPath:indexPath];
Photo *photo = ([footage isKindOfClass:[Photo class]]) ? (Photo *)footage : nil;
if (photo) {
//
// Photo
//
[photoCell setPhoto:photo withImage:[self.galleryCache objectForKey:photo.footageID]];
}
return photoCell;
}
Here are the other relevant methods:
- (void)galleryPhotoCollectionViewCell:(DIGalleryPhotoCollectionViewCell *)cell didLoadImage:(UIImage *)image
{
NSIndexPath *indexPath = [self.galleryCollectionView indexPathForCell:cell];
Footage *footage = [self footageForIndexPath:indexPath];
if ([footage isKindOfClass:[Footage class]]) {
Photo *photo = (Photo *)footage;
UIImage *cachedImage = [self.galleryCache objectForKey:photo.footageID];
if (!cachedImage) {
cachedImage = image;
[self.galleryCache setObject:image forKey:photo.footageID];
}
[cell setPhoto:photo withImage:image];
}
}
And also my getter method for the NSCache property galleryCache
- (NSCache *)galleryCache
{
if (!_galleryCache) {
_galleryCache = [[NSCache alloc] init];
}
return _galleryCache;
}
EDIT
Here is a snapshot of Instruments showing the retain count history of one of the NSCache once its owner (a View Controller) is dismissed.
I'm not seeing anything obvious here, though I'd suggest putting a breakpoint where you purge the cache and make sure that's actually happening like you think it is.
If you still don't find it, you can run Allocations tool in Instruments and turn on "record reference counts" (see latter part of this answer, iOS app with ARC, find who is owner of an object), and you can find out precisely where your lingering strong reference is, at which point you can tackle the remediation.
The other obvious solution is to eliminate all of this code and use a proven image caching tool, like SDWebImage which does a lot of the memory and persistent storage caching for you. It's a pretty decent implementation.
OK, so after re examining my own code and re examining properties for the billionth x n time, it turns out my error was assigning the delegate property as a 'strong' type. Lesson learned: ALWAYS set delegates as WEAK.
I will definitely have to learn more about Instruments, however.
I have issue with redrawing images of uicollectionview cells - images are downloaded from URL parsed from JSON. I have 10 cells and with the start of app only first 6 are displayed, but images are not loaded, when I scroll down to those other cells, they have their images, and when I scroll back to the top, first 4 cells have their images as well, only cells 5 and 6 are not redrawn(they were visible for the whole time). I've been trying to debug this for long time but no success.
in cellForItemAtIndexPath I'm calling SDWebImage(but it doesn't really matter):
[cell.backgroundImage setImageWithURL:[NSURL URLWithString:timeSnap.thumbnailImageURL] placeholderImage:[UIImage imageNamed:#"placeholder.png"]];
but when cellForItemAtIndexPath is called for the first time, timeSnap.thumbnailImageURL(where timeSnap entity is model for cell) is not initialised yet and so it's null
after initialisation of timeSnap.thumbnailImageURL I have:
dispatch_async(dispatch_get_main_queue(), ^{
[self.collectionView reloadData];
});
edit1:
adding my code, it's a bit complex - first I'll get JSON from server API with items to be displayed in collection view, then for each item I have to get another JSON from server API, from which I can build URL for timeSnap.thumbnailImageURL
viewController class:
- (void)viewDidLoad
{
[super viewDidLoad];
[self refreshNewTimeSnapsFeed];
}
- (void)refreshNewTimeSnapsFeed {
Adapter *adapter = [AppDelegate instance].adapter;
[adapter getNewTimeSnapsWithCompletion:^(NSArray* jsonResponse) {
[self newTimeSnapsFeedRefreshed:jsonResponse];
}];
}
- (void)newTimeSnapsFeedRefreshed:(NSArray*)jsonResponse {
Adapter *adapter = [AppDelegate instance].adapter;
for (NSDictionary *timeSnapDict in jsonResponse) {
TimeSnap *timeSnap = [[TimeSnap alloc] initWithJSON:timeSnapDict];
[adapter getTimeSnapSnapsforId:timeSnap.id withCompletion:^(NSArray* jsonResponse) {
[timeSnap getSnapsJSON:jsonResponse];
[timeSnap getTimeSnapThumbnailImageURL];
}];
[self.timeSnaps addObject:timeSnap];
}
dispatch_async(dispatch_get_main_queue(), ^{
[self.collectionView reloadData];
});
}
- (UICollectionViewCell *)collectionView:(UICollectionView *)collectionView cellForItemAtIndexPath:(NSIndexPath *)indexPath{
TimeSnapCell *cell = (TimeSnapCell*)[collectionView dequeueReusableCellWithReuseIdentifier:#"TimeSnapCell" forIndexPath:indexPath];
TimeSnap *timeSnap = self.timeSnaps[indexPath.row];
cell.label.text = timeSnap.name;
[cell.backgroundImage setImageWithURL:[NSURL URLWithString:timeSnap.thumbnailImageURL] placeholderImage:[UIImage imageNamed:#"placeholder.png"]];
return cell;
}
adapter class:
- (void)getNewTimeSnapsWithCompletion:(void (^)(NSArray* jsonResponse))completion {
NSString *urlAsString = [NSString stringWithFormat:#"..."];
NSURL *url = [[NSURL alloc] initWithString:urlAsString];
[self getJSONWithCompletion:completion fromURL:url forKey:#"Items"];
}
- (void)getTimeSnapSnapsforId:(NSNumber*)id withCompletion:(void (^)(NSArray* jsonResponse))completion {
NSString *urlAsString = [NSString stringWithFormat:#"..."];
NSURL *url = [[NSURL alloc] initWithString:urlAsString];
[self getJSONWithCompletion:completion fromURL:url forKey:#"Items"];
}
- (void)getJSONWithCompletion:(void (^)(NSArray* jsonResponse))completion fromURL:(NSURL*)url forKey:(NSString*)key {
//code for getting JSON from server API, then parsing into NSArray *items
dispatch_async(dispatch_get_main_queue(), ^{
if(completion){
completion(items);
}
});
}
You need to reload the cell when the second JSON response comes back:
for (NSDictionary *timeSnapDict in jsonResponse) {
TimeSnap *timeSnap = [[TimeSnap alloc] initWithJSON:timeSnapDict];
NSIndexPath *indexPath = [NSIndexPath indexPathForItem:self.timeSnaps.count inSection:0];
[self.timeSnaps addObject:timeSnap];
[adapter getTimeSnapSnapsforId:timeSnap.id withCompletion:^(NSArray* jsonResponse) {
[timeSnap getSnapsJSON:jsonResponse];
[timeSnap getTimeSnapThumbnailImageURL];
[self.collectionView reloadItemsAtIndexPaths:#[indexPath]];
}];
}
Your adapter class executes the completion block on the main queue, so you don't need to use dispatch_async here (unless you don't consider that part of the adapter's contract).
remove the dispatch into the reloadData and also remove reloadData and add just this code
dispatch_async(dispatch_get_main_queue(), ^{
[cell.backgroundImage setImageWithURL:[NSURL URLWithString:timeSnap.thumbnailImageURL] placeholderImage:[UIImage imageNamed:#"placeholder.png"]];
});
I'm using SDWebImage and grabbing Images associated with a news article from a news API.
The problem is, the images for the cells on screen aren't loading until I start scrolling on the UITableView. Once I scroll past a cell, and it goes off screen, once I come back to it the Image will finally be loaded.
Here is my (UITableViewCell *)tableView:(UITableView *)tableView cellForRowAtIndexPath:(NSIndexPath *)indexPath code:
if ([feedLocal.images count] == 0) {
[cell.imageView setImage:[UIImage imageNamed:#"e.png"]];
}
else {
Images *imageLocal = [feedLocal.images objectAtIndex:0];
NSString *imageURL = [NSString stringWithFormat:#"%#", imageLocal.url];
NSLog(#"img url: %#", imageURL);
// Here we use the new provided setImageWithURL: method to load the web image
__weak UITableViewCell *wcell = cell;
[cell.imageView setImageWithURL:[NSURL URLWithString:[NSString stringWithFormat:#"%#", imageURL]]
placeholderImage:[UIImage imageNamed:#"115_64.png"]
completed:^(UIImage *image, NSError *error, SDImageCacheType cacheType) {
if(image == nil) {
[wcell.imageView setImage:[UIImage imageNamed:#"115_64.png"]];
//];
}
}
];
}
Any idea why this would be happening? It just seems like when the UITableView loads, the Images aren't being told to load or something until scrolling begins?
Any suggestion is much appreciated, thanks!
There is little chance this will solve your problem, but this is too long to fit in a comment:
Tip 1:
If you are reusing cells, you should not do [wcell.imageView setImage:] in the callback. At the time the callback code is executed, there a non-null chance that wcell will point to a different cell in the table view than the one you wanted to change the image.
Instead, use the indexPath to refer to the cell you wanted to modify:
completed:^(UIImage *image, NSError *error, SDImageCacheType cacheType) {
if(image == nil) {
UITableViewCell *actualCell = [tableView cellForRowAtIndexPath:indexPath];
[actualCell.imageView setImage:[UIImage imageNamed:#"115_64.png"]];
}
}
Note that if the cell you wanted to change the image is not shown anymore, cellForRowAtIndexPath: will return nil, which is absolutely fine:
Return Value
An object representing a cell of the table or nil if the cell is not visible or indexPath is out of range.
Tip 2:
There is no need to re-create a string when you already have one ;)
[NSURL URLWithString:[NSString stringWithFormat:#"%#", imageURL]]
[NSURL URLWithString:imageURL] // imageURL is already a string
Your problem:
I'm a little bit puzzled, the code you showed really is a simple application of SDWebImage "how-to" examples, and I just tested with the v3.3 of the framework, and my cells update just fine. So try to reduce your code to the bare minimum to identify the real issue.
I'd say get rid of all your application logic (the feedLocal.images for example), and just find out if the problem actually comes from SDWebImage or not.
Not sure if you have solved your problem, but I get my problem solved by the following code.
Basic idea is to set the cell reference usable inside block and manually set the cell's image in the completed method. Hope it helps.
__block UITableViewCell *cell2 = cell;
id data = [[self itemArray] objectAtIndex:[indexPath item]];
if ([data isKindOfClass:[MyItems class]]) {
MyItems *myData = (MyItems *)data;
[[cell2 imageView] setImageWithURL:[myData url]
placeholderImage:[UIImage imageNamed:#"placeHolder.png"]
completed:^(UIImage *image, NSError *error, SDImageCacheType cacheType) {
// do check that this is the right cell to put your image
// your methods here
if (image) {
[[cell2 imageView] setImage:image];
}
}];
}
For the checking if that is the right cell, I guess it is something like this (I don't have time to check it)
__block UITableViewCell *cell2 = cell;
id data = [[self itemArray] objectAtIndex:[indexPath item]];
if ([data isKindOfClass:[MyItems class]]) {
__block MyItems *myData = (MyItems *)data;
[[cell2 imageView] setImageWithURL:[myData url]
placeholderImage:[UIImage imageNamed:#"placeHolder.png"]
completed:^(UIImage *image, NSError *error, SDImageCacheType cacheType) {
// do check that this is the right cell to put your image
// your methods here
id currentData = [[self itemArray] objectAtIndex:[indexPath item]];
if ([currentData isKindOfClass:[MyItems class]] && [ [[(MyItems *)currentData url] absoluteString] isEqualToString:[[myData url] absoluteString] ]) {
// it is the right cell to put in :)
if (image) {
[[cell2 imageView] setImage:image];
}
}
}];
}
I have earlier encountered a similar issue and it turned out the images in the tableview were downloading correctly. The real issue you are facing is the refresh issue. When each image is downloaded, it has to be refreshed in order to be shown in the tableview. In my case, the downloading part was done in a separate file, so i used NSNotificationCenter to tell the tableview controller class to refresh it. Here is what you can do with your code:
if ([feedLocal.images count] == 0) {
[cell.imageView setImage:[UIImage imageNamed:#"e.png"]];
}
else {
Images *imageLocal = [feedLocal.images objectAtIndex:0];
NSString *imageURL = [NSString stringWithFormat:#"%#", imageLocal.url];
NSLog(#"img url: %#", imageURL);
// Here we use the new provided setImageWithURL: method to load the web image
__weak UITableViewCell *wcell = cell;
[cell.imageView setImageWithURL:[NSURL URLWithString:[NSString stringWithFormat:#"%#", imageURL]]
placeholderImage:[UIImage imageNamed:#"115_64.png"]
completed:^(UIImage *image, NSError *error, SDImageCacheType cacheType) {
if(image == nil) {
[wcell.imageView setImage:[UIImage imageNamed:#"115_64.png"]];
[[NSNotificationCenter defaultCenter] postNotificationName:#"ImageDownloaded" object:nil];
//];
}
}
];
}
and then you can call reload data using it as below:
- (void) imageDownloaded:(NSNotification *)notification{
[self.tableView reloadData];
}
This way you don't need to scroll in order to see the image, instead they will be shown right after they are downloaded.
Hope this helps!
NSString *mainimg=[NSString stringWithFormat:#"%#",[[xmlDataDictionary valueForKeyPath:#"eg.main.img1"]objectAtIndex:indexPath.row]];
NSURL *url = [NSURL URLWithString:mainimg];
NSData *imge = [[NSData alloc] initWithContentsOfURL:url];
cell.img.image=[UIImage imageWithData:imge];