Download images from parse and show in UICollection View - ios

Question

I am downloading the images from parse and after that I am showing that images in uicollection view but when I scroll the collection view it hangs. Here is my code
-(void)viewWillAppear:(BOOL)animated
{
CGRect screen = [[UIScreen mainScreen] bounds];
CGFloat height = CGRectGetHeight(screen);
PFQuery * query = [PFQuery queryWithClassName:#"Static_Wallpaper"];
[query selectKeys:#[#"thumbnail"]];
if (height == 480) {
[query selectKeys:#[#"image4s"]];
}
else{
[query selectKeys:#[#"image6s"]];
}
[query findObjectsInBackgroundWithBlock:^(NSArray * objects, NSError * error){
if (!error) {
[imgArry arrayByAddingObjectsFromArray:objects];
imgArry = [[NSMutableArray alloc] initWithArray:objects];
NSLog(#"%lu",(unsigned long)imgArry.count);
[cllectionView reloadData];
}
}];
}
and Here is the code populating the images in collection view
- (NSInteger)collectionView:(UICollectionView *)collectionView numberOfItemsInSection:(NSInteger)section {
return imgArry.count;
}
- (UICollectionViewCell *)collectionView:(UICollectionView *)collectionView cellForItemAtIndexPath:(NSIndexPath *)indexPath{
static NSString *identifier = #"Cell";
CustomCollectionViewCell *cell = [collectionView dequeueReusableCellWithReuseIdentifier:identifier forIndexPath:indexPath];
PFObject *imageObject = [imgArry objectAtIndex:indexPath.row];
PFFile *imageFile = [imageObject objectForKey:#"image4s"];
[imageFile getDataInBackgroundWithBlock:^(NSData *data, NSError *error) {
if (!error){
NSLog(#"is there any data? %#", data);
cell.imgView.image = [UIImage imageWithData:data];
;
}
else {
NSLog(#"no data!");
}
}];
return cell;
}

Answer 1

By adding SDWebimage you need to do code like following:
- (UICollectionViewCell *)collectionView:(UICollectionView *)collectionView cellForItemAtIndexPath:(NSIndexPath *)indexPath{
static NSString *identifier = #"Cell";
CustomCollectionViewCell *cell = [collectionView dequeueReusableCellWithReuseIdentifier:identifier forIndexPath:indexPath];
PFObject *imageObject = [imgArry objectAtIndex:indexPath.row];
PFFile *imageFile = [imageObject objectForKey:#"image4s"];
NSString *UserProfile = [file url];
if([[SDWebImageManager sharedManager] diskImageExistsForURL:[NSURL URLWithString:UserProfile]])
{
NSString *key = [[SDWebImageManager sharedManager] cacheKeyForURL:[NSURL URLWithString:UserProfile]];
UIImage *image = [[SDImageCache sharedImageCache] imageFromDiskCacheForKey:key];
cell.imgView.image=image;
}
else
{
cell.imgView.image=[UIImage imageNamed:#"UserUpdationImageCell.png"];
[cell.imgView sd_setImageWithURL:[NSURL URLWithString:UserProfile] placeholderImage:[UIImage imageNamed:#"UserUpdationImageCell.png"]];
}
return cell;
}

Answer 2

Your download task may block the main thread.You can try to use SDWebImage or asynchrous download task and display image