Failed to load image in a UICollectionView - ios

Question

I need to show flickr public images in a UICollectionView. I have done all the things, but images don't load in the UICollectionView. I am new to objective-c. Please help.
authorIds = [[NSMutableArray alloc] init];
dateTaken = [[NSMutableArray alloc] init];
smallImageUrlArray = [[NSMutableArray alloc] init];
largeImageUrlArray = [[NSMutableArray alloc] init];
smallImageArray = [[NSMutableArray alloc] init];
UICollectionViewFlowLayout *layout = [[UICollectionViewFlowLayout alloc] init];
layout.minimumLineSpacing = 10;
layout.minimumInteritemSpacing = 10;
layout.sectionInset = UIEdgeInsetsMake(110, 20, 20, 20);
_collectionView = [[UICollectionView alloc] initWithFrame:self.view.frame collectionViewLayout:layout];
[_collectionView setDataSource:self];
[_collectionView setDelegate:self];
[_collectionView registerClass:[UICollectionViewCell class] forCellWithReuseIdentifier:#"cellIdentifier"];
[_collectionView setBackgroundColor:[UIColor blackColor]];
[self.view addSubview:_collectionView];
- (NSInteger)collectionView:(UICollectionView *)collectionView numberOfItemsInSection:(NSInteger)section
{
return totalImageNo;
}
- (UICollectionViewCell *)collectionView:(UICollectionView *)collectionView cellForItemAtIndexPath:(NSIndexPath *)indexPath
{
UICollectionViewCell *cell = [collectionView dequeueReusableCellWithReuseIdentifier:#"cellIdentifier" forIndexPath:indexPath];
UIImageView *cellImageView = (UIImageView *)[cell viewWithTag:100];
cellImageView.image = [UIImage imageNamed:[smallImageUrlArray objectAtIndex:indexPath.row]];
//[self.view addSubview:cellImageView];
[cell.backgroundView addSubview:cellImageView];
// NSLog(#"%#",[smallImageUrlArray objectAtIndex:indexPath.row]); //Here can show Img's values correctly
cell.backgroundColor=[UIColor darkGrayColor];
return cell;
}
- (CGSize)collectionView:(UICollectionView *)collectionView layout:(UICollectionViewLayout*)collectionViewLayout sizeForItemAtIndexPath:(NSIndexPath *)indexPath
{
return CGSizeMake(160, 160);
}
In below I am fetching Flickr images and storing in array. then want to load the smallImageArray in the UICollection view. but nothing shows up.
-(void)fetchFlickrPublicImages
{
NSString *urlString = [NSString stringWithFormat:#"http://api.flickr.com/services/feeds/photos_public.gne?format=json&tags=data"];
NSURL *url = [NSURL URLWithString:urlString];
NSData *badJSON = [NSData dataWithContentsOfURL:url];
NSString *dataAsString = [NSString stringWithUTF8String:[badJSON bytes]];
NSString *correctedJSONString = [NSString stringWithString:[dataAsString substringWithRange:NSMakeRange (15, dataAsString.length-15-1)]];
correctedJSONString = [correctedJSONString stringByReplacingOccurrencesOfString:#"\\'" withString:#"'"];
NSData *correctedData = [correctedJSONString dataUsingEncoding:NSUTF8StringEncoding];
NSError* error;
NSDictionary *json = [NSJSONSerialization JSONObjectWithData:correctedData options:kNilOptions error:&error];
NSArray *images = [json objectForKey:#"items"];
for (NSDictionary *image in images)
{
NSString *authorId = [image objectForKey:#"author_id"];
[authorIds addObject:(authorId.length > 0 ? authorId: #"Untitled")];
NSString *largeImageUrl = [NSString stringWithFormat:#"%#",[[image objectForKey:#"media"] objectForKey:#"m"]];
NSString *smallImageUrl = [largeImageUrl stringByReplacingOccurrencesOfString:#"_m" withString:#"_s"];
[smallImageUrlArray addObject:smallImageUrl];
[dateTaken addObject:[NSString stringWithFormat:#"%#",[image objectForKey:#"date_taken"]]];
[largeImageUrlArray addObject:[NSString stringWithFormat:#"%#",[[image objectForKey:#"media"] objectForKey:#"m"]]];
totalImageNo = authorIds.count;
}
for (int i=0; i< smallImageUrlArray.count; i++) {
UIImage * image = [UIImage imageWithData:[NSData dataWithContentsOfURL:
[NSURL URLWithString:[smallImageUrlArray objectAtIndex:i]]]];
[smallImageArray addObject:image];
}
NSLog(#"%#", smallImageArray);
NSLog(#"%ld", (long)totalImageNo);
// NSLog(#"authorIds: %#\n\n", authorIds);
// NSLog(#"photoURLsLareImage: %#\n\n", smallImageUrlArray);
// NSLog(#"photoURLsLareImage: %#\n\n", largeImageUrlArray);
}

Answer 1

You should add your UIImageView to the collection view cell's contentView, NOT backgroundView.

Answer 2

In your code ,
- (UICollectionViewCell *)collectionView:(UICollectionView *)collectionView cellForItemAtIndexPath:(NSIndexPath *)indexPath
{
UIImageView *cellImageView = (UIImageView *)[cell viewWithTag:100];
cellImageView.image = [UIImage imageNamed:[smallImageUrlArray objectAtIndex:indexPath.row]];
[cell.backgroundView addSubview:cellImageView];
}
you are assigning image as url . but in your method named fetchFlickrPublicImages where you are downloading images directly.
better you write code like
- (UICollectionViewCell *)collectionView:(UICollectionView *)collectionView cellForItemAtIndexPath:(NSIndexPath *)indexPath
{
UIImageView *cellImageView = (UIImageView *)[cell viewWithTag:100];
cellImageView.image =(UIImage*)[smallImageArray objectAtIndex:indexPath.row];
[cell.contentView addSubView cellImageView];
}