How to Display first 9 images in UICollectionview? - ios

Question

I have a image url plist with 50 image urls.Iam trying to display that in a UICollectionview but it getting too slow.Iam displaying 9 cells(images) at a time like 3x3 (3 rows and 3 columns).How can i display first 9 images at loading time and next 9 images on next scrolling .?is that possible? i tried SDWebImages for loading images ,Its not working for me.Please help me.
CODE INSIDE collectionView cellForItemAtIndexPath: ()
the code inside comment take lots of time for loading image,that code is used for loading image from document directory if image is not there then i will display in one place holder image
cell = nil;
cell = (GMMCollectionViewCell *)[self.collectionView dequeueReusableCellWithReuseIdentifier:#"test" forIndexPath:indexPath];
cell.tag = indexPath.row;
docPath = [NSSearchPathForDirectoriesInDomains(NSDocumentDirectory, NSUserDomainMask, YES) objectAtIndex:0];
NSString *path;
BOOL isImageLoaded = YES;
/////////////////////PROBLEM CODE:TAKING TOO MUCH TIME TO LOAD IMAGE //////////////////////
bookImage = [UIImage imageWithContentsOfFile:[NSString stringWithFormat:#"%#/%#", docPath, [[allbooksImage objectAtIndex:indexPath.row] lastPathComponent]]];
//////////////////////////////////////////////////////////////////////////////////
if(bookImage == nil){
isImageLoaded = NO;
}
if(!isImageLoaded){
[[cell grid_image] setImage:[UIImage imageNamed:#"App-icon-144x144.png"]];
} else{
[[cell grid_image] setImage:bookImage];
}
sharedManager.bookID=bookId;
return cell;
This is what iam expecting
But iam getting like this ,
App Loading time Without any scroll (first image:3 columns are empty)
App screen after first scroll (second image:last column displaying 2 images ,rest of the part still empty )
App screen after a long scroll (third image: last colum some images are there ,rest of the columns still empty)
App screen again scroll to top,so the first image changed

Answer 1

You can try the below code
[[cell grid_image] setImage:nil];
dispatch_queue_t concurrentQueue = dispatch_get_global_queue(DISPATCH_QUEUE_PRIORITY_DEFAULT, 0);
dispatch_async(concurrentQueue, ^{
bookImage = [UIImage imageWithContentsOfFile:[NSString stringWithFormat:#"%#/%#", docPath, [[allbooksImage objectAtIndex:indexPath.row] lastPathComponent]]];
dispatch_async(dispatch_get_main_queue(), ^{
if (bookImage)
{
[[cell grid_image] setImage:bookImage];
}
else
{
[[cell grid_image] setImage:[UIImage imageNamed:#"App-icon-144x144.png"]];
}
});
});
hope it will work for you.