Cache UIImage using uitableview from url - ios

Question

I hava a uitableview , with custom cell containing two UImages. The logo images are taken from an online website, that's why there's a need to cache the images. Loading the image till now is made like this :
NSURL * imageURL = [NSURL URLWithString:[arra1 objectAtIndex:indexPath.row / 2]];
NSData * imageData = [NSData dataWithContentsOfURL:imageURL];
NSURL * imageURL2 = [NSURL URLWithString:[arra2 objectAtIndex:indexPath.row / 2]];
NSData * imageData2 = [NSData dataWithContentsOfURL:imageURL2];
cell.ima1.image = [UIImage imageWithData:imageData];
cell.ima2.image2 = [UIImage imageWithData:imageData2];
What i learned from searching , is that dataWithContentsOfURL is not asynchronous , and while scrolling it will take a lot of time. I tried several methods but i can't seem to get to right one. This is my first time caching UIImages , i would highly appreciate a detailed explanation with implementation so i could learn aside from getting the job done.
Many Thanks

Answer 1

I use this Library which is just perfect
SDWebImage
You just need to #import <SDWebImage/UIImageView+WebCache.h> to your project, and you can define also the placeholder when image is being downloaded with just this code:
- (UITableViewCell *)tableView:(UITableView *)tableView cellForRowAtIndexPath:(NSIndexPath *)indexPath
{
static NSString *MyIdentifier = #"MyIdentifier";
UITableViewCell *cell = [tableView dequeueReusableCellWithIdentifier:MyIdentifier];
if (cell == nil)
{
cell = [[[UITableViewCell alloc] initWithStyle:UITableViewCellStyleDefault
reuseIdentifier:MyIdentifier] autorelease];
}
// Here we use the new provided setImageWithURL: method to load the web image
[cell.imageView setImageWithURL:[NSURL URLWithString:#"http://www.domain.com/path/to/image.jpg"]
placeholderImage:[UIImage imageNamed:#"placeholder.png"]];
cell.textLabel.text = #"My Text";
return cell;
}
It also cache downloaded images and gives you great performance.
Hope it will help you!

Answer 2

SDWebImage, in my opinion, is the best option.
You simply include it in your app and use it like this:
SDWebImageManager *manager = [SDWebImageManager sharedManager];
[manager downloadWithURL:[NSURL URLWithString:image_url]
options:0
progress:nil
completed:^(UIImage *images, NSError *error, SDImageCacheType cacheType, BOOL complete) {
myImageView.image = images;
}] ;
It download images asynchronously, so it does not block UI.

Answer 3

You can check these sample application
LazyTableImages - Sample application from Apple
MonoTouch-LazyTableImages
robertmryan- LazyTableImages - Explains clearly the limitations from apple's sample application.
Hope this helps.

Answer 4

Checkout UIImageLoader https://github.com/gngrwzrd/UIImageLoader
Easy to load an image, and you get callbacks for all the scenarios you would want to handle:
NSURL * imageURL = myURL;
[[UIImageLoader defaultLoader] loadImageWithURL:imageURL \
hasCache:^(UIImage *image, UIImageLoadSource loadedFromSource) {
//there was a cached image available. use that.
self.imageView.image = image;
} sendRequest:^(BOOL didHaveCachedImage) {
//a request is being made for the image.
if(!didHaveCachedImage) {
//there was not a cached image available, set a placeholder or do nothing.
self.loader.hidden = FALSE;
[self.loader startAnimating];
self.imageView.image = [UIImage imageNamed:#"placeholder"];
}
} requestCompleted:^(NSError *error, UIImage *image, UIImageLoadSource loadedFromSource) {
//network request finished.
[self.loader stopAnimating];
self.loader.hidden = TRUE;
if(loadedFromSource == UIImageLoadSourceNetworkToDisk) {
//the image was downloaded and saved to disk.
//since it was downloaded it has been updated since
//last cached version, or is brand new
self.imageView.image = image;
}
}];