How to improve images loading issues. is there any cache like solution - iphone

Question

I have built an iOS app using Parse.com.
In my app i have displayed a lot of data from network.
To load the data speedily i used cache kPFCachePolicyCacheThenNetwork. It loads data fine but while scrolling images are takes some amount of time to load.
First white image and then image loads.
Is there any solution like cache to display images in imageviews with out interruption.
Thanks.

Answer 1

You can use SDWebImage for doing this.
Also you can use NSCache for caching purpose.

Answer 2

Yes you can use AFNetworking UIImageview category and you are sorted
you can also disable caching of a particular image usually needed if you edit an existing image and then dwnload it from same URL, by manipulagting its
-(void)setImageWithURL:(NSURL *)url
placeholderImage:(UIImage *)placeholderImage
as mentioned in this blog
An other option could be ASImageView with facility to refresh cache.

Answer 3

I write the code with the help of gcd , you just have to pass the object of imageView and pass the url , it manages all the things, like cache.
-(void)downloadingServerImageFromUrl:(UIImageView*)imgView AndUrl:(NSString*)strUrl{
strUrl = [strUrl encodeUrl];
NSString* theFileName = [NSString stringWithFormat:#"%#.png",[[strUrl lastPathComponent] stringByDeletingPathExtension]];
NSFileManager *fileManager =[NSFileManager defaultManager];
NSString *fileName = [NSHomeDirectory() stringByAppendingPathComponent:[NSString stringWithFormat:#"tmp/%#",theFileName]];
imgView.backgroundColor = [UIColor darkGrayColor];
UIActivityIndicatorView *actView = [[UIActivityIndicatorView alloc]initWithActivityIndicatorStyle:UIActivityIndicatorViewStyleWhite];
[imgView addSubview:actView];
[actView startAnimating];
CGSize boundsSize = imgView.bounds.size;
CGRect frameToCenter = actView.frame;
// center horizontally
if (frameToCenter.size.width < boundsSize.width)
frameToCenter.origin.x = (boundsSize.width - frameToCenter.size.width) / 2;
else
frameToCenter.origin.x = 0;
// center vertically
if (frameToCenter.size.height < boundsSize.height)
frameToCenter.origin.y = (boundsSize.height - frameToCenter.size.height) / 2;
else
frameToCenter.origin.y = 0;
actView.frame = frameToCenter;
dispatch_queue_t queue = dispatch_get_global_queue(DISPATCH_QUEUE_PRIORITY_DEFAULT, 0);
dispatch_async(queue, ^{
NSData *dataFromFile = nil;
NSData *dataFromUrl = nil;
dataFromFile = [fileManager contentsAtPath:fileName];
if(dataFromFile==nil){
dataFromUrl=[[[NSData alloc] initWithContentsOfURL:[NSURL URLWithString:strUrl]] autorelease];
}
dispatch_sync(dispatch_get_main_queue(), ^{
if(dataFromFile!=nil){
imgView.image = [UIImage imageWithData:dataFromFile];
}else if(dataFromUrl!=nil){
imgView.image = [UIImage imageWithData:dataFromUrl];
NSString *fileName = [NSHomeDirectory() stringByAppendingPathComponent:[NSString stringWithFormat:#"tmp/%#",theFileName]];
BOOL filecreationSuccess = [fileManager createFileAtPath:fileName contents:dataFromUrl attributes:nil];
if(filecreationSuccess == NO){
NSLog(#"Failed to create the html file");
}
}else{
imgView.image = [UIImage imageNamed:#"NO_Image.png"];
}
[actView removeFromSuperview];
[actView release];
[imgView setBackgroundColor:[UIColor clearColor]];
});
});
}

Answer 4

Here is the code for loading image in background . check this Code

Answer 5

you should use EGOImageLoading(EGOImageLoading) for lazy loading of images and can save images using NSUserDefaults.
It is best way i advice as i have used it in many projects.

Answer 6

Sorry to say it, but Parse is already doing all these things. Parse uses AFNetworking to get the images, puts them in an NSCache, and uses disk caching very aggressively so that redundant network trips are completely avoided (the version is part of the URL, so Parse doesn't even need to use an if-modified-since GET).
The biggest issue you might be encountering is that PFFile throttles downloads to only download 3 images at a time. After experimentation this was the best number because it ensured incremental feedback to the user and avoided a nasty issue where some iOS devices would get very poor performance after too many threads. The best advice I could offer you would be to prefetch some images if possible. As mentioned earlier, PFFile images are very aggressively cached. The kPFCachePolicy... stuff only affects queries which might grow stale; the images those queries point to are always cached (though only initially downloaded on demand).