Question

I have a UITableView with custom cells showng text and an image.(image on right side).
At first, it all worked fine, but then I noticed that when scrolling, the whole tableview was lagging. This was because the app probably downloaded the cells image as the cell was entering the screen when re-using them. I added an NSCache to store the downloaded images, and told the cellForRowAtIndexPath to load the imageName if it existed, otherwise, download from the internet again. However, the cache is so short-term storage, that if I exit my app with home-button, and re-enter, then only some of the images remains, and have to download the images again.

I am trying to find out the best possible way to store images more long-term than with cache. I have read some about NSDirectory, and storing in app library, but haven’t figured it out yet..

The most logic solution, I believe, would be to do something like this:

- (UITableViewCell *)tableView:(UITableView *)tableView cellForRowAtIndexPath:(NSIndexPath *)indexPath
{

     /*stuff*/

    NSString *imageName = [dictionary objectForKey:@"Image"];
    UIImage *image = [--Cache-directory-- objectForKey:imageName]; //Try to get it from cache

    if(image) //If image was received from cache:
    {
        cell.imageView.Image = image;
    }
    else //If not in cache:
    {
        image = [--local-directory-- objectForKey:imageName]; //Check some local directory

        if(image) //If image received from directory:
        {
            cell.imageView.Image = image;
            // + Also save it to the cache?
        }
        else //If image was in neither cache or local directory, get it from the website with given URL
        {
            image = [[UIImage alloc] initWithData:[NSData dataWithContentsOfURL:imageURL]];
            //Then save to cache and to file?
        }
    }


}

The images are rarily changed or switched out, but not so rarily that I am willing to implement them in the app beforehand so that I must release an update every time an image is added.

This is what seems logical to me. Am I on the right tracks at all? And how do I “call” the local directory? Like, if I add images to a NSDirectory-object or something, wouldn’t this be reset every time? How do I access the local folder?

Answer 1

Theres no need to save all those images.

If you are getting your image from a url then just use AsyncImageLoader

Use that link and get the h and m files of ASyncImageView and save them in your project.

Import the h file where ever you are doing this

#import 'AsyncImageView.h'

Then use the following code

[[AsyncImageLoader sharedLoader] cancelLoadingURL:image.imageURL];

image.imageURL=[NSURL URLWithString:@"imageURL"];