Question

I’m loading pictures into a table view that correspond to the cell text, so each image is different. As the user scrolls down, iOS has to manually reload each image from the SSD, so scrolling is very choppy. How do I cache images or prevent the table view cells from needing to be recreated? Others have had their issues solved by using imageNamed: as iOS will automatically cache your images, but I am loading images from the documents directory, not the app bundle. What should I do? Thanks.

- (NSInteger)numberOfSectionsInTableView:(UITableView *)tableView {

    // Return the number of sections.
    return 1;

}


- (NSInteger)tableView:(UITableView *)tableView numberOfRowsInSection:(NSInteger)section {

    // Return the number of rows in the section.
    return [issues count];

}

// Customize the appearance of table view cells.
- (UITableViewCell *)tableView:(UITableView *)tableView cellForRowAtIndexPath:(NSIndexPath *)indexPath {

    NSString *CellIdentifier = @"Cell";

    UITableViewCell *cell = [tableView dequeueReusableCellWithIdentifier:CellIdentifier];
    if (cell == nil) {

        cell = [[[UITableViewCell alloc] initWithFrame:CGRectZero reuseIdentifier:CellIdentifier] autorelease];

    }


    // Set up the cell...
    NSDictionary *dic = [self.issues objectAtIndex:indexPath.row];

    cell.text = [dic objectForKey:@"Date"];

    cell.imageView.image = [UIImage imageWithContentsOfFile:[NSString stringWithFormat:@"%@/issues/%@/cover.png", documentsDirectory, [dic objectForKey:@"Directory Name"]]];

    return cell;

}

- (CGFloat)tableView:(UITableView *)tableView heightForRowAtIndexPath:(NSIndexPath *)indexPath {

        return 150;

}

Answer 1

Along with caching you may also consider loading the images in background using Grand central dispatch. When the cell is loaded put a UIActivityIndicator then replace it with an image in a separate thread.

Also checkout this related answer for image stutter:
Non-lazy image loading in iOS