Question

Sorry for question title. I can not find a suitable title.

I have UITableView content images from url when i open the UITableView the View did not show until the images loaded and that takes along time.

I get the images from JSON by php.

I want to show the table and then images loading process.

This is code from my app:

NSDictionary *info = [json objectAtIndex:indexPath.row];
cell.lbl.text = [info objectForKey:@"title"];
NSString *imageUrl = [info objectForKey:@"image"];
cell.img.image = [UIImage imageWithData:[NSData dataWithContentsOfURL:[NSURL URLWithString:imageUrl]]];
[cell.img.layer setBorderColor: [[UIColor blackColor] CGColor]];
[cell.img.layer setBorderWidth: 1.0];

return cell;

Sorry my english is weak.

Answer 1

Perform the web request on a separate thread, to not block the UI. Here is an example using NSOperation. Remember to only update the UI on the main thread, as shown with performSelectorOnMainThread:.

- (void)loadImage:(NSURL *)imageURL
{
    NSOperationQueue *queue = [NSOperationQueue new];
    NSInvocationOperation *operation = [[NSInvocationOperation alloc]
                                        initWithTarget:self
                                        selector:@selector(requestRemoteImage:)
                                        object:imageURL];
    [queue addOperation:operation];
}

- (void)requestRemoteImage:(NSURL *)imageURL
{
    NSData *imageData = [[NSData alloc] initWithContentsOfURL:imageURL];
    UIImage *image = [[UIImage alloc] initWithData:imageData];

    [self performSelectorOnMainThread:@selector(placeImageInUI:) withObject:image waitUntilDone:YES];
}

- (void)placeImageInUI:(UIImage *)image
{
    [_image setImage:image];
}