Question

I currently have a very simple view which displays info from a JSON feed. The problem I’m facing is the few second pause I encounter once I press this tab. How can I make this view load instantly and then have the label.text areas load after? Preferable with an activity indicator?

Should I use threads?

Thanks in advance!

Code:

- (NSString *)stringWithUrl:(NSURL *)url {
    NSURLRequest *urlRequest = [NSURLRequest requestWithURL:url cachePolicy:NSURLRequestReloadRevalidatingCacheData timeoutInterval:30];
    NSData *urlData;
    NSURLResponse *response;
    NSError *error;

    urlData = [NSURLConnection sendSynchronousRequest:urlRequest returningResponse:&response error:&error];
    return [[NSString alloc] initWithData:urlData encoding:NSUTF8StringEncoding];
    }


- (id)objectWithUrl:(NSURL *)url {
    SBJsonParser *jsonParser = [SBJsonParser new];
    NSString *jsonString = [self stringWithUrl:url];
    return [jsonParser objectWithString:jsonString error:NULL];
    }


- (NSDictionary *)downloadStats {
    id response = [self objectWithUrl:[NSURL URLWithString:@"http://www.example.com/JSON"]];
    NSDictionary *feed = (NSDictionary *)response;
    return feed;
    [feed release];
    }

- (void)viewDidLoad {
    [super viewDidLoad];

    [GlobalStatsScrollView setScrollEnabled:YES];
    [GlobalStatsScrollView setContentSize:CGSizeMake(320, 360)];
}

- (void)viewWillAppear:(BOOL)animated {
    NSLog(@"View appears");

    // Download JSON Feed
    NSDictionary *feed = [self downloadStats];      
    totalproduced.text = [feed valueForKey:@"Produced"];
    totalno.text = [feed valueForKey:@"Total"];
    mostcommon.text = [feed valueForKey:@"Most Common"];
    }

Answer 1

- (void)viewWillAppear:(BOOL)animated {
    NSLog(@"View appears");

    UIActivityIndicatorView* spiner = [[UIActivityIndicatorView alloc] initWithActivityIndicatorStyle: UIActivityIndicatorViewStyleWhiteLarge];
    spiner.tag = 123;
    [self.view addSubview: spiner];
    [spiner startAnimating];
    [spiner release];

    NSThread* thread = [[NSThread alloc] initWithTarget: self 
                                               selector: @selector(loadFeed) object: nil];
    [thread start];

}

-(void) loadFeed {
    // Download JSON Feed
    NSDictionary *feed = [self downloadStats];      
    totalproduced.text = [feed valueForKey:@"Produced"];
    totalno.text = [feed valueForKey:@"Total"];
    mostcommon.text = [feed valueForKey:@"Most Common"];

    [[self.view viewWithTag: 123] removeFromSuperview];
}

don’t forget to release your thread after.
You should also check docs for NSOperationQueue

Another option would be using asynchronous requests.