Question

I’m using a UISearchBar in my application and the problem is when I call a few json methods searchBarSearchButtonClicked seems to not resign the keyboard until the other methods are done loading the data. I’ve tried alternatively using UIAlertView and UIButtons to replace the searchBarSearchButtonClicked function but they appear to literally freeze and stay in a “pressed down” state too. I was also wondering if this would be a reason why [UIApplication sharedApplication].networkActivityIndicatorVisible = YES; wouldn’t show an activity indicator in the device’s status bar.

- (void)searchBarSearchButtonClicked:(UISearchBar *)searchBar{
    self.args = searchBar.text;
    [self grabData];
    [self fillVars];
    [searchBar resignFirstResponder];
    [self.tableView reloadData];
}

[self grabData] is where I grab the JSON data and [self fillVars] just fills a few things that are later used.

-(void)grabData{
    self.args = [self.args stringByAddingPercentEscapesUsingEncoding:NSASCIIStringEncoding];

urlString = [NSString stringWithFormat:@"%@%@?key=%@&q=%@",baseUrl,func,apiKey,args];
url = [NSURL URLWithString:urlString];
NSData *jsonData = [NSData dataWithContentsOfURL:url];
NSError *error; 
NSDictionary *json = [NSJSONSerialization JSONObjectWithData:jsonData options:kNilOptions error:&error];
self.matches = [json objectForKey:@"matches"];
[UIApplication sharedApplication].networkActivityIndicatorVisible=YES;

}

Answer 1

You will have to use threading. All manipulation with your interface happens on the main thread, so when you perform a lengthy task on the main thread, the interface won’t be able to update itself before the task has completed.

In a UIViewController you can do [self performSelectorInBackground:@selector(grabData) withObject:self], which is a convenience method for dispatching a new queue (thread) using grand central dispact.

You could also do that manually, using the GCD API. You would do something along the lines of this:

dispatch_queue_t jsonQueue = dispatch_queue_create("JSON Queue", NULL);
dispatch_async(jsonQueue, ^{

    // fetch JSON data ...

    dispatch_async(dispatch_get_main_queue(), ^{

        // perhaps do something back on the main queue once you're done!

    });
});