Question

I have a subclassed UITableViewCell named AccountView which contains an UIActivityIndicatorView. Each cell is supposed to contain a Twitter account. When the user posts a message to Twitter, the UIActivityIndicatorView is supposed to start spinning, then stop animating when the twitter request handler is executed:

[postRequest performRequestWithHandler:^(NSData *responseData, NSHTTPURLResponse *urlResponse, NSError *error){
        if (error != nil) {
            NSLog(@"TWITTER ERROR: %@",error);
        }
        NSLog(@"Posted successfully");
        AccountCell *cell = (AccountCell *)[accountTable cellForRowAtIndexPath:[NSIndexPath indexPathForRow:[accounts indexOfObject:account] inSection:0]];
        NSLog(@"Cell isSpinning?  :%d",[[cell activity] isAnimating]);
        [[cell activity] stopAnimating];
        NSLog(@"Cell isSpinning?  :%d",[[cell activity] isAnimating]);
    }];

This all works fine when posting a short message to Twitter, however, when the TWRequest contains an image to be uploaded, after a few seconds, the post with image appears on Twitter, and I see the following message in the console:

2011-12-10 00:13:22.085 TwitTest[14954:1a03] Posted Successfully
2011-12-10 00:13:22.086 TwitTest[14954:1a03] Cell isSpinning?  :1
2011-12-10 00:13:22.088 TwitTest[14954:1a03] Cell isSpinning?  :0

But the UIActivityIndicatorView keeps spinning indefinitely (or at least a delay of several seconds), even though the Log messages indicate otherwise. The fact that this only breaks with image upload leads me to believe that maybe I should send the request on a background thread, but I have never dealt with threads before, and couldn’t say for sure if that is the problem.

One last thing, if I navigate to different view and return, the UIActivityIndicatorView appears frozen – if I navigate away and return a second time, then it disappears for good.

Answer 1

From Apple Developer’s documentation: “This handler is not guaranteed to be called on any particular thread.” Perhaps your interface loop is working and modifications are taken in account after each run loop.

Try to execute interface changes in main thread. Use performSelectorOnMainThread:withObject: