Activity indicator (spinner) with UIActivityIndicatorView

Question

I have a tableView that loads an XML feed as follows:

- (void)viewDidAppear:(BOOL)animated {
    [super viewDidAppear:animated];

    if ([stories count] == 0) {         


        

Answer 1

Here's the problem: NSXMLParser is a synchronous API. That means that as soon as you call parse on your NSXMLParser, that thread is going to be totally stuck parsing xml, which means no UI updates.

Here's how I usually solve this:

- (void) startThingsUp {
  //put the spinner onto the screen
  //start the spinner animating

  NSString *path = @"http://myurl.com/file.xml";
  [self performSelectorInBackground:@selector(parseXMLFileAtURL:) withObject:path];
}

- (void) parseXMLFileAtURL:(NSString *)path {
  //do stuff
  [xmlParser parse];
  [self performSelectorOnMainThread:@selector(doneParsing) withObject:nil waitUntilDone:NO];
}

- (void) doneParsing {
  //stop the spinner
  //remove it from the screen
}

I've used this method many times, and it works beautifully.