iOS Code: Implementing UIActivityIndicator

-(void) viewDidLoad
{

...

    UIActivityIndicatorView *ai = [[UIActivityIndicatorView alloc] initWithActivityIndicatorStyle:UIActivityIndicatorViewStyleWhiteLarge];

    ai.center = self.view.center;

    ai.hidesWhenStopped = YES;

    ai.hidden = YES;

    ai.color = [UIColor blackColor];

    // [[ai.layer setBackgroundColor:CFBridgingRetain([UIColor whiteColor])];

    self.activityIndicator = ai;

    [self.view addSubview:self.activityIndicator];

}

- (void) threadStartAnimating:(id)data {

    self.activityIndicator.hidden = NO;

    

    [self.activityIndicator startAnimating];

}

// line to start animation

    [NSThread detachNewThreadSelector:@selector(threadStartAnimating:) toTarget:self withObject:nil];

// line to stop animation

        [self.activityIndicator stopAnimating];