Using one ActivityIndicator with two classes - objective-c

Question

I have an UIActivityIndicator that starts animating on the top of all of my views. Right after he starts animating, the parent view of this current view is popped. Now, after he's animating, I'm calling another class with a block and runs some server commands.
My problem is, that in the other class im getting the response from the server, but I cannot tell the
UIActivityIndicator to stop, because he is in the other class. (I have to say that I don't want to implement nothing on the Application Delegate).
On the server class, after I get the response, a UIAlertView appears, but the UIAlertView is implemented inside the server class. That's where I want the UIActivityIndicator to stop.
I Hope that I understand it well, if not, please tell me.
Thank you.
- (void)buttonPressed:(id)sender
{
UIView * darkView = [[UIView alloc]initWithFrame:CGRectMake(0, 0, 320, 480)];
darkView.backgroundColor = [UIColor blackColor];
darkView.alpha = 0.5f;
UIActivityIndicatorView * activityIndicator = [[UIActivityIndicatorView alloc]initWithActivityIndicatorStyle:UIActivityIndicatorViewStyleWhiteLarge];
[darkView addSubview:activityIndicator];
activityIndicator.center = darkView.center;
[activityIndicator startAnimating];
[[UIApplication sharedApplication].keyWindow addSubview:darkView];
// Inside this class (ShareByEmail) there is a UIAlertView that should stop the
// animation that already running right now.
ShareByEmail *sbe = [[ShareByEmail alloc]init];
[sbe share];
[self.navigationController popViewControllerAnimated:YES];
}

Answer 1

One option is to keep the UIActivityIndicator as singleton object and use it from anywhere in the project. Another option is to try this with notifications. You need to add and remove observer to this activity indicator and whenever a request is fired/executed, you need to post a notification to start/stop activity indicator.
Update:
In your case either you can set it as [[NSNotificationCenter defaultCenter] addObserver:activityIndicator selector:#selector(startAnimating) name:#"startActivityIndicator" object:nil] and [[NSNotificationCenter defaultCenter] addObserver:activityIndicator selector:#selector(stopAnimating) name:#"stopActivityIndicator" object:nil] immediately after allocating memory for the activity indicator. Now whenever you want to start or stop it, call [[NSNotificationCenter defaultCenter] postNotificationName:#"startActivityIndicator" object:nil] or [[NSNotificationCenter defaultCenter] postNotificationName:#"stopActivityIndicator" object:nil]. Make sure that the activity indicator is not released. I would suggest you to declare your activity indicator as a class level variable in this class and allocate memory in init method or so. In your button pressed method, you can just use [darkView addSubview:activityIndicator];