Can't display UIActivityIndicator on top of mapview - ios

Question

In my code, I initialize a UIActivityIndicator, and add it as a subview, but it never appears. What's going wrong?
-(void) update {
UIActivityIndicatorView *activityView=[[UIActivityIndicatorView alloc] initWithActivityIndicatorStyle:UIActivityIndicatorViewStyleGray];
activityView.center=self.view.center;
[self.view addSubview:activityView];
[activityView startAnimating];
/** Stuff to access to server, this stuff works correctly.*/
[activityView stopAnimating];
}

Answer 1

As you are starting and stoping the activity as same runloop so it will not get change to update the UI.You are doing all server stuff on same synchronously than you are blocking the runLoop and do not giving time to activity indicator to start.You should start server stuff on next runLoop so activity indicator will get time to start.So use performSelector with delay 0.0 it will start the activity indicator and than perform your server stuff on immediate next runloop and than stop the activityInddicator
-(void) update {
UIActivityIndicatorView *activityView=[[UIActivityIndicatorView alloc] initWithActivityIndicatorStyle:UIActivityIndicatorViewStyleGray];
activityView.center=self.view.center;
[self.view addSubview:activityView];
[activityView startAnimating];
//Use performSelector with 0.0 so activity indicator starts
[self performSelector:#selector(thisWillStartAtNextRunLoop) withObject:nil afterDelay:0.0];
}
-(void)thisWillStartAtNextRunLoop{
/** Stuff to access to server, this stuff works correctly.*/
[activityView stopAnimating];
}
Edit execute it on main thread as all UI updation must be on main thread
Try
-(void) update {
dispatch_async(dispatch_get_main_queue(), ^{
UIActivityIndicatorView *activityView=[[UIActivityIndicatorView alloc] initWithActivityIndicatorStyle:UIActivityIndicatorViewStyleGray];
activityView.center=self.view.center;
[self.view addSubview:activityView];
[activityView startAnimating];
});
/** Stuff to access to server, this stuff works correctly.*/
}