// Create spinner
UIActivityIndicatorView *myIndicator = [[UIActivityIndicatorView alloc] 
  initWithActivityIndicatorStyle:UIActivityIndicatorViewStyleWhite];
 
// Position the spinner
[myIndicator setCenter:CGPointMake(myButton.frame.size.width / 2,myButton.frame.size.height / 2)];
 
// Add to button
[myButton addSubview:myIndicator];
 
// Start the animation
[myIndicator startAnimating];