Activity indicator timing

If I've got code like this:

....
// start activity indicator
[class callMethod];
// stop activity indicator
...

If [class callMethod] takes 10 seconds (as an example), the indicator will be animated in this time right? After calling the metho开发者_如何学God the code will be blocked?

Only if you call the [class callMethod] on any thread other than main (because this will block UI, which will in turn block the indicator from spinning.