Launch UIActivityIndicatorView when the main thread is busy

Question

Is there a way to display an animated spinning wheel while the main thread performs a lengthy operation? The animation is handled by the same thread that created the UIActivityIndicatorView, right? If so, can views belonging to several threads be in the same view hierarchy?

All other failures, I do not mind moving a large operation to the background thread, but then I will have to somehow freeze the interface while it works. This I am not sure how to do it.

EDIT: "Long" is about 2 seconds on a 1st generation device.

Answer 1

, , , , . :

[activity startAnimating];
[self performSelector:@selector(lengthyOperation) withObject:nil afterDelay:0];

performSelector, , , .

Answer 2

- , , , . , , NSOperationQueue NSInvocationOperation. , , .