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Question

Run an UIActivityIndicatorView while the main thread is busy

Answer 1

+2 A:

The solution is to start the animation at least one iteration through the run loop before running the lengthy operation. For example:

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

You don't have to use the performSelector method, just some way to set the method to run later so the activity indicator has a chance to start animating before you get busy.

Ed Marty 2010-03-06 04:26:03

Heck, I was close :) Tried performSelectorOnMainThread, but it seems like delay was the key.

Seva Alekseyev 2010-03-06 04:31:19

@Seva Running lengthy operations on the main thread is generally a bad idea.

Giao 2010-03-06 04:41:55

What Giao says is true. However, if you need the application to pause while it's happening, it doesn't seem like a TERRIBLE idea. A better solution, however, might be to use [[UIApplication sharedApplication] beginIgnoringInteractionEvents] and endIgnoringInteractionEvents when you're done.

Ed Marty 2010-03-06 04:57:26

I have to agree with Giao; the main thread/run loop should *never* be stalled--the OS will terminate an application that has its main thread stalled for too long.

rpetrich 2010-03-06 05:52:12

Answer 2

+3 A:

The right answer is definitely to move the lengthly operation to a background thread and have it communicate to the main thread when it's done. If you don't know how to do this, read on NSOperationQueue and NSInvocationOperation. Your app and your users will thank you for the minimal time it will take to learn.

marcc 2010-03-06 04:28:50

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Run an UIActivityIndicatorView while the main thread is busy

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