问题
How can I block UI thread without using sleep?
Just to be clear: I understand that UI will freeze for user, but that is the idea.
Can I run empty RunLoops? Any other ways.
回答1:
If you just want to block all interaction with your UI, call the UIApplication method -beginIgnoringInteractionEvents. If you're actually trying to prevent the entire UI from doing anything (which is not a good idea—your application might block the appearance of a system notification, for instance), then yes, an NSRunLoop would probably be the right approach.
来源：https://stackoverflow.com/questions/3113680/how-to-block-ui-in-iphone