UIView Animate不尊重延迟吗？

Question

Why does this not work?

[UIView animateWithDuration:0 delay:3 options:0 animations:^(void) { 
    NSLog(@"after duration, please!");
}  completion:nil];

The NSLog fires immediately.

I'm not looking for workarounds (there are many), but rather wondering why this would be.

Answer 1

The intermediate frames of core animation are actually happening in another background thread. The first and last frame of the animation are often created immediately. So the NSLog can fire in the main UI thread without waiting or even knowing about any background animation in progress.