how can I detect the completion of an animation triggered by CATransaction

问题

I have a CALayer which I merely create and add to a subview of my view controller's main view in the controller's initWithNibName: And then, I perform the following animation:

  [CATransaction begin];
  [CATransaction setAnimationDuration:2];
  [logoLayer setOpacity:0];
  [CATransaction commit];

How can I tell when this animation is done? the performSelector: delayed by 2 secs. approach doesn't seem "the right way" to go about it.

回答1:

According to the doc, [CATransaction setCompletionBlock:] could be used for what you want.

It says

The completion block object is guaranteed to be called (on the main thread) as soon as all animations subsequently added by this transaction group have completed (or have been removed.) If no animations are added before the current transaction group is committed (or the completion block is set to a different value,) the block will be invoked immediately.

Try adding something like this before you begin the animation transaction.

[CATransaction setCompletionBlock:^{
    // Action after the animation completion
}];

来源：https://stackoverflow.com/questions/9049410/how-can-i-detect-the-completion-of-an-animation-triggered-by-catransaction