How to unset delegate on UIView setAnimationDelega

问题:

I am receiving crash reports that appear to be from a UIView animation calling a delegate that has been dealloced.

    Thread 0 Crashed:
0   libobjc.A.dylib                 0x334776f6 objc_msgSend + 18
1   UIKit                           0x31c566c4 -[UIViewAnimationState sendDelegateAnimationDidStop:finished:]
2   UIKit                           0x31c565d2 -[UIViewAnimationState animationDidStop:finished:]
3   QuartzCore                      0x30045a26 run_animation_callbacks

I am setting the current view controller as the delegate for animations using the following pattern:

[UIView beginAnimations:nil context:NULL];
[UIView setAnimationBeginsFromCurrentState:YES];
[UIView setAnimationDuration:0.5];
[UIView setAnimationDelegate:self];
...
[UIView commitAnimations];

My question is, how do I set that delegate reference to nil in my dealloc method? Is there some way to retain a reference to an animation? Or fetch animations in progress?

回答1:

The CALayer class handles all animations for UIViews. You can access the UIView's layer using the layer property. If you were to replace the first argument of [UIView beginAnimations: context:] with an actual string, it would be possible to access that animation directly using CALayer's animationForKey: and removeAnimationForKey: methods.

In this case though, it might be enough to call [view.layer removeAllAnimations] before dealloc calls [super dealloc]. This will stop any custom UIView animations and, obviously, remove them from its layer.