为任意自定义的View隐藏时添加动画效果

覆盖系统默认提供的hide方法，在hide方法中添加动画效果即可。

-(void)setHidden:(BOOL)hidden{

CATransition *animation = [CATransition
animation];

animation.timingFunction =
UIViewAnimationCurveEaseInOut;

animation.type =
kCATransitionFade;
animation.duration =
0.4;
[self.layer
addAnimation:animation
forKey:nil];

// self.hidden = hidden;

[super
setHidden:hidden];
}