// 方法一

CATransition *animation = [CATransition animation];

animation.timingFunction = [CAMediaTimingFunction functionWithName:kCAMediaTimingFunctionEaseInEaseOut];

animation.type = kCATransitionFade;

animation.duration =0.75;

[self.label.layer addAnimation:animation forKey:@"kCATransitionFade"];

self.label.text =@"New";

// 方法二

[UIView transitionWithView:self.label

                  duration:0.25f

                   options:UIViewAnimationOptionTransitionCrossDissolve

                animations:^{

                    self.label.text =@"Well done!";

                } completion:nil];

// 方法三

[UIView animateWithDuration:1.0

                 animations:^{

                     self.label.alpha =0.0f;

                     self.label.text =@"newText";

                     self.label.alpha =1.0f;

                 }];