animateWithDuration 动画的速度选择

+ (void)animateWithDuration:(NSTimeInterval)duration delay:(NSTimeInterval)delay options:(UIViewAnimationOptions)options animations:(void (^)(void))animations completion:(void (^)(BOOL finished))completion NS_AVAILABLE_IOS(4_0);

UIViewAnimationOptionCurveEaseIn 先慢后快

UIViewAnimationOptionCurveEaseOut 先快后慢

UIViewAnimationOptionCurveLinear 匀速

UIViewAnimationOptionCurveEaseInOut 慢块慢

原文：http://www.cnblogs.com/zhujin/p/3997857.html