CASpringAnimation

iOS9新出现的

/** Subclass for mass-spring animations. */

 

@interface CASpringAnimation : CABasicAnimation

 

/* The mass of the object attached to the end of the spring. Must be greater

   than 0. Defaults to one. */

 

@property CGFloat mass;

 

/* The spring stiffness coefficient. Must be greater than 0.

 * Defaults to 100. */

 

@property CGFloat stiffness;

 

/* The damping coefficient. Must be greater than or equal to 0.

 * Defaults to 10. */

 

@property CGFloat damping;

 

/* The initial velocity of the object attached to the spring. Defaults

 * to zero, which represents an unmoving object. Negative values

 * represent the object moving away from the spring attachment point,

 * positive values represent the object moving towards the spring

 * attachment point. */

 

@property CGFloat initialVelocity;

 

/* Returns the estimated duration required for the spring system to be

 * considered at rest. The duration is evaluated for the current animation

 * parameters. */

 

@property(readonly) CFTimeInterval settlingDuration;

 

@end