弹力碰撞小动画

//实现动画 @property (nonatomic, strong)UIDynamicAnimator *dynamicAnimator;

//动画元素行为 @property (nonatomic, strong)UIDynamicItemBehavior *dynamicItemBehavior;

//碰撞行为 @property (nonatomic, strong)UICollisionBehavior *collisionBehavior;

//重力行为 @property (nonatomic, strong)UIGravityBehavior *gravityBehavior;

github 下载地址：https://github.com/Wanghongchao12138/WHCAnimalDemo.git