iOS核心动画详解（CABasicAnimation）

前言

　　上一篇已经介绍了核心动画在UI渲染中的位置和基本概念，但是没有具体介绍CAAnimation子类的用法，本文将介绍CABasicAnimation及其子类CASpringAnimation的用法和一些注意事项。

一、CABasicAnimation

1.什么是CABasicAnimation

　　CABasicAnimation是核心动画类簇中的一个类，其父类是CAPropertyAnimation，其子类是CASpringAnimation，它的祖父是CAAnimation。它主要用于制作比较单一的动画，例如，平移、缩放、旋转、颜色渐变、边框的值的变化等，也就是将layer的某个属性值从一个值到另一个值的变化。类似x -> y这种变化，然而对于x -> y -> z甚至更多的变化是不行的。

2.常用属性

　　@property(nullable, strong) id fromValue;

　　@property(nullable, strong) id toValue;

　　@property(nullable, strong) id byValue;

　　很明显，fromvalue表示初始状态，tovalue表示最终状态，byvalue是在fromvalue的基础上发生的变化，这个可以慢慢测试，主要还是from和to。

3.实例化方法

　　+ (instancetype)animationWithKeyPath:(nullable NSString *)path;

　　下面是对keypath比较全面的总结，每个keypath对应一种属性值的变化，其中涉及到颜色变化的都必须使用CGColor，因为对应是对layer的属性。

 #ifndef AnimationKeyPathName_h
 #define AnimationKeyPathName_h
 #import <Foundation/Foundation.h>
 /* CATransform3D Key Paths */
 /* 旋转x,y,z分别是绕x,y,z轴旋转 */
 static NSString *kCARotation = @"transform.rotation";
 static NSString *kCARotationX = @"transform.rotation.x";
 static NSString *kCARotationY = @"transform.rotation.y";
 static NSString *kCARotationZ = @"transform.rotation.z";

 /* 缩放x,y,z分别是对x,y,z方向进行缩放 */
 static NSString *kCAScale = @"transform.scale";
 static NSString *kCAScaleX = @"transform.scale.x";
 static NSString *kCAScaleY = @"transform.scale.y";
 static NSString *kCAScaleZ = @"transform.scale.z";

 /* 平移x,y,z同上 */
 static NSString *kCATranslation = @"transform.translation";
 static NSString *kCATranslationX = @"transform.translation.x";
 static NSString *kCATranslationY = @"transform.translation.y";
 static NSString *kCATranslationZ = @"transform.translation.z";

 /* 平面 */
 /* CGPoint中心点改变位置，针对平面 */
 static NSString *kCAPosition = @"position";
 static NSString *kCAPositionX = @"position.x";
 static NSString *kCAPositionY = @"position.y";

 /* CGRect */
 static NSString *kCABoundsSize = @"bounds.size";
 static NSString *kCABoundsSizeW = @"bounds.size.width";
 static NSString *kCABoundsSizeH = @"bounds.size.height";
 static NSString *kCABoundsOriginX = @"bounds.origin.x";
 static NSString *kCABoundsOriginY = @"bounds.origin.y";

 /* 透明度 */
 static NSString *kCAOpacity = @"opacity";
 /* 背景色 */
 static NSString *kCABackgroundColor = @"backgroundColor";
 /* 圆角 */
 static NSString *kCACornerRadius = @"cornerRadius";
 /* 边框 */
 static NSString *kCABorderWidth = @"borderWidth";
 /* 阴影颜色 */
 static NSString *kCAShadowColor = @"shadowColor";
 /* 偏移量CGSize */
 static NSString *kCAShadowOffset = @"shadowOffset";
 /* 阴影透明度 */
 static NSString *kCAShadowOpacity = @"shadowOpacity";
 /* 阴影圆角 */
 static NSString *kCAShadowRadius = @"shadowRadius";
 #endif /* AnimationKeyPathName_h */

4.简单用法

　　下面的类是用来测试不同keypath对应的动画，有些省略了，因为原理都是一样的。

　　#define SCREEN_WIDTH [UIScreen mainScreen].bounds.size.width

　　#define SCREEN_HEIGHT [UIScreen mainScreen].bounds.size.height

 #import "BaseAnimationView.h"

 @interface BaseAnimationView()<UITableViewDelegate,UITableViewDataSource>
 @property (nonatomic, strong) UIView *squareView;
 @property (nonatomic, strong) UILabel *squareLabel;
 @property (nonatomic, strong) UITableView *tableView;
 @property (nonatomic, strong) NSMutableArray *dataSource;
 @end

 @implementation BaseAnimationView

 - (instancetype)init{
     if (self = [super initWithFrame:CGRectMake(, , SCREEN_WIDTH, SCREEN_HEIGHT)]) {
         [self initData];
         [self setupUI];
     }
     return self;
 }
 - (void)setupUI{
     self.squareView = [[UIView alloc] initWithFrame:CGRectMake(, , , )];
     self.squareView.backgroundColor = [UIColor cyanColor];
     self.squareView.layer.borderColor = [UIColor redColor].CGColor;
     self.squareView.center = CGPointMake(SCREEN_WIDTH/2.0, );
     self.squareView.layer.shadowOpacity = 0.6;
     self.squareView.layer.shadowOffset = CGSizeMake(, );
     self.squareView.layer.shadowRadius = ;
     self.squareView.layer.shadowColor = [UIColor redColor].CGColor;
     [self addSubview:self.squareView];

     self.squareLabel = [[UILabel alloc] initWithFrame:self.squareView.bounds];
     self.squareLabel.text = @"label";
     self.squareLabel.textAlignment = NSTextAlignmentCenter;
     self.squareLabel.textColor = [UIColor blackColor];
     self.squareLabel.font = [UIFont systemFontOfSize:];
     [self.squareView addSubview:self.squareLabel];

     self.tableView = [[UITableView alloc] initWithFrame:CGRectMake(, , SCREEN_WIDTH, SCREEN_HEIGHT-) style:UITableViewStylePlain];
     self.tableView.delegate = self;
     self.tableView.dataSource = self;
     [self addSubview:self.tableView];
 }

 - (CABasicAnimation *)getAnimationKeyPath:(NSString *)keyPath fromValue:(id)fromValue toValue:(id)toValue{
     CABasicAnimation *basicAnimation = [CABasicAnimation animationWithKeyPath:keyPath];
     basicAnimation.fromValue = fromValue;
     /*byvalue是在fromvalue的值的基础上增加量*/
     //basicAnimation.byValue = @1;
     basicAnimation.toValue = toValue;
     basicAnimation.timingFunction = [CAMediaTimingFunction functionWithName:kCAMediaTimingFunctionLinear];;
     basicAnimation.duration = ;
     basicAnimation.repeatCount = ;
     /* animation remove from view after animation finish */
     basicAnimation.removedOnCompletion = YES;
     return basicAnimation;
 }
 - (void)initData{
     /*
      kCAScaleZ 缩放z 没有意义，因为是平面图形
      kCAPositionX设置y没有意义，可以随意设置，同理kCAPositionY设置x没有意义
      kCABackgroundColor,颜色变化必须要用CGColor
      用到shadow的几个属性变化的时候，需要先设置shadow
      */
     NSValue *startPoint = [NSValue valueWithCGPoint:self.squareView.center];
     NSValue *endPoint = [NSValue valueWithCGPoint:CGPointMake(, )];
     NSValue *shadowStartPoint = [NSValue valueWithCGPoint:CGPointMake(, )];
     NSValue *shadowEndPoint = [NSValue valueWithCGPoint:CGPointMake(, )];
     id startColor = (id)([UIColor cyanColor].CGColor);
     id endColor = (id)([UIColor redColor].CGColor);
     id shadowStartColor = (id)[UIColor clearColor].CGColor;
     id shadowEndColor = (id)[UIColor redColor].CGColor;
     self.dataSource = [NSMutableArray array];
     NSArray *keypaths   = @[kCARotation,kCARotationX,kCARotationY,kCARotationZ,
                             kCAScale,kCAScaleX,kCAScaleZ,kCAPositionX,
                             kCABoundsSizeW,kCAOpacity,kCABackgroundColor,kCACornerRadius,
                             kCABorderWidth,kCAShadowColor,kCAShadowRadius,kCAShadowOffset];

     NSArray *fromValues = @[@,@,@,@,
                             @,@,@,startPoint,
                             @,@,startColor,@,
                             @,shadowStartColor,@,shadowStartPoint];

     NSArray *toValues   = @[@(M_PI),@(M_PI),@(M_PI),@(M_PI),
                             @,@,@,endPoint,
                             @,@,endColor,@,
                             @,shadowEndColor,@,shadowEndPoint];
     for (int i=; i<keypaths.count; i++) {
         AnimationModel *model = [[AnimationModel alloc] init];
         model.keyPaths = keypaths[i];
         model.fromValue = fromValues[i];
         model.toValue = toValues[i];
         [self.dataSource addObject:model];
     }
 }
 - (NSInteger)numberOfSectionsInTableView:(UITableView *)tableView{
     return ;
 }
 - (NSInteger)tableView:(UITableView *)tableView numberOfRowsInSection:(NSInteger)section{
     return [self.dataSource count];
 }
 - (UITableViewCell *)tableView:(UITableView *)tableView cellForRowAtIndexPath:(NSIndexPath *)indexPath{
     AnimationModel *model = [self.dataSource objectAtIndex:indexPath.row];
     UITableViewCell *cell = [tableView dequeueReusableCellWithIdentifier:@"CellID"];
     if (cell==nil) {
         cell = [[UITableViewCell alloc] initWithStyle:UITableViewCellStyleDefault reuseIdentifier:@"CellID"];
     }
     cell.textLabel.text = model.keyPaths;
     cell.selectionStyle = ;
     return cell;
 }
 - (void)tableView:(UITableView *)tableView didSelectRowAtIndexPath:(NSIndexPath *)indexPath{
     AnimationModel *model = [self.dataSource objectAtIndex:indexPath.row];
     CABasicAnimation *animation = [self getAnimationKeyPath:model.keyPaths fromValue:model.fromValue toValue:model.toValue];
     [self.squareView.layer addAnimation:animation forKey:nil];
 }
 @end

　　之所以在执行动画的view上加入一个label，是为了测试当layer放大时其子类的变化。layer进行缩放时，它的大小并没有发生改变，我们看到它变大或变小是因为它离我们的距离在发生改变，所以其子视图会随着一起变化。然而，改变其frame，它的大小和坐标是确实发生了改变，其子视图正常情况下是不会发生变化的。CABasicAnimation用法非常简单，下面介绍其子类CASpringAnimation。

二、CASpringAnimation

1.什么是CASpringAnimation

　　CASpringAnimation是在CABasicAnimation的基础上衍生的另一个动画类，它比CABasicAnimation多了动画的弹性，是动画不再是从一个状态变成另一个状态时显得生硬。CASpringAnimation是iOS9.0之后新加的。

2.新增属性

　　@property CGFloat mass;       //质量（影响弹簧的惯性，质量越大，弹簧惯性越大，运动的幅度越大）

　　@property CGFloat stiffness;  //弹性系数（弹性系数越大，弹簧的运动越快）

　　@property CGFloat damping;    //阻尼系数（阻尼系数越大，弹簧的停止越快）

　　@property CGFloat initialVelocity;  //初始速率（弹簧动画的初始速度大小，弹簧运动的初始方向与初始速率的正负一致，若初始速率为0，表示忽略该属性）

　　@property CGFloat settlingDuration; //结算时间（根据动画参数估算弹簧开始运动到停止的时间，动画设置的时间最好根据此时间来设置）

　　这三个属性可以设置动画在执行到最终状态后的弹性效果，具体值需要调试，下面给出一个具体的类来实现这一功能。

 #import "SpringAnimationView.h"
 #import "UIView+HPAdditions.h"

 @interface SpringAnimationView()<UITableViewDelegate,UITableViewDataSource>
 @property (nonatomic, strong) UIView *squareView;
 @property (nonatomic, strong) UITableView *tableView;
 @property (nonatomic, strong) NSMutableArray *dataSource;
 @property (nonatomic, strong) UISlider *massSlider;
 @property (nonatomic, strong) UISlider *stiffnessSlider;
 @property (nonatomic, strong) UISlider *dampingSlider;
 @property (nonatomic, strong) UILabel *massLabel;
 @property (nonatomic, strong) UILabel *stiffnessLabel;
 @property (nonatomic, strong) UILabel *dampingLabel;
 @end

 @implementation SpringAnimationView

 - (instancetype)init{
     if (self = [super initWithFrame:CGRectMake(, , SCREEN_WIDTH, SCREEN_HEIGHT)]) {
         [self initData];
         [self setupUI];
     }
     return self;
 }
 - (void)setupUI{
     self.squareView = [[UIView alloc] initWithFrame:CGRectMake(, , , )];
     self.squareView.backgroundColor = [UIColor cyanColor];
     self.squareView.layer.borderColor = [UIColor redColor].CGColor;
     self.squareView.center = CGPointMake(SCREEN_WIDTH/2.0, );
     self.squareView.layer.shadowOpacity = 0.6;
     self.squareView.layer.shadowOffset = CGSizeMake(, );
     self.squareView.layer.shadowRadius = ;
     self.squareView.layer.shadowColor = [UIColor redColor].CGColor;
     [self addSubview:self.squareView];

     self.massSlider = [[UISlider alloc] initWithFrame:CGRectMake(, , , )];
     self.massSlider.minimumValue = ;
     self.massSlider.maximumValue = ;
     self.massSlider.tintColor = [UIColor cyanColor];
     self.massSlider.thumbTintColor = [UIColor redColor];
     self.massSlider.top = self.squareView.bottom + ;
     [self addSubview:self.massSlider];
     [self.massSlider addTarget:self action:@selector(durationChange:) forControlEvents:UIControlEventValueChanged];

     self.stiffnessSlider = [[UISlider alloc] initWithFrame:CGRectMake(, , , )];
     self.stiffnessSlider.minimumValue = ;
     self.stiffnessSlider.maximumValue = ;
     self.stiffnessSlider.tintColor = [UIColor cyanColor];
     self.stiffnessSlider.thumbTintColor = [UIColor redColor];
     self.stiffnessSlider.top = self.massSlider.bottom + ;
     [self addSubview:self.stiffnessSlider];
     [self.stiffnessSlider addTarget:self action:@selector(durationChange:) forControlEvents:UIControlEventValueChanged];

     self.dampingSlider = [[UISlider alloc] initWithFrame:CGRectMake(, , , )];
     self.dampingSlider.minimumValue = ;
     self.dampingSlider.maximumValue = ;
     self.dampingSlider.tintColor = [UIColor cyanColor];
     self.dampingSlider.thumbTintColor = [UIColor redColor];
     self.dampingSlider.top = self.stiffnessSlider.bottom + ;
     [self addSubview:self.dampingSlider];
     [self.dampingSlider addTarget:self action:@selector(durationChange:) forControlEvents:UIControlEventValueChanged];

     self.massLabel = [[UILabel alloc] initWithFrame:CGRectMake(, , , )];
     self.massLabel.text = @"mass";
     self.massLabel.centerY = self.massSlider.centerY;
     self.massLabel.left = self.massSlider.right+;
     self.massLabel.textAlignment = NSTextAlignmentLeft;
     self.massLabel.textColor = [UIColor blackColor];
     self.massLabel.font = [UIFont systemFontOfSize:];
     [self addSubview:self.massLabel];

     self.stiffnessLabel = [[UILabel alloc] initWithFrame:CGRectMake(, , , )];
     self.stiffnessLabel.text = @"stiffness";
     self.stiffnessLabel.centerY = self.stiffnessSlider.centerY;
     self.stiffnessLabel.left = self.stiffnessSlider.right+;
     self.stiffnessLabel.textAlignment = NSTextAlignmentLeft;
     self.stiffnessLabel.textColor = [UIColor blackColor];
     self.stiffnessLabel.font = [UIFont systemFontOfSize:];
     [self addSubview:self.stiffnessLabel];

     self.dampingLabel = [[UILabel alloc] initWithFrame:CGRectMake(, , , )];
     self.dampingLabel.text = @"damping";
     self.dampingLabel.centerY = self.dampingSlider.centerY;
     self.dampingLabel.left = self.dampingSlider.right+;
     self.dampingLabel.textAlignment = NSTextAlignmentLeft;
     self.dampingLabel.textColor = [UIColor blackColor];
     self.dampingLabel.font = [UIFont systemFontOfSize:];
     [self addSubview:self.dampingLabel];

     self.tableView = [[UITableView alloc] initWithFrame:CGRectMake(, self.dampingSlider.bottom+, SCREEN_WIDTH, SCREEN_HEIGHT-self.dampingSlider.bottom-) style:UITableViewStylePlain];
     self.tableView.delegate = self;
     self.tableView.dataSource = self;
     [self addSubview:self.tableView];
 }

  /* 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;

 - (CASpringAnimation *)getAnimationKeyPath:(NSString *)keyPath fromValue:(id)fromValue toValue:(id)toValue{
     CASpringAnimation *springAnimation = [CASpringAnimation animationWithKeyPath:keyPath];
     springAnimation.fromValue = fromValue;
     springAnimation.toValue = toValue;
     springAnimation.mass = self.massSlider.value;
     springAnimation.stiffness = self.stiffnessSlider.value;
     springAnimation.damping = self.dampingSlider.value;
     springAnimation.timingFunction = [CAMediaTimingFunction functionWithName:kCAMediaTimingFunctionLinear];;
     springAnimation.duration = ;
     springAnimation.repeatCount = ;
     /* animation remove from view after animation finish */
     springAnimation.removedOnCompletion = YES;
     /*
      只有当removedOnCompletion设置为no时，fillmode设置为kCAFillModeBoth或者kCAFillModeForwards才有效，
      kCAFillModeRemoved //动画执行完成后回到初始状态
      kCAFillModeBackwards //动画执行完成后回到初始状态
      kCAFillModeForwards //动画执行完成后保留最后状态
      kCAFillModeBoth //动画执行完成后保留最后状态
      */
     springAnimation.fillMode = kCAFillModeForwards;
     /*
      动画执行完成后按原动画返回执行，default no
      */
 //    springAnimation.autoreverses = YES;
     return springAnimation;
 }
 - (void)initData{
     /*
      kCAScaleZ 缩放z 没有意义，因为是平面图形
      kCAPositionX设置y没有意义，可以随意设置，同理kCAPositionY设置x没有意义
      kCABackgroundColor,颜色变化必须要用CGColor
      用到shadow的几个属性变化的时候，需要先设置shadow
      */
     NSValue *shadowStartPoint = [NSValue valueWithCGPoint:CGPointMake(, )];
     NSValue *shadowEndPoint = [NSValue valueWithCGPoint:CGPointMake(, )];
     id startColor = (id)([UIColor cyanColor].CGColor);
     id endColor = (id)([UIColor redColor].CGColor);
     id shadowStartColor = (id)[UIColor clearColor].CGColor;
     id shadowEndColor = (id)[UIColor redColor].CGColor;
     self.dataSource = [NSMutableArray array];
     NSArray *keypaths   = @[kCARotation,kCARotationX,kCARotationY,kCARotationZ,
                             kCAScale,kCAScaleX,kCAScaleZ,kCAPositionY,
                             kCABoundsSizeW,kCAOpacity,kCABackgroundColor,kCACornerRadius,
                             kCABorderWidth,kCAShadowColor,kCAShadowRadius,kCAShadowOffset];

     NSArray *fromValues = @[@,@,@,@,
                             @,@,@,@,
                             @,@,startColor,@,
                             @,shadowStartColor,@,shadowStartPoint];

     NSArray *toValues   = @[@(M_PI),@(M_PI),@(M_PI),@(M_PI),
                             @,@,@,@,
                             @,@,endColor,@,
                             @,shadowEndColor,@,shadowEndPoint];
     for (int i=; i<keypaths.count; i++) {
         AnimationModel *model = [[AnimationModel alloc] init];
         model.keyPaths = keypaths[i];
         model.fromValue = fromValues[i];
         model.toValue = toValues[i];
         [self.dataSource addObject:model];
     }
 }
 - (NSInteger)numberOfSectionsInTableView:(UITableView *)tableView{
     return ;
 }
 - (NSInteger)tableView:(UITableView *)tableView numberOfRowsInSection:(NSInteger)section{
     return [self.dataSource count];
 }
 - (UITableViewCell *)tableView:(UITableView *)tableView cellForRowAtIndexPath:(NSIndexPath *)indexPath{
     AnimationModel *model = [self.dataSource objectAtIndex:indexPath.row];
     UITableViewCell *cell = [tableView dequeueReusableCellWithIdentifier:@"CellID"];
     if (cell==nil) {
         cell = [[UITableViewCell alloc] initWithStyle:UITableViewCellStyleDefault reuseIdentifier:@"CellID"];
     }
     cell.textLabel.text = model.keyPaths;
     cell.selectionStyle = ;
     return cell;
 }
 - (void)tableView:(UITableView *)tableView didSelectRowAtIndexPath:(NSIndexPath *)indexPath{
     [self.squareView.layer removeAllAnimations];
     AnimationModel *model = [self.dataSource objectAtIndex:indexPath.row];
     CABasicAnimation *animation = [self getAnimationKeyPath:model.keyPaths fromValue:model.fromValue toValue:model.toValue];
     [self.squareView.layer addAnimation:animation forKey:@"animation"];
 }
 - (void)durationChange:(UISlider *)slider{
     [slider setValue:slider.value];
     if (slider==self.massSlider) {
         self.massLabel.text = [NSString stringWithFormat:@"mass   %.2f", slider.value];
     }else if (slider==self.stiffnessSlider) {
         self.stiffnessLabel.text = [NSString stringWithFormat:@"stiffness   %.2f", slider.value];
     }else if (slider==self.dampingSlider) {
         self.dampingLabel.text = [NSString stringWithFormat:@"damping   %.2f", slider.value];
     }
 }
 @end

 --------------------------------------------------------------------------------------
 #import <UIKit/UIKit.h>

 @interface UIView (HPAdditions)
 @property (nonatomic) CGFloat top;
 @property (nonatomic) CGFloat bottom;
 @property (nonatomic) CGFloat left;
 @property (nonatomic) CGFloat right;

 @property (nonatomic) CGFloat width;
 @property (nonatomic) CGFloat height;
 @property (nonatomic) CGPoint origin;
 @property (nonatomic) CGSize size;

 @property (nonatomic) CGFloat centerX;
 @property (nonatomic) CGFloat centerY;

 @end

 #import "UIView+HPAdditions.h"

 @implementation UIView (HPAdditions)
 - (CGFloat)top{
     return self.frame.origin.y;
 }
 - (void)setTop:(CGFloat)top{
     CGRect frame = self.frame;
     frame.origin.y = top;
     self.frame = frame;
 }
 - (CGFloat)bottom{
     return self.frame.origin.y+self.frame.size.height;
 }
 - (void)setBottom:(CGFloat)bottom{
     CGRect frame = self.frame;
     frame.origin.y = bottom-frame.size.height;
     self.frame = frame;
 }
 - (CGFloat)left{
     return self.frame.origin.x;
 }
 - (void)setLeft:(CGFloat)left{
     CGRect frame = self.frame;
     frame.origin.x = left;
     self.frame = frame;
 }
 - (CGFloat)right{
     return self.frame.origin.x+self.frame.size.width;
 }
 - (void)setRight:(CGFloat)right{
     CGRect frame = self.frame;
     frame.origin.x = right-frame.size.width;
     self.frame = frame;
 }

 - (CGFloat)width{
     return self.frame.size.width;
 }
 - (void)setWidth:(CGFloat)width{
     CGRect frame = self.frame;
     frame.size.width = width;
     self.frame = frame;
 }
 - (CGFloat)height{
     return self.frame.size.height;
 }
 - (void)setHeight:(CGFloat)height{
     CGRect frame = self.frame;
     frame.size.height = height;
     self.frame = frame;
 }
 - (CGFloat)centerX{
     return self.center.x;
 }
 - (void)setCenterX:(CGFloat)centerX{
     self.center = CGPointMake(centerX, self.center.y);
 }
 - (CGFloat)centerY{
     return self.center.y;
 }
 - (void)setCenterY:(CGFloat)centerY{
     self.center = CGPointMake(self.center.x, centerY);
 }
 - (CGPoint)origin{
     return self.frame.origin;
 }
 - (void)setOrigin:(CGPoint)origin{
     CGRect frame = self.frame;
     frame.origin = origin;
     self.frame = frame;
 }
 - (CGSize)size{
     return self.frame.size;
 }
 - (void)setSize:(CGSize)size{
     CGRect frame = self.frame;
     frame.size = size;
     self.frame = frame;
 }

 @end

　　CABasicAnimation及其子类CASpringAnimation使用都是非常简单的，CASpringAnimation能够做出更加优雅的动画，建议使用。但是这两种动画能过制作的动画都是需要给定初始和最终状态值的，而中间过程需要系统去处理，这样的动画比较单一，下一篇将会介绍添加中间过程的动画CAKeyFrameAnimation关键帧动画，它能做出更加炫酷的动画。