可以保存一组动画对象，将CAAnimationGroup对象加入层后，组中所有动画对象可以同时并发运行

属性解析：

animations：用来保存一组动画对象的NSArray

默认情况下，一组动画对象是同时运行的，也可以通过设置动画对象的beginTime属性来更改动画的开始时间

#import "ViewController.h" @interface ViewController ()@property(nonatomic,strong)UIButton *btn; @end @implementation ViewController - (void)viewDidLoad {    [super viewDidLoad];    self.btn=[UIButton buttonWithType:UIButtonTypeCustom];    self.btn.frame=CGRectMake(50, 100, 80, 60);    [self.btn setTitle:@"按钮" forState:UIControlStateNormal];    [self.btn setTitleColor:[UIColor blackColor] forState:UIControlStateNormal];    [self.btn addTarget:self action:@selector(btnClick:) forControlEvents:UIControlEventTouchUpInside];    [self.view addSubview:self.btn];}-(void)btnClick:(id)sender{    CABasicAnimation *a1 = [CABasicAnimation animation];    a1.keyPath = @"transform.translation.y";    a1.toValue = @(100);    // 缩放动画    CABasicAnimation *a2 = [CABasicAnimation animation];    a2.keyPath = @"transform.scale";    a2.toValue = @(2.0);    // 旋转动画    CABasicAnimation *a3 = [CABasicAnimation animation];    a3.keyPath = @"transform.rotation";    a3.toValue = @(-3.1415926/4);         // 组动画    CAAnimationGroup *groupAnima = [CAAnimationGroup animation];    groupAnima.animations = @[a1, a2, a3];         //设置组动画的时间    groupAnima.duration = 2;    groupAnima.fillMode = kCAFillModeForwards;    groupAnima.removedOnCompletion = NO;    [self.btn.layer addAnimation:groupAnima forKey:nil];} - (void)didReceiveMemoryWarning {    [super didReceiveMemoryWarning];}@end