重要的两个方法：1.动画的数组：animations 2.启动的时间 beginTime
注意：动画组设置了持续时间（duration）可能会导致动画组里面的持续时间不管用
代码如下：
#import "ViewController.h"
@interface ViewController ()
{
CALayer * fllowers;
}
@end
@implementation ViewController
- (void)viewDidLoad {
[super viewDidLoad];
[self addBgView];
[self addFllower];
}
点击屏幕开始动画
-(void)touchesBegan:(NSSet *)touches withEvent:(UIEvent *)event{
[self addAnimationGroup];
}
背景图
-(void)addBgView{
UIImageView * image = [[UIImageView alloc]initWithFrame:self.view.frame];
image.image = [UIImage imageNamed:@"背景.jpg"];
[self.view addSubview:image];
}
在背景图上添加CALayer（花瓣）
-(void)addFllower{
UIImage * img = [UIImage imageNamed:@"花瓣"];
fllowers = [[CALayer alloc]init];
fllowers.position = CGPointMake(100, 200);
fllowers.bounds = CGRectMake(0, 0, img.size.width, img.size.height);
fllowers.contents = (id)img.CGImage;
[self.view.layer addSublayer:fllowers];
}
#pragma mark -------------添加动画组----------------
-(void)addAnimationGroup{
CAAnimationGroup *group = [CAAnimationGroup animation];
group.animations = @[[self rotationAnimation],[self dropAnimation]];
group.duration = 10;
// 动画开始的时间
// CACurrentMediaTime() 获得当前的时间
// 从调用这个方法开始，5秒之后 执行这个动画
group.beginTime = CACurrentMediaTime()+5;
group.removedOnCompletion = NO;
group.fillMode = kCAFillModeBoth;
[fllowers addAnimation:group forKey:@"group"];
}
//旋转效果
-(CABasicAnimation *)rotationAnimation{
CABasicAnimation *rotation = [CABasicAnimation animationWithKeyPath:@"transform.rotation.z"];
rotation.toValue = @(M_2_PI*3);
rotation.removedOnCompletion = NO;
return rotation;
}
//关键帧动画，设置花瓣掉落的曲线
-(CAKeyframeAnimation *)dropAnimation{
CAKeyframeAnimation * drop = [CAKeyframeAnimation animationWithKeyPath:@"position"];
// drop.path =
CGPathRef pathref = CGPathCreateMutable();
CGPathMoveToPoint(pathref, NULL, fllowers.position.x, fllowers.position.y);
// CGFloat cp1x, CGFloat cp1y, 设置两个点，在这两个点之间画曲线
// CGFloat x, CGFloat y 终止点
CGPoint endPoint = CGPointMake(80, 600);
CGPathAddCurveToPoint(pathref, NULL,160 ,280 ,-30 ,500 , endPoint.x, endPoint.y);
drop.path = pathref;
CGPathRelease(pathref);
return drop;
}
- (void)didReceiveMemoryWarning {
[super didReceiveMemoryWarning];
// Dispose of any resources that can be recreated.
}
@end
二.背景图和花瓣图
花瓣： 
三.
