雪花下落效果

#import "ViewController.h"

@interface ViewController ()

@property (nonatomic,strong) UIImageView *imageView;

@end

@implementation ViewController

- (void)viewDidLoad {
    [super viewDidLoad];
    
    [self.view addSubview:self.imageView];
}

- (void)touchesBegan:(NSSet<UITouch *> *)touches withEvent:(UIEvent *)event {
    [self.imageView.layer addAnimation:[self rainAnimationWithDuration:10] forKey:nil];
    [self.imageView.layer addAnimation:[self rainAlphaWithDuration:10] forKey:nil];
    [self.imageView.layer addAnimation:[self sunshineAnimationWithDuration:10] forKey:nil];//雪花旋转
}

- (UIImageView *)imageView {
    if (!_imageView) {
        _imageView = [[UIImageView alloc] init];
        _imageView.image = [UIImage imageNamed:@"zrx4.jpg"];
        _imageView.frame = CGRectMake(100, 100, 50, 50);
    }
    return _imageView;
}

//下雨动画方法
- (CABasicAnimation *)rainAnimationWithDuration:(NSInteger)duration {
    CABasicAnimation* caBaseTransform = [CABasicAnimation animation];
    caBaseTransform.duration = duration;
    caBaseTransform.keyPath = @"transform";
    caBaseTransform.repeatCount = MAXFLOAT;
    caBaseTransform.removedOnCompletion = NO;
    caBaseTransform.fillMode = kCAFillModeForwards;
    caBaseTransform.fromValue = [NSValue valueWithCATransform3D:CATransform3DMakeTranslation(0, 0, 0)];
    caBaseTransform.toValue = [NSValue valueWithCATransform3D:CATransform3DMakeTranslation(300, 300, 0)];
    return caBaseTransform;
}

//透明度动画
- (CABasicAnimation *)rainAlphaWithDuration:(NSInteger)duration {
    CABasicAnimation *showViewAnn = [CABasicAnimation animationWithKeyPath:@"opacity"];
    showViewAnn.fromValue = [NSNumber numberWithFloat:1.0];
    showViewAnn.toValue = [NSNumber numberWithFloat:0.1];
    showViewAnn.duration = duration;
    showViewAnn.repeatCount = MAXFLOAT;
    showViewAnn.fillMode = kCAFillModeForwards;
    showViewAnn.timingFunction = [CAMediaTimingFunction functionWithName:kCAMediaTimingFunctionEaseInEaseOut];
    showViewAnn.removedOnCompletion = NO;
    return showViewAnn;
}

//动画旋转方法
- (CABasicAnimation *)sunshineAnimationWithDuration:(NSInteger)duration {
    //旋转动画
    CABasicAnimation* rotationAnimation = [CABasicAnimation animationWithKeyPath:@"transform.rotation.z"];
    rotationAnimation.toValue = [NSNumber numberWithFloat: M_PI * 2.0 ];
    [CAMediaTimingFunction functionWithName:kCAMediaTimingFunctionEaseInEaseOut];
    rotationAnimation.duration = duration;
    rotationAnimation.repeatCount = MAXFLOAT;
    rotationAnimation.cumulative = NO;
    rotationAnimation.removedOnCompletion = NO;
    rotationAnimation.fillMode = kCAFillModeForwards;
    return rotationAnimation;
}

@end