雪花效果

@interface ViewController ()
{
    UIImage *image;
}
- (IBAction)didAction:(id)sender;

@end

@implementation ViewController

- (void)viewDidLoad {
    [super viewDidLoad];
    self.view.backgroundColor = [UIColor cyanColor];
    //雪花圖片
    image = [UIImage imageNamed:@"iconfont-xuehua"];
    //啓動定時器
    [NSTimer scheduledTimerWithTimeInterval:0.5 target:self selector:@selector(showTime) userInfo:nil repeats:YES];
    // Do any additional setup after loading the view, typically from a nib.
}

- (void)showTime {
    //建立雪花
    UIImageView *imageV = [[UIImageView alloc] initWithImage:image];
    //添加
    [self.view addSubview:imageV];
    
    NSInteger startX = arc4random()%356 + 10;
    //雪花開始位置
    imageV.frame = CGRectMake(startX, 50, 50, 50);
    //動畫
    [UIView animateWithDuration:2 animations:^{
        //雪花下落位置
        imageV.frame = CGRectMake(startX, self.view.frame.size.height, 30, 30);
    } completion:^(BOOL finished) {
        //動畫完成移除雪花
        [imageV removeFromSuperview];
    }];
    
}

- (void)didReceiveMemoryWarning {
    [super didReceiveMemoryWarning];
    // Dispose of any resources that can be recreated.
}

- (IBAction)didAction:(id)sender {
    
    WebViewController *web = [[WebViewController alloc] initWithNibName:@"WebViewController" bundle:nil];
    [self.navigationController pushViewController:web animated:YES];
}
@end