IOS,图片切换动画

_Vi = [[UIView alloc]initWithFrame:CGRectMake(100, 200, 200, 200)];
//定义数组，存放所有图片对象
NSArray *images=[NSArray arrayWithObjects:[UIImage imageNamed:@"image003.jpg"],[UIImage imageNamed:@"image004.jpg"], nil];
//        //定义结构体，方块大小
//        CGRect frame=CGRectMake(100, 100, 200, 200);
//初始化图像视图对象，大小是frame
_imageView = [[UIImageView alloc] initWithFrame:_Vi.bounds];
//imageView的动画图片是数组images
_imageView.animationImages = images;
//按照原始比例缩放图片，保持纵横比
_imageView.contentMode = UIViewContentModeScaleAspectFit;
//切换动作的时间0.5秒，来控制图像显示的速度有多快，
_imageView.animationDuration = 0.5;
//动画的重复次数，想让它无限循环就赋成0
_imageView.animationRepeatCount = 0;
//开始动画
[_imageView startAnimating];
//添加控件
[_Vi addSubview:_imageView];
[self.view addSubview:_Vi];