我想实现的是一个UIScrollView动态加载照片的程序，使用的是SDImageManager开源代码来实现图片的下载和缓存的使用； 在block做为参数的回调函数中一张一张添加图片UIImageView到 Scrollview上

 completed:^(UIImage *image, NSError *error, SDImageCacheType cacheType, BOOL finished, NSURL *imageURL) {
         if (image) {
             imageview = [[UIImageView alloc] initWithFrame:CGRectMake(scrollview.frame.size.width*i, 10.0,scrollview.frame.size.width, scrollview.frame.size.height-20)];
            imageview.image = image;
            [scrollview addSubview:imageview];
         }
     }];

在block代码体里面，可以打印看到UIImageview 都添加到了ScrollView上了。但是在block代码体外访问ScrollView里面的子视图都是空的，并有没添加任何ImageView. 而且scrollview的delegate方法都失效了，目前不知道什么原因，请各位老师指点，指教。下面附上.m的实现代码 谢谢！

@implementation AlbumScroll
-(void)setArrOfImages:(NSMutableArray *)arr
{
mm= 80;
scrollview = [[UIScrollView alloc] initWithFrame:CGRectMake(0, 30, 734, 550)];
scrollview.contentSize = CGSizeMake((scrollview.frame.size.width+10)*([arrOfImages count])+10, scrollview.frame.size.height);

//用它指定 ScrollView 中内容的当前位置，即相对于 ScrollView 的左上顶点的偏移
scrollview.contentOffset = CGPointMake(0, 0);

//按页滚动，总是一次一个宽度，或一个高度单位的滚动
scrollview.pagingEnabled = YES;
[scrollview setDelegate:self];
scrollview.scrollEnabled = YES;
scrollview.showsVerticalScrollIndicator = NO;
scrollview.showsHorizontalScrollIndicator = YES;
[self addSubview:scrollview];

arrOfImages = arr;
CLog(@"arrofimages is %@",arrOfImages);
//配置每一张imageView 图片，并添加到scrollview
SDWebImageManager *manager = [SDWebImageManager sharedManager];
for (int i =0; i<arrOfImages.count ; i++) {
    NSString *picturePath = [arrOfImages objectAtIndex:i];
    NSURL *imageUrl = [NSURL URLWithString:picturePath];

    [manager
     downloadImageWithURL:imageUrl
     options:0
     progress:^(NSInteger receivedSize, NSInteger expectedSize) {
     }

     completed:^(UIImage *image, NSError *error, SDImageCacheType cacheType, BOOL finished, NSURL *imageURL) {
         if (image) {
             imageview = [[UIImageView alloc] initWithFrame:CGRectMake(scrollview.frame.size.width*i, 10.0,scrollview.frame.size.width, scrollview.frame.size.height-20)];
            imageview.image = image;
            [scrollview addSubview:imageview];
         }
     }];
}

pageControl = [[UIPageControl alloc] init];
pageControl.frame = CGRectMake(336,620, 122, 36);
pageControl.numberOfPages = arrOfImages.count;
pageControl.currentPage = 0;
[pageControl addTarget:self
                action:@selector(pageTurn:)forControlEvents:UIControlEventValueChanged];
[self addSubview:pageControl];
CLog(@"scrollview.subviews is %@",scrollview.subviews);
}
@end