sdwebimage

[cell.imageView sd_setImageWithURL:[NSURL URLWithString:app.icon] placeholderImage:[UIImage imageNamed:@"placeholder"] options:0 progress:^(NSInteger receivedSize, NSInteger expectedSize) {
        // expectedSize: 图片的总字节数
        // receivedSize: 已经接收的图片字节数
        
        NSLog(@"下载进度：%f", 1.0 * receivedSize / expectedSize);
    } completed:^(UIImage *image, NSError *error, SDImageCacheType cacheType, NSURL *imageURL) {
        NSLog(@"下载完图片");
    }];

[[SDWebImageManager sharedManager] downloadImageWithURL:nil options:0 progress:^(NSInteger receivedSize, NSInteger expectedSize) {
        
    } completed:^(UIImage *image, NSError *error, SDImageCacheType cacheType, BOOL finished, NSURL *imageURL) {
        
    }];
// SDWebImage的图片缓存周期是多长:1个星期

- (void)applicationDidReceiveMemoryWarning:(UIApplication *)application
{
    // 清除内存缓存
    [[SDWebImageManager sharedManager].imageCache clearMemory];
    // 取消所有下载
    [[SDWebImageManager sharedManager] cancelAll];
}