ios - 如何在缓存中存储图像数据

Question

我有一个来自 url 的字典存储图像的可变数组。那么如何将图像存储在应用程序缓存中，并且我可以在没有互联网连接时查看图像。

- (UICollectionViewCell *)collectionView:(UICollectionView *)collectionView cellForItemAtIndexPath:(NSIndexPath *)indexPath{
    static NSString * CellIndentifier=@"CustomCell";
    CustomCell *cell = (CustomCell*)[collectionView dequeueReusableCellWithReuseIdentifier:CellIndentifier forIndexPath:indexPath];
    NSDictionary *dictVideo = [self.videoList objectAtIndex:indexPath.row];
    [cell.indicator startAnimating];
    //set title
    NSString *titleVideo = [dictVideo objectForKey:@"Title"];
    [cell.myLabel setText:titleVideo];
    // set image url
    NSString *urlVideo = [dictVideo objectForKey:@"Url"];
    NSURL *url = [NSURL URLWithString:urlVideo];
    cell.imageView.image = nil;
    dispatch_async(dispatch_get_global_queue(DISPATCH_QUEUE_PRIORITY_DEFAULT, 0), ^{
        NSData *data = [NSData dataWithContentsOfURL:url];
        UIImage * img = [[UIImage alloc]initWithData:data];
        dispatch_sync(dispatch_get_main_queue(), ^{
            NSLog(@"%ld  %@  %@",(long)indexPath.row,titleVideo,url);
                [cell.imageView setImage: img];
                [cell.indicator stopAnimating];
        });
          });
           return cell;
    }

Answer 1

你可以像 Umar Farooq 说的那样使用 SDWebImage 库，它支持 iOS 6 和 7然后你可以在你的 .m 文件中使用下面的代码

#import "UIImageView+WebCache.h"
 UIImage *Noimg = [UIImage imageNamed:@"noimg.png"];
     [cell.PlaceImg  setImageWithURL:[NSURL URLWithString:strImgname]  placeholderImage:Noimg];

这里的Noimg是占位图片，当图片所在位置找不到图片时，由库自动管理