AFNetworking缓存图像是自动加载还是我们必须手动加载?

Question

我正在使用AFNetworking从JSON提要加载图像。

在这里，当用户第一次打开应用程序时，图像从互联网加载。它很好。

但是当用户从另一个视图返回时，在使用应用程序时，图像应该从缓存加载，而不是从互联网加载。

我该怎么做呢?

- (void)loadDetailData
{
    detailPost  = nil;
    NSString *detailUrl = [NSString stringWithFormat:@"%@", self.Details.firsturl];
    AFHTTPRequestOperationManager *detailManager = [AFHTTPRequestOperationManager manager];
    [detailManager GET:detailUrl parameters:nil success:^(AFHTTPRequestOperation *operation, id responseObject) {
        detailPosts = (NSDictionary *)responseObject;
        detailPost = [NSMutableArray array];
        NSArray *result = [detailPosts objectForKey:@"posts"];
        for (NSDictionary *all in result)
        {
            Categories *newCategory = [Categories new];
            NSDictionary *thumbnail_images = [all objectForKey:@"thumbnail_images"];
            NSDictionary *mediumImages = [thumbnail_images objectForKey:@"medium"];
            newCategory.detailimageUrl = [mediumImages objectForKey:@"url"];
            newCategory.title = [all objectForKey:@"title"];
            newCategory.mogowebUrl = [all objectForKey:@"url"];
//            NSLog(@"%@", newCategory.title);
            [detailPost addObject:newCategory];
            [self.maintableView reloadData];
        }

    } failure:^(AFHTTPRequestOperation *operation, NSError *error) {
    }];
}

- (NSInteger)numberOfSectionsInTableView:(UITableView *)tableView
{
    return 1;
}
- (NSInteger)tableView:(UITableView *)tableView numberOfRowsInSection:(NSInteger)section
{
    return [detailPost count];;
}
- (UITableViewCell *)tableView:(UITableView *)tableView cellForRowAtIndexPath:(NSIndexPath *)indexPath
{
    FirstTableViewCell *cell = [tableView dequeueReusableCellWithIdentifier:@"reuseIdentifier"];
    Categories *details = [detailPost objectAtIndex:indexPath.row];

    cell.detailTitle.text = details.title;
    NSString *imageurl = [NSString stringWithFormat:@"%@", details.detailimageUrl];
    NSURL *imgurl = [NSURL URLWithString:imageurl];
    [cell.detailImageView setImageWithURL:imgurl placeholderImage:nil];


//    [cell addSubview:cell.subView];
    cell.layer.masksToBounds = NO;
    cell.layer.cornerRadius = 5;
    cell.layer.borderColor = [UIColor blackColor].CGColor;
    cell.layer.shadowOffset = CGSizeMake(0, 1);
    cell.layer.shadowRadius = 2.0;
    cell.layer.shadowColor = [UIColor lightGrayColor].CGColor;

    return cell;
}

Answer 1

tl;

使用-setImageWithURLRequest: placeholderImage:成功失败:

  NSURLRequest *imageRequest =
      [NSURLRequest requestWithURL:[NSURL URLWithString:imgurl]
                       cachePolicy:NSURLRequestReturnCacheDataElseLoad
                   timeoutInterval:60];
  [cell.detailImageView setImageWithURLRequest:imageRequest
                              placeholderImage:nil
                                       success:nil
                                       failure:nil];

Image Cache + AFNetworking

导入UIImageView+AFNetworking头文件和viola!UIImageView类现在有几个方法来下载图像，也可以缓存它们!

内存缓存:您可以使用以下方法进行简单的内存缓存:

• - setImageWithURL:
• - setImageWithURL: placeholderImage:

图像将从内存缓存中检索，如果图像存在，则从URL下载并存储在内存缓存中。

的例子:

[imageView setImageWithURL:[NSURL URLWithString:imageURL]];
//here, placeholder image is set immediately.
[imageView setImageWithURL:[NSURL URLWithString:imageURL]
          placeholderImage:[UIImage imageNamed:@"placeholder.png"]];

磁盘缓存:如果需要缓存映像的时间超过用户的会话，可以使用以下方法。(提示:检查NSURLRequest类中的NSURLRequestCachePolicy)

• -setImageWithURLRequest: placeholderImage:成功:失败:

注意:如果指定了一个成功块，则该块负责在返回之前设置图像视图的图像。如果没有指定成功块，则应用默认行为设置带有self.image = image的映像。

的例子:

  NSURLRequest *imageRequest =
      [NSURLRequest requestWithURL:[NSURL URLWithString:imageURL]
                       cachePolicy:NSURLRequestReturnCacheDataElseLoad
                   timeoutInterval:60];
  [imageView setImageWithURLRequest:imageRequest
                   placeholderImage:[UIImage imageNamed:@"placeholder.png"]
                            success:nil
                            failure:nil];