Question

- (UITableViewCell *)tableView:(UITableView *)tableView cellForRowAtIndexPath:(NSIndexPath *)indexPath
{
     static NSString *CellIdentifier = @"cell";
     TVcell *cell = [tableView dequeueReusableCellWithIdentifier:CellIdentifier];
     if (cell == nil) {
         cell = [[TVcell alloc] initWithStyle:UITableViewCellStyleDefault reuseIdentifier:CellIdentifier];
     }
     cell.titleLabel.text = [[[arrayData objectAtIndex:indexPath.row]valueForKey:@"title"]stringByTrimmingCharactersInSet:[NSCharacterSet whitespaceAndNewlineCharacterSet]];

     cell.txtlabel.text = [[[arrayData objectAtIndex:indexPath.row] valueForKey:@"description"]stringByTrimmingCharactersInSet:[NSCharacterSet whitespaceAndNewlineCharacterSet]];
     cell.tag = indexPath.row;
     cell.imageView.image = nil;
     dispatch_queue_t queue = dispatch_get_global_queue(DISPATCH_QUEUE_PRIORITY_HIGH, 0ul);
     dispatch_async(queue, ^(void) {

     NSData *imageData = [NSData dataWithContentsOfURL:[NSURL URLWithString:[enclosureUrlArray objectAtIndex:indexPath.row]]];

     UIImage* image = [[UIImage alloc] initWithData:imageData];
     if (image) {
         dispatch_async(dispatch_get_main_queue(), ^{
             if (cell.tag == indexPath.row) {
                 cell.IMGLabel.image = image;
                 [cell setNeedsLayout];
                 }
              });
          }
      });
      return cell;

}

当我滚动时，相同的图像出现在单元格上，哪些单元格正在重复使用。我还使用了滚动视图委托。存储在enclosureUrlArray中的URL并且我正在传递。

Answer 1

在下载图片前将cell.IMGLabel.image = nil放入cellForRowAtIndexPath，即在此行的cell.imageView.image = nil;下方。

或设置一些占位符图像（在界面构建器中没有图像可用的图像类型到单元格的图像），因此如果未下载图像，则会显示此占位符图像，否则将显示下载的图像。

SDWebImage对这种情况有好处。它会缓存图像，因此它也会提供更好的性能。使用任何好的第三方库都没有错。

Answer 2

使用SDWeb图像：

#import <SDWebImage/UIImageView+WebCache.h>

...

- (UITableViewCell *)tableView:(UITableView *)tableView cellForRowAtIndexPath:(NSIndexPath *)indexPath {
    static NSString *MyIdentifier = @"MyIdentifier";

    UITableViewCell *cell = [tableView dequeueReusableCellWithIdentifier:MyIdentifier];
    if (cell == nil) {
        cell = [[[UITableViewCell alloc] initWithStyle:UITableViewCellStyleDefault
                                       reuseIdentifier:MyIdentifier] autorelease];
    }

    // Here we use the new provided sd_setImageWithURL: method to load the web image
    [cell.imageView sd_setImageWithURL:[NSURL URLWithString:@"http://www.domain.com/path/to/image.jpg"]
                      placeholderImage:[UIImage imageNamed:@"placeholder.png"]];

    cell.textLabel.text = @"My Text";
    return cell;
}

Answer 3

您也可以使用NSURLSession，请参阅此链接

Async image loading from url inside a UITableView cell - image changes to wrong image while scrolling

 NSURL *url = [NSURL URLWithString:[enclosureUrlArray objectAtIndex:indexPath.row]];
 NSURLSessionTask *task = [[NSURLSession sharedSession] dataTaskWithURL:url completionHandler:^(NSData * _Nullable data, NSURLResponse * _Nullable response, NSError * _Nullable error) {
    if (data) {
        UIImage *image = [UIImage imageWithData:data];
        if (image) {
            dispatch_async(dispatch_get_main_queue(), ^{
                MyCell *updateCell = (id)[tableView cellForRowAtIndexPath:indexPath];
                if (updateCell)
                    updateCell.IMGLabel.image = image;
            });
        }
    }
}];
[task resume];

对我来说很完美..

Answer 4

在sdwebimage的帮助下，您可以显示如下图像： -

NSString *string2 = [[businessListArray objectAtIndex:indexPath.row ]valueForKey:@"logo"];
    NSURL *url1 = [NSURL URLWithString:
                   [NSString stringWithFormat:
                    @"%@%@",
                    @"http://dev-demo.info.bh-in-15./upload/post/",
                    string2]];

    UIImageView *imageView = (UIImageView *)[cell.contentView viewWithTag:301];

    [imageView sd_setImageWithURL:url1
                 placeholderImage:[UIImage imageNamed:@"pocket.png"]
                        completed:^(UIImage *image, NSError *error, SDImageCacheType cacheType, NSURL *imageURL) {
                            imageView.image = image;
                        }];

tabelviewcell中的异步图像下载？

4 个答案: