iphone - 滚动 UITableView 时单元格图像发生变化

Question

嗨，我的问题是，当我滚动 UITableView 单元格图像时，这些图像实际上位于网络服务器上，并且我使用 asyncdownloading 下载它。我在 UITableViewCell 上添加了 UIImageView 。图像在 UITableViewCell 上成功显示，但是当我滚动 tableview 图像时，这就是代码

- (UITableViewCell *)tableView:(UITableView *)tableView cellForRowAtIndexPath:(NSIndexPath *)indexPath
{
    UITableViewCell *cell = [tableView dequeueReusableCellWithIdentifier:@"DefaultCell"];
       searchobjectval =[self.arrSearchResult objectAtIndex:indexPath.row];
    if(cell == nil)
    {
        cell =[[UITableViewCell alloc] initWithStyle:UITableViewCellStyleDefault reuseIdentifier:@"DefaultCell"];



    }

    UILabel *areaLbl = (UILabel *)[cell viewWithTag:1];
    UILabel *postTitle = (UILabel *)[cell viewWithTag:2];
    UILabel *roomCost = (UILabel *)[cell viewWithTag:3];
    UILabel *description = (UILabel *)[cell viewWithTag:4];
    areaLbl.text =searchobjectval.location;
    postTitle.text = searchobjectval.title;
    roomCost.text = searchobjectval.roomCost;
    description.text =searchobjectval.description;

    [tableView setSeparatorColor:[UIColor blueColor]];

    UIView *myView = [[UIView alloc] init];
    if (indexPath.row % 2)
    {
        UIColor* clr = [UIColor colorWithRed:0.4f green:0.6f blue:0.8f alpha:1];
        myView.backgroundColor = clr;
    }
    else
    {
        myView.backgroundColor = [UIColor whiteColor];
    }
    cell.backgroundView = myView;

    NSLog(@" search object image %@",searchobjectval.imgLink);


    // Pass along the URL to the image (or change it if you are loading there locally)
    [AsyncImagesDownloading processImageDataWithURLString:[NSString stringWithFormat: @"http://192.95.48.72/bedspace/new_arrivals_img/%@",searchobjectval.idVal ] andBlock:^(NSData *imageData)
     {
         if (self.view.window)
         {
             UIImage *image = [UIImage imageWithData:imageData];
             UIImageView *imgVw = (UIImageView *)[cell viewWithTag:10];
             imgVw.image = image;
         }
     }];




    return cell;
}

Answer 1

出于内存管理目的，UITableView 重用其单元格 UITableViewCell *cell = [tableView dequeueReusableCellWithIdentifier:@"DefaultCell"]; 并在向上或向下滚动时加载单元格内容。如果您不将数据提取到单元格的元素中，那么当您滚动回该单元格时，您将获得上次使用该单元格时提取的最后一个值。

就您而言:

// Pass along the URL to the image (or change it if you are loading there locally)
    [AsyncImagesDownloading processImageDataWithURLString:[NSString stringWithFormat: @"http://192.95.48.72/bedspace/new_arrivals_img/%@",searchobjectval.idVal ] andBlock:^(NSData *imageData)
     {
         if (self.view.window)
         {
             UIImage *image = [UIImage imageWithData:imageData];
             UIImageView *imgVw = (UIImageView *)[cell viewWithTag:10];
             imgVw.image = image;
         }
     }];

因此，当 !self.view.window 时，您将获得最后一次使用单元格的图像(if 子句返回 TRUE)，并且它会在滚动时发生变化。您需要做的是:

// Pass along the URL to the image (or change it if you are loading there locally)
    [AsyncImagesDownloading processImageDataWithURLString:[NSString stringWithFormat: @"http://192.95.48.72/bedspace/new_arrivals_img/%@",searchobjectval.idVal ] andBlock:^(NSData *imageData)
     {
         if (self.view.window)
         {
             UIImage *image = [UIImage imageWithData:imageData];
             UIImageView *imgVw = (UIImageView *)[cell viewWithTag:10];
             imgVw.image = image;

         } else {

             UIImage *image = [UIImage imageNamed:@"placeHolder.png"];
             UIImageView *imgVw = (UIImageView *)[cell viewWithTag:10];
             imgVw.image = image;

        }

     }];

希望这是明确有用的:)