从 URL 加载 UITableViewCell 的图像(需要异步加载它们) [英] Loading images for UITableViewCell from URL (need to load them asynchronously)

问题描述

我有一个自定义类，它通过 XML 解析并获取图像的 URL 字符串(我存储在数组中).然后我想检索这些字符串以加载图像并在 UITableViewCell 中显示每个字符串.这是我的代码:

I have a custom class that parses through an XML and gets URL strings for images (which I store in an array). Then I want to retrieve those strings to load images and display each in a UITableViewCell. Here is my code:

- (UITableViewCell *)tableView:(UITableView *)tableView cellForRowAtIndexPath:(NSIndexPath *)indexPath
{
    static NSString *CellIdentifier = @"Cell";
    UITableViewCell *cell = [tableView dequeueReusableCellWithIdentifier:CellIdentifier forIndexPath:indexPath];

    UILabel *labelText = (UILabel *)[cell viewWithTag:1000];
    labelText.text = [[self.listOfPlaceDetails objectAtIndex:indexPath.row] objectForKey:@"name"];

    NSURL *imageURL = [NSURL URLWithString:[[self.listOfPlaceDetails objectAtIndex:indexPath.row]objectForKey:@"imageCell"]];
    NSData *imageData = [NSData dataWithContentsOfURL:imageURL];
    UIImage *image = [UIImage imageWithData:imageData];
    cell.imageView.image = image;

    return cell;
}

显然，当我向下滚动表格时，应用会加载更多图像，而在加载图像时，用户将无能为力.看起来应用程序冻结了.我要加载的图像不是很大(大约 8kb).也许有一种方法可以在后台加载和存储它们?我还想给用户更多的自由，比如向下滚动和查看带有文本但没有图像的单元格.然后强制应用加载用户当前正在查看的单元格的图像.

Obviously, when I scroll down the table, the app loads more images, and when the images are loading, the user can't do anything. It looks like the app froze. The images I want to load are not very large (about 8kb). Maybe there is a way I could load and store them in the background? I also want to give more freedom to the user, like scrolling down and viewing cells with text but without an image. Then force the app to load the images for the cells the user is currently viewing.

有什么方法可以修改我的代码或任何其他解决方案，以便从 URL 字符串正确加载图像?

Is there any way to modify my code or any other solution for proper loading of images from URL strings?

任何建议将不胜感激，谢谢.

Any advice would be appreciated, thanks.

推荐答案

用于异步加载 imageview 的方式

Use this for asynchronus way of loading imageview

  - (UITableViewCell *)tableView:(UITableView *)_tableView cellForRowAtIndexPath:(NSIndexPath *)indexPath
{
static NSString *CellIdentifier = @"Cell";
UITableViewCell *cell = [tableView dequeueReusableCellWithIdentifier:CellIdentifier forIndexPath:indexPath];

 UILabel *labelText = (UILabel *)[cell viewWithTag:1000];
 labelText.text = [[self.listOfPlaceDetails objectAtIndex:indexPath.row] objectForKey:@"name"];


   //get a dispatch queue
   dispatch_queue_t concurrentQueue = dispatch_get_global_queue(DISPATCH_QUEUE_PRIORITY_DEFAULT, 0);
//this will start the image loading in bg
dispatch_async(concurrentQueue, ^{
        NSURL *imageURL = [NSURL URLWithString:[[self.listOfPlaceDetails objectAtIndex:indexPath.row]objectForKey:@"imageCell"]];

    NSData *image = [[NSData alloc] initWithContentsOfURL:imageURL];

    //this will set the image when loading is finished
    dispatch_async(dispatch_get_main_queue(), ^{
       cell.imageView.image = [UIImage imageWithData:image];
    });
      });

   return cell;
   }

这篇关于从 URL 加载 UITableViewCell 的图像(需要异步加载它们)的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持IT屋！