Ios 阵列中的第一个图像未显示在collectionview单元格中

第一个图像未加载，如果我滚动显示collectionview图像，并且我使用了collectionview的autolayout，我认为您应该尝试异步下载图像，而不是同步，类似这样

- (UICollectionViewCell *)collectionView:(UICollectionView *)collectionView cellForItemAtIndexPath:(NSIndexPath *)indexPath { 
 cell =[self.imgCllvw dequeueReusableCellWithReuseIdentifier:@"Cell" forIndexPath:indexPath];
        if(!cell)
        {
            cell = [collectionView dequeueReusableCellWithReuseIdentifier:@"Cell" forIndexPath:indexPath];
        }
        NSDictionary *tmpDict = [images objectAtIndex:indexPath.row];

        NSURL *url = [NSURL URLWithString:[tmpDict objectForKey:@"img"]];
        dispatch_async(dispatch_get_global_queue(DISPATCH_QUEUE_PRIORITY_DEFAULT,0), ^{
        NSData *data = [NSData dataWithContentsOfURL:url];
        UIImage *imge= [[UIImage alloc]initWithData:data];
              dispatch_async(dispatch_get_main_queue(), ^{
        cell.imageView.image = imge;
              });
        });
        cell.layer.borderWidth=1.0f;
        cell.layer.borderColor=[UIColor colorWithRed:215.0/255.0 green:214.0/255.0 blue:214.0/255.0 alpha:1.0].CGColor;

                return cell;
}

---

您可以使用dispatch\u sync而不是dispatch\u async，如下所示

- (UICollectionViewCell *)collectionView:(UICollectionView *)collectionView cellForItemAtIndexPath:(NSIndexPath *)indexPath {
  cell =[self.imgCllvw dequeueReusableCellWithReuseIdentifier:@"Cell" forIndexPath:indexPath];
  if(!cell)
  {
    cell = [collectionView dequeueReusableCellWithReuseIdentifier:@"Cell" forIndexPath:indexPath];
  }
  NSDictionary *tmpDict = [images objectAtIndex:indexPath.row];

  NSURL *url = [NSURL URLWithString:[tmpDict objectForKey:@"img"]];
  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 *cell = (id)[collectionView cellForItemAtIndexPath:indexPath];
          if (cell)
            cell.imageView.image = image;
        });
      }
    }
  }];
  [task resume];
  cell.layer.borderWidth=1.0f;
  cell.layer.borderColor=[UIColor colorWithRed:215.0/255.0 green:214.0/255.0 blue:214.0/255.0 alpha:1.0].CGColor;

  return cell;
}

---

还有一件事，停止引用

UICollectionView

委托和数据源方法中的

行

。引用

indexPath.item

。但如果我加载更多图像，它会被洗牌，因为在集合单元格中会被重用。正在存储下载的图像数据吗？如果未将其存储在阵列/核心数据中，并在下载前检查图像数据是否存在，然后将其分配给cell image view else download

dispatch_sync(dispatch_get_main_queue(), ^{
    cell.imageView.image = imge;
          });