title: UICollectionView cellForItemAt not called after InsertItems(at:) - How to preload next cell?
body: <p>I'm working on a horizontal UICollectionView with full screen cells.</p>
  
  <p>Cells have WKWebview inside, which loads next cell's url. </p>
  
  <p>When the next url loaded, the new cell is inserted. </p>
  
  <pre><code>extension ViewController {
      func collectionView(_ collectionView: UICollectionView, cellForItemAt indexPath: IndexPath) -&gt; UICollectionViewCell {
          guard let cell = collectionView.dequeueReusableCell(withReuseIdentifier: WebCell.reuseId, for: indexPath) as? WebCell else { fatalError("Unexpected indexPath") } 
  
          cell.configure()
          cell.startLoadingURL(urls[indexPath.item])
  
          return cell
      }
  }
  </code></pre>
  
  <pre><code>extension ViewController: WebCellDelegate {
      func onNextURLLoaded(_ sender: WebCell, nextUrl: URL) {
          ...
          urls.append(nextUrl)
          horizontalCollectionView.performBatchUpdates({
              horizontalCollectionView.insertItems(at: [IndexPath(item: urls.count-1, section: 0)])
          }, completion: nil)
  
      }
  }
  </code></pre>
  
  <p>What I want to do is - rendering next cell in advance.</p>
  
  <p>The problem is - cellForItemAt method is not called after insertItems(at:).</p>
  
  <p>But when I reduce cells' sizes so that next cell being visible, then cellForItemAt method is called and renders the next cell.</p>
  
  <p>I want to preload next cell without reducing cell's size.
  Is there any solutions?</p>