ios - UICollectionview Scrolling choppy when loading cells

Question

I have a gallery in my app utilizing a UICollectionView. The cells are approximately 70,70 size. I am using ALAssets from the ALAssetLibrary in the gallery which I have stored in a list.

I am using the usual pattern for populating the cells:

-(UICollectionViewCell*)collectionView:(UICollectionView *)collectionView cellForItemAtIndexPath:(NSIndexPath *)indexPath
{

  mycell = [collectionView dequeueReusableCellWithReuseIdentifier:cellIdentifier forIndexPath:indexPath];
  mycell.imageView.image = [[UIImage imageWithCGImage:[alassetList objectAtIndex:indexpath.row] thumbnail]];
  return mycell;
}

My gallery is scrolling choppy. I don't understand why this is. I've tried adding a NSCache to cache the thumbnail images (thinking maybe creating the images was expensive) but this did not help for the performance.

I would expect the UI to be as buttery as the stock app.

I am now suspecting it may be something in the UICollectionViewCell prepareForReuse that may be holding up the dequeueReusableCellWithReuseIdentifier method but using instruments I was not able to find this.

Any other thing that may be be causing this? Is there a "faster" way to prepare the UICollectionViewCell or to dequeue them in a faster fashion?

Answer 1

So anybody having scrolling issues should do this

add these 2 lines after your dequeue

cell.layer.shouldRasterize = YES;
cell.layer.rasterizationScale = [UIScreen mainScreen].scale;