如何删除两个单元格之间的空间UiCollectionView?最小间距不起作用.

- (CGSize)collectionView:(UICollectionView *)collectionView layout:(UICollectionViewLayout*)collectionViewLayout sizeForItemAtIndexPath:(NSIndexPath *)indexPath
{
if (collectionView.tag==101)
{
return CGSizeMake((_collView.frame.size.width),(_collView.frame.size.height));
}
else
{
return CGSizeMake((_collView2.frame.size.width/3)-20,300);
}
}
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但这不起作用.