 private let mainCellReuseID = UICollectionViewCell.nameOfClass
 
 class BQMainViewController: UIViewController {
+    
+    var itemSize = CGSize.zero
     
     // MARK: - Properties
     fileprivate lazy var subControllers: [UIViewController] = {

extension BQMainViewController: UICollectionViewDelegateFlowLayout {
    
    func collectionView(_ collectionView: UICollectionView, layout collectionViewLayout: UICollectionViewLayout, sizeForItemAt indexPath: IndexPath) -> CGSize {
        return collectionView.size
    }
}

    }
    
    func hiddenNavigationBar(with notification: Notification) {
        DispatchQueue.main.async {
            if let hidden = notification.object as? Bool {
                if hidden {
                    self.itemSize = CGSize(width: self.collcetionView.width, height: self.collcetionView.height + kStatusAndNavigationHeight)
                } else {
                    self.itemSize = CGSize(width: self.collcetionView.width, height: self.collcetionView.height - kStatusAndNavigationHeight)
                }
                self.collcetionView.reloadData()
                self.itemSize = .zero
                self.navigationController?.setNavigationBarHidden(hidden, animated: false)
            }
        }
    }
}
