ios - Horizontal scrolling collection view shifts up when scrolled in parent container

Question

I have created a horizontal scrolling collection view within a parent UIView, which I add in my UIViewController. But the scrolling view shifts up when I scroll on it.

This is how the container view is initialized:

 override init(frame: CGRect){
        let layout = UICollectionViewFlowLayout()
        layout.scrollDirection = .horizontal
        layout.itemSize = UICollectionViewFlowLayoutAutomaticSize
        layout.estimatedItemSize = CGSize(width: 100, height: 50)
        
        countryCollectionView = UICollectionView(frame: CGRect.zero, collectionViewLayout: layout)
        
        viewTitleLabel = UILabel()
        super.init(frame: frame)
        setupTableView()
        sortedDummyData = dummyData.sorted(by: <)
    }

Constraints on my child views:

 NSLayoutConstraint.activate([
            viewTitleLabel.leadingAnchor.constraint(equalTo: self.leadingAnchor, constant: 5),
            viewTitleLabel.centerYAnchor.constraint(equalTo: self.centerYAnchor),
            viewTitleLabel.heightAnchor.constraint(equalToConstant: 30),
            viewTitleLabel.widthAnchor.constraint(equalToConstant: 90),
            
            countryCollectionView.leadingAnchor.constraint(equalTo: viewTitleLabel.trailingAnchor, constant: 10),
            countryCollectionView.centerYAnchor.constraint(equalTo: self.centerYAnchor),
            countryCollectionView.trailingAnchor.constraint(equalTo: self.trailingAnchor, constant: -10),
            countryCollectionView.heightAnchor.constraint(equalToConstant: 50)
            
 ])

Constraints on container view when adding to UIViewContoller:

 countryCountView.translatesAutoresizingMaskIntoConstraints = false
 countryCountView.isUserInteractionEnabled = true
 view.addSubview(countryCountView)
        
 NSLayoutConstraint.activate([
      countryCountView.leadingAnchor.constraint(equalTo: view.leadingAnchor, constant: 0),
      countryCountView.trailingAnchor.constraint(equalTo: view.trailingAnchor),
      countryCountView.topAnchor.constraint(equalTo: headerContainer.bottomAnchor),
      countryCountView.heightAnchor.constraint(equalToConstant: 60)
 ])

My UICollectionViewCell:

override init(frame: CGRect) {
        countryNameLabel = UILabel()
        countryUserCountLabel = UILabel()
        super.init(frame: frame)

        contentView.addSubview(countryNameLabel)
        countryNameLabel.translatesAutoresizingMaskIntoConstraints = false
        countryNameLabel.font = UIFont.boldSystemFont(ofSize: 13)
        countryNameLabel.textColor = .white
        
        contentView.addSubview(countryUserCountLabel)
        countryUserCountLabel.translatesAutoresizingMaskIntoConstraints = false
        countryUserCountLabel.font = UIFont.systemFont(ofSize: 13)
        countryUserCountLabel.textColor = .white
        
        NSLayoutConstraint.activate([
            countryNameLabel.leadingAnchor.constraint(equalTo: self.leadingAnchor, constant: 5),
            countryNameLabel.heightAnchor.constraint(equalToConstant: 30),
            countryNameLabel.topAnchor.constraint(equalTo: self.topAnchor, constant: 5),
            countryNameLabel.bottomAnchor.constraint(equalTo: self.bottomAnchor, constant: -5),
//            countryNameLabel.widthAnchor.constraint(greaterThanOrEqualToConstant: 0),
//            countryNameLabel.widthAnchor.constraint(equalToConstant: 20),

            countryUserCountLabel.leadingAnchor.constraint(equalTo: countryNameLabel.trailingAnchor, constant: 5),
            countryUserCountLabel.topAnchor.constraint(equalTo: self.topAnchor, constant: 5),
            countryUserCountLabel.bottomAnchor.constraint(equalTo: self.bottomAnchor, constant: -5),
            countryUserCountLabel.trailingAnchor.constraint(equalTo: self.trailingAnchor, constant: -5),
            countryUserCountLabel.heightAnchor.constraint(equalToConstant: 30),
//            countryUserCountLabel.widthAnchor.constraint(equalToConstant: 40)
        ])
    }

Height returned by delegate method:

    func collectionView(_ collectionView: UICollectionView, layout collectionViewLayout: UICollectionViewLayout, sizeForItemAt indexPath: IndexPath) -> CGSize {
        return CGSize(width: 70, height: 40)
//        return CGSize.zero
    }

Before scrolling:

After scrolling:

Edit:

Setting collectionView.showsHorizontalScrollIndicator = false does not help.

Also setting layout.estimatedItemSize = CGSize.zero fixes the shifting up but stops the cells from resizing correctly.

Answer 1

Is it possible that a Scroll Indicator is present but you cant see it? Try this. collectionView.showsHorizontalScrollIndicator = false

If it doesn't work check view your hierarchy after it's moved up.