带有UIRefreshControl reloadData（）的水平方向UICollectionView不起作用

Question

I need to implement horizontal UICollectionView . Sometimes, I need to update the data, So I decided to implement a refreshcontrol .

I called reloadData() with refreshcontrol . It seems to be working, but cellForItemAt is not called the correct time. So, when the cell count has changed it will be crashed.

class ViewController: UIViewController, UICollectionViewDelegate {


    @IBOutlet weak var collectionView: UICollectionView!

    private let refreshControl = UIRefreshControl()
    private var cellCount = 1

    override func viewDidLoad() {
        super.viewDidLoad()

        collectionView.delegate = self
        collectionView.dataSource = self

        collectionView.refreshControl = refreshControl
        refreshControl.addTarget(self, action: #selector(refresh(sender:)), for: .valueChanged)

        collectionView.register(UINib(nibName: "TopCollectionViewCell", bundle: nil), forCellWithReuseIdentifier: "Cell")

        if let layout = collectionView.collectionViewLayout as? UICollectionViewFlowLayout {
            layout.scrollDirection = .horizontal // not working
//            layout.scrollDirection = .vertical //working
        }
    }

    @objc func refresh(sender: UIRefreshControl) {
        cellCount = cellCount + 1
        collectionView.reloadData()
        sender.endRefreshing()
    }
}

extension ViewController: UICollectionViewDataSource {
    func collectionView(_ collectionView: UICollectionView, numberOfItemsInSection section: Int) -> Int {
        return cellCount
    }

    func collectionView(_ collectionView: UICollectionView, cellForItemAt indexPath: IndexPath) -> UICollectionViewCell {
        let cell: TopCollectionViewCell = collectionView.dequeueReusableCell(withReuseIdentifier: "Cell", for: indexPath) as! TopCollectionViewCell

        return cell
    }
}

If the direction change to vertical, it is working. Is it correct behavior? or just a bug?

Answer 1

在viewDidLoad() alwaysBounceVertical collectionView的alwaysBounceVertical属性设置为true ，即

collectionView.alwaysBounceVertical = true