ios - UICollectionview 的无限滚动

Question

我试图在我的应用程序中无限滚动，我正在从 API 调用数据，至少它在某种程度上有效，但是当我在 Collection View 中滚动时，它开始在下方填充并剪切上面的那些，所以我无法向上滚动到它们，然后在填充它之后只是跳过并超出范围，这里有一些代码请帮忙。

var fetchMore = false
var pageNumber = 0

var productPageString: String {
    if pageNumber == 0 {
        return "pageNumber=0&"
    } else {
        return "pageNumber=\(pageNumber)&"
    }
}

func fetchProducts() {
    fetchMore = false
    let validatedTextString = UserDefaults.standard.object(forKey: "productsSearchValue")
    let searchText = validatedTextString!
    let urlString = APIConstants.baseurl + APIConstants.products + "?searchString=\(searchText)&\(productPageString)itemsPerPage=20"
    guard let url = URL(string: urlString) else { return }
    URLSession.shared.dataTask(with: url) { (data, response, error) in
        if error != nil {
            print(error!)
            return
        }
        do {
            let jsonData = try JSONDecoder().decode(ProductSearch.self, from: data!)

            self.productSearchResults = [Products]()

            for dictionary in jsonData.data {
                let product = Products(productId: dictionary.productId, categoryId: dictionary.categoryId, storeId: dictionary.storeId, name: dictionary.name, description: dictionary.description, imageUrl: dictionary.imageUrl, price: dictionary.price)
                self.productSearchResults?.append(product)
                self.fetchMore = true
            }

        } catch let jsonError {
            print(jsonError)
        }
        }.resume()
}

override func scrollViewDidScroll(_ scrollView: UIScrollView) {
    let offsetY = scrollView.contentOffset.y
    let contentHeight = scrollView.contentSize.height

    if offsetY > contentHeight - scrollView.frame.height {
        if fetchMore {
            fetchProducts()
            pageNumber += 1
        }
    }
}

它最初显示每页 20 个项目，但随着页码的增加，它会不断填充该特定页面中的其他内容，但我仍然只能查看每页 20 个项目。我希望能够向上滚动到之前的内容，而且，为什么它最终会自动将我带到最后？谢谢

Answer 1

你需要重新加载

 for dictionary in jsonData.data {
    let product = Products(productId: dictionary.productId, categoryId: dictionary.categoryId, storeId: dictionary.storeId, name: dictionary.name, description: dictionary.description, imageUrl: dictionary.imageUrl, price: dictionary.price)
    self.productSearchResults?.append(product)
 }

 self.fetchMore = true

 DispatchQueue.main.async {
   self.collectionView.reloadData()
 }