我正在开发一个应用程序，该应用程序从后端API获取100个数据，我在collectionView中显示此数据，但是一次显示100个数据可能会很长而且很烦人，所以我想为了通过我的研究实现对UICollectionView的分页，我尝试实现一些代码行，但是当我向上滚动时，什么也看不到。没有UIActivityIndicator不显示任何内容。我已经连续搜索了三天，但没有任何积极的结果。我在下面粘贴了我的代码，希望有人能提供帮助。预先感谢
class MainVC: UIViewController {
@IBOutlet weak var collectionView: UICollectionView!
@IBAction func prepareForUnwind(segue: UIStoryboardSegue) {}
@IBOutlet weak var spinner: UIActivityIndicatorView!
var itemArray = OfflineFunctions.instance.getDataFromDB()
var flickrArray = ServiceProvider.instance.flickerPhotos // This returns 100 items
var offline: Bool = false
var isLoadMore: Bool = false
var isLastPageReached: Bool = false
var limit = 10
let totalEntries = ServiceProvider.instance.flickerPhotos.count // This returns 100 items
override func viewDidLoad() {
super.viewDidLoad()
collectionView.delegate = self
collectionView.dataSource = self
setupWithPhotos()
collectionView.isPagingEnabled = true
}
override func viewDidAppear(_ animated: Bool) {
super.viewDidAppear(animated)
collectionView.reloadData()
}
// Function that gets the items
func setupWithPhotos() -> Void {
spinner.isHidden = false
spinner.startAnimating()
ServiceProvider.instance.getPhotos {[weak self] (success, error) in
if success {
self?.collectionView.reloadData()
self?.spinner.isHidden = true
self?.spinner.stopAnimating()
self?.offline = false
}
if error != nil {
alert.addAction(UIAlertAction(title: "Ok", style: .cancel) { (action:UIAlertAction!) in
self?.spinner.isHidden = true
self?.spinner.stopAnimating()
self?.collectionView.reloadData()
self?.offline = true
})
self?.present(alert, animated: true)
}
}
}
@IBAction func reloadPressed(_ sender: Any) {
setupWithPhotos()
}
@IBAction func closePressed(_ sender: Any) {
performSegue(withIdentifier: UNWIND, sender: nil)
}
func scrollViewWillEndDragging(_ scrollView: UIScrollView, withVelocity velocity: CGPoint, targetContentOffset: UnsafeMutablePointer<CGPoint>) {
targetContentOffset.pointee = scrollView.contentOffset
var indexes = self.collectionView.indexPathsForVisibleItems
indexes.sort()
var index = indexes.first!
let cell = self.collectionView.cellForItem(at: index)!
let position = self.collectionView.contentOffset.y - cell.frame.origin.y
if position > cell.frame.size.height/2{
index.row = index.row+1
}
self.collectionView.scrollToItem(at: index, at: .left, animated: true )
}
}
extension MainVC: UICollectionViewDelegate, UICollectionViewDataSource, UICollectionViewDelegateFlowLayout {
func collectionView(_ collectionView: UICollectionView, cellForItemAt indexPath: IndexPath) -> UICollectionViewCell {
if let cell = collectionView.dequeueReusableCell(withReuseIdentifier: PHOTO_CELL, for: indexPath) as? MainCell {
cell.offline = offline
if !offline {
let flickerPhoto = ServiceProvider.instance.flickerPhotos[indexPath.row]
cell.configueCell(flickerPhotoModel: flickerPhoto, index: indexPath.item)
return cell
} else {
let flickerPhoto = itemArray[indexPath.row]
cell.configueOfflineCell(flickerPhotoModel: flickerPhoto, index: indexPath.item)
return cell
}
}
return MainCell()
}
func numberOfSections(in collectionView: UICollectionView) -> Int {
return 1
}
func collectionView(_ collectionView: UICollectionView, numberOfItemsInSection section: Int) -> Int {
if !offline {
return ServiceProvider.instance.flickerPhotos.count
} else {
return itemArray.count
}
}
func collectionView(_ collectionView: UICollectionView, layout collectionViewLayout: UICollectionViewLayout, sizeForItemAt indexPath: IndexPath) -> CGSize {
// setting cells based on screen size
var numOfColums : CGFloat = 2
if UIScreen.main.bounds.width > 320 {
numOfColums = 1
}
let spaceBtwCells : CGFloat = 10
let padding: CGFloat = 40
let cellDimension = ((collectionView.bounds.width - padding) - (numOfColums - 1) * spaceBtwCells) / numOfColums
return CGSize(width: cellDimension, height: cellDimension)
}
func collectionView(_ collectionView: UICollectionView, layout
collectionViewLayout: UICollectionViewLayout,
referenceSizeForFooterInSection section: Int) -> CGSize {
if flickrArray.count > 0 && isLastPageReached == false {
return CGSize(width:(collectionView.frame.size.width), height: 100.0)
}
return CGSize.zero
}
func collectionView(_ collectionView: UICollectionView, viewForSupplementaryElementOfKind kind: String, at indexPath: IndexPath) -> UICollectionReusableView {
if kind == UICollectionView.elementKindSectionFooter {
let vew = collectionView.dequeueReusableSupplementaryView(ofKind: UICollectionView.elementKindSectionFooter, withReuseIdentifier: "footer", for: indexPath)
let loading = UIActivityIndicatorView()
loading.style = .gray
loading.translatesAutoresizingMaskIntoConstraints = false
loading.tintColor = UIColor.gray
loading.tag = -123456
vew.addSubview(loading)
vew.addConstraint(NSLayoutConstraint(item: loading, attribute: .centerX, relatedBy: .equal, toItem: vew, attribute: .centerX, multiplier: 1, constant: 0))
vew.addConstraint(NSLayoutConstraint(item: loading, attribute: .centerY, relatedBy: .equal, toItem: vew, attribute: .centerY, multiplier: 1, constant: 0))
return vew
}
return UICollectionReusableView()
}
func collectionView(_ collectionView: UICollectionView, willDisplaySupplementaryView view: UICollectionReusableView, forElementKind elementKind: String, at indexPath: IndexPath) {
if elementKind == UICollectionView.elementKindSectionFooter {
if let loadingView = view.viewWithTag(-123456) as? UIActivityIndicatorView{
if flickrArray.count > 0 && isLastPageReached == false {
loadingView.startAnimating()
print("END REACH 1")
}
else {
self.isLoadMore = false
}
}
}
}
func collectionView(_ collectionView: UICollectionView, didEndDisplayingSupplementaryView view: UICollectionReusableView, forElementOfKind elementKind: String, at indexPath: IndexPath) {
if elementKind == UICollectionView.elementKindSectionFooter{
if let loadingView = view.viewWithTag(-123456) as? UIActivityIndicatorView{
loadingView.stopAnimating()
loadingView.removeFromSuperview()
self.isLoadMore = false
}
}
}
func collectionView(_ collectionView: UICollectionView, didSelectItemAt indexPath: IndexPath) {
if !offline {
let flickerPhoto = ServiceProvider.instance.flickerPhotos[indexPath.item]
ServiceProvider.instance.selectedPhoto = flickerPhoto
performSegue(withIdentifier: DETAIL_VC_SEGUE, sender:indexPath)
} else {
let offlineList = OfflineFunctions.instance.offlineItems?[indexPath.item]
OfflineFunctions.instance.selectedImage = offlineList
performSegue(withIdentifier: MAIN_TO_SAVED_DETAIL_VC_SEGUE, sender:indexPath)
}
NotificationCenter.default.post(name: NOTIFY_PHOTO_SELECTED, object: nil)
}
override func prepare(for segue: UIStoryboardSegue, sender: Any?) {
if (segue.identifier == SAVED_DETAIL_VC) {
let popUp = segue.destination as! SavedDetailVC
popUp.doneSaving = { [weak self] in
self?.collectionView.reloadData()
}
}
}
}
这是我的API获取https://www.flickr.com/services/api/explore/flickr.photos.getRecent的链接 根据要求可以添加更多代码