Question

所以我的collectionView出现问题。目前我的设置是有两个部分的设置。每个部分中的数据都是从某个数据库中提取出来的，然后是基于相应的部分。

以下是我的主要homeFeedController的代码

class HomeFeedController: UICollectionViewController, UICollectionViewDelegateFlowLayout {
    // let dropDownLauncher = DropDownLauncher()
    let dispatchGroup = DispatchGroup()
    var isFinishedPaging = false
    var userLocation: CLLocation?
    var allEvents = [Event]()
    var eventKeys = [String]()
    var featuredEvents = [Event]()
    private let cellID = "cellID"
    private let catergoryCellID = "catergoryCellID"
    var images: [String] = ["gear1","gear4","snakeman","gear4","gear1"]
        var images1: [String] = ["sage","sagemode","kyubi","Naruto_Part_III","team7"]
    var featuredEventsHeaderString = "Featured Events"
    var categories : [String] = ["Seize The Night","Seize The Day","21 & Up", "Friends Events"]

    override func viewDidLoad() {
        super.viewDidLoad()
//        navigationItem.title = "Featured Events"
        collectionView?.backgroundColor = .white
        collectionView?.showsVerticalScrollIndicator = false
        SVProgressHUD.dismiss()
        grabUserLoc()
        collectionView?.register(HomeFeedCell.self, forCellWithReuseIdentifier: cellID)
                collectionView?.register(CategoryCell.self, forCellWithReuseIdentifier: catergoryCellID)
       // reloadHomeFeed()
    }
    override func viewWillAppear(_ animated: Bool) {
        super.viewWillAppear(animated)

        self.navigationController?.setNavigationBarHidden(true, animated: false)
    }

    override func viewDidDisappear(_ animated: Bool) {
        super.viewDidDisappear(animated)
//        self.view.removeFromSuperview()
    }

    deinit {
        NotificationCenter.default.removeObserver(self)
        print("EventDetailViewController class removed from memory")
    }




    @objc func grabUserLoc(){

        LocationService.getUserLocation { (location) in
            guard let currentLocation = location else {
                return
            }
            PostService.showEvent(for: currentLocation, completion: { [unowned self](events) in
                self.allEvents = events
                print("Event count in PostService Closure:\(self.allEvents.count)")
                DispatchQueue.main.async {
                   // self.dynamoCollectionView.reloadData()
                    //self.dynamoCollectionViewTop.reloadData()
                }

            })

            PostService.showFeaturedEvent(for: currentLocation, completion: { [unowned self] (events) in

                self.featuredEvents = events
                print("Event count in Featured Events Closure is:\(self.featuredEvents.count)")
                DispatchQueue.main.async {
                    // self.dynamoCollectionView.reloadData()
                   // self.dynamoCollectionViewTop.reloadData()
                }
            }
            )
            print("Latitude: \(currentLocation.coordinate.latitude)")
            print("Longitude: \(currentLocation.coordinate.longitude)")
        }

    }

    override func collectionView(_ collectionView: UICollectionView, cellForItemAt indexPath: IndexPath) -> UICollectionViewCell {

        if indexPath.section == 0 {
            let cell = collectionView.dequeueReusableCell(withReuseIdentifier: cellID, for: indexPath) as! HomeFeedCell
            cell.sectionNameLabel.text = "Featured Events"
            cell.featuredEvents = featuredEvents
            return cell
        }

        let cell = collectionView.dequeueReusableCell(withReuseIdentifier: catergoryCellID, for: indexPath) as! CategoryCell
        cell.sectionNameLabel.text = categories[indexPath.item]
        print(categories[indexPath.item])
        print(indexPath.item)
        cell.categoryEvents = allEvents
        return cell

    }

    override func numberOfSections(in collectionView: UICollectionView) -> Int {
        return 2
    }

    override func collectionView(_ collectionView: UICollectionView, numberOfItemsInSection section: Int) -> Int {
        if section == 1{
            return 4
        }
        return 1
    }

    func collectionView(_ collectionView: UICollectionView, layout collectionViewLayout: UICollectionViewLayout, sizeForItemAt indexPath: IndexPath) -> CGSize {

        if indexPath.section == 0 {
             return CGSize(width: view.frame.width, height: 300)
        }
        return CGSize(width: view.frame.width, height: 290)

    }

    func collectionView(_ collectionView: UICollectionView, layout collectionViewLayout: UICollectionViewLayout, insetForSectionAt section: Int) -> UIEdgeInsets {
        if section == 0 {
            return UIEdgeInsets(top: 5, left: 0, bottom: 10, right: 0)
        }
        return UIEdgeInsets(top: 0, left: 8, bottom: 0, right: 8)
    }

在此家庭饲料控制器中创建的单元格在每个单元格中都有collectionViews，它们创建了某种可滚动的网格布局。此外，每个单元格都传递一个事件，该事件包含渲染其大部分单元格所需的信息。我单元格的基本布局如下。

import UIKit

class CategoryCell: UICollectionViewCell, UICollectionViewDataSource, UICollectionViewDelegate, UICollectionViewDelegateFlowLayout {
    private let cellID = "cellID"
    var categoryEvents: [Event]?{
        didSet{
            categoryCollectionView.reloadData()
        }
    }
    var titles: String? {
        didSet {
            guard let titles = titles else {
                return
            }
             sectionNameLabel.text = titles
        }
    }


    let sectionNameLabel : UILabel =  {
        let sectionNameLabel = UILabel()
        sectionNameLabel.font = UIFont(name:"HelveticaNeue-Bold", size: 16.0)
        return sectionNameLabel
    }()

    let categoryCollectionView: UICollectionView = {
        let layout = UICollectionViewFlowLayout()
        layout.scrollDirection = .horizontal
        let cv = UICollectionView(frame: .zero, collectionViewLayout: layout)
        cv.backgroundColor = .clear
        return cv
    }()

    func collectionView(_ collectionView: UICollectionView, numberOfItemsInSection section: Int) -> Int {
        guard let currentEventCount = categoryEvents?.count else{
            return 0
        }
        return currentEventCount
    }

    func collectionView(_ collectionView: UICollectionView, cellForItemAt indexPath: IndexPath) -> UICollectionViewCell {
        let cell = collectionView.dequeueReusableCell(withReuseIdentifier: cellID, for: indexPath) as! CategoryEventCell
        cell.event = categoryEvents?[indexPath.item]
        return cell
    }

    func collectionView(_ collectionView: UICollectionView, layout collectionViewLayout: UICollectionViewLayout, sizeForItemAt indexPath: IndexPath) -> CGSize {
        return CGSize(width: 200, height: frame.height - 30)
    }

    func collectionView(_ collectionView: UICollectionView, layout collectionViewLayout: UICollectionViewLayout, insetForSectionAt section: Int) -> UIEdgeInsets {
        return UIEdgeInsets(top: 0, left: 14, bottom: 0, right: 14)
    }

    override init(frame: CGRect) {
        super.init(frame: frame)
        setupViews()
    }

    required init?(coder aDecoder: NSCoder) {
        fatalError("init(coder:) has not been implemented")
    }


    @objc func setupViews(){
        backgroundColor = .clear
        addSubview(categoryCollectionView)
        addSubview(sectionNameLabel)
        sectionNameLabel.anchor(top: topAnchor, left: leftAnchor, bottom: nil, right: nil, paddingTop: 0, paddingLeft: 14, paddingBottom: 0, paddingRight: 0, width: 0, height: 0)
                categoryCollectionView.anchor(top: sectionNameLabel.bottomAnchor, left: leftAnchor, bottom: bottomAnchor, right: rightAnchor, paddingTop: 0, paddingLeft: 0, paddingBottom: 0, paddingRight: 0, width: 0, height: 0)
                categoryCollectionView.delegate = self
                categoryCollectionView.dataSource = self
                categoryCollectionView.showsHorizontalScrollIndicator = false
        categoryCollectionView.register(CategoryEventCell.self, forCellWithReuseIdentifier: cellID)

    }
}

这个包含collectionView的单元格最终会将一个特定事件传递给一个单元格，最终会获取渲染自身所需的内容。代码如下。

import UIKit
import Firebase
import FirebaseDatabase

class CategoryEventCell: BaseRoundedCardCell {

    var event: Event? {
    didSet{
        guard let currentEvent = event else {
            return
        }
        guard let url = URL(string: currentEvent.currentEventImage) else { return }
        backgroundImageView.af_setImage(withURL: url)
        eventNameLabel.text = currentEvent.currentEventName.capitalized
    }
    }

    public var backgroundImageView: CustomImageView = {
        let firstImage = CustomImageView()
        firstImage.clipsToBounds = true
        firstImage.translatesAutoresizingMaskIntoConstraints = false
        firstImage.contentMode = .scaleToFill
        firstImage.layer.cornerRadius = 15
        return firstImage
    }()

    let eventNameLabel : UILabel =  {
        let sectionNameLabel = UILabel()
        sectionNameLabel.font = UIFont(name:"HelveticaNeue-Bold", size: 14.0)
        return sectionNameLabel
    }()


    override init(frame: CGRect) {
        super.init(frame: frame)

        setupViews()
    }

    @objc func setupViews(){
        backgroundColor = .clear
       // setCellShadow()
        addSubview(backgroundImageView)
        addSubview(eventNameLabel)
        backgroundImageView.setContentCompressionResistancePriority(UILayoutPriority(600), for: .vertical)
        backgroundImageView.anchor(top: topAnchor, left: leftAnchor, bottom: eventNameLabel.topAnchor, right: rightAnchor, paddingTop: 0, paddingLeft: 0, paddingBottom: 0, paddingRight: 0, width: 0, height: 0)
        eventNameLabel.anchor(top: backgroundImageView.bottomAnchor, left: leftAnchor, bottom: bottomAnchor, right: nil, paddingTop: 0, paddingLeft: 0, paddingBottom: 0, paddingRight: 0, width: 0, height: 0)

    }

    required init?(coder aDecoder: NSCoder) {
        fatalError("init(coder:) has not been implemented")
    }

}

问题似乎是在应用程序启动时出于某种原因加载内容而没有内容加载。但是一旦滚动，一切都开始加载。除此之外，还有一个部分甚至在其余内容完成时甚至根本不加载任何内容。当我进入屏幕而不是滚动时，我希望所有单元格都加载其内容。如果这是一个新手的错误，我道歉，但这不是我想要的方式。也有一次UI实际上被锁定了。我目前的UI看起来像这样。任何帮助表示赞赏。这困扰了我好几个小时

我理解当一个单元格在视图中时，collectionView会加载，问题是它们都没有加载，直到我向下或向上滚动任何方向。

Answer 1

UICollectionView可以在索引路径上安装一个单元格，只有当它在显示内时才会存在。如果单元格不在可见集合视图中。将要求单元格重用于另一个索引。因此，当您使用每个单元格获取数据时...在cellForRowAtIndexPath所有单元格都不会创建，只会创建可见单元格。

您可以优先考虑收藏视图预取功能，以便在数据出现之前加载数据。

您可以参考预取UICollectionView

的更多详细信息

https://www.captechconsulting.com/blogs/uicollectionview-prefetching-in-ios-10

在我滚动之前CollectionView未加载？

1 个答案: