ios - 以编程方式在 collectionView swift 中无限滚动

Question

我想以编程方式无限滚动 collectionView 中的 10 张图像。根据我的选择，图像来自 json 的网络。我一次无法滚动 20 张图片。这是我的代码

import Foundation


import UIKit

let categoryCellid = "categoryCellid"


class ProductByCategoryCollectionView: UICollectionViewController, UICollectionViewDelegateFlowLayout {

    var headercellId = "headercellId"


    var callCategoryObject = [Product]()


    func getPropductListByCategory(){

        // has api code, that was well
    }




    override func viewDidLoad() {
        super.viewDidLoad()



        self.getPropductListByCategory()


        collectionView?.backgroundColor = .white

        navigationItem.title = "Product"
        navigationItem.backBarButtonItem = UIBarButtonItem(title: "Back", style: .plain, target: nil, action: nil)
        navigationItem.rightBarButtonItem = UIBarButtonItem(title: "Sort By", style: .plain, target: nil, action: nil)



        self.setupHeaderView()

        collectionView?.register(ProductByCategoryCollectionViewCell.self, forCellWithReuseIdentifier: categoryCellid)
    }



    func showCategoryDetailSegue() {

        let detailcontroller = UIViewController()
        navigationController?.pushViewController(detailcontroller, animated: true)
    }



    func sortBtnTarget() {

    }



    func filterBtnTarget() {

    }

    let dividedLine: UIView = {
        let view = UIView()

        view.backgroundColor = UIColor(white: 0.4, alpha: 0.4)
        return view

    }()

    let totalItemLabel: UILabel = {
        let label = UILabel()

        label.text = ""
        label.textAlignment = .center
        label.font = UIFont.systemFont(ofSize: 15)
        label.backgroundColor = UIColor.white

        return label
    }()



    let dividerLineView: UIView = {
        let view = UIView()
        view.backgroundColor = UIColor.white

        return view
    }()



    func setupHeaderView(){


        view.backgroundColor = UIColor(white: 0.4, alpha: 0.4)


        dividedLine.frame = CGRect(x: 0, y: 95, width: view.frame.width, height: 1)
        totalItemLabel.frame = CGRect(x: 0, y: 55, width: view.frame.width, height: 40)

        view.addSubview(totalItemLabel)

        view.addSubview(dividedLine)





    }



    override func collectionView(_ collectionView: UICollectionView, numberOfItemsInSection section: Int) -> Int {


        return callCategoryObject.count
    }

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


        let cell = collectionView.dequeueReusableCell(withReuseIdentifier: categoryCellid, for: indexPath) as! ProductByCategoryCollectionViewCell
        cell.callProductObject4Cell = callCategoryObject[indexPath.item]



        return cell
    }

    func collectionView(_ collectionView: UICollectionView, layout collectionViewLayout: UICollectionViewLayout, sizeForItemAt indexPath: IndexPath) -> CGSize {
        return CGSize(width: 172, height: 300)
    }

    func collectionView(_ collectionView: UICollectionView, layout collectionViewLayout: UICollectionViewLayout, insetForSectionAt section: Int) -> UIEdgeInsets {
        return UIEdgeInsetsMake(32, 10, 0, 10)
    }

    func collectionView(_ collectionView: UICollectionView, layout collectionViewLayout: UICollectionViewLayout, minimumInteritemSpacingForSectionAt section: Int) -> CGFloat {
        return 0
    }

    override func collectionView(_ collectionView: UICollectionView, didSelectItemAt indexPath: IndexPath) {


        let layout = UICollectionViewFlowLayout()
        layout.scrollDirection = .horizontal
        let controller1 = DetailsController(collectionViewLayout: layout)
        navigationController?.pushViewController(controller1, animated: true)

    }

}

class ProductByCategoryCollectionViewCell: UICollectionViewCell {

    var callProductObject4Cell: Product? {
        didSet {
            productLabel.text = callProductObject4Cell?.name

            // priceLabel.text = String(describing: callProductObject4Cell?.price)

            if let price = callProductObject4Cell?.price {
                priceLabel.text = "$\(price)"
            } else {
                priceLabel.text = ""
            }




            if let profileImageUrl = callProductObject4Cell?.image {
                productImage.loadImageUsingUrlString(profileImageUrl)
            }


        }
    }

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

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

    let productImage: UIImageView = {
        let image = UIImageView()

        image.image = UIImage(named: "default")
        image.contentMode = .scaleAspectFit
        image.layer.borderWidth = 1
        image.layer.borderColor = UIColor.orange.cgColor
        image.layer.masksToBounds = true
        return image
    }()

    let productLabel: UILabel = {
        let label = UILabel()
        label.text = "productName"
        label.textColor = .black
        label.numberOfLines = 0
        label.font = UIFont.boldSystemFont(ofSize: 10)

        return label
    }()

    let priceLabel: UILabel = {
        let label = UILabel()
        //        label.backgroundColor = .lightGray
        label.text = ""
        label.textColor = .orange
        label.font = UIFont.systemFont(ofSize: 13)

        return label
    }()

    func setupcategoryCell() {

        addSubview(productImage)
        addSubview(productLabel)
        addSubview(priceLabel)

        addConstraintsWithFormat("H:|[v0]|", views: productImage)
        addConstraintsWithFormat("V:|[v0(230)]-2-[v1][v2(10)]-5-|", views: productImage,productLabel, priceLabel)

        addConstraintsWithFormat("H:|[v0]|", views: productLabel)

        addConstraintsWithFormat("H:|[v0]|", views: priceLabel)
    }
}

Answer 1

将此代码用于无限 UIScrollView:

import Foundation
import UIKit

enum LoadMoreStatus {
    case loading
    case finished
    case haveMore
}

class ViewController: UICollectionViewController, UICollectionViewDelegateFlowLayout {

    var verticalDataSource = [String]()

    var firstCellid = "firstcellid"
    var firstFooterCellid = "firstfootercellid"
    var numberOfCells = 5
    var loadingStatus = LoadMoreStatus.haveMore

    func reloadData() {
        //numberOfCells = 10
        collectionView?.reloadData()
        if numberOfCells > 0 {
            collectionView?.scrollToItem(at: IndexPath(row: 0, section: 0), at: .left, animated: true)
        }
    }

    func loadMore() {
        if numberOfCells >= 40 { 
            // here will show untill finished number
            loadingStatus = .finished
            collectionView?.reloadData()
            return
        }

        // Replace code with web service and append to data source
        Timer.schedule(delay: 2) { timer in
            self.numberOfCells += 2
            self.collectionView?.reloadData()
        }
    }

    override func viewDidLoad() {
        super.viewDidLoad()

        self.automaticallyAdjustsScrollViewInsets = false

        collectionView?.register(VerticalCollectionViewCell.self, forCellWithReuseIdentifier: firstCellid)
        collectionView?.register(VerticalCollectionViewCell2.self, forSupplementaryViewOfKind: UICollectionElementKindSectionFooter, withReuseIdentifier: firstFooterCellid)
    }

    override func didReceiveMemoryWarning() {
        super.didReceiveMemoryWarning()
        // Dispose of any resources that can be recreated.
    }

    //MARK - Rotation methods

    override func didRotate(from fromInterfaceOrientation: UIInterfaceOrientation) {
        var text=""

        switch UIDevice.current.orientation {
        case .portrait:
            text="Portrait"
        case .portraitUpsideDown:
            text="PortraitUpsideDown"
        case .landscapeLeft:
            text="LandscapeLeft"
        case .landscapeRight:
            text="LandscapeRight"
        default:
            text="Another"
        }

        NSLog("You have moved: \(text)")

        collectionView?.reloadData()
    }

    override func collectionView(_ collectionView: UICollectionView, numberOfItemsInSection section: Int) -> Int {
        return numberOfCells
    }

    // The cell that is returned must be retrieved from a call to -dequeueReusableCellWithReuseIdentifier:forIndexPath:
    override func collectionView(_ collectionView: UICollectionView, cellForItemAt indexPath: IndexPath) -> UICollectionViewCell {

        if(indexPath.row==numberOfCells-1) {
            if loadingStatus == .haveMore {
                self.perform(#selector(ViewController.loadMore), with: nil, afterDelay: 0)
            }
        }       

        let cell = collectionView.dequeueReusableCell(withReuseIdentifier: firstCellid, for: indexPath) as! VerticalCollectionViewCell
        cell.menuHeaderLabel.text = "Labet text no \(indexPath.item)"
        return cell

    }

    func collectionView(_ collectionView: UICollectionView, layout collectionViewLayout: UICollectionViewLayout, sizeForItemAt indexPath: IndexPath) -> CGSize {
        return CGSize(width: self.view.frame.width, height: 100)
    }

    override func collectionView(_ collectionView: UICollectionView, viewForSupplementaryElementOfKind kind: String, at indexPath: IndexPath) -> UICollectionReusableView {
        var footerView:VerticalCollectionViewCell2!

        if (kind ==  UICollectionElementKindSectionFooter) && (loadingStatus != .finished) {
            footerView = collectionView.dequeueReusableSupplementaryView(ofKind: kind, withReuseIdentifier: firstFooterCellid, for: indexPath) as! VerticalCollectionViewCell2
        }

        return footerView
    }

    func collectionView(_ collectionView: UICollectionView, layout collectionViewLayout: UICollectionViewLayout, referenceSizeForFooterInSection section: Int) -> CGSize {
        return (loadingStatus == .finished) ? CGSize.zero : CGSize(width: self.view.frame.width, height: 50)
    }        
}

class VerticalCollectionViewCell: UICollectionViewCell {

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

        setupCell()
    }

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

    let menuHeaderLabel: UILabel = {
        let label = UILabel()
        label.text = "lable text"
        label.textColor = .orange
        label.textAlignment = .center
        label.font = UIFont.boldSystemFont(ofSize: 15)
        label.translatesAutoresizingMaskIntoConstraints = false

        return label
    }()

    func setupCell() {
        addSubview(menuHeaderLabel)

        // addTaskButton.addTarget(self, action: #selector(MenuHeader.addTask), for: .touchUpInside)

        addConstraints(NSLayoutConstraint.constraints(withVisualFormat: "H:|-8-[v0]|", options: NSLayoutFormatOptions(), metrics: nil, views: ["v0": menuHeaderLabel]))

        addConstraints(NSLayoutConstraint.constraints(withVisualFormat: "V:|-5-[v0(30)]|", options: NSLayoutFormatOptions(), metrics: nil, views: ["v0": menuHeaderLabel]))
    }
}

class VerticalCollectionViewCell2: UICollectionViewCell {
    override init(frame: CGRect) {
        super.init(frame: frame)
        backgroundColor = .white
        setupCell()
    }

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

    let menuHeaderLabel: UILabel = {
        let label = UILabel()
        label.text = "loadin more waiting"
        label.textColor = .green
        label.textAlignment = .center
        label.font = UIFont.boldSystemFont(ofSize: 15)
        label.translatesAutoresizingMaskIntoConstraints = false
        return label
    }()

    func setupCell() {
        addSubview(menuHeaderLabel)

        // addTaskButton.addTarget(self, action: #selector(MenuHeader.addTask), for: .touchUpInside)

        addConstraints(NSLayoutConstraint.constraints(withVisualFormat: "H:|-8-[v0]|", options: NSLayoutFormatOptions(), metrics: nil, views: ["v0": menuHeaderLabel]))

        addConstraints(NSLayoutConstraint.constraints(withVisualFormat: "V:|-5-[v0(30)]|", options: NSLayoutFormatOptions(), metrics: nil, views: ["v0": menuHeaderLabel]))
    }
}

extension Timer {
    class func schedule(delay: TimeInterval, handler: @escaping (Timer!) -> Void) -> Timer {
        let fireDate = delay + CFAbsoluteTimeGetCurrent()
        let timer = CFRunLoopTimerCreateWithHandler(kCFAllocatorDefault, fireDate, 0, 0, 0, handler)
        CFRunLoopAddTimer(CFRunLoopGetCurrent(), timer, CFRunLoopMode.commonModes)
        return timer!
    }

    class func schedule(repeatInterval interval: TimeInterval, handler: @escaping (Timer!) -> Void) -> Timer {
        let fireDate = interval + CFAbsoluteTimeGetCurrent()
        let timer = CFRunLoopTimerCreateWithHandler(kCFAllocatorDefault, fireDate, interval, 0, 0, handler)
        CFRunLoopAddTimer(CFRunLoopGetCurrent(), timer, CFRunLoopMode.commonModes)
        return timer!
    }
}