ios - 快速重新加载 Collection View 不起作用

Question

我是 swift 的新手。我按照一些教程开发社交应用程序，如 Twitter 应用程序以遵循 tutorial .我开始实现跟随按钮功能。它调用另一个 API 调用，但相同的响应带有较小的修改(例如 - 追随者属性的数量增加一个)。通话也能正常工作。但 Collection View 没有重新加载。我的代码是。

View Controller

import LBTAComponents
import TRON
import SwiftyJSON

class HomeDatasourceController: DatasourceController {

    let errorMessageLabel: UILabel = {
        let label = UILabel()
        label.text = "Apologies something went wrong. Please try again later..."
        label.textAlignment = .center
        label.numberOfLines = 0
        label.isHidden = true
        return label
    }()

    override func willTransition(to newCollection: UITraitCollection, with coordinator: UIViewControllerTransitionCoordinator) {
        collectionViewLayout.invalidateLayout()
    }

    func follow(){
    print("inside controller")
    Service.sharedInstance.fetchfollowHomeFeed { (homeDatasource, err) in
    if let err = err {
        self.errorMessageLabel.isHidden = false

    if let apiError = err as? APIError<Service.JSONError> {

    if apiError.response?.statusCode != 200 {
    self.errorMessageLabel.text = "Status code was not 200"
    }
    }

    return
    }
    self.datasource = homeDatasource
        self.collectionView?.reloadData()
    }
    }

    override func viewDidLoad() {
        super.viewDidLoad()

        view.addSubview(errorMessageLabel)
        errorMessageLabel.fillSuperview() //LBTA method call

        collectionView?.backgroundColor = UIColor(r: 232, g: 236, b: 241)

        setupNavigationBarItems()

        Service.sharedInstance.fetchHomeFeed { (homeDatasource, err) in
            if let err = err {
                self.errorMessageLabel.isHidden = false

                if let apiError = err as? APIError<Service.JSONError> {

                    if apiError.response?.statusCode != 200 {
                        self.errorMessageLabel.text = "Status code was not 200"
                    }
                }

                return
            }

            self.datasource = homeDatasource
        }
    }

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

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

        //first section of users
        if indexPath.section == 0 {
            guard let user = self.datasource?.item(indexPath) as? User else { return .zero }

            let estimatedHeight = estimatedHeightForText(user.bioText)
            return CGSize(width: view.frame.width, height: estimatedHeight + 66)
        } else if indexPath.section == 1 {
            //our tweets size estimation

            guard let tweet = datasource?.item(indexPath) as? Tweet else { return .zero }

            let estimatedHeight = estimatedHeightForText(tweet.message)

            return CGSize(width: view.frame.width, height: estimatedHeight + 74)
        }


        return CGSize(width: view.frame.width, height: 200)
    }

    private func estimatedHeightForText(_ text: String) -> CGFloat {
        let approximateWidthOfBioTextView = view.frame.width - 12 - 50 - 12 - 2
        let size = CGSize(width: approximateWidthOfBioTextView, height: 1000)
        let attributes = [NSFontAttributeName: UIFont.systemFont(ofSize: 15)]

        let estimatedFrame = NSString(string: text).boundingRect(with: size, options: .usesLineFragmentOrigin, attributes: attributes, context: nil)

        return estimatedFrame.height
    }

    func collectionView(_ collectionView: UICollectionView, layout collectionViewLayout: UICollectionViewLayout, referenceSizeForHeaderInSection section: Int) -> CGSize {
        if section == 1 {
            return .zero
        }
        return CGSize(width: view.frame.width, height: 50)
    }

    func collectionView(_ collectionView: UICollectionView, layout collectionViewLayout: UICollectionViewLayout, referenceSizeForFooterInSection section: Int) -> CGSize {
        if section == 1 {
            return .zero
        }
        return CGSize(width: view.frame.width, height: 64)
    }

}

数据源

import LBTAComponents
import TRON
import SwiftyJSON

extension Collection where Iterator.Element == JSON {
    func decode<T: JSONDecodable>() throws -> [T] {
        return try map{try T(json: $0)}
    }
}

class HomeDatasource: Datasource, JSONDecodable {

    let users: [User]

    required init(json: JSON) throws {
        guard let usersJsonArray = json["users"].array, let tweetsJsonArray = json["tweets"].array else {
            throw NSError(domain: "com.letsbuildthatapp", code: 1, userInfo: [NSLocalizedDescriptionKey: "Parsing JSON was not valid."])
        }

//        self.users = usersJsonArray.map{User(json: $0)}
//        self.tweets = tweetsJsonArray.map{Tweet(json: $0)}

        self.users = try usersJsonArray.decode()
        self.tweets = try tweetsJsonArray.decode()

    }

    let tweets: [Tweet]

    override func footerClasses() -> [DatasourceCell.Type]? {
        return [UserFooter.self]
    }

    override func headerClasses() -> [DatasourceCell.Type]? {
        return [UserHeader.self]
    }

    override func cellClasses() -> [DatasourceCell.Type] {
        return [UserCell.self, TweetCell.self]
    }

    override func item(_ indexPath: IndexPath) -> Any? {
        if indexPath.section == 1 {
            return tweets[indexPath.item]
        }
        return users[indexPath.item]
    }

    override func numberOfSections() -> Int {
        return 2
    }

    override func numberOfItems(_ section: Int) -> Int {
        if section == 1 {
            return tweets.count
        }
        return users.count
    }

}

数据单元格

import LBTAComponents

class UserCell: DatasourceCell {

    override var datasourceItem: Any? {
        didSet {
            guard let user = datasourceItem as? User else { return }
            followButton.addTarget(self, action: #selector(follow), for: .touchUpInside)
            nameLabel.text = user.name
            usernameLabel.text = user.username
            bioTextView.text = user.bioText

            profileImageView.loadImage(urlString: user.profileImageUrl)
        }
    }

    let profileImageView: CachedImageView = {
        let imageView = CachedImageView()
        imageView.image = #imageLiteral(resourceName: "profile_image")
        imageView.layer.cornerRadius = 5
        imageView.clipsToBounds = true
        return imageView
    }()

    let nameLabel: UILabel = {
        let label = UILabel()
        label.text = "Brian Voong"
        label.font = UIFont.boldSystemFont(ofSize: 16)
        return label
    }()

    let usernameLabel: UILabel = {
        let label = UILabel()
        label.text = "@buildthatapp"
        label.font = UIFont.systemFont(ofSize: 14)
        label.textColor = UIColor(r: 130, g: 130, b: 130)
        return label
    }()

    let bioTextView: UITextView = {
        let textView = UITextView()
        textView.text = "iPhone, iPad, iOS Programming Community. Join us to learn Swift, Objective-C and build iOS apps!"
        textView.font = UIFont.systemFont(ofSize: 15)
        textView.backgroundColor = .clear
        return textView
    }()

    let followButton: UIButton = {
        let button = UIButton()
        button.layer.cornerRadius = 5
        button.layer.borderColor = twitterBlue.cgColor
        button.layer.borderWidth = 1
        button.setTitle("Follow", for: .normal)
        button.titleLabel?.font = UIFont.boldSystemFont(ofSize: 14)
        button.setTitleColor(twitterBlue, for: .normal)
        button.setImage(#imageLiteral(resourceName: "follow"), for: .normal)
        button.imageView?.contentMode = .scaleAspectFit
        button.imageEdgeInsets = UIEdgeInsets(top: 0, left: -8, bottom: 0, right: 0)
        //        button.titleEdgeInsets = UIEdgeInsets
        return button
    }()
    func follow(){
        print("inside source")
        var link = HomeDatasourceController()
        link.follow()
    }
    override func setupViews() {
        super.setupViews()

        backgroundColor = .white

        separatorLineView.isHidden = false
        separatorLineView.backgroundColor = UIColor(r: 230, g: 230, b: 230)

        addSubview(profileImageView)
        addSubview(nameLabel)
        addSubview(usernameLabel)
        addSubview(bioTextView)
        addSubview(followButton)

        profileImageView.anchor(self.topAnchor, left: self.leftAnchor, bottom: nil, right: nil, topConstant: 12, leftConstant: 12, bottomConstant: 0, rightConstant: 0, widthConstant: 50, heightConstant: 50)

        nameLabel.anchor(profileImageView.topAnchor, left: profileImageView.rightAnchor, bottom: nil, right: followButton.leftAnchor, topConstant: 0, leftConstant: 8, bottomConstant: 0, rightConstant: 12, widthConstant: 0, heightConstant: 20)

        usernameLabel.anchor(nameLabel.bottomAnchor, left: nameLabel.leftAnchor, bottom: nil, right: nameLabel.rightAnchor, topConstant: 0, leftConstant: 0, bottomConstant: 0, rightConstant: 0, widthConstant: 0, heightConstant: 20)

        bioTextView.anchor(usernameLabel.bottomAnchor, left: usernameLabel.leftAnchor, bottom: self.bottomAnchor, right: self.rightAnchor, topConstant: -4, leftConstant: -4, bottomConstant: 0, rightConstant: 0, widthConstant: 0, heightConstant: 0)

        followButton.anchor(topAnchor, left: nil, bottom: nil, right: self.rightAnchor, topConstant: 12, leftConstant: 0, bottomConstant: 0, rightConstant: 12, widthConstant: 120, heightConstant: 34)
    }
}

它使用 LBTA components .i 试过 self.collectionView?.reloadData() 但它没有重新加载。请帮我解决这个问题。下载我的完整源代码 here请帮助我

Answer 1

我看过你的项目并发现了你做的问题。在 UserCell.swift 类中，您应该使用下一个代码:

func follow(){
    print("inside source")
    guard let link = controller as? HomeDatasourceController else { return }
    link.follow()
}

解释问题

这是您项目中的代码

func follow(){
    print("inside source")
    var link = HomeDatasourceController() // in this place you create a new local instance of class 'HomeDatasourceController'
    link.follow()
}