Ios UITableView分页，将无限显示加载

我正在尝试在我的应用程序中实现一个聊天功能，它将模拟iMessages的拉拽来加载更多的消息。我的API在每次调用中发送20条消息以及pageIndex和其他值，以跟踪页面和消息

我正在使用TableView willDisplay和pull来实现分页以刷新功能

我无法添加正确的逻辑以在willDisplay中加载更多消息，它将进入无限循环。有人能通过看下面的代码给我指出正确的方向吗

import UIKit

class ChatViewController: UIViewController, UITableViewDelegate, UITableViewDataSource, UITextViewDelegate  {

@IBOutlet weak var messagesTable: UITableView!
@IBOutlet weak var activityIndicator: UIActivityIndicatorView!

var messages: Messages!
var messageArray = [Message]()

// Pagination
var isLoading = false
var pageSize = 10
var totalPages: Int!
var currentPage: Int!

// Pull To Refresh
let refreshControl = UIRefreshControl()

override func viewWillAppear(_ animated: Bool){
    super.viewWillAppear(animated)

    activityIndicator.startAnimating()

    fetchMessages(page: 1, completed: {

        self.totalPages = self.messages.pageCount
        self.currentPage = self.messages.currentPage

        // Sort message by ID so that latest message appear at the bottom.
        self.messageArray = self.messages.messages!.sorted(by: {$0.id! < $1.id!})

        self.messagesTable.reloadData()

        // Scroll to the bottom of table
        self.messagesTable.scrollToBottom(animated: false)

        self.activityIndicator.stopAnimating()
    })

}

// MARK: - Table view data source
func numberOfSections(in tableView: UITableView) -> Int {
    return 1
}

func tableView(_ tableView: UITableView, numberOfRowsInSection section: Int) -> Int {
    return messageArray.count
}

func tableView(_ tableView: UITableView, willDisplay cell: UITableViewCell, forRowAt indexPath: IndexPath) {

    if !self.isLoading && indexPath.row == 0 {

        self.isLoading = true

        fetchMessages(page: self.currentPage, completed: {

            if self.currentPage == 0 {
                self.messageArray.removeAll()
            }

            self.messageArray.append(contentsOf: self.messages!.messages!)
            self.messageArray = self.messageArray.sorted(by: {$0.id! < $1.id!})

            self.messagesTable.reloadData()

            // Scroll to the top
            self.messagesTable.scrollToRow(at: indexPath, at: UITableViewScrollPosition.top, animated: true)

            self.currentPage = self.currentPage + 1
        })

        self.isLoading = false
    }

}

func tableView(_ tableView: UITableView, cellForRowAt indexPath: IndexPath) -> UITableViewCell {

    guard let cell = tableView.dequeueReusableCell(withIdentifier: "MessageCell", for: indexPath) as? MessageCell else {
        fatalError("Can't find cell")
    }

    return cell
}


private func fetchMessages(page: Int, completed: @escaping () -> ()){

    guard let url = URL(string: "http://example.com/....") else { return }

    URLSession.shared.dataTask(with: url) { (data, response, error) in
        if error != nil {
            print("Error in fetching data..........")
            print(error!.localizedDescription)
        }

        guard let data = data else { return }
        if let str = String(data: data, encoding: .utf8) { print(str) }

        do {
            let resultData = try JSONDecoder().decode(messagesStruct.self, from: data)

            DispatchQueue.main.async {
                print("DispatchQueue.main.async")
                self.messages = resultData.data!

                completed()
            }

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

//Pull to refresh
@objc func refresh(_ refreshControl: UIRefreshControl) {

    fetchMessages(completed: {
        self.messagesTable.reloadData()
    })

    refreshControl.endRefreshing()
}

}

willDisplayCell不是检查tableView是否实际滚动到底的安全位置，而不是使用scrollViewDelegate

---

希望对你有帮助，我已经试过了。第一个问题是，scrollViewDidScroll在调用任何viewXYZAppear方法之前就被调用了，并进入fetch&reload表。这正常吗？@davems:我个人更喜欢这样，而不是手动调用fetchMessagespage:1，在ViewWillDisplay中，但很难相信，当tableView中没有数据时，messagesTable.contentOffset.y>=messagesTable.contentSize.height-messagesTable.frame.size.height条件将永远存在pass@davems：但如果出于任何奇怪的原因发生这种情况，它将使您不再手动调用fetchMessagespage:1，哪一个更干净：这有点像创建自启动加载机制：但我几乎不怀疑如果它没有内容开始，scrollViewDidScroll是否会被调用，即使它被调用，我也非常怀疑它是否会通过条件。在调用任何viewXXXApepar之前，请放置一个断点并再次检查这是第一次打印：isLoading:false messagesTable.contentOffset.y:0.0 messagesTable.contentSize.height:0.0 messagesTable.frame.size.height:590.0条件变为真。@davems:hmmmm有意思，请给我一秒钟：但请相信我评论一下您的评论viewwillfetchmessagespage:1，您将看到您有一个很好的分页系统，它会自动启动：P尽管在那之前启动本身并不是目的，让我检查一下我是如何解决它的

func scrollViewDidScroll(_ scrollView: UIScrollView) {
        if !self.isLoading && (messagesTable.contentOffset.y >= (messagesTable.contentSize.height - messagesTable.frame.size.height)) {
            self.isLoading = true

            fetchMessages(page: self.currentPage, completed: {[weak self]

                guard let strongSelf = self else {
                    return
                }
                strongSelf.isLoading = false
                if strongSelf.currentPage == 0 {
                    strongSelf.messageArray.removeAll()
                }

                strongSelf.messageArray.append(contentsOf: strongSelf.messages!.messages!)
                strongSelf.messageArray = strongSelf.messageArray.sorted(by: {$0.id! < $1.id!})

                strongSelf.messagesTable.reloadData()

                strongSelf.currentPage = strongSelf.currentPage + 1
            })
        }
    }