ios - TableView 数据源未显示所有行

Question

我是一名经验丰富的 Web 和 Android 开发人员，我正在使用《使用 Swift 2 开始 iPhone 开发》一书在运行 xCode 8.2 的 MacBook 上自学 iPhone 开发。我在将书中的示例转换为 Swift 3 时遇到了问题，但是能够应对其中的大部分。

然而，这些表格进行得并不顺利。我已经转换了所有我能想到的方法，但我无法在任何示例中显示所有表格数据。这是我的代码:

//
//  RootViewController.swift
//  Fonts
//
//  Created by Thomas Hehl on 12/21/16.
//

import UIKit

class RootViewController: UITableViewController {

    private var familyNames: [String]!
    private var cellPointSize: CGFloat!
    private var favoritesList: FavoritesList!
    private static let familyCell = "FamilyName"
    private static let favoritesCell = "Favorites"

    override func viewDidLoad() {
        super.viewDidLoad()

        // Uncomment the following line to preserve selection between presentations
        // self.clearsSelectionOnViewWillAppear = false

        // Uncomment the following line to display an Edit button in the navigation bar for this view controller.
        // self.navigationItem.rightBarButtonItem = self.editButtonItem()

        familyNames = (UIFont.familyNames as [String]).sorted()
        let preferredTableViewFont = UIFont.preferredFont(forTextStyle: UIFontTextStyle.headline)
        cellPointSize = preferredTableViewFont.pointSize
        favoritesList = FavoritesList.sharedFavoritesList
        tableView.estimatedRowHeight = cellPointSize

    }

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

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

    func fontForDisplay(atIndexPath indexPath: NSIndexPath) -> UIFont? {
        if indexPath.section == 0 {
            let familyName = familyNames[ indexPath.row]
            let fontName = UIFont.fontNames(forFamilyName: familyName).first
            return fontName != nil ? UIFont(name: fontName!, size: cellPointSize) : nil
        } else {
            return nil
        }
    }

    // MARK: - Table view data source

    override func numberOfSections(in tableView: UITableView) -> Int {
        // return the number of sections
        return favoritesList.favorites.isEmpty ? 1 : 2
    }

    override func tableView(_ tableView: UITableView, numberOfRowsInSection section: Int) -> Int {
        return section == 0 ? familyNames.count : 1
    }

    override func tableView(_ tableView: UITableView, titleForHeaderInSection section: Int) -> String? {
        return section == 0 ? "All Font Families" : "My Favorite Fonts"
    }

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

        if indexPath.section == 0 {
            // the font names list
            let cell = tableView.dequeueReusableCell(withIdentifier: RootViewController.familyCell, for: indexPath)
            cell.textLabel?.font = fontForDisplay(atIndexPath: indexPath as NSIndexPath)
            cell.textLabel?.text = familyNames[indexPath.row]
            cell.detailTextLabel?.text = familyNames[indexPath.row]
            return cell
        } else {
            //the favorites list
            return tableView.dequeueReusableCell(withIdentifier: RootViewController.favoritesCell, for: indexPath)
        }
    }


    /*
    // Override to support conditional editing of the table view.
    override func tableView(_ tableView: UITableView, canEditRowAt indexPath: IndexPath) -> Bool {
        // Return false if you do not want the specified item to be editable.
        return true
    }
    */

    /*
    // Override to support editing the table view.
    override func tableView(_ tableView: UITableView, commit editingStyle: UITableViewCellEditingStyle, forRowAt indexPath: IndexPath) {
        if editingStyle == .delete {
            // Delete the row from the data source
            tableView.deleteRows(at: [indexPath], with: .fade)
        } else if editingStyle == .insert {
            // Create a new instance of the appropriate class, insert it into the array, and add a new row to the table view
        }    
    }
    */

    /*
    // Override to support rearranging the table view.
    override func tableView(_ tableView: UITableView, moveRowAt fromIndexPath: IndexPath, to: IndexPath) {

    }
    */

    /*
    // Override to support conditional rearranging of the table view.
    override func tableView(_ tableView: UITableView, canMoveRowAt indexPath: IndexPath) -> Bool {
        // Return false if you do not want the item to be re-orderable.
        return true
    }
    */

    /*
    // MARK: - Navigation

    // In a storyboard-based application, you will often want to do a little preparation before navigation
    override func prepare(for segue: UIStoryboardSegue, sender: Any?) {
        // Get the new view controller using segue.destinationViewController.
        // Pass the selected object to the new view controller.
    }
    */

}

不幸的是，即使 familyNames 包含 75 个条目，该表也只显示了第一屏。这是屏幕截图。

如您所见，滚动条一直位于底部，但这几乎不是所有字体。

Answer 1

[编辑 - 聊天后，问题似乎仅仅是 OP 不知道如何滚动。 OP 向我发送了实际项目，我运行了它，它工作得很好。]

您的代码运行良好。我实际上只是将您的代码复制并粘贴到 Master-Detail 模板中，进行了一些调整(注释掉第二部分的内容，因为您没有提供任何相关信息)，并得到了这个: