其实之前做OC的时候一直以为上拉刷新和下拉加载都是用运行时的原理去做的，可是今天看到案例的时候，发现有一个UIRefreshControl是专门做这个的，下面我们看看这个简单的下拉刷新具体是怎么做的吧

各项元素初始化#

    let cellIdentifer = "NewCellIdentifier"
    
    let favoriteEmoji = ["🤗🤗🤗🤗🤗", "", ""]
    let newFavoriteEmoji = ["", "", "", "🤗🤗🤗🤗🤗", "", "" ]
    var emojiData = [String]()
    var tableViewController = UITableViewController(style: .plain)
    
    var refreshControl = UIRefreshControl()
    var navBar: UINavigationBar = UINavigationBar(frame: CGRect(x: 0, y: 0, width: 375, height: 64))

ViewDidLoad方法对视图进行调整#

    override func viewDidLoad() {
        super.viewDidLoad()
        emojiData = favoriteEmoji
        let emojiTableView = tableViewController.tableView
        
        emojiTableView?.backgroundColor = UIColor(red:0.092, green:0.096, blue:0.116, alpha:1)
        emojiTableView?.dataSource = self
        emojiTableView?.register(UITableViewCell.self, forCellReuseIdentifier: cellIdentifer)
        
        tableViewController.refreshControl = self.refreshControl
        self.refreshControl.addTarget(self, action: #selector(didRoadEmoji), for: .valueChanged)
        
        self.refreshControl.backgroundColor = UIColor(red:0.113, green:0.113, blue:0.145, alpha:1)
        let attributes = [NSForegroundColorAttributeName: UIColor.white]
        self.refreshControl.attributedTitle = NSAttributedString(string: "Last updated on \(NSDate())", attributes: attributes)
        self.refreshControl.tintColor = UIColor.white
        
        self.title = "emoji"
        self.navBar.barStyle = UIBarStyle.blackTranslucent
        
        emojiTableView?.rowHeight = UITableViewAutomaticDimension
        emojiTableView?.estimatedRowHeight = 60.0
        emojiTableView?.tableFooterView = UIView(frame:.zero)
        emojiTableView?.separatorStyle = UITableViewCellSeparatorStyle.none
        
        
        self.view.addSubview(emojiTableView!)
        self.view.addSubview(navBar)
    }
    func didRoadEmoji() {
        self.emojiData = newFavoriteEmoji
        self.tableViewController.tableView.reloadData()
        self.refreshControl.endRefreshing()
    }

TableView数据代理#

    func tableView(_ tableView: UITableView, numberOfRowsInSection section: Int) -> Int {
        return emojiData.count
    }
    
    private func numberOfSectionsInTableView(tableView: UITableView) -> Int {
        return 1
    }
    
    
    func tableView(_ tableView: UITableView, cellForRowAt indexPath: IndexPath) -> UITableViewCell {
        let cell = tableView.dequeueReusableCell(withIdentifier: cellIdentifer)! as UITableViewCell
        
        cell.textLabel!.text = self.emojiData[indexPath.row]
        cell.textLabel!.textAlignment = NSTextAlignment.center
        cell.textLabel!.font = UIFont.systemFont(ofSize: 50)
        cell.backgroundColor = UIColor.clear
        cell.selectionStyle = UITableViewCellSelectionStyle.none
        
        return cell
    }

基本的代码就是这样，有机会会对此做相应的改造，争取能封装成一个开源类库，本例代码请戳使用UIRefreshControl实现下拉刷新