用Swift5写的比较完整的tableview，包括上滑继续加载，下拉刷新

class HKPovertyFamilyController: UITableViewController {
    
    
    //表格底部用来提示数据加载的视图
    var loadMoreView:UIView?
    //用了记录当前是否允许加载新数据（正则加载的时候会将其设为false，放置重复加载）
    var loadMoreEnable = true
    //下拉刷新控件
    let refresh = UIRefreshControl()
    //存放最后一条数据的ID
    let newDataDefaults = UserDefaults.standard
    
    lazy var familyViewModel = HKPovertyFamilyViewModel()
    
    
    override func viewDidLoad() {
        super.viewDidLoad()
        setRefresh()
        tableView.rowHeight = 100
        loadFamilyData()
    }
    

    override func tableView(_ tableView: UITableView, numberOfRowsInSection section: Int) -> Int {
        return familyViewModel.povertyModelList.count
    }
    
    override func tableView(_ tableView: UITableView, cellForRowAt indexPath: IndexPath) -> UITableViewCell {
        let poverty = familyViewModel.povertyModelList[indexPath.row]
        let cell: HKPovertyFamilyCell = tableView.dequeueReusableCell(withIdentifier: "povertyFamily") as! HKPovertyFamilyCell
        cell.householderLabel.text = "户主："+poverty.name
        cell.populationLabel.text = "人口："+poverty.family
        cell.helpTimesLabel.text = "帮扶次数："+poverty.num + "次"
        if (poverty.bfzrr == "") {
            cell.helpResponsibleLabel.text = "帮扶责任人：暂无"
        } else if (poverty.bfzrr == nil){
            cell.helpResponsibleLabel.text = "帮扶责任人："+(poverty.bfzrr ?? "暂无")
        }
        if (poverty.time == "") {
            cell.recentHelpLabel.text = "最近帮扶：暂无"
        } else if (poverty.time == nil) {
            cell.recentHelpLabel.text = "最近帮扶："+(poverty.time ?? "暂无")
        }
        //当下拉到底部，执行loadMore()
        if (loadMoreEnable && indexPath.row == familyViewModel.povertyModelList.count - 1) {
            loadMore()
        }
        
        return cell
    }
    override func tableView(_ tableView: UITableView, didSelectRowAt indexPath: IndexPath) {
            let story = UIStoryboard.init(name: "HKPovertyFamily", bundle: nil)
            let detailVC = story.instantiateViewController(withIdentifier: "povertyFamilyDetail")
            let poverty = familyViewModel.povertyModelList[indexPath.row]
            let useDefaults = UserDefaults.standard
            useDefaults.set(poverty.id, forKey: "poor_id")
            useDefaults.synchronize()
    //        print("--------id\(poverty.id)")
            
            self.navigationController?.pushViewController(detailVC, animated: true)
        }
    
    //上拉刷新视图
    private func setupInfiniteScrollingView() {
        self.loadMoreView = UIView(frame: CGRect(x:0, y:self.tableView.contentSize.height,
                                                 width:self.tableView.bounds.size.width, height:60))
        self.loadMoreView!.autoresizingMask = UIView.AutoresizingMask.flexibleWidth
        self.loadMoreView!.backgroundColor = UIColor.orange
         
        //添加中间的环形进度条
        let activityViewIndicator = UIActivityIndicatorView(style: .white)
        activityViewIndicator.color = UIColor.darkGray
        let indicatorX = self.view.frame.width/2-activityViewIndicator.frame.width/2
        let indicatorY = self.loadMoreView!.frame.size.height/2-activityViewIndicator.frame.height/2
        activityViewIndicator.frame = CGRect(x:indicatorX, y:indicatorY,
                                             width:activityViewIndicator.frame.width,
                                             height:activityViewIndicator.frame.height)
        activityViewIndicator.startAnimating()
        self.loadMoreView!.addSubview(activityViewIndicator)
    }
    
}

extension HKPovertyFamilyController {
    //加载数据
    func loadFamilyData() -> Void {
        familyViewModel.returnData {
            //将最后一条信息存入defaults中，为了下拉刷新判断是否是新数据
            
            let newElement = self.familyViewModel.povertyModelList.last!
            self.newDataDefaults.setValue(newElement.id, forKey: "newId")
            self.tableView.reloadData()
        }
    }
    //加载更多数据（上拉加载的数据)
    func loadMore(){
        print("加载新数据！")
        loadMoreEnable = false
        self.familyViewModel.returnData {
            self.familyViewModel.startAt += 10
            self.tableView.reloadData()
        }
        loadMoreEnable = true
    }
    //下拉刷新方法
    @objc func loadNewData() -> Void {
        //取出ID和后面作比较
        let newElement = self.newDataDefaults.string(forKey: "newId")
        familyViewModel.returnData {
            if newElement != self.familyViewModel.povertyModelList.last?.id {
                let newMessage = self.familyViewModel.povertyModelList.last
                self.familyViewModel.povertyModelList.insert(newMessage!, at: 0)
                self.tableView.reloadData()
            }
        }
        
        self.refresh.endRefreshing()
    }
}

extension HKPovertyFamilyController {
    //设置刷新控件
    func setRefresh() -> Void {
        refresh.tintColor = .red
        refresh.attributedTitle = NSAttributedString(string: "正在刷新")
        refresh.addTarget(self, action: #selector(loadNewData), for: .valueChanged)
        self.tableView.addSubview(refresh)
    }
}