这个错误告诉你，刷新没有初始化。注意，你选择使refresh不是可选的，这在Swift中意味着它必须在调用super之前有一个值。Init(或者隐式调用，这似乎是你的情况)。要么使刷新是可选的(可能是你想要的)，要么以某种方式初始化它。

我建议你再读一遍Swift的介绍文档，里面详细地介绍了这一点。

最后，正如@Anil指出的，iOS中有一个内置的名为UIRefresControl的拉刷新控件，这可能是值得研究的东西。

在Swift中使用这个，

如果你想在WebView中刷新，

所以试试这段代码:

override func viewDidLoad() {
    super.viewDidLoad()
    addPullToRefreshToWebView()
}

func addPullToRefreshToWebView(){
    var refreshController:UIRefreshControl = UIRefreshControl()

    refreshController.bounds = CGRectMake(0, 50, refreshController.bounds.size.width, refreshController.bounds.size.height) // Change position of refresh view
    refreshController.addTarget(self, action: Selector("refreshWebView:"), forControlEvents: UIControlEvents.ValueChanged)
    refreshController.attributedTitle = NSAttributedString(string: "Pull down to refresh...")
    YourWebView.scrollView.addSubview(refreshController)

}

func refreshWebView(refresh:UIRefreshControl){
    YourWebView.reload()
    refresh.endRefreshing()
}

细节

Xcode版本10.3 (10G8)， Swift 5

特性

能够使“拉刷新”编程 保护从多个“拉刷新”事件 当视图控制器切换(例如在TabController的情况下)时，继续动画活动指示器的能力

解决方案

import UIKit

class RefreshControl: UIRefreshControl {

    private weak var actionTarget: AnyObject?
    private var actionSelector: Selector?
    override init() { super.init() }

    convenience init(actionTarget: AnyObject?, actionSelector: Selector) {
        self.init()
        self.actionTarget = actionTarget
        self.actionSelector = actionSelector
        addTarget()
    }

    private func addTarget() {
        guard let actionTarget = actionTarget, let actionSelector = actionSelector else { return }
        addTarget(actionTarget, action: actionSelector, for: .valueChanged)
    }

    required init?(coder aDecoder: NSCoder) { super.init(coder: aDecoder) }

    func endRefreshing(deadline: DispatchTime? = nil) {
        guard let deadline = deadline else { endRefreshing(); return }
        DispatchQueue.global(qos: .default).asyncAfter(deadline: deadline) { [weak self] in
            DispatchQueue.main.async { self?.endRefreshing() }
        }
    }

    func refreshActivityIndicatorView() {
        guard let selector = actionSelector else { return }
        let _isRefreshing = isRefreshing
        removeTarget(actionTarget, action: selector, for: .valueChanged)
        endRefreshing()
        if _isRefreshing { beginRefreshing() }
        addTarget()
    }

    func generateRefreshEvent() {
        beginRefreshing()
        sendActions(for: .valueChanged)
    }
}

public extension UIScrollView {

    private var _refreshControl: RefreshControl? { return refreshControl as? RefreshControl }

    func addRefreshControll(actionTarget: AnyObject?, action: Selector, replaceIfExist: Bool = false) {
        if !replaceIfExist && refreshControl != nil { return }
        refreshControl = RefreshControl(actionTarget: actionTarget, actionSelector: action)
    }

    func scrollToTopAndShowRunningRefreshControl(changeContentOffsetWithAnimation: Bool = false) {
        _refreshControl?.refreshActivityIndicatorView()
        guard   let refreshControl = refreshControl,
                contentOffset.y != -refreshControl.frame.height else { return }
        setContentOffset(CGPoint(x: 0, y: -refreshControl.frame.height), animated: changeContentOffsetWithAnimation)
    }

    private var canStartRefreshing: Bool {
        guard let refreshControl = refreshControl, !refreshControl.isRefreshing else { return false }
        return true
    }

    func startRefreshing() {
        guard canStartRefreshing else { return }
        _refreshControl?.generateRefreshEvent()
    }

    func pullAndRefresh() {
        guard canStartRefreshing else { return }
        scrollToTopAndShowRunningRefreshControl(changeContentOffsetWithAnimation: true)
        _refreshControl?.generateRefreshEvent()
    }

    func endRefreshing(deadline: DispatchTime? = nil) { _refreshControl?.endRefreshing(deadline: deadline) }
}

使用

// Add refresh control to UICollectionView / UITableView / UIScrollView
private func setupTableView() {
    let tableView = UITableView()
    // ...
    tableView.addRefreshControll(actionTarget: self, action: #selector(refreshData))
}

@objc func refreshData(_ refreshControl: UIRefreshControl) {
    tableView?.endRefreshing(deadline: .now() + .seconds(3))
}

// Stop refreshing in UICollectionView / UITableView / UIScrollView
tableView.endRefreshing()

// Simulate pull to refresh in UICollectionView / UITableView / UIScrollView
tableView.pullAndRefresh()

完整的样品

不要忘记在这里添加解决方案代码

import UIKit

class ViewController: UIViewController {

    private weak var tableView: UITableView?

    override func viewDidLoad() {
        super.viewDidLoad()
        setupTableView()
    }

    private func setupTableView() {
        let tableView = UITableView()
        view.addSubview(tableView)
        tableView.translatesAutoresizingMaskIntoConstraints = false
        tableView.topAnchor.constraint(equalTo: view.topAnchor).isActive = true
        tableView.leftAnchor.constraint(equalTo: view.leftAnchor).isActive = true
        tableView.rightAnchor.constraint(equalTo: view.rightAnchor).isActive = true
        tableView.bottomAnchor.constraint(equalTo: view.bottomAnchor).isActive = true
        tableView.dataSource = self
        tableView.delegate = self
        tableView.addRefreshControll(actionTarget: self, action: #selector(refreshData))
        self.tableView = tableView
    }
}

extension ViewController {
    @objc func refreshData(_ refreshControl: UIRefreshControl) {
        print("refreshing")
        tableView?.endRefreshing(deadline: .now() + .seconds(3))
    }
}

extension ViewController: UITableViewDataSource {
    func numberOfSections(in tableView: UITableView) -> Int { return 1 }
    func tableView(_ tableView: UITableView, numberOfRowsInSection section: Int) -> Int { return 20 }
    func tableView(_ tableView: UITableView, cellForRowAt indexPath: IndexPath) -> UITableViewCell {
        let cell = UITableViewCell()
        cell.textLabel?.text = "\(indexPath)"
        return cell
    }
}

extension ViewController: UITableViewDelegate {
    func tableView(_ tableView: UITableView, didSelectRowAt indexPath: IndexPath) {
        tableView.pullAndRefresh()
    }
}

对于拉刷新，我正在使用

DGElasticPullToRefresh

https://github.com/gontovnik/DGElasticPullToRefresh

安装

豆荚的DGElasticPullToRefresh

import DGElasticPullToRefresh

然后把这个函数放到你的swift文件中，然后从你的

override func viewWillAppear(_ animated: Bool)

     func Refresher() {
      let loadingView = DGElasticPullToRefreshLoadingViewCircle()
      loadingView.tintColor = UIColor(red: 255.0/255.0, green: 255.0/255.0, blue: 255.0/255.0, alpha: 1.0)
      self.table.dg_addPullToRefreshWithActionHandler({ [weak self] () -> Void in

          //Completion block you can perfrom your code here.

           print("Stack Overflow")

           self?.table.dg_stopLoading()
           }, loadingView: loadingView)
      self.table.dg_setPullToRefreshFillColor(UIColor(red: 255.0/255.0, green: 57.0/255.0, blue: 66.0/255.0, alpha: 1))
      self.table.dg_setPullToRefreshBackgroundColor(self.table.backgroundColor!)
 }

不要忘记在视图消失时删除引用

要删除拉刷新，请将此代码放入您的

重写func viewDidDisappear(_ animated: Bool)

override func viewDidDisappear(_ animated: Bool) {
      table.dg_removePullToRefresh()

 }

看起来就像

快乐编码:)

其他答案是正确的，但更多细节请查看这篇文章拉到刷新

在故事板中启用刷新

当你使用UITableViewController时，解决方案相当简单:首先，在你的故事板中选择表视图控制器，打开属性检查器，并启用刷新:

UITableViewController自带一个UIRefreshControl的引用。您只需要连接一些东西，以便在用户下拉时启动和完成刷新。

Override viewDidLoad（）

在你重写viewDidLoad()时，添加一个目标来处理刷新，如下所示:

override func viewDidLoad() {
    super.viewDidLoad()
    // Do any additional setup after loading the view, typically from a nib.
        
    self.refreshControl?.addTarget(self, action: "handleRefresh:", forControlEvents: UIControlEvents.ValueChanged)
}

因为我指定了“handleRefresh:”(注意冒号!)作为 action参数，我需要在这里定义一个函数 UITableViewController类的同名。此外, 函数应该有一个参数 我们希望这个动作在UIControlEvent被调用时被调用 ValueChanged 别忘了调用refreshControl.endRefreshing()

要了解更多信息，请去提到链接，所有的功劳都归于那个帖子

我构建了一个RSS提要应用程序，在其中我有一个Pull To refresh功能，它最初有上面列出的一些问题。

但是为了补充上面用户的答案，我到处寻找我的用例，但没有找到它。我正在从网络(RSSFeed)下载数据，我想下拉我的故事tableView来刷新。

上面提到的内容涵盖了正确的领域，但人们遇到了一些问题，以下是我所做的，它很有效:

我采取了@Blankarsch的方法，去了我的主。然后选择表视图来使用刷新，然后没有提到的是创建IBOutlet和IBAction来有效地使用刷新

//Created from main.storyboard cntrl+drag refresh from left scene to assistant editor @IBOutlet weak var refreshButton: UIRefreshControl override func viewDidLoad() { ...... ...... //Include your code ...... ...... //Is the function called below, make sure to put this in your viewDidLoad //method or not data will be visible when running the app getFeedData() } //Function the gets my data/parse my data from the web (if you havnt already put this in a similar function) //remembering it returns nothing, hence return type is "-> Void" func getFeedData() -> Void{ ..... ..... } //From main.storyboard cntrl+drag to assistant editor and this time create an action instead of outlet and //make sure arguments are set to none and note sender @IBAction func refresh() { //getting our data by calling the function which gets our data/parse our data getFeedData() //note: refreshControl doesnt need to be declared it is already initailized. Got to love xcode refreshControl?.endRefreshing() }

希望这能帮助到和我处境相同的人