拉动刷新不起作用

Posted 2023-03-15

【中文标题】拉动刷新不起作用

【英文标题】：Pull to refresh not working

【发布时间】：2016-12-20 15:21:25

【问题描述】：

我正在使用 Alamofire 在 Swift 3 中构建我的应用程序。我有 JSON 数据进入列表视图。每次我拉刷新内容，而不是刷新内容，它只是在列表视图的列表底部添加更多项目，而不是刷新可见列表。我不知道我做错了什么，到目前为止我的代码是：

import UIKit
import Alamofire
import SVProgressHUD

struct postinput 
    let mainImage : UIImage!
    let name : String!
    let author : String!
    let summary : String!
    let content : String!





class TableViewController: UITableViewController 

    //var activityIndicatorView: UIActivityIndicatorView!

    var postsinput = [postinput]()

    var refresh = UIRefreshControl()

    var mainURL = "https://www.example.com/api"

    typealias JSONstandard = [String : AnyObject]

    override func viewDidLoad() 
        super.viewDidLoad()
        // Do any additional setup after loading the view, typically from a nib.
        tableView.separatorStyle = UITableViewCellSeparatorStyle.none


        self.tableView.addSubview(refresh)

        //;refresh.attributedTitle = NSAttributedString(string: "Refreshing...", attributes:[NSForegroundColorAttributeName : UIColor.black])
        refresh.backgroundColor = UIColor(red:0.93, green:0.93, blue:0.93, alpha:1.0)
        //refresh.tintColor = UIColor.white

        refresh.addTarget(self, action: #selector(self.refreshData), for: UIControlEvents.valueChanged)
        //refresh.addTarget(self, action: #selector(getter: TableViewController.refresh), for: UIControlEvents.valueChanged)
        refresh.attributedTitle = NSAttributedString(string: "Updated: \(NSDate())")


        //activityIndicatorView = UIActivityIndicatorView(activityIndicatorStyle: UIActivityIndicatorViewStyle.gray)
        //tableView.backgroundView = activityIndicatorView

        callAlamo(url: mainURL)


    

    func refreshData() 

        Alamofire.request("https://www.example.com/api").responseJSON(completionHandler: 
            response in
            self.parseData(JSONData: response.data!)
            self.tableView.separatorStyle = UITableViewCellSeparatorStyle.singleLine

            DispatchQueue.main.async 
                self.tableView.reloadData()
                self.refresh.endRefreshing()
            


        )



    



    func callAlamo(url : String)
        //activityIndicatorView.startAnimating()
        SVProgressHUD.show(withStatus: "Loading...")
        SVProgressHUD.setDefaultStyle(SVProgressHUDStyle.dark)
        SVProgressHUD.setDefaultAnimationType(SVProgressHUDAnimationType.native)
        SVProgressHUD.setDefaultMaskType(SVProgressHUDMaskType.black)
        Alamofire.request(url).responseJSON(completionHandler: 
            response in
            self.parseData(JSONData: response.data!)
            self.tableView.separatorStyle = UITableViewCellSeparatorStyle.singleLine
            //self.activityIndicatorView.stopAnimating()
            SVProgressHUD.dismiss()


        )


    


    func parseData(JSONData : Data) 
        do 
            var readableJSON = try JSONSerialization.jsonObject(with: JSONData, options: .mutableContainers) as! JSONstandard
            // print(readableJSON)

            if let posts = readableJSON["posts"] as? [JSONstandard] 
                for post in posts 
                    let title = post["title"] as! String

                    let author = post["author"] as! String

                    guard let dic = post["summary"] as? [String: Any], let summary = dic["value"] as? String else 
                        return
                    
                    let str = summary.replacingOccurrences(of: "<[^>]+>", with: "", options: .regularExpression, range: nil)
                    print(str)

                    guard let dic1 = post["content"] as? [String: Any], let content = dic1["value"] as? String else 
                        return
                    
                    let str1 = content.replacingOccurrences(of: "<[^>]+>", with: "", options: .regularExpression, range: nil)
                    print(str1)





                    //print(author)

                    if let imageUrl = post["image"] as? String 
                        let mainImageURL = URL(string: imageUrl )
                        let mainImageData = NSData(contentsOf: mainImageURL!)
                        let mainImage = UIImage(data: mainImageData as! Data)

                        postsinput.append(postinput.init(mainImage: mainImage, name: title, author: author, summary: summary, content: content))
                    
                
                DispatchQueue.main.async 
                    self.tableView.reloadData()
                
            


        


        catch 
            print(error)
        


    


    override func tableView(_ tableView: UITableView, numberOfRowsInSection section: Int) -> Int 
        return postsinput.count
    

    override func tableView(_ tableView: UITableView, cellForRowAt indexPath: IndexPath) -> UITableViewCell 
        let cell = tableView.dequeueReusableCell(withIdentifier: "cell")

        // cell?.textLabel?.text = titles[indexPath.row]

        let mainImageView = cell?.viewWithTag(2) as! UIImageView

        mainImageView.image = postsinput[indexPath.row].mainImage

        mainImageView.layer.cornerRadius = 5.0
        mainImageView.clipsToBounds = true

        //(cell?.viewWithTag(2) as! UIImageView).image = postsinput[indexPath.row].mainImage

        let mainLabel = cell?.viewWithTag(1) as! UILabel

        mainLabel.text = postsinput[indexPath.row].name

        mainLabel.font = UIFont.boldSystemFont(ofSize: 18)

        mainLabel.sizeToFit()

        mainLabel.numberOfLines = 0;

        let autLabel = cell?.viewWithTag(3) as! UILabel

        autLabel.text = postsinput[indexPath.row].author

        autLabel.font = UIFont(name: "Helvetica", size:16)

        autLabel.textColor = UIColor(red: 0.8784, green: 0, blue: 0.1373, alpha: 1.0) /* #e00023 */

        let sumLabel = cell?.viewWithTag(4) as! UILabel

        sumLabel.text = (postsinput[indexPath.row].summary).replacingOccurrences(of: "<[^>]+>", with: "", options: .regularExpression, range: nil)

        sumLabel.font = UIFont(name: "Helvetica", size:16)

        sumLabel.textColor = UIColor(red:0.27, green:0.27, blue:0.27, alpha:1.0)

        //let contentLabel = cell?.viewWithTag(0) as! UILabel

        //contentLabel.text = (postsinput[indexPath.row].content).replacingOccurrences(of: "<[^>]+>", with: "", options: .regularExpression, range: nil)



        //(cell?.viewWithTag(3) as! UILabel).text = postsinput[indexPath.row].author

        return cell!
    

    override func prepare(for segue: UIStoryboardSegue, sender: Any?) 
        SVProgressHUD.show()
        let indexPath = self.tableView.indexPathForSelectedRow?.row

        let vc = segue.destination as! nextVC


        vc.articleImage = postsinput[indexPath!].mainImage
        vc.articleMainTitle = postsinput[indexPath!].name
        vc.articleContent = postsinput[indexPath!].content
        SVProgressHUD.dismiss()

        let backItem = UIBarButtonItem()
        backItem.title = "Back"
        navigationItem.backBarButtonItem = backItem // This will show in the next view controller being pushed



    


    override func tableView(_ tableView: UITableView, commit editingStyle: UITableViewCellEditingStyle, forRowAt indexPath: IndexPath) 
        if editingStyle == .delete 
            postsinput.remove(at: indexPath.row)
            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 func didReceiveMemoryWarning() 
        super.didReceiveMemoryWarning()
        // Dispose of any resources that can be recreated.
    

【参考方案1】：

您的问题在这里：

postsinput.append(postinput.init(mainImage: mainImage, name: title, author: author, summary: summary, content: content))

您不断将新数据附加到旧数据。如果要在添加新数据之前彻底清除旧数据，只需从postsinput 数组中删除所有元素即可。

【讨论】：

但据我了解，该行将所有元素添加到列表视图中，如果我删除它，数据将如何进入列表视图？

@Sole 在添加来自您的网络请求的新数据之前，您删除了当前在数组中的所有元素。

@Sole 在postsinput.append 之前调用postsinput.removeAll()。

【参考方案2】：

您在下拉刷新中的任务是刷新列表中现有的数据并添加新项目（如果有）。因此，您需要做的不是每次拉动刷新时都继续将项目添加到列表中，而只需提供一个来自服务器的新列表到您的 tableView。您已经拥有数组postsinput，因此请确保在添加之前删除所有项目。以下是您可以进行更改的代码。

 func parseData(JSONData : Data) 

    postsinput.removeAll()

    do 

        ...
        ...
               if let imageUrl = post["image"] as? String 
                    let mainImageURL = URL(string: imageUrl )
                    let mainImageData = NSData(contentsOf: mainImageURL!)
                    let mainImage = UIImage(data: mainImageData as! Data)

                    postsinput.append(postinput.init(mainImage: mainImage, name: title, author: author, summary: summary, content: content))
                
            
            DispatchQueue.main.async 
                self.tableView.reloadData()
            
       ...
       ...