在 Swift 4 中滚动 UITableView 时如何更新 UISlider 值

Question

当我设置滑块值时，请查看此 screenshort

然后tableview向下滚动然后值被改变看到这个屏幕短

问题是当我向下滚动时值会发生变化，我已经看到了很多答案，但在 Objective-C 中，请在 Swift 中帮助我解决这个问题。我正在使用 Xcode 9.2 和 Swift 4 非常感谢！

在这里我将使用 CoreData，但我只想要 Slider 问题！

class ViewController: UIViewController {

    @IBOutlet var tableView: UITableView!
    var arrData = [String]()
    var studentData = [Student]()
    override func viewDidLoad() {
        super.viewDidLoad()
        studentData = DatabaseHelper.shareInstance.getAllData()
        arrData = [
            "https://is3-ssl.mzstatic.com/image/thumb/Music1/v4/53/58/26/5358265a-e225-2cfb-61da-e6cb68ea5866/source/100x100bb.jpg","https://is3-ssl.mzstatic.com/image/thumb/Music118/v4/3b/cf/4c/3bcf4c0d-a040-3d74-81e9-6ca62c3664ab/source/100x100bb.jpg",
            "https://is2-ssl.mzstatic.com/image/thumb/Music/v4/4f/a6/a3/4fa6a31a-26f0-c025-4f1c-a20da9dd4a32/source/100x100bb.jpg","https://is5-ssl.mzstatic.com/image/thumb/Music5/v4/eb/43/a3/eb43a360-d92e-7dbd-feb8-73b8496ba66f/source/100x100bb.jpg"
        ]
        for arr in arrData{
            DatabaseHelper.shareInstance.save(object: arr)
            self.tableView.reloadData()
        }
    }

}

extension ViewController: UITableViewDelegate, UITableViewDataSource{

    func tableView(_ tableView: UITableView, numberOfRowsInSection section: Int) -> Int {
        return studentData.count
    }

    func tableView(_ tableView: UITableView, cellForRowAt indexPath: IndexPath) -> UITableViewCell {
        let cell = tableView.dequeueReusableCell(withIdentifier: "TableViewCell", for: indexPath) as! TableViewCell
        cell.studentData = studentData[indexPath.row]
        return cell
    }

    func tableView(_ tableView: UITableView, heightForRowAt indexPath: IndexPath) -> CGFloat {
        return 80
    }

// TableViewCell

class TableViewCell: UITableViewCell {


    @IBOutlet var slider: UISlider!
    @IBOutlet var img: UIImageView!
    var studentData:Student!{
        didSet{
            let url = ImageResource(downloadURL: URL(string: studentData.photo!)!, cacheKey: studentData.photo)
            img.kf.setImage(with: url)
            slider.value = studentData.valueslider
        }
    }
    override func awakeFromNib() {
        super.awakeFromNib()
        // Initialization code
        DatabaseHelper.shareInstance.saveValue(object: slider.value)
    }

    override func setSelected(_ selected: Bool, animated: Bool) {
        super.setSelected(selected, animated: animated)

        // Configure the view for the selected state
    }


    @IBAction func sliderBtnClick(_ sender: UISlider) {
        img.alpha = CGFloat(slider.value)
    }


}

//数据库助手

class DatabaseHelper{
    static let shareInstance = DatabaseHelper()

    let context = (UIApplication.shared.delegate as! AppDelegate).persistentContainer.viewContext

    func save(object:String){
        let entity = NSEntityDescription.insertNewObject(forEntityName: "Student", into: context) as! Student
        entity.photo = object
        do{
            try context.save()
        }catch{
            print("Data not save")
        }
    }

    func saveValue(object:Float){
        let entity = NSEntityDescription.insertNewObject(forEntityName: "Student", into: context) as! Student
        entity.valueslider = object
        do{
            try context.save()
        }catch{
            print("Data not save")
        }
    }

    func getAllData() -> [Student]{
        var arrData = [Student]()
        let fetchRequest = NSFetchRequest<NSManagedObject>(entityName: "Student")
        do{
            arrData = try context.fetch(fetchRequest) as! [Student]
        }catch{
            print("Data not get")
        }
        return arrData
    }
}

数据核心数据类

导入基础 导入核心数据

@objc(学生) 公共课学生：NSManagedObject {

}

import Foundation
import CoreData

extension Student {

 @nonobjc public class func fetchRequest() -> NSFetchRequest<Student> {
    return NSFetchRequest<Student>(entityName: "Student")
 }

 @NSManaged public var photo: String?
 @NSManaged public var valueslider: Float

}

Answer 1

protocol SliderDelegate: class {
    func sliderValueChanged(withValue: Int, cell: TableViewCell)
}

class TableViewCell: UITableViewCell {
    weak var delegate: SliderDelegate?
    @IBAction func sliderBtnClick(_ sender: UISlider) {
       img.alpha = CGFloat(slider.value)
       delegate?.sliderValueChanged(withValue: slider.value, cell: self)  
    }

}

在您的视图控制器的表视图数据源方法中

func tableView(_ tableView: UITableView, cellForRowAt indexPath: IndexPath) -> UITableViewCell {
        let cell = tableView.dequeueReusableCell(withIdentifier: "TableViewCell", for: indexPath) as! TableViewCell
        cell.delegate = self
        cell.studentData = studentData[indexPath.row]
        return cell
 }

并符合 Sliderdelegate

extension ViewController: SliderDelegate {
    func sliderValueChanged(withValue: Int, cell: TableViewCell) {
        guard let indexPath = yourTable.indexPath(for: cell) else {
            return
        }
        // Save Slider value to database (Database.save... your logic to update the slider value for the data at this indexPath, goes here) and then reload data like follows
        yourTable.reloadRows(at: [indexPath], with: .none)
}

Answer 2

ViewController.swift

import UIKit

class ViewController: UIViewController, UITableViewDataSource, UITableViewDelegate, TableViewCellDelegate {

    @IBOutlet var tableView: UITableView!
    var studentData = [Student]()
    var arrData = [String]()

    override func viewDidLoad() {
        super.viewDidLoad()
        // Do any additional setup after loading the view, typically from a nib.


        arrData = [
            "https://is3-ssl.mzstatic.com/image/thumb/Music1/v4/53/58/26/5358265a-e225-2cfb-61da-e6cb68ea5866/source/100x100bb.jpg",
            "https://is3-ssl.mzstatic.com/image/thumb/Music118/v4/3b/cf/4c/3bcf4c0d-a040-3d74-81e9-6ca62c3664ab/source/100x100bb.jpg",
            "https://is2-ssl.mzstatic.com/image/thumb/Music/v4/4f/a6/a3/4fa6a31a-26f0-c025-4f1c-a20da9dd4a32/source/100x100bb.jpg",
            "https://is5-ssl.mzstatic.com/image/thumb/Music5/v4/eb/43/a3/eb43a360-d92e-7dbd-feb8-73b8496ba66f/source/100x100bb.jpg"
        ]

        for urlStr in arrData {
            let student = Student(fromPhotoUrl:urlStr);
            studentData.append(student);
        }

        tableView.register(TableViewCell.nib(), forCellReuseIdentifier: TableViewCell.identifier())
        tableView.reloadData();
    }

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

    public func tableView(_ tableView: UITableView, numberOfRowsInSection section: Int) -> Int {
        return studentData.count
    }

    public func tableView(_ tableView: UITableView, cellForRowAt indexPath: IndexPath) -> UITableViewCell {
        var cell = tableView.dequeueReusableCell(withIdentifier: TableViewCell.identifier(), for: indexPath) as! TableViewCell
        let student = studentData[indexPath.row];
        cell = TableViewCell.configureCell(cell: cell, forStudent: student, atIndex: indexPath.row);
        cell.delegate = self;
        return cell
    }

    public func tableView(_ tableView: UITableView, heightForRowAt indexPath: IndexPath) -> CGFloat {
        return TableViewCell.height();
    }

    func sliderValueChanged(cell:TableViewCell, sliderChanged changedValue:Float) {
        let student = studentData[cell.tag];
        student.valueslider = changedValue;
        studentData[cell.tag] = student;
    }

}

TableViewCell.swift

import UIKit

class Student {
    var photo: String
    var valueslider:Float = 0.0;
    init(fromPhotoUrl url: String) {
        self.photo = url
    }
}

protocol TableViewCellDelegate: class {
    func sliderValueChanged(cell:TableViewCell, sliderChanged changedValue:Float);
}

class TableViewCell: UITableViewCell {

    var delegate:TableViewCellDelegate? = nil;
    @IBOutlet var slider: UISlider!
    @IBOutlet var img: UIImageView!

    override func awakeFromNib() {
        super.awakeFromNib()
        // Initialization code
    }

    override func setSelected(_ selected: Bool, animated: Bool) {
        super.setSelected(selected, animated: animated)
        // Configure the view for the selected state
    }

    @IBAction func sliderBtnClick(_ sender: UISlider) {
        img.alpha = CGFloat(sender.value);
        self.delegate?.sliderValueChanged(cell: self, sliderChanged: sender.value);
    }

    class func nib() -> UINib {
       return UINib.init(nibName: "TableViewCell", bundle: nil);
    }

    class func identifier() -> String {
        return "TableViewCell";
    }

    class func height() -> CGFloat {
        return CGFloat.init(80);
    }

    class func configureCell(cell:TableViewCell, forStudent student:Student, atIndex index:Int) -> TableViewCell {
        //background task to get data from url
        DispatchQueue.global(qos: .userInitiated).async {
            if let imgUrl = URL(string: student.photo) {
                do {
                    let imageData:Data = try Data(contentsOf: imgUrl as URL)
                    // Bounce back to the main thread to update the UI
                    DispatchQueue.main.async {
                        cell.img.image = UIImage(data: imageData)
                    }
                } catch {
                    print("Unable to load data: \(error)")
                }
            }
        }

        cell.tag = index;
        cell.slider.value = student.valueslider;
        return cell;
    }
}

WORKING-CODE.ZIP