快速選擇和取消選擇tableview單元格時面臨的問題-有解無憂

我在 tableview 中顯示 pincodes，當我選擇一個單元格時，它應該選擇，如果我再次點擊同一個單元格，那么它應該取消選擇（點擊單元格應該像開關一樣作業）

快速選擇和取消選擇tableview單元格時面臨的問題

但是下面的代碼

問題 1：最初我無法選擇第一行，但在選擇任何其他行后，然后能夠選擇第一行..為什么？我哪里錯了？

問題 2：只有一次我可以選擇兩次點擊取消選擇同一行，如果我連續點擊第三次然后無法選擇同一行，為什么？..請指導

class PincodeModel{
var name: String?
var id: Int?
var isSelected: Bool

init(name: String?, id: Int?, isSelected: Bool) {
    self.name = name
    self.id = id
    self.isSelected = isSelected
}
}


class FilterViewController: UIViewController {

var pincodePreviousIndex: Int = -1
var pincodes = [PincodeModel]()

override func viewDidAppear(_ animated: Bool) {
    super.viewDidAppear(animated)
    
    for pincode in pincodeList {
        self.pincodes.append(PincodeModel(name: pincode, id: 0, isSelected: false))
    }
}


func tableView(_ tableView: UITableView, cellForRowAt indexPath: IndexPath) -> UITableViewCell {

        let cell = tableView.dequeueReusableCell(withIdentifier: "SubFilterTableViewCell", for: indexPath) as! SubFilterTableViewCell
        cell.title.text = self.pincodes[indexPath.row].name

        if !self.pincodes.isEmpty {
            if self.pincodes[indexPath.row].isSelected == true {
                cell.tickImageView.image =  #imageLiteral(resourceName: "iconTick")
            }else {
                cell.tickImageView.image = UIImage()
            }
        }
    return cell
}

 // EDITED Code according to below answer
func tableView(_ tableView: UITableView, didSelectRowAt indexPath: IndexPath) {
   
    self.pincodes[indexPath.row].isSelected = !self.pincodes[indexPath.row].isSelected

if self.pincodes[indexPath.row].isSelected == true {
self.filterData.pincode = pincodes[indexPath.row].name ?? ""
}else {
self.filterData.pincode = ""
}
if pincodePreviousIndex > 0 && pincodePreviousIndex != indexPath.row {
pincodes[pincodePreviousIndex].isSelected = false
}
pincodePreviousIndex = indexPath.row

}

當我從索引 = 1 中選擇時，這可以正常作業，但是如果我選擇第一行（索引 = 0），那么如果我選擇另一行，正確的標記仍然存在，為什么？

o/p 帶有編輯過的代碼：

快速選擇和取消選擇tableview單元格時面臨的問題

uj5u.com熱心網友回復：

對于問題 1 - 通過使用這行代碼：

var pincodePreviousIndex: Int = 0

您不能單擊第一行，直到您單擊另一行，因為

pincodes[pincodePreviousIndex].isSelected = false

由于您在開始時默認為 0，因此與第一行相關。

對于問題 2 - 如果您選擇第 2 行（已選擇），然后再次選擇它以取消選擇它： pincodePreviousIndex 將保存該行的值，然后再次取消選擇它

pincodes[pincodePreviousIndex].isSelected = false

因此，即使您選擇了它，它也會取消選擇它。

我會在頂部這樣做： var pincodePreviousIndex: Int = -1

在底部：

if pincodePreviousIndex > 0 && pincodePreviousIndex != indexPath.row {
    pincodes[pincodePreviousIndex].isSelected = false
}

uj5u.com熱心網友回復：

您可以采取幾種方法來為自己省去一些麻煩。

首先，.selectionStyle = .none在您的單元格上設定，然后在您的單元格類中，覆寫setSelected(...). 例如，我向我的單元格添加了一個影像視圖，并為其提供了一個空框作為其影像，并為其提供了一個復選框作為其突出顯示的影像：

override func setSelected(_ selected: Bool, animated: Bool) {
    super.setSelected(selected, animated: animated)
    imgView.isHighlighted = selected ? true : false
}

現在，單元格外觀將反映其由表格視圖維護的選定狀態。

接下來，didSelectRowAt我們將實作willSelectRowAt... 如果當前選擇了單元格，我們將取消選擇它（并更新我們的資料）：

func tableView(_ tableView: UITableView, willSelectRowAt indexPath: IndexPath) -> IndexPath? {
    // is a row already selected?
    if let idx = tableView.indexPathForSelectedRow {
        if idx == indexPath {
            // tapped row is already selected, so
            //  deselect it
            tableView.deselectRow(at: indexPath, animated: false)
            //  update our data
            pincodes[indexPath.row].isSelected = false
            //  tell table view NOT to select the row
            return nil
        } else {
            // some other row is selected, so
            //  update our data
            //  table view will automatically deselect that row
            pincodes[idx.row].isSelected = false
        }
    }
    // tapped row should now be selected, so
    //  update our data
    pincodes[indexPath.row].isSelected = true
    //  tell table view TO select the row
    return indexPath
}

這是一個完整的例子：

class PincodeModel{
    var name: String?
    var id: Int?
    var isSelected: Bool
    
    init(name: String?, id: Int?, isSelected: Bool) {
        self.name = name
        self.id = id
        self.isSelected = isSelected
    }
}

class SelMethodTableViewController: UIViewController {

    var pincodes: [PincodeModel] = []
    
    let tableView = UITableView()
    
    let infoView: UIView = {
        let v = UILabel()
        v.backgroundColor = UIColor(white: 0.9, alpha: 1.0)
        return v
    }()
    let infoTitle: UILabel = {
        let v = UILabel()
        v.text = "Info:"
        return v
    }()
    let infoLabel: UILabel = {
        let v = UILabel()
        v.numberOfLines = 0
        return v
    }()

    override func viewDidLoad() {
        super.viewDidLoad()

        for i in 0..<20 {
            let pcm = PincodeModel(name: "\(i)", id: i, isSelected: false)
            pincodes.append(pcm)
        }

        [tableView, infoView, infoTitle, infoLabel].forEach { v in
            v.translatesAutoresizingMaskIntoConstraints = false
        }
        [infoTitle, infoLabel].forEach { v in
            infoView.addSubview(v)
        }
        [tableView, infoView].forEach { v in
            view.addSubview(v)
        }
        
        let g = view.safeAreaLayoutGuide
        
        NSLayoutConstraint.activate([
            
            // constrain the table view on right-side of view
            tableView.topAnchor.constraint(equalTo: g.topAnchor, constant: 40.0),
            tableView.widthAnchor.constraint(equalTo: g.widthAnchor, multiplier: 0.5),
            tableView.trailingAnchor.constraint(equalTo: g.trailingAnchor, constant: -20.0),
            tableView.bottomAnchor.constraint(equalTo: infoView.topAnchor, constant: -16.0),

            // let's add a tappable "info" view below the table view
            infoView.leadingAnchor.constraint(equalTo: g.leadingAnchor, constant: 20.0),
            infoView.trailingAnchor.constraint(equalTo: g.trailingAnchor, constant: -20.0),
            infoView.bottomAnchor.constraint(equalTo: g.bottomAnchor, constant: -20.0),
            infoView.heightAnchor.constraint(equalToConstant: 120.0),
            
            // add labels to infoView
            infoTitle.topAnchor.constraint(equalTo: infoView.topAnchor, constant: 8.0),
            infoTitle.leadingAnchor.constraint(equalTo: infoView.leadingAnchor, constant: 8.0),
            infoTitle.trailingAnchor.constraint(equalTo: infoView.trailingAnchor, constant: -8.0),
            infoLabel.topAnchor.constraint(equalTo: infoTitle.bottomAnchor, constant: 8.0),
            infoLabel.leadingAnchor.constraint(equalTo: infoView.leadingAnchor, constant: 8.0),
            infoLabel.trailingAnchor.constraint(equalTo: infoView.trailingAnchor, constant: -8.0),
            //infoLabel.bottomAnchor.constraint(lessThanOrEqualTo: infoView.bottomAnchor, constant: -8.0),
            
        ])

        tableView.dataSource = self
        tableView.delegate = self
        
        tableView.register(MyToggleCell.self, forCellReuseIdentifier: "toggleCell")
        
        // just so we can see the frame of the table view
        tableView.layer.borderWidth = 1.0
        tableView.layer.borderColor = UIColor.red.cgColor

        let t = UITapGestureRecognizer(target: self, action: #selector(showInfo(_:)))
        infoView.addGestureRecognizer(t)
        infoView.isUserInteractionEnabled = true
    }

    @objc func showInfo(_ g: UIGestureRecognizer) -> Void {
        var s: String = ""
        
        let selectedFromData = pincodes.filter( {$0.isSelected == true} )

        s  = "Data reports:"
        if selectedFromData.count > 0 {
            selectedFromData.forEach { ob in
                let obID = ob.id ?? -1
                s  = " \(obID)"
            }
        } else {
            s  = " Nothing selected"
        }
        s  = "\n"
        s  = "Table reports: "
        if let selectedFromTable = tableView.indexPathsForSelectedRows {
            selectedFromTable.forEach { idx in
                s  = " \(idx.row)"
            }
        } else {
            s  = " No rows selected"
        }
        infoLabel.text = s
    }
}

extension SelMethodTableViewController: UITableViewDataSource, UITableViewDelegate {
    func tableView(_ tableView: UITableView, numberOfRowsInSection section: Int) -> Int {
        return pincodes.count
    }
    func tableView(_ tableView: UITableView, cellForRowAt indexPath: IndexPath) -> UITableViewCell {
        let c = tableView.dequeueReusableCell(withIdentifier: "toggleCell", for: indexPath) as! MyToggleCell
        c.label.text = pincodes[indexPath.row].name
        c.selectionStyle = .none
        return c
    }
    func tableView(_ tableView: UITableView, willSelectRowAt indexPath: IndexPath) -> IndexPath? {
        // is a row already selected?
        if let idx = tableView.indexPathForSelectedRow {
            if idx == indexPath {
                // tapped row is already selected, so
                //  deselect it
                tableView.deselectRow(at: indexPath, animated: false)
                //  update our data
                pincodes[indexPath.row].isSelected = false
                //  tell table view NOT to select the row
                return nil
            } else {
                // some other row is selected, so
                //  update our data
                //  table view will automatically deselect that row
                pincodes[idx.row].isSelected = false
            }
        }
        // tapped row should now be selected, so
        //  update our data
        pincodes[indexPath.row].isSelected = true
        //  tell table view TO select the row
        return indexPath
    }
}

class MyToggleCell: UITableViewCell {
    let imgView: UIImageView = {
        let v = UIImageView()
        return v
    }()
    let label: UILabel = {
        let v = UILabel()
        return v
    }()
    
    override init(style: UITableViewCell.CellStyle, reuseIdentifier: String?) {
        super.init(style: style, reuseIdentifier: reuseIdentifier)
        commonInit()
    }
    required init?(coder: NSCoder) {
        super.init(coder: coder)
        commonInit()
    }
    func commonInit() -> Void {
        [imgView, label].forEach { v in
            v.translatesAutoresizingMaskIntoConstraints = false
            contentView.addSubview(v)
        }
        let g = contentView.layoutMarginsGuide
        
        // give bottom anchor less-than-required
        //  to avoid auto-layout complaints
        let b = imgView.bottomAnchor.constraint(equalTo: g.bottomAnchor, constant: -4.0)
        b.priority = .required - 1
        
        NSLayoutConstraint.activate([
            imgView.leadingAnchor.constraint(equalTo: g.leadingAnchor, constant: 0.0),
            imgView.topAnchor.constraint(equalTo: g.topAnchor, constant: 4.0),
            imgView.widthAnchor.constraint(equalToConstant: 32.0),
            imgView.heightAnchor.constraint(equalTo: imgView.widthAnchor),
            b,
            
            label.centerYAnchor.constraint(equalTo: g.centerYAnchor, constant: 0.0),
            label.leadingAnchor.constraint(equalTo: imgView.trailingAnchor, constant: 16.0),
            label.trailingAnchor.constraint(equalTo: g.trailingAnchor, constant: 0.0),
        ])
        if let img1 = UIImage(systemName: "square"),
           let img2 = UIImage(systemName: "checkmark.square") {
            imgView.image = img1
            imgView.highlightedImage = img2
        }
    }

    override func setSelected(_ selected: Bool, animated: Bool) {
        super.setSelected(selected, animated: animated)
        imgView.isHighlighted = selected ? true : false
    }
}

它看起來像這樣：

快速選擇和取消選擇tableview單元格時面臨的問題

運行時：

點擊一行將選擇該行
點擊不同的行將選擇新行并取消選擇當前選定的行
點擊已選擇的行將取消選擇它
點擊灰色的“資訊視圖”將報告資料和表格視圖中的選擇狀態

快速選擇和取消選擇tableview單元格時面臨的問題

請注意，如果所選行滾動到視圖外，它將保持選中狀態（并且在滾動回視圖時將顯示選中狀態）并且資料和表視圖選擇狀態將繼續正確。

編輯

如果我們想使用didSelectRowAt（也許用于其他用途），我們可以像這樣“切換”選定的行：

func tableView(_ tableView: UITableView, willSelectRowAt indexPath: IndexPath) -> IndexPath? {
    
    // if the tapped row is already selected
    if let indexPathForSelectedRow = tableView.indexPathForSelectedRow,
       indexPathForSelectedRow == indexPath {
        tableView.deselectRow(at: indexPath, animated: false)
        // calling .deselectRow(at: ...) does NOT trigger a call to didDeselectRowAt
        // so update our data here
        pincodes[indexPath.row].isSelected = false
        return nil
    }
    return indexPath
    
}

func tableView(_ tableView: UITableView, didSelectRowAt indexPath: IndexPath) {
    print("did select", indexPath)
    pincodes[indexPath.row].isSelected = true
}
func tableView(_ tableView: UITableView, didDeselectRowAt indexPath: IndexPath) {
    print("did deselect", indexPath)
    pincodes[indexPath.row].isSelected = false
}

轉載請註明出處，本文鏈接：https://www.uj5u.com/qianduan/381613.html

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