Updating UIImageView without reloading all data

Question

I have been stuck on this problem for a few days now. I have an image view set as invisible until the long press gesture is triggered. However, I can not wrap my head around on how to make the UIImageView to become visible after such. This is within a Cell in tableView. I have used reloadData(), but the issue is the table loses its place. It scrolls upwards by the time you release your finger. The long gesture triggers a boolean on the database side that toggles saveShow. When data is loaded, the query checks and displays the UIImageView if true. So I believe I would have to reload the data since it is based on the query..? Any help will be greatly appreciated!

class SecondViewController: UIViewController, UITableViewDelegate, UITableViewDataSource, UIPickerViewDelegate, UIPickerViewDataSource {

    let db = DatabaseController()

    @IBOutlet weak var tableView: UITableView!
    @IBOutlet weak var cityPicker: UIPickerView!

    override func viewDidLoad() {
        super.viewDidLoad()
        tableView.delegate = self
        tableView.dataSource = self
        cityPicker.delegate = self
        cityPicker.dataSource = self

        self.tableView.autoresizingMask = UIView.AutoresizingMask.flexibleHeight;
        self.db.createTable()

        //////////////////////////////////////////////////////////////////
        let longPressGesture:UILongPressGestureRecognizer = UILongPressGestureRecognizer(target: self, action: #selector(longPress))
        longPressGesture.minimumPressDuration = 1.0 // 1 second press
        longPressGesture.delegate = self as? UIGestureRecognizerDelegate
        self.tableView.addGestureRecognizer(longPressGesture)
        ////////////////////////////////////////////////////////////////


        ////////////////////////////////////////////////////
        Alamofire.request("http://url.com/jsonfile").responseJSON { response in
            if (response.result.value != nil) {
                let strOutput = JSON(response.result.value ?? "nil")

                if let resObj = strOutput.arrayObject {
                    arrRes2 = resObj as! [[String:AnyObject]]
                    self.db.addShowsToDatabase(arrRes: arrRes2)
                }
            }

            self.db.deleteOldShows()
            self.grabData(id: 1)
            self.tableView.reloadData()
        }
        ////////////////////////////////////////////////////////////////////
    }

    func grabData(id: Int) -> Void {
        regionResults = self.db.listAllShows(id: id)
        self.tableView.reloadData()
    }

    func numberOfComponents(in pickerView: UIPickerView) -> Int {
        return 1
    }

    func pickerView(_ pickerView: UIPickerView, numberOfRowsInComponent component: Int) -> Int {
        return cities.count
    }

    func pickerView(_ pickerView: UIPickerView, titleForRow row: Int, forComponent component: Int) -> String? {
        return cities[row]
    }

    func pickerView(_ pickerView: UIPickerView, didSelectRow row: Int, inComponent component: Int) {
        cheapFix = row + 1
        grabData(id: row + 1)
    }

    func tableView(_ tableView: UITableView, numberOfRowsInSection section: Int) -> Int {
        if regionResults.isEmpty {
            return 1
        } else {
            return regionResults.count
        }
    }

    func tableView(_ tableView: UITableView, cellForRowAt indexPath: IndexPath) -> UITableViewCell {
        let cell = tableView.dequeueReusableCell(withIdentifier: "bandCustomCell") as! BandTableViewCell
        if regionResults.isEmpty {
            cell.bandPic.image = UIImage(named: "flyer.jpg")
            cell.bandSummary?.text = "No Shows Announced!"
            cell.bandVenue?.text = "None"
            cell.bandDate?.text = "None"
        } else {
            let show = regionResults[indexPath.row]
            //print(try! show.get(Expression<String>("show_summary")))

            let strDateFull = try! show.get(Expression<String>("show_date"))
            var strDate: Array = ((strDateFull as AnyObject).components(separatedBy: "T"))

            // Setting up the date
            var dateArr: Array = strDate[0].components(separatedBy: "-")
            let dateStr: String = "\(dateArr[1])-\(dateArr[2])-\(dateArr[0])"

            // Setting up the time
            var timeArr: Array = strDate[1].components(separatedBy: ":")
            var timeStr: Int? = Int(timeArr[0])

            // Changing military time to standard
            if timeStr! > 12 {
                timeStr = timeStr! - 12
            }
            let saved = try! show.get(Expression<Bool>("save_show"))

            if (saved == true) {
                cell.bandSavedShow.isHidden = false
            } else if (saved == false) {
                cell.bandSavedShow.isHidden = true
            }

            cell.bandSummary?.text = "\(try! show.get(Expression<String>("show_summary"))), \(timeStr!):\(timeArr[1])PM"
            cell.bandVenue?.text = try! show.get(Expression<String>("venue_name"))
            /*if (show["shows_img"] as? String != "null") {
                let url = URL(string: show["shows_img"] as! String)
                cell.bandPic.kf.setImage(with: url)
            } else {*/
            cell.bandPic.image = UIImage(named: "flyer.jpg")
            //}
            cell.bandDate?.text = dateStr

            tableView.isScrollEnabled = true

        }
        return cell
    }

    func tableView(_ tableView: UITableView, didSelectRowAt indexPath: IndexPath) {

        myIndex2 = indexPath.row
        //performSegue(withIdentifier: "segue2", sender: self)
    }

    @objc func longPress(_ longPressGestureRecognizer: UILongPressGestureRecognizer) {
        if longPressGestureRecognizer.state == UIGestureRecognizer.State.began {
            let touchPoint = longPressGestureRecognizer.location(in: self.tableView)
            if let indexPath = self.tableView.indexPathForRow(at: touchPoint) {

                let show = regionResults[indexPath.row]
                let summary = try! show.get(Expression<String>("show_summary"))
                let date = try! show.get(Expression<String>("show_date"))
                let saved = try! show.get(Expression<Bool>("save_show"))

                self.db.toogleSaveShows(summary: summary, date: date, saved: saved)
                reload(tableView: self.tableView, indexPath: indexPath)
            }
            //grabData(id: cheapFix)

        }
    }

    func reload(tableView: UITableView, indexPath: IndexPath) {
        //found on stackoverflow
        let contentOffset = tableView.contentOffset
        tableView.beginUpdates()
        tableView.reloadRows(at: [indexPath], with: UITableView.RowAnimation.none)
        tableView.setContentOffset(contentOffset, animated: false)
        tableView.endUpdates()
    }
}

Answer 1

Firstly you must add gesture recogniser on the cell being used instead of the whole table view as in selector method of gesture you are trying to get the indexpath of cell being pressed.

Then try reloading the cell with found indexpath.

    self.tableView.reloadRows(at: [indexpath], with: .automatic)

Answer 2

update the longPressGesture method as below:

let touchPoint = longPressGestureRecognizer.location(in: self.tableView)
        if let indexPath = self.tableView.indexPathForRow(at: touchPoint) {
              let cell = tableView.cellForRow(at: indexPath) as? BandTableViewCell;
              cell.bandPic.image = ....//provide image here.
        }

Here, it is not required to reload full table, instead just access the cell and set imageview there.