Swift - Drag And Drop TableViewCell with Long Gesture Recognizer

Question

So I have seen a lot of posts about reordering cells that pertain to using "edit mode", but none for the problem I have. (Excuse me if I am wrong).

I am building a ranking app, and looking for a way to use a long gesture recognizer to reorder the cells in my UITableView. Essentially a user will be able to reorder and "Rank" the cells full of strings in a group with their friends.

I would go the standard route of using an "edit" bar button item in the nav bar, but I am using the top right of the nav bar for adding new strings to the tableview already. (The following image depicts what I mean).

So far, I have added `

    var lpgr = UILongPressGestureRecognizer(target: self, action: "longPressDetected:")

    lpgr.minimumPressDuration = 1.0;
    tableView.addGestureRecognizer(lpgr)`

to my viewDidLoad method, and started creating the following function:

    func longPressDetected(sender: AnyObject) {

    var longPress:UILongPressGestureRecognizer = sender as UILongPressGestureRecognizer
    var state:UIGestureRecognizerState = longPress.state

    let location:CGPoint = longPress.locationInView(self.tableView) as CGPoint
    var indexPath = self.tableView.indexPathForRowAtPoint(location)?

    var snapshot:UIView!
    var sourceIndexPath:NSIndexPath!

}

All of the resources I have scowered for on the internet end up showing me a HUGE, LONG list of additives to that function in order to get the desired result, but those examples involve core data. It seems to me that there must be a far easier way to simply reorder tableview cells with a long press?

enter image description here

Yeah, you definitely don't need to use core data. You just want to drag and drop to reorder cells? Duplicate the tableview cell as a draggable view upon gesture recognition, then remove that view and update the table contents accordingly once that gesture is over. — Lyndsey Scott
Possible duplicate of Using long press gesture to reorder cells in tableview? — Grant Kamin

Teetz Teetz · Accepted Answer · 2017-09-22T05:38:32

Dave's answer is great. Here is the swift 4 version of this tutorial:

WayPointCell is your CustomUITableViewCell and wayPoints is the dataSource array for the UITableView

First, put this in your viewDidLoad, like Alfi mentionend:

override func viewDidLoad() {
    super.viewDidLoad()

    let longpress = UILongPressGestureRecognizer(target: self, action: #selector(longPressGestureRecognized(gestureRecognizer:)))
    self.tableView.addGestureRecognizer(longpress)
}

Then implement the method:

func longPressGestureRecognized(gestureRecognizer: UIGestureRecognizer) {

    let longpress = gestureRecognizer as! UILongPressGestureRecognizer
    let state = longpress.state
    let locationInView = longpress.location(in: self.tableView)
    var indexPath = self.tableView.indexPathForRow(at: locationInView)

    switch state {
    case .began:
        if indexPath != nil {
            Path.initialIndexPath = indexPath
            let cell = self.tableView.cellForRow(at: indexPath!) as! WayPointCell
            My.cellSnapShot = snapshopOfCell(inputView: cell)
            var center = cell.center
            My.cellSnapShot?.center = center
            My.cellSnapShot?.alpha = 0.0
            self.tableView.addSubview(My.cellSnapShot!)

            UIView.animate(withDuration: 0.25, animations: {
                center.y = locationInView.y
                My.cellSnapShot?.center = center
                My.cellSnapShot?.transform = CGAffineTransform(scaleX: 1.05, y: 1.05)
                My.cellSnapShot?.alpha = 0.98
                cell.alpha = 0.0
            }, completion: { (finished) -> Void in
                if finished {
                    cell.isHidden = true
                }
            })
        }

    case .changed:
        var center = My.cellSnapShot?.center
        center?.y = locationInView.y
        My.cellSnapShot?.center = center!
        if ((indexPath != nil) && (indexPath != Path.initialIndexPath)) {

            self.wayPoints.swapAt((indexPath?.row)!, (Path.initialIndexPath?.row)!)
            //swap(&self.wayPoints[(indexPath?.row)!], &self.wayPoints[(Path.initialIndexPath?.row)!])
            self.tableView.moveRow(at: Path.initialIndexPath!, to: indexPath!)
            Path.initialIndexPath = indexPath
        }

    default:
        let cell = self.tableView.cellForRow(at: Path.initialIndexPath!) as! WayPointCell
        cell.isHidden = false
        cell.alpha = 0.0
        UIView.animate(withDuration: 0.25, animations: {
            My.cellSnapShot?.center = cell.center
            My.cellSnapShot?.transform = .identity
            My.cellSnapShot?.alpha = 0.0
            cell.alpha = 1.0
        }, completion: { (finished) -> Void in
            if finished {
                Path.initialIndexPath = nil
                My.cellSnapShot?.removeFromSuperview()
                My.cellSnapShot = nil
            }
        })
    }
}

func snapshopOfCell(inputView: UIView) -> UIView {

    UIGraphicsBeginImageContextWithOptions(inputView.bounds.size, false, 0.0)
    inputView.layer.render(in: UIGraphicsGetCurrentContext()!)
    let image = UIGraphicsGetImageFromCurrentImageContext()!
    UIGraphicsEndImageContext()
    let cellSnapshot : UIView = UIImageView(image: image)
    cellSnapshot.layer.masksToBounds = false
    cellSnapshot.layer.cornerRadius = 0.0
    cellSnapshot.layer.shadowOffset = CGSize(width: -5.0, height: 0.0)
    cellSnapshot.layer.shadowRadius = 5.0
    cellSnapshot.layer.shadowOpacity = 0.4
    return cellSnapshot
}

struct My {
    static var cellSnapShot: UIView? = nil
}

struct Path {
    static var initialIndexPath: IndexPath? = nil
}

Swift - Drag And Drop TableViewCell with Long Gesture Recognizer

3 Answers