Swift: pull down to close the `UITableViewController`

Question

I want to collapse to reject UITableViewController, so I used the method scrollViewDidScroll, but it does not work!

    class CommentViewController: PFQueryTableViewController {

        private let tableHeaderHeight: CGFloat = 350.0



extension CommentViewController
{
    override func scrollViewDidScroll(scrollView: UIScrollView)
    {



            // Pull down to dismiss TVC 
            let offsetY = scrollView.contentOffset.y
            let adjustment: CGFloat = 130.0

            // for later use
            if (-offsetY) > (tableHeaderHeight+adjustment) {
                self.dismissViewControllerAnimated(true, completion: nil)
                }
 }
    }

Answer 1

You must implement an optional pan gesture recognizer that recognizes the scrollView pan gesture recognizer. You can then determine if the user is panning with the finger when the table has already been scrolled to the top. eg

var isTrackingPanLocation = false
var panGestureRecognizer: UIPanGestureRecognizer!

public override func viewDidLoad() {
    super.viewDidLoad()
    tableView.bounces = false
    panGestureRecognizer = UIPanGestureRecognizer(target: self, 
                                                  action: #selector(panRecognized(gestureRecognizer:)))
    panGestureRecognizer.delegate = self
    tableView.addGestureRecognizer(panGestureRecognizer)
}

public func panRecognized(recognizer: UIPanGestureRecognizer) {
    if recognizer.state == .began && tableView.contentOffset.y == 0 {
        recognizer.setTranslation(CGPoint.zero, inView : tableView)

        isTrackingPanLocation = true
    } else if recognizer.state != .ended && 
              recognizer.state != .cancelled && 
              recognizer.state != .failed && 
              isTrackingPanLocation {
        let panOffset = recognizer.translationInView(tableView)

        // determine offset of the pan from the start here. 
        // When offset is far enough from table view top edge - 
        // dismiss your view controller. Additionally you can 
        // determine if pan goes in the wrong direction and 
        // then reset flag isTrackingPanLocation to false

        let eligiblePanOffset = panOffset.y > 200
        if eligiblePanOffset {
            recognizer.enabled = false
            recognizer.enabled = true
            dismissViewControllerAnimated(true, completion: nil)
        }

        if panOffset.y < 0 {
            isTrackingPanLocation = false
        }
    } else {
        isTrackingPanLocation = false
    }
}

public func gestureRecognizer(gestureRecognizer: UIGestureRecognizer, 
    shouldRecognizeSimultaneouslyWithGestureRecognizer 
                    otherGestureRecognizer: UIGestureRecognizer) -> Bool {
    return true
}

Answer 2

Swift 4

var panGestureRecognizer : UIPanGestureRecognizer!

override func viewDidLoad() {
    mainTableView.bounces = true
    panGestureRecognizer = UIPanGestureRecognizer(target: self, action: #selector(self.panRecognized))
    panGestureRecognizer.delegate = self
    mainTableView.addGestureRecognizer(panGestureRecognizer)
}


@objc func panRecognized(recognizer: UIPanGestureRecognizer) {
    if recognizer.state == .began && mainTableView.contentOffset.y == 0 {

    } else if recognizer.state != .ended && recognizer.state != .cancelled && recognizer.state != .failed {
        let panOffset = recognizer.translation(in: mainTableView)
        let eligiblePanOffset = panOffset.y > 300
        if eligiblePanOffset {
            recognizer.isEnabled = false
            recognizer.isEnabled = true
            self.dismiss(animated: true, completion: nil)
        }
    }
}


func gestureRecognizer(_ gestureRecognizer: UIGestureRecognizer, shouldRecognizeSimultaneouslyWith otherGestureRecognizer: UIGestureRecognizer) -> Bool {
    return true
}

Answer 3

(offsetY) scrollViewDidScroll. , (-offsetY) > (tableHeaderHeight+adjustment) - , , .