在特定条件下启用和禁用平移手势

Question

@IBOutlet weak var topViewHeightConstraint: NSLayoutConstraint!
@IBOutlet weak var bottomViewHeightConstraint: NSLayoutConstraint!
@IBOutlet var panGesture: UIPanGestureRecognizer!

@IBAction func panGestureAction(_ sender: UIPanGestureRecognizer) {
    if sender.state == .began || sender.state == .changed{
        let translation = sender.translation(in: sender.view)
        let changeX = (sender.view?.center.x)!
        let changeY = (sender.view?.center.y)! + translation.y
        topViewHeightConstraint.constant = topViewHeightConstraint.constant + translation.y
        bottomViewHeightConstraint.constant = bottomViewHeightConstraint.constant - translation.y
        sender.view?.center = CGPoint(x: changeX, y: changeY)
        sender.setTranslation(CGPoint.zero, in: sender.view)
    }
}

The above code will decrease the top view's height when the yellow view is dragged upward and increase top view's height on dragging downward. Vice versa for bottom view as well.

Now I want the pan gesture to stop dragging upward if the top view's height is reduced to certain height lets say 200 px but user should be able to drag downward. Also for bottom view as well user should not go downward if the bottom view's height becomes 200 px.

Anyone please help me with the solution will be greatfull. Thank You!

Answer 1

Inside panGestureAction function use a logic like this.

 @objc func panGestureAction(_ recognizer: UIPanGestureRecognizer) {
        if  your_view_height < 200 && recognizer.translation(in: self.view).y < 0{
            //This will stop moving upwards
            return
        }
  }

Use the same logic with necessary changes for the other case as well.