Create a subView using CGPath and than adding UIPanGestureRecognizer on that subview

Question

I have seen several answers about adding a GestureRecognzier to subViews but my problem is that I don't have the subView's frame available beforehand. I am drawing a CGPath and at the Touches Ended method, I want to create a new subView with frame equal to CGPath bounding box. After that, I want to drag that subView with PanGestureRecognizer. I am trying to implement Evernote crop functionality where the user selects a certain area of view and move it to other position. Is this the right approach to that solution?

Answer 1

Not quite understand the relationship between UIGestureRecognizer and .frame. you can simply add UIGestureRecognizer to object, once its init work finished. Try to add gesture in TouchEnd method directly after drawing subview.

import UIKit

class GestureResearchVC: UIViewController{

    var subViewByCGPath: UIView?

    override func viewDidLoad() {
        super.viewDidLoad()
    }

    func createSubView(){
        //creat subview
        subViewByCGPath = UIView(frame: CGRect(x: 100, y: 100, width: 100, height: 100))
        subViewByCGPath?.backgroundColor = UIColor.yellow
        let circlePath = UIBezierPath(arcCenter: CGPoint(x: 50,y: 50), radius: CGFloat(20), startAngle: CGFloat(0), endAngle:CGFloat(M_PI * 2), clockwise: true)

        let shapeLayer = CAShapeLayer()
        shapeLayer.path = circlePath.cgPath
        shapeLayer.strokeColor = UIColor.red.cgColor

        subViewByCGPath?.layer.addSublayer(shapeLayer)
        self.view.addSubview(subViewByCGPath!)

        //add pan gesture to subViewByCGPath
        let gesture = UIPanGestureRecognizer(target: self, action: #selector(panGestureAction(rec:)))
        subViewByCGPath?.addGestureRecognizer(gesture)
}

    override func touchesEnded(_ touches: Set<UITouch>, with event: UIEvent?) {
        if subViewByCGPath == nil {
            print("touch end once")
            createSubView()
        }else{
            print("touch end repeatedly")
        }
    }

    func panGestureAction(rec: UIPanGestureRecognizer){
        print("pannnnnnn~")
        let transPoint = rec.translation(in: self.view)
        let x = rec.view!.center.x + transPoint.x
        let y = rec.view!.center.y + transPoint.y

        rec.view!.center = CGPoint(x: x, y: y)
        rec.setTranslation(CGPoint(x: 0, y: 0), in: self.view)

        //distinguish state
        switch rec.state {
            case .began:
                print("began")
            case .changed:
                print("changed")
            case .ended:
                print("ended")
            default:
                print("???")
        }
    }
}