How to resize UIView by dragging from its edges?

Question

In my iPad app, I want the users to be able to resize a UIView by dragging the view from its edges. I\'ll be using iOS 5 SDK, so what\'s the cleanest approach t

Answer 1

This is a Swift 4.2 Solution which works with AutoLayout & Constraint-Animation.

Since it is recommended to animate the constraints rather than the actual size of a rectangle when working with AutoLayout, this solutions does exactly that.

Additional features:

• Resize only one side when not on the edge.
• Move the whole rectangle on touch in the middle of the it.

Checkout a video of it here: https://imgur.com/a/CrkARLi

Import is to connect the constraints as outlets, to animate them.

import UIKit

class ViewController: UIViewController {


@IBOutlet weak var topConstraint: NSLayoutConstraint!
@IBOutlet weak var rightConstraint: NSLayoutConstraint!
@IBOutlet weak var leftConstraint: NSLayoutConstraint!
@IBOutlet weak var bottomConstraint: NSLayoutConstraint!
@IBOutlet weak var rect: UIView!

struct ResizeRect{
    var topTouch = false
    var leftTouch = false
    var rightTouch = false
    var bottomTouch = false
    var middelTouch = false
}

var touchStart = CGPoint.zero
var proxyFactor = CGFloat(10)
var resizeRect = ResizeRect()

override func viewDidLoad() {
    super.viewDidLoad()
    // Do any additional setup after loading the view, typically from a nib.
}

override func touchesBegan(_ touches: Set, with event: UIEvent?) {
    if let touch = touches.first{

        let touchStart = touch.location(in: self.view)
        print(touchStart)

        resizeRect.topTouch = false
        resizeRect.leftTouch = false
        resizeRect.rightTouch = false
        resizeRect.bottomTouch = false
        resizeRect.middelTouch = false

        if  touchStart.y > rect.frame.minY + (proxyFactor*2) &&  touchStart.y < rect.frame.maxY - (proxyFactor*2) &&  touchStart.x > rect.frame.minX + (proxyFactor*2) &&  touchStart.x < rect.frame.maxX - (proxyFactor*2){
            resizeRect.middelTouch = true
            print("middle")
            return
        }

        if touchStart.y > rect.frame.maxY - proxyFactor &&  touchStart.y < rect.frame.maxY + proxyFactor {
            resizeRect.bottomTouch = true
            print("bottom")
        }

        if touchStart.x > rect.frame.maxX - proxyFactor && touchStart.x < rect.frame.maxX + proxyFactor {
            resizeRect.rightTouch = true
            print("right")
        }

        if touchStart.x > rect.frame.minX - proxyFactor &&  touchStart.x < rect.frame.minX + proxyFactor {
            resizeRect.leftTouch = true
            print("left")
        }

        if touchStart.y > rect.frame.minY - proxyFactor &&  touchStart.y < rect.frame.minY + proxyFactor {
            resizeRect.topTouch = true
            print("top")
        }

    }
}

override func touchesMoved(_ touches: Set, with event: UIEvent?) {
    if let touch = touches.first{
        let currentTouchPoint = touch.location(in: self.view)
        let previousTouchPoint = touch.previousLocation(in: self.view)

        let deltaX = currentTouchPoint.x - previousTouchPoint.x
        let deltaY = currentTouchPoint.y - previousTouchPoint.y


        if resizeRect.middelTouch{
            topConstraint.constant += deltaY
            leftConstraint.constant += deltaX
            rightConstraint.constant -= deltaX
            bottomConstraint.constant -= deltaY
        }

        if resizeRect.topTouch {
            topConstraint.constant += deltaY
        }

        if resizeRect.leftTouch {
            leftConstraint.constant += deltaX
        }
        if resizeRect.rightTouch {
            rightConstraint.constant -= deltaX
        }
        if resizeRect.bottomTouch {
            bottomConstraint.constant -= deltaY
        }


        UIView.animate(withDuration: 0.25, delay: 0, options: UIView.AnimationOptions.curveEaseIn, animations: {
            self.view.layoutIfNeeded()
        }, completion: { (ended) in

        })
    }
   } 
  }

I put this as working project on Github too: https://github.com/ppoh71/resizeRectangleOnTouchDrag