圆形UIView的大小调整，动画保持圆形形状

Question

I have a UIView which I am making the background a circular shape with:

 self.colourView.layer.cornerRadius = 350
 self.colourView.clipsToBounds = true

With the view being a 700 by 700 square.

I am then trying to change the size of this view using:

UIView.animate(withDuration: zoomLength,
                                   delay: 0,
                                   options: .curveEaseIn,
                                   animations: {
                                    self.colorViewWidth.constant = 100
                                    self.colorViewHeight.constant = 100

                                    self.colourView.layer.cornerRadius = 50
                                    self.colourView.clipsToBounds = true
                                    self.view.layoutIfNeeded()
                                    },
                                   completion: { finished in

                                        })

                                    })

The problem with this is the corner radius of the view switch to 50 instantly. So that as the view shrinks in size it doesn't look like a circle shrinking but a square with rounded corners until it reaches the 100 by 100 size.

How can I take a view that circule in shape and shrink it down while maintaining the circlare shape during the animation.

Answer 1

You could always animate the corner radius as well with a CABasicAnimation along side the UIView animations. See example below.

import UIKit

class ViewController: UIViewController {

    //cause 'merica
    var colorView = UIView()
    var button = UIButton()

    var colorViewWidth : NSLayoutConstraint!
    var colorViewHeight : NSLayoutConstraint!

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


        colorView.frame = CGRect(x: 0, y: 0, width: 750, height: 750)
        colorView.center = self.view.center
        colorView.backgroundColor = .blue
        colorView.layer.cornerRadius = 350
        colorView.clipsToBounds = true
        colorView.layer.allowsEdgeAntialiasing = true
        colorView.translatesAutoresizingMaskIntoConstraints = false

        //set up constraints

        colorViewWidth = NSLayoutConstraint(item: colorView, attribute: .width, relatedBy: .equal, toItem: nil, attribute: .notAnAttribute, multiplier: 1, constant: 750)
        colorViewWidth.isActive = true

        colorViewHeight = NSLayoutConstraint(item: colorView, attribute: .height, relatedBy: .equal, toItem: nil, attribute: .notAnAttribute, multiplier: 1, constant: 750)
        colorViewHeight.isActive = true

        self.view.addSubview(colorView)
        colorView.centerXAnchor.constraint(equalTo: self.view.centerXAnchor).isActive = true
        colorView.centerYAnchor.constraint(equalTo: self.view.centerYAnchor).isActive = true

        //button for action
        button = UIButton(frame: CGRect(x: 0, y: 0, width: self.view.bounds.width - 20, height: 50))
        button.center = self.view.center
        button.center.y = self.view.bounds.height - 70
        button.addTarget(self, action: #selector(ViewController.pressed(sender:)), for: .touchUpInside)
        button.setTitle("Animate", for: .normal)
        button.setTitleColor(.blue, for: .normal)

        self.view.addSubview(button)

    }

    func pressed(sender:UIButton) {

        self.colorViewWidth.constant = 100
        self.colorViewHeight.constant = 100

        UIView.animate(withDuration: 1.0,
                       delay: 0,
                       options: .curveEaseIn,
                       animations: {
                        self.view.layoutIfNeeded()

        },

                       completion: { finished in

        })

        //animate cornerRadius and update model
        let animation = CABasicAnimation(keyPath: "cornerRadius")
        animation.duration = 1.0
        //super important must match
        animation.timingFunction = CAMediaTimingFunction(name: kCAMediaTimingFunctionEaseIn)
        animation.fromValue = colorView.layer.cornerRadius
        animation.toValue = 50
        colorView.layer.add(animation, forKey: nil)
        //update model important
        colorView.layer.cornerRadius = 50

    }
}

Result:

Answer 2

Try to put your image inside a viewDidLayoutSubviews()

override func viewDidLayoutSubviews() {
    super.viewDidLayoutSubviews()

 colourView.layer.cornerRadius  = colourView.frame.size.width/2
 colourView.layer.masksToBounds = true
 colourView.layer.borderWidth = 3.0
 colourView.layer.borderColor = UIColor(red: 142.0/255.5, green: 142.0/255.5, blue: 142.0/255.5, alpha: 1.0).cgColor

}

let me know how it goes

Cheers

Answer 3

Regarding animation you need to create the CAShapeLayer object and then set the cgpath of the layer object.

let circleLayer = CAShapeLayer()
let radius = view.bounds.width * 0.5
//Value of startAngle and endAngle should be in the radian.
let path = UIBezierPath(arcCenter: center, radius: radius, startAngle: startAngle, endAngle: endAngle, clockwise: true)
circleLayer.path = path.cgPath

The above will draw the circle for you. After that you can apply the animation on layer object.

let animation = CABasicAnimation(keyPath: "strokeEnd")
animation.fromValue = fromValue//you can update the value here by default it will be 0
animation.toValue = toValue //you can update the value here by default it will be 1
animation.duration = CFTimeInterval(remainingTime)
    circleLayer
circleLayer.removeAnimation(forKey: "stroke")
circleLayer.add(animation, forKey: "stroke")