ios - Custom view with CALayer wired effect when animating bounds change

Question

I have implemented a custom view with adding CALayer as sublayer for UIView. When I animate the view with the following:UIView.animateWithDuration(2.0) { self.slider.bounds.size *= 2.0}, the scaling animation is kind of wrong. The CALayer start at the wrong position with scaled size and move to the final position instead of scaling with the view.

The CustomeView Code :

import UIKit

class GridMaskView: UIView {
    private let cornerLayer: CAShapeLayer
    private let borderLayer: CAShapeLayer
    private let gridLayer: CAShapeLayer

    private let gridSize: (horizontal: UInt, vertical: UInt) = (3, 3)
    private let cornerThickness: CGFloat = 3.0
    private let cornerLength: CGFloat = 20.0
    private let borderThickness: CGFloat = 2.0
    private let gridThickness: CGFloat = 1.0
    private let lineColor: UIColor = UIColor(r: 120, g: 179, b: 193, a: 1)

    var showGridLines: Bool = true {
        didSet {
            gridLayer.hidden = !showGridLines
        }
    }

    required init?(coder aDecoder: NSCoder) {
        fatalError("init(coder:) has not been implemented")
    }

    override init(frame: CGRect) {
        cornerLayer = CAShapeLayer()
        cornerLayer.fillColor = lineColor.CGColor

        borderLayer = CAShapeLayer()
        borderLayer.fillColor = UIColor.clearColor().CGColor
        borderLayer.strokeColor = lineColor.CGColor
        borderLayer.lineWidth = borderThickness

        gridLayer = CAShapeLayer()
        gridLayer.strokeColor = lineColor.CGColor
        gridLayer.lineWidth = gridThickness

        super.init(frame: frame)
        layer.addSublayer(cornerLayer)
        layer.addSublayer(borderLayer)
        layer.addSublayer(gridLayer)
    }

    override func layoutSubviews() {
        super.layoutSubviews()
        layoutLayers()
    }

    private func layoutLayers() {
        drawCorner()
        drawBorder()
        drawGrid()
    }

    private func drawCorner() {
        cornerLayer.frame = bounds.insetBy(dx: -cornerThickness, dy: -cornerThickness)
        cornerLayer.path = cornerPath(forBounds: cornerLayer.bounds)
    }

    private func cornerPath(forBounds bounds: CGRect) -> CGPathRef {
        let horizontalSize = CGSize(width: cornerLength, height: cornerThickness)
        let verticalSize = CGSize(width: cornerThickness, height: cornerLength)

        let corners: [(CGRectEdge, CGRectEdge)] = [(.MinXEdge, .MinYEdge), (.MinXEdge, .MaxYEdge), (.MaxXEdge, .MinYEdge), (.MaxXEdge, .MaxYEdge)]

        var cornerRects = [CGRect]()
        for corner in corners {
            cornerRects.append(bounds.align(horizontalSize, corner: corner.0, corner.1))
            cornerRects.append(bounds.align(verticalSize, corner: corner.0, corner.1))
        }

        let cornerPath = CGPathCreateMutable()
        CGPathAddRects(cornerPath, nil, cornerRects, cornerRects.count)

        return cornerPath
    }

    private func drawBorder() {
        borderLayer.frame = bounds
        borderLayer.path = borderPath(forBounds: borderLayer.bounds)
    }

    private func borderPath(forBounds bounds: CGRect) -> CGPathRef {
        let borderPath = CGPathCreateMutable()
        let borderCornerPoints = [bounds.topLeft, bounds.topRight, bounds.bottomRight, bounds.bottomLeft, bounds.topLeft]
        CGPathAddLines(borderPath, nil, borderCornerPoints, borderCornerPoints.count)

        return borderPath
    }

    private func drawGrid() {
        gridLayer.frame = bounds
        gridLayer.path = gridPath(forBounds: gridLayer.bounds)
    }

    private func gridPath(forBounds bounds: CGRect) -> CGPathRef {
        let stepSize = bounds.size / (CGFloat(gridSize.horizontal), CGFloat(gridSize.vertical))

        let gridPath = CGPathCreateMutable()
        for i in (1...gridSize.vertical) {
            let x = CGFloat(i) * stepSize.width
            CGPathMoveToPoint(gridPath, nil, x, 0)
            CGPathAddLineToPoint(gridPath, nil, x, bounds.size.height)
        }

        for i in (1...gridSize.horizontal) {
            let y = CGFloat(i) * stepSize.height
            CGPathMoveToPoint(gridPath, nil, 0, y)
            CGPathAddLineToPoint(gridPath, nil, bounds.size.width, y)
        }
        return gridPath
    }

    override func intrinsicContentSize() -> CGSize {
        return CGSize(width: cornerLength * 2, height: cornerLength * 2)
    }
}

Anyone know how to fit this?

Answer 1

The problem is that when you do view animation you don't get any automatic animation of sublayers. You'd be better off using a subview of your original UIView, because view animation will animate that together with the original view, according to its autolayout constraints.