Match UISegmentedControl's color with that of translucent navigation bar

Question

I am adding a segmented control directly under the (translucent) navigation bar, and want it to have the same color. I am trying to make it look like it's part of the navigation bar.

isOpaque = false
layer.opacity = 0.85
let bkImg = UIImage(color: .systemBackground.withAplhaComponent(0.85), size: CGSize(width: 1, height: 16))
segmentedCtrl.setBackgroundImage(bkImg, for: .normal, barMetrics: .default)
setDividerImage(bkImg, forLeftSegmentState: .normal, rightSegmentState: .normal, barMetrics: .default)

I've tried playing with the opacity of the segmented control, and the color of bkImg, but that has no effect at all. It would have been quicker to just write a custom tab bar from scratch - the segmented control in iOS 13 is impossible to customize.

Answer 1

This is a total hack, but it looks good.

class CustomSegmentedControl: UISegmentedControl {
    private var underline: UIView!

    init() {
        super.init(frame: .zero)

        underline = UIView()
        underline.backgroundColor = tintColor
        view.addSubvie(underline)
    }

    override func layoutSubviews() {
        super.layoutSubviews()

        // Set background color to match navigation bar
        let bgColor = UIColor.systemBackground.hsbComponents.brightness == 1.0
            ? UIColor.black.withAlphaComponent(0.028) // light
            : UIColor.white.withAlphaComponent(0.073) // dark
        let img = UIImage(color: bgColor, size: CGSize(width: 1, height: 16))
        setBackgroundImage(img, for: .normal, barMetrics: .default)
        setDividerImage(img, forLeftSegmentState: .normal, rightSegmentState: .normal, barMetrics: .default)

        // Bonus: underline below selected tab
        var frame = underline.frame
        let tabWidth = self.frame.width / CGFloat(numberOfSegments)
        frame.origin.x = CGFloat(selectedSegmentIndex) * tabWidth
        frame.origin.y = self.frame.height - 2.0
        frame.size.width = tabWidth
        underline.frame = frame
    }
}