細かい部分の調整

ThemeSegmentedControl.swift

import UIKit

public final class ThemeSegmentedControl: UISegmentedControl {
	private var observer: NSObjectProtocol?
	
	private weak var selectedLayer: CALayer!
	
	public override var frame: CGRect {
		didSet {
			guard let selectedLayer = selectedLayer else { return }
			selectedLayer.frame.size.height = frame.size.height
			selectedLayer.cornerRadius = 0.5 * frame.size.height
		}
	}
	
	public override var selectedSegmentIndex: Int {
		didSet { update(at: selectedSegmentIndex) }
	}
	
	public override var tintColor: UIColor! {
		get { return themeTintColor }
		set {
			guard themeTintColor != newValue else { return }
			themeTintColor = newValue
			setupDesign()
		}
	}
	private var themeTintColor: UIColor?
	
	public override init(frame: CGRect) {
		super.init(frame: frame)
		setup()
	}
	
	public override init(items: [Any]?) {
		super.init(items: items)
	}
	
	required init?(coder aDecoder: NSCoder) {
		super.init(coder: aDecoder)
		setup()
	}
	
	deinit {
		if let observer = observer {
			self.observer = nil
			
			NotificationCenter.default.removeObserver(observer)
		}
	}
	
	private func setup() {
		backgroundColor = .clear
		super.tintColor = .clear
		addTarget(self, action: #selector(update(sender:)), for: .valueChanged)
		
		observer = NotificationCenter.default
			.addObserver(forName: UIAccessibility.darkerSystemColorsStatusDidChangeNotification,
						 object: nil,
						 queue: OperationQueue.main,
						 using: darkerSystemColorsStatusDidChange)
		
		setupDesign()
	}
	
	private func darkerSystemColorsStatusDidChange(notification: Notification) {
		if tintColor == nil {
			setupDesign()
		}
	}
	
	private func setupDesign() {
		var selectedColor: UIColor
		if let tintColor = tintColor {
			selectedColor = tintColor
		} else if UIAccessibility.isDarkerSystemColorsEnabled {
			selectedColor = UIColor(red: 0.0, green: 0.25, blue: 0.87, alpha: 1.0)
		} else {
			selectedColor = UIColor(red: 0.0, green: 122.0 / 255.0, blue: 1.0, alpha: 1.0)
		}
		
		// Normal
		let normalAttrs: [NSAttributedString.Key: Any] = [.foregroundColor: selectedColor]
		setTitleTextAttributes(normalAttrs, for: .normal)
		setTitleTextAttributes(normalAttrs, for: .highlighted)
		
		// Selected
		let selectedState: [UIControl.State] = [
			.selected,
			[.selected, .highlighted],
		]
		let selectedAttrs: [NSAttributedString.Key: Any] = [.foregroundColor: UIColor.white]
		selectedState.forEach { setTitleTextAttributes(selectedAttrs, for: $0) }
		
		// Disable
		let disabledAttrs: [NSAttributedString.Key: Any] = [.foregroundColor: UIColor(white: 0.48, alpha: 0.35)]
		setTitleTextAttributes(disabledAttrs, for: .disabled)
		
		let selectedLayer = self.selectedLayer ?? createSelectedLayer()
		selectedLayer.backgroundColor = selectedColor.cgColor
		selectedLayer.shadowColor = selectedColor.cgColor
		
		if selectedSegmentIndex != -1 {
			update(at: selectedSegmentIndex)
		}
	}
	
	private func createSelectedLayer() -> CALayer {
		let selectedLayer = CALayer()
		selectedLayer.cornerRadius = 0.5 * frame.size.height
		selectedLayer.frame.size.height = frame.size.height
		selectedLayer.rasterizationScale = UIScreen.main.scale
		selectedLayer.shadowOffset = CGSize(width: 0.0, height: 2.0)
		selectedLayer.shadowOpacity = 0.4
		selectedLayer.shadowRadius = 2.0
		selectedLayer.shouldRasterize = true
		self.selectedLayer = selectedLayer
		layer.addSublayer(selectedLayer)
		return selectedLayer
	}
	
	public override func layoutSubviews() {
		super.layoutSubviews()
		
		if selectedSegmentIndex != -1 {
			update(at: selectedSegmentIndex)
		}
	}
	
	@objc private func update(sender: ThemeSegmentedControl!) {
		update(at: selectedSegmentIndex)
	}
	
	private func update(at index: Int) {
		let sortedSubviews = subviews.sorted { $0.frame.origin.x < $1.frame.origin.x }
		let selectedFrame = sortedSubviews[index].frame
		UIView.animate(withDuration: 0.3) {
			self.selectedLayer.frame = selectedFrame
		}
	}
}