How to adjust sublayer on UINavigationController? - ios

Question

In my Swift project, I added a sublayer to UINavigationController.
But after adding this GAGradientLayer, I can't see the navigation title text or back button.
The weird thing is that in the view hierarchy, the CAGradientLayer(which was added as sublayer) is behind the title and button.
I tried to reload navigationController layer with LayoutIfNeeded, setNeedsLayout or setNeedsDisplay but nothing worked.
And I also just tried to change the navigation title but it doesn't work.
(Actually The text of navigation title is loaded on the view controller behind, so I don't want to change this on this VC.)
So, How can I show my navigation title text and button with CAGradientlayer above?
Here's the screenshot
Here's the codes needed
import UIKit
import SnapKit
class BulletinBoardViewController: UIViewController {
// ...
var backgroundGradientLayer: CAGradientLayer?
let bulletinBoardView = BulletinBoardView()
// MARK: - Lifecycles
override func viewDidLoad() {
super.viewDidLoad()
setBulletinBoardView()
setCells()
}
override func viewWillAppear(_ animated: Bool) {
setupBackgroundLayer()
}
override func viewWillDisappear(_ animated: Bool) {
self.backgroundGradientLayer?.removeFromSuperlayer()
}
// MARK: - Helpers
func setupBackgroundLayer() {
DispatchQueue.main.async {
if let backgroundGradientLayer = self.backgroundGradientLayer {
backgroundGradientLayer.frame = CGRect(x: 0, y: -59, width: 500, height: 103)
self.navigationController?.navigationBar.layer.addSublayer(backgroundGradientLayer)
}
}
}
func setBulletinBoardView() {
self.view.addSubview(bulletinBoardView)
bulletinBoardView.snp.makeConstraints { make in
make.right.left.top.equalTo(self.view.safeAreaLayoutGuide)
make.bottom.equalTo(self.view)
}
}
// ...
}
The origin navigation controller setting is below
class MainPageViewController: UIViewController {
// ...
func setupNav() {
navigationController?.navigationBar.tintColor = .black
navigationItem.rightBarButtonItem = listButton
navigationItem.leftBarButtonItem = settingButton
let backBarButtonItem = UIBarButtonItem(title: "",
style: .plain,
target: self,
action: nil)
self.navigationItem.backBarButtonItem = backBarButtonItem
let appearance = UINavigationBarAppearance()
appearance.configureWithOpaqueBackground()
appearance.backgroundColor = .systemGray3
appearance.titleTextAttributes = [NSAttributedString.Key.font: UIFont(name: AppFontName.bold, size: 20)!]
navigationController?.navigationBar.standardAppearance = appearance
navigationController?.navigationBar.scrollEdgeAppearance =
navigationController?.navigationBar.standardAppearance
}
// ...
}