Xcode 13 在子类中实现backIndicatorImag

需要在swift 控制器下重新对backIndicatorImage赋值

if #available(iOS 13.0, *) {

            guard let img = UIImage(named: "nav_bar_icon")?.withRenderingMode(.alwaysOriginal) else {

                return

            }

            letappearance =UINavigationBarAppearance()

            appearance.backgroundColor= .white

            appearance.titleTextAttributes = [.foregroundColor: UIColor.black]

            appearance.setBackIndicatorImage(img, transitionMaskImage: img)

            let back = UIBarButtonItemAppearance()

            back.normal.titleTextAttributes = [.foregroundColor: UIColor.clear]

            appearance.backButtonAppearance= back

            navigationController?.navigationBar.tintColor = .white

            navigationController?.navigationBar.standardAppearance = appearance

            navigationController?.navigationBar.compactAppearance = appearance

            navigationController?.navigationBar.scrollEdgeAppearance = appearance

        }