SwiftUI NavigationBar height

Question

How to get current NavigationBar height? In UIKit we could get

navigationController?.navigationBar.frame.height

but can't find anything for SwiftUI...

Answer 1

Based on this post (thanks to Asperi): https://stackoverflow.com/a/59972635/12299030

struct NavBarAccessor: UIViewControllerRepresentable {
    var callback: (UINavigationBar) -> Void
    private let proxyController = ViewController()

    func makeUIViewController(context: UIViewControllerRepresentableContext<NavBarAccessor>) ->
                              UIViewController {
        proxyController.callback = callback
        return proxyController
    }

    func updateUIViewController(_ uiViewController: UIViewController, context: UIViewControllerRepresentableContext<NavBarAccessor>) {
    }

    typealias UIViewControllerType = UIViewController

    private class ViewController: UIViewController {
        var callback: (UINavigationBar) -> Void = { _ in }

        override func viewWillAppear(_ animated: Bool) {
            super.viewWillAppear(animated)
            if let navBar = self.navigationController {
                self.callback(navBar.navigationBar)
            }
        }
    }
}

And then we can call this from any View:

.background(NavBarAccessor { navBar in
      print(">> NavBar height: \(navBar.bounds.height)")
                // !! use as needed, in calculations, @State, etc.
 })

Answer 2

Building on @yoprst 's response, rather than configure calculations and @State variables, you could also return a View to insert directly into the hierarchy:

struct NavigationBarAccessor: UIViewControllerRepresentable {
    var callback: (UINavigationBar) -> (AnyView)
    private let proxyViewController = ProxyViewController()

    func makeUIViewController(context: UIViewControllerRepresentableContext<NavigationBarAccessor>) -> UIViewController {
        self.proxyViewController.callback = callback
        return proxyViewController
    }

    func updateUIViewController(_ uiViewController: UIViewController, context: UIViewControllerRepresentableContext<NavigationBarAccessor>) {
    }

    private class ProxyViewController: UIViewController {
        var callback: ((UINavigationBar) -> AnyView)?

        override func viewWillAppear(_ animated: Bool) {
            super.viewWillAppear(animated)
            if let navigationBar = self.navigationController?.navigationBar {
                _ = self.callback?(navigationBar)
            }
        }
    }
}

Usage:

VStack {
    NavigationBarAccessor { navigationBar in
        Spacer()
            .frame(height: navigationBar.frame.height)
    }
}