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...

Polygenesis

The approach can be the same as for TabBar in Programmatically detect Tab Bar or TabView height in SwiftUI – Ptolemaic

TY, this is the answer – Polygenesis

Answer 1

Based on this post (thanks to Asperi): https://mcmap.net/q/957021/-programmatically-detect-tab-bar-or-tabview-height-in-swiftui

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.
 })

Polygenesis

This works fine. But don't use it on the NavigationView, since navigation controller will be nil then. Also, the typealias in the NavBarAccessor can be removed. – Trilbi

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)
    }
}

Emperor

a generic constraint would be more preferable rather than AnyView using – Hashum