How to Hide the Navigationbar When Embedding Swiftui in Uikit

SwiftUI hide navigation bar of UIKit UINavigationController(rootViewController: _)

The UINavigationController should be in view hierarchy so that could have effect.

Here is worked variant, assuming you inject it into window in SceneDelegate (tested with Xcode 11.4 / iOS 13.4)

extension UIViewController{
    func inNavigation() -> UIViewController {
        let navigationController = UINavigationController(rootViewController: self)
        DispatchQueue.main.async {
            navigationController.isNavigationBarHidden = true
        }
        return navigationController
    }
}

How to hide a navigation bar from first ViewController in Swift?

If you know that all other views should have the bar visible, you could use viewWillDisappear to set it to visible again.

In Swift:

override func viewWillAppear(_ animated: Bool) {
    super.viewWillAppear(animated)
    navigationController?.setNavigationBarHidden(true, animated: animated)
}

override func viewWillDisappear(_ animated: Bool) {
    super.viewWillDisappear(animated)
    navigationController?.setNavigationBarHidden(false, animated: animated)
}

How to remove the default Navigation Bar space in SwiftUI NavigationView

For some reason, SwiftUI requires that you also set .navigationBarTitle for .navigationBarHidden to work properly.

NavigationView {
    FileBrowserView(jsonFromCall: URLRetrieve(URLtoFetch: applicationDelegate.apiURL))
        .navigationBarTitle("")
        .navigationBarHidden(true)
}

Update

As @Peacemoon pointed out in the comments, the navigation bar remains hidden as you navigate deeper in the navigation stack, regardless of whether or not you set navigationBarHidden to false in subsequent views. As I said in the comments, this is either a result of poor implementation on Apple's part or just dreadful documentation (who knows, maybe there is a "correct" way to accomplish this).

Whatever the case, I came up with a workaround that seems to produce the original poster's desired results. I'm hesitant to recommend it because it seems unnecessarily hacky, but without any straightforward way of hiding and unhiding the navigation bar, this is the best I could do.

This example uses three views - View1 has a hidden navigation bar, and View2 and View3 both have visible navigation bars with titles.

struct View1: View {
    @State var isNavigationBarHidden: Bool = true

    var body: some View {
        NavigationView {
            ZStack {
                Color.red
                NavigationLink("View 2", destination: View2(isNavigationBarHidden: self.$isNavigationBarHidden))
            }
            .navigationBarTitle("Hidden Title")
            .navigationBarHidden(self.isNavigationBarHidden)
            .onAppear {
                self.isNavigationBarHidden = true
            }
        }
    }
}

struct View2: View {
    @Binding var isNavigationBarHidden: Bool

    var body: some View {
        ZStack {
            Color.green
            NavigationLink("View 3", destination: View3())
        }
        .navigationBarTitle("Visible Title 1")
        .onAppear {
            self.isNavigationBarHidden = false
        }
    }
}

struct View3: View {
    var body: some View {
        Color.blue
            .navigationBarTitle("Visible Title 2")
    }
}

Setting navigationBarHidden to false on views deeper in the navigation stack doesn't seem to properly override the preference of the view that originally set navigationBarHidden to true, so the only workaround I could come up with was using a binding to change the preference of the original view when a new view is pushed onto the navigation stack.

Like I said, this is a hacky solution, but without an official solution from Apple, this is the best that I've been able to come up with.

Navigation Bar Items not shown when UIKit SwiftUI UIKit

SwiftUI view used its own navigation controller and it ignores the UIKit navigation controller so the possible solution is to set your navigation bar to parent controller and set your navigation bar element by coding.

like this

class MyUIKitViewController: UIViewController {
    override func viewDidLoad() {
        super.viewDidLoad()
        // ADD NAV BUTTON HERE - must be in DispatchQueue
        DispatchQueue.main.async {
            self.parent?.navigationItem.title = "Your Title"
            self.parent?.navigationItem.rightBarButtonItems?.append(UIBarButtonItem(systemItem: .camera))
        }
    }
}

Another solution is to use self.navigationController?.navigationBar.topItem?. This is the exact same as above. It gives a topItem.

class MyUIKitViewController: UIViewController {
    override func viewDidLoad() {
        super.viewDidLoad()
        // ADD NAV BUTTON HERE - must be in DispatchQueue
        DispatchQueue.main.async {
            self.navigationController?.navigationBar.topItem?.title = "Your Title"
            self.navigationController?.navigationBar.topItem?.rightBarButtonItems?.append(UIBarButtonItem(systemItem: .camera))
        }
    }
}

I used DispatchQueue for when the view is initiated then the parent is not set at this time. (You can use also use viewWillAppear instead of DispatchQueue.main.async)

Edit

If you don't want to add elements programmatically and if you need to use the same element from the storyboard then you can use this approch.

class MyUIKitViewController: UIViewController {
    override func viewDidLoad() {
        super.viewDidLoad()
        // ADD NAV BUTTON HERE
        navigationItem.rightBarButtonItems?.append(UIBarButtonItem(systemItem: .camera))
        
        DispatchQueue.main.async { //<--Here
            self.navigationController?.navigationBar.topItem?.title = self.navigationItem.title
            self.navigationController?.navigationBar.topItem?.rightBarButtonItems = self.navigationItem.rightBarButtonItems
        }
    }
}

How to dynamically hide the status bar and the home indicator in SwiftUI?

I was able to solve the problem with the SwiftUI view not extending beyond the safe area insets for the status bar and the home indicator by completely switching to a storyboard based project template and embedding my views through a custom UIHostingController as described in this solution by Casper Zandbergen.
Before I was re-integrating the hosting controller into the SwiftUI view hierarchy by wrapping it with a UIViewRepresentable instance, which must have caused the complications in handling the safe area.

By managing the whole app through the custom UIHostingController subclass it was even easier to get the hiding of the home indicator working. As much as I love SwiftUI I had to realize that, with its current limitations, UIKit was the better option here.

Final code (optimized version of the solution linked above):

ViewController.swift

import SwiftUI
import UIKit

struct HideUIPreferenceKey: PreferenceKey {
    static var defaultValue: Bool = false
    
    static func reduce(value: inout Bool, nextValue: () -> Bool) {
        value = nextValue() || value
    }
}

extension View {
    func userInterfaceHidden(_ value: Bool) -> some View {
        preference(key: HideUIPreferenceKey.self, value: value)
    }
}

class ViewController: UIHostingController<AnyView> {
    init() {
        weak var vc: ViewController? = nil
        super.init(
            rootView: AnyView(
                ContentView()
                    .onPreferenceChange(HideUIPreferenceKey.self) {
                        vc?.userInterfaceHidden = $0
                    }
            )
        )
        vc = self
    }

    @objc required dynamic init?(coder: NSCoder) {
        weak var vc: ViewController? = nil
        super.init(
            coder: coder,
            rootView: AnyView(
                ContentView()
                   .onPreferenceChange(HideUIPreferenceKey.self) {
                       vc?.userInterfaceHidden = $0
                   }
           )
        )
        vc = self
    }
    
    private var userInterfaceHidden = false {
        didSet { setNeedsUpdateOfHomeIndicatorAutoHidden() }
    }
    
    override var prefersStatusBarHidden: Bool {
        userInterfaceHidden
    }
    
    override var prefersHomeIndicatorAutoHidden: Bool {
        userInterfaceHidden
    }
}