Why The Navigation Title doesn't show up using SwiftUI?

.navigationBarTitle() and .navigationBarItem() are modifiers on the View inside of the NavigationView, not on the NavigationView itself:

struct LandmarkList: View {
    var body: some View {
        NavigationView {
            List(landmarkData) { landmark in
                LandmarkRow(landmark: landmark)
            }
            .navigationBarItem(title: Text("Done"))
            .navigationBarTitle(Text("Landmarks"))
        }
    }
}

and if you think about it, this makes sense. As the View within the NavigationView changes, the new View dictates what the title and contents of the navigation bar should be.

Description:

NavigationView is just a container around some content. Contents are changing when you navigating from page to page, but the NavigationView persists.

The point is that NavigationView shows each view's content when it shows it. So it will encapsulate with the destination.

Finally, you should add all navigation modifiers inside the navigation (on the content)

---

Example:

struct Content: View {
    var body: some View {
        Text("Some. content")
            .navigationBarItem(title: Text("Done"))
            .navigationBarTitle(Text("Landmarks"))
    }
}

struct Parent: View {
    var body: some View {
        NavigationView {
            Content() // This contains navigation modifiers inside the view itself
        }
    }
}