Navigation bar only have background when scroll – Ios swift

I am trying to implement a detail view which is linked from a navigation view.
In this detail view, there is a default nav bar on top with a back button.
But the bar only show some color when I scroll up. I have no idea why.

No Scroll:

Scroll:

Initially, the nav bar doesn’t have background either when it’s scrolling or not.
So I created an init() method for setting up the style.

 init(fruit: Fruit) {
    self.fruit = fruit
    if #available(iOS 15.0, *) {
        let navigationBarAppearance = UINavigationBarAppearance()
        navigationBarAppearance.configureWithDefaultBackground()
        
        UINavigationBar.appearance().standardAppearance = navigationBarAppearance
        UINavigationBar.appearance().compactAppearance = navigationBarAppearance
        UINavigationBar.appearance().scrollEdgeAppearance = navigationBarAppearance
    }
  }

The Body View is a Navigation View on the outside and scroll view inside.
** For anyone wonder why I set the navbar to hidden in the VStack, is because if I don’t hide it, there would be some huge space above the image. (I have no idea why)

** Updated Code **
I updated my code which use the Opaque background.
But it seems like none of those config are visible.

init(fruit: Fruit) {
    self.fruit = fruit
    let navBarAppearance = UINavigationBarAppearance()
    navBarAppearance.configureWithOpaqueBackground()
    UINavigationBar.appearance().scrollEdgeAppearance = navBarAppearance
    UINavigationBar.appearance().standardAppearance = navBarAppearance
}

var body: some View {
    NavigationView {
        ScrollView(.vertical, showsIndicators: false) {
            VStack(alignment: .center, spacing: 20) {
                // HEADER
                FruitHeaderView(fruit: fruit)
                
                VStack(alignment: .leading, spacing: 20) {
                    // TITLE
                    Text(fruit.title)
                        .font(.largeTitle)
                        .fontWeight(.heavy)
                        .foregroundColor(fruit.gradientColors[1])
                    
                    
                } //: VSTACK
                .padding(.horizontal, 20)
                .frame(maxWidth: 640, alignment: .center)
            } //: VSTACK
            .navigationBarHidden(true)
        } //: SCROLL
        .edgesIgnoringSafeArea(.top)
    } //: NAVIGATION
    .navigationBarTitle(fruit.title, displayMode: .inline)
    .navigationViewStyle(StackNavigationViewStyle())
}

*** Solution ***
It turns out I have to put the configurations code of the nav bar in the parent view. During init().
Can anyone explain why this on the parent view? Or if I want different style in parent and child what should I do?

    init() {
        let navBarAppearance = UINavigationBarAppearance()
        navBarAppearance.configureWithOpaqueBackground()
        UINavigationBar.appearance().scrollEdgeAppearance = navBarAppearance
         UINavigationBar.appearance().standardAppearance = navBarAppearance
    }

var body: some View {
    NavigationView {
        List {
            ForEach(fruits.shuffled()) { item in
                NavigationLink {
                    FruitDetailView(fruit: item)
                } label: {
                    FruitRowView(fruit: item)
                        .padding(.vertical, 4)
                }
            }
        }
        .listStyle(.plain)
        .navigationTitle("Fruits")
    } //: NAVIGATION

}