How to remove the default Navigation Bar space in SwiftUI NavigiationView

问题

I am new to SwiftUI (like most people) and trying to figure out how to remove some whitespace above a List that I embedded in a NavigationView

In this image, you can see that there is some white space above the List

What I want to accomplish is this

I've tried using

.navigationBarHidden(true)

but this did not make any noticeable changes.

i'm currently setting up my navigiationView like this

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

where FileBrowserView is a view with a List and Cells defined like this

List {
   Section(header: Text("Root")){
    FileCell(name: "Test", fileType: "JPG",fileDesc: "Test number 1")

                    FileCell(name: "Test 2", fileType: "txt",fileDesc: "Test number 2")
                    FileCell(name: "test3", fileType: "fasta", fileDesc: "")
}
}

I do want to note that the ultimate goal here is that you will be able to click on these cells to navigate deeper into a file tree and thus should display a Back button on the bar on deeper navigation, but I do not want anything at the top as such during my initial view.

回答1:

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.

回答2:

The purpose of a NavigationView is to add the navigation bar on top of your view. In iOS, there are 2 kinds of navigation bars: large and standard.

If you want no navigation bar:

FileBrowserView(jsonFromCall: URLRetrieve(URLtoFetch: applicationDelegate.apiURL))

If you want a large navigation bar (generally used for your top-level views):

NavigationView {
    FileBrowserView(jsonFromCall: URLRetrieve(URLtoFetch: applicationDelegate.apiURL))
    .navigationBarTitle(Text("Title"))
}

If you want a standard (inline) navigation bar (generally used for sub-level views):

NavigationView {
    FileBrowserView(jsonFromCall: URLRetrieve(URLtoFetch: applicationDelegate.apiURL))
    .navigationBarTitle(Text("Title"), displayMode: .inline)
}

Hope this answer will help you.

More information: Apple Documentation

回答3:

This is a bug present in SwiftUI (still as of Xcode 11.2.1). I wrote a ViewModifier to fix this, based on code from the existing answers:

public struct NavigationBarHider: ViewModifier {
    @State var isHidden: Bool = false

    public func body(content: Content) -> some View {
        content
            .navigationBarTitle("")
            .navigationBarHidden(isHidden)
            .onAppear { self.isHidden = true }
    }
}

extension View {
    public func hideNavigationBar() -> some View {
        modifier(NavigationBarHider())
    }
}

回答4:

Similar to the answer by @graycampbell but a little simpler:

struct YourView: View {

    @State private var isNavigationBarHidden = true

    var body: some View {
        NavigationView {
            VStack {
                Text("This is the master view")
                NavigationLink("Details", destination: Text("These are the details"))
            }
                .navigationBarHidden(isNavigationBarHidden)
                .navigationBarTitle("Master")
                .onAppear {
                    self.isNavigationBarHidden = true
                }
                .onDisappear {
                    self.isNavigationBarHidden = false
                }
        }
    }
}

Setting the title is necessary since it is shown next to the back button in the views you navigate to.

回答5:

Try putting the NavigationView inside a GeometryReader.

GeometryReader {
    NavigationView {
        Text("Hello World!")
    }
}

I’ve experienced weird behavior when the NavigationView was the root view.

来源：https://stackoverflow.com/questions/57517803/how-to-remove-the-default-navigation-bar-space-in-swiftui-navigiationview