maui-shell-navigation（毛伊岛贝壳导航）

.NET MAUI Shell Navigation

Implement page navigation in.NET MAUI apps using Shell. Shell provides URI-based navigation, a flyout menu, tab bars, and a four-level visual hierarchy — all configured declaratively in XAML.

When to Use

• Setting up top-level app navigation with tabs or a flyout menu
• Navigating between pages programmatically with GoToAsync
• Passing data between pages via query parameters or object parameters
• Registering detail-page routes for push navigation
• Guarding navigation with confirmation dialogs (e.g., unsaved changes)
• Customizing back button behavior per page

When Not to Use

• Deep linking from external URLs or app links — see .NET MAUI deep linking docs
• Data binding on navigation target pages — use maui-data-binding
• Dependency injection for pages and view models — use maui-dependency-injection
• Apps using NavigationPage without Shell (different navigation API)

Inputs

• A.NET MAUI project with AppShell.xaml as the root shell
• Pages (ContentPage) to navigate between
• Route names for detail pages not in the visual hierarchy

Shell Visual Hierarchy

Shell uses a four-level hierarchy. Each level wraps the one below it:

Shell
 ├── FlyoutItem / TabBar          (top-level grouping)
 │    ├── Tab                     (bottom-tab grouping)
 │    │    ├── ShellContent        (page slot → ContentPage)
 │    │    └── ShellContent        (multiple = top tabs)
 │    └── Tab
 └── FlyoutItem / TabBar

• FlyoutItem — appears in the flyout menu; contains Tab children
• TabBar — bottom tab bar with no flyout entry
• Tab — groups ShellContent; multiple children produce top tabs
• ShellContent — each points to a ContentPage

Implicit Conversion

You can omit intermediate wrappers. Shell auto-wraps:

Workflow: Set Up AppShell

1. Define AppShell.xaml inheriting from Shell
2. Add FlyoutItem or TabBar elements for top-level navigation
3. Add Tab elements for bottom tabs; nest multiple ShellContent for top tabs
4. Always use ContentTemplate with DataTemplate so pages load on demand
5. Register detail-page routes in the AppShell constructor

<Shell xmlns="http://schemas.microsoft.com/dotnet/2021/maui"
       xmlns:x="http://schemas.microsoft.com/winfx/2009/xaml"
       xmlns:views="clr-namespace:MyApp.Views"
       x:Class="MyApp.AppShell"
       FlyoutBehavior="Flyout">

    <FlyoutItem Title="Animals" Icon="animals.png">
        <Tab Title="Cats">
            <ShellContent Title="Domestic"
                          ContentTemplate="{DataTemplate views:DomesticCatsPage}" />
            <ShellContent Title="Wild"
                          ContentTemplate="{DataTemplate views:WildCatsPage}" />
        </Tab>
        <Tab Title="Dogs" Icon="dogs.png">
            <ShellContent ContentTemplate="{DataTemplate views:DogsPage}" />
        </Tab>
    </FlyoutItem>

    <TabBar>
        <ShellContent Title="Home" Icon="home.png"
                      ContentTemplate="{DataTemplate views:HomePage}" />
        <ShellContent Title="Settings" Icon="settings.png"
                      ContentTemplate="{DataTemplate views:SettingsPage}" />
    </TabBar>
</Shell>

// AppShell.xaml.cs
public partial class AppShell : Shell
{
    public AppShell()
    {
        InitializeComponent();
        Routing.RegisterRoute("animaldetails", typeof(AnimalDetailsPage));
        Routing.RegisterRoute("editanimal", typeof(EditAnimalPage));
    }
}

Workflow: Navigate with GoToAsync

All programmatic navigation uses Shell.Current.GoToAsync. Always await the call.

Route Prefixes

Navigation Examples

// 1. Absolute — switch to a specific hierarchy location
await Shell.Current.GoToAsync("//animals/cats/domestic");

// 2. Relative — push a registered detail page
await Shell.Current.GoToAsync("animaldetails");

// 3. With query string parameters
await Shell.Current.GoToAsync($"animaldetails?id={animal.Id}");

// 4. Go back one page
await Shell.Current.GoToAsync("..");

// 5. Go back two pages
await Shell.Current.GoToAsync("../..");

// 6. Go back one page, then push a different page
await Shell.Current.GoToAsync("../editanimal");

Workflow: Pass Data Between Pages

Option 1: IQueryAttributable (Preferred)

Implement on ViewModels to receive all parameters in one call:

public class AnimalDetailsViewModel : ObservableObject, IQueryAttributable
{
    public void ApplyQueryAttributes(IDictionary<string, object> query)
    {
        if (query.TryGetValue("id", out var id))
            AnimalId = id.ToString();
    }
}

Option 2: QueryProperty Attribute

Apply directly on the page class:

[QueryProperty(nameof(AnimalId), "id")]
public partial class AnimalDetailsPage : ContentPage
{
    public string AnimalId { get; set; }
}

Option 3: Complex Objects via ShellNavigationQueryParameters

Pass objects without serializing to strings:

var parameters = new ShellNavigationQueryParameters
{
    { "animal", selectedAnimal }
};
await Shell.Current.GoToAsync("animaldetails", parameters);

Receive via IQueryAttributable:

public void ApplyQueryAttributes(IDictionary<string, object> query)
{
    Animal = query["animal"] as Animal;
}

Workflow: Guard Navigation

Use GetDeferral() in OnNavigating for async checks (e.g., "save unsaved changes?"):

// In AppShell.xaml.cs
protected override async void OnNavigating(ShellNavigatingEventArgs args)
{
    base.OnNavigating(args);
    if (hasUnsavedChanges && args.Source == ShellNavigationSource.Pop)
    {
        var deferral = args.GetDeferral();
        bool discard = await ShowConfirmationDialog();
        if (!discard)
            args.Cancel();
        deferral.Complete();
    }
}

Tab Configuration

Bottom Tabs

Multiple ShellContent (or Tab) children inside a TabBar or FlyoutItem produce bottom tabs.

Top Tabs

Multiple ShellContent children inside a single Tab produce top tabs:

<Tab Title="Photos">
    <ShellContent Title="Recent"    ContentTemplate="{DataTemplate views:RecentPage}" />
    <ShellContent Title="Favorites" ContentTemplate="{DataTemplate views:FavoritesPage}" />
</Tab>

Tab Bar Appearance

<!-- Hide the tab bar on a specific page -->
<ContentPage Shell.TabBarIsVisible="False" ... />

Flyout Configuration

FlyoutBehavior

Set on Shell: Disabled, Flyout, or Locked.

<Shell FlyoutBehavior="Flyout"> ... </Shell>

FlyoutDisplayOptions

Controls how children appear in the flyout:

• AsSingleItem (default) — one flyout entry for the group
• AsMultipleItems — each child Tab gets its own entry

<FlyoutItem Title="Animals" FlyoutDisplayOptions="AsMultipleItems">
    <Tab Title="Cats" ... />
    <Tab Title="Dogs" ... />
</FlyoutItem>

MenuItem (Non-Navigation Flyout Entries)

<MenuItem Text="Log Out"
          Command="{Binding LogOutCommand}"
          IconImageSource="logout.png" />

Back Button Behavior

Customize the back button per page:

<Shell.BackButtonBehavior>
    <BackButtonBehavior Command="{Binding BackCommand}"
                       IconOverride="back_arrow.png"
                       TextOverride="Cancel"
                       IsVisible="True" />
</Shell.BackButtonBehavior>

Properties: Command, CommandParameter, IconOverride, TextOverride, IsVisible, IsEnabled.

Inspecting Navigation State

// Current URI location
string location = Shell.Current.CurrentState.Location.ToString();

// Current page
Page page = Shell.Current.CurrentPage;

// Navigation stack of the current tab
IReadOnlyList<Page> stack = Shell.Current.Navigation.NavigationStack;

Navigation Events

Override in AppShell:

protected override void OnNavigated(ShellNavigatedEventArgs args)
{
    base.OnNavigated(args);
    // args.Current, args.Previous, args.Source
}

ShellNavigationSource values: Push, Pop, PopToRoot, Insert, Remove, ShellItemChanged, ShellSectionChanged, ShellContentChanged, Unknown.

Common Pitfalls

• Eager page creation: Using Content directly instead of ContentTemplate with DataTemplate creates all pages at Shell init, hurting startup time. Always use ContentTemplate.
• Duplicate route names: Routing.RegisterRoute throws ArgumentException if a route name matches an existing route or a visual hierarchy route. Every route must be unique across the app.
• Relative routes without registration: You cannot GoToAsync("somepage") unless somepage was registered with Routing.RegisterRoute. Visual hierarchy pages use absolute // routes.
• Fire-and-forget GoToAsync: Not awaiting GoToAsync causes race conditions and silent failures. Always await the call.
• Wrong absolute route path: Absolute routes must match the full path through the visual hierarchy (//FlyoutItem/Tab/ShellContent). Wrong paths produce silent no-ops, not exceptions.
• Manipulating Tab.Stack directly: The navigation stack is read-only. Use GoToAsync for all navigation changes.
• Forgetting GetDeferral() for async guards: Synchronous cancellation in OnNavigating works, but async checks require GetDeferral() / deferral.Complete() to avoid race conditions.

References

• references/shell-navigation-api.md — Full API reference for Shell hierarchy, routes, tabs, flyout, and navigation
• .NET MAUI Shell Navigation
• .NET MAUI Shell Tabs
• .NET MAUI Shell Flyout
• .NET MAUI Shell Pages