Advanced startup navigation

README.md

@@ -225,10 +225,46 @@ navigationService.Navigate(navigationUri);
 ```
 
 ## Choosing the start page of your app
+### (navigationService, serviceProvider)
+
+In the below example, we use both an `INavigationService` and an `IServiceProvider`. The `IServiceProvider` is used to resolve the .NET MAUI service, [`IPreferences`](https://learn.microsoft.com/en-us/dotnet/maui/platform-integration/storage/preferences?tabs=android). If a username is stored in preferences, we use the `INavigationService` to go to the `HomePage` of the app. Otherwise, we go to the `LoginPage`.
+
+``` csharp
+public static class MauiProgram
+{
+    public static MauiApp CreateMauiApp()
+    {
+        var builder = MauiApp.CreateBuilder();
+        builder
+            .UseMauiApp<App>()
+            .UseBurkusMvvm(burkusMvvm =>
+            {
+                burkusMvvm.OnStart(async (navigationService, serviceProvider) =>
+                {
+                    var preferences = serviceProvider.GetRequiredService<IPreferences>();
+
+                    if (preferences.ContainsKey(PreferenceKeys.Username))
+                    {
+                        // we are logged in to the app
+                        await navigationService.Push<HomePage>();
+                    }
+                    else
+                    {
+                        // logged out so we need to get the user to login
+                        await navigationService.Push<LoginPage>();
+                    }
+                });
+            })
+            ...
+```
+### (IServiceProvider serviceProvider)
+
 It is possible to have a service that decides which page is most appropriate to navigate to. This service could decide to:
   - Navigate to the "Terms & Conditions" page if the user has not agreed to the latest terms yet
   - Navigate to the "Signup / Login" page if the user is logged out
   - Navigate to the "Home" page if the user has used the app before and doesn't need to do anything
+
+In the below example, we only resolve a `IServiceProvider` which allows us to resolve `IAppStartupService`. The `IAppStartupService` will call the `INavigationService` internally to do the navigation.
 ```csharp
 public static class MauiProgram
 {
@@ -238,9 +274,9 @@ public static class MauiProgram
             .UseMauiApp<App>()
             .UseBurkusMvvm(burkusMvvm =>
             {
-                burkusMvvm.OnStart(async (navigationService) =>
+                burkusMvvm.OnStart(async (IServiceProvider serviceProvider) =>
                 {
-                    var appStartupService = ServiceResolver.Resolve<IAppStartupService>();
+                    var appStartupService = serviceProvider.GetRequiredService<IAppStartupService>();
                     await appStartupService.NavigateToFirstPage();
                 });
             })

samples/DemoApp/MauiProgram.cs

@@ -1,4 +1,5 @@
 using DemoApp.Abstractions;
+using DemoApp.Models;
 using DemoApp.Services;
 using DemoApp.ViewModels;
 using DemoApp.Views;
@@ -15,9 +16,19 @@ public static MauiApp CreateMauiApp()
             .UseMauiApp<App>()
             .UseBurkusMvvm(burkusMvvm =>
             {
-                burkusMvvm.OnStart(async (navigationService) =>
+                burkusMvvm.OnStart(async (navigationService, serviceProvider) =>
                 {
-                    await navigationService.Push<LoginPage>();
+                    var preferences = serviceProvider.GetRequiredService<IPreferences>();
+
+                    if (preferences.ContainsKey(PreferenceKeys.Username))
+                    {
+                        // we are logged in to the app
+                        await navigationService.Push<HomePage>();
+                    }
+                    else
+                    {
+                        await navigationService.Push<LoginPage>();
+                    }
                 });
             })
             .RegisterViewModels()
@@ -62,6 +73,7 @@ public static MauiAppBuilder RegisterViews(this MauiAppBuilder mauiAppBuilder)
 
     public static MauiAppBuilder RegisterServices(this MauiAppBuilder mauiAppBuilder)
     {
+        mauiAppBuilder.Services.AddSingleton(Preferences.Default);
         mauiAppBuilder.Services.AddSingleton<IWeatherService, WeatherService>();
 
         return mauiAppBuilder;

samples/DemoApp/Models/NavigationParameterKeys.cs

@@ -0,0 +1,6 @@
+namespace DemoApp.Models;
+
+public static class NavigationParameterKeys
+{
+    public static readonly string Username = "username";
+}

samples/DemoApp/Models/PreferenceKeys.cs

@@ -0,0 +1,10 @@
+namespace DemoApp.Models;
+
+public static class PreferenceKeys
+{
+    #region Preference keys
+
+    public static readonly string Username = "username";
+
+    #endregion Preference keys
+}

samples/DemoApp/ViewModels/ChangeUsernameViewModel.cs

@@ -1,12 +1,17 @@
-using CommunityToolkit.Mvvm.ComponentModel;
+using Burkus.Mvvm.Maui;
+using CommunityToolkit.Mvvm.ComponentModel;
 using CommunityToolkit.Mvvm.Input;
+using DemoApp.Models;
+using DemoApp.Properties;
 
 namespace DemoApp.ViewModels;
 
 public partial class ChangeUsernameViewModel : BaseViewModel
 {
     #region Fields
 
+    private IPreferences preferences { get; }
+
     private bool wasAnimatedNavigationUsed;
 
     #endregion Fields
@@ -21,9 +26,11 @@ public partial class ChangeUsernameViewModel : BaseViewModel
     #region Constructors
 
     public ChangeUsernameViewModel(
-        INavigationService navigationService)
+        INavigationService navigationService,
+        IPreferences preferences)
         : base(navigationService)
     {
+        this.preferences = preferences;
     }
 
     #endregion Constructors
@@ -43,9 +50,15 @@ public override async Task OnNavigatingFrom(NavigationParameters parameters)
     {
         await base.OnNavigatingFrom(parameters);
 
-        // pass 'Username' back regardless if the user presses the button
-        // or uses a different method of closing the modal (e.g. Android back button)
-        parameters.Add("username", Username);
+        if (IsValidUsername())
+        {
+            // save username as a preference
+            preferences.Set(PreferenceKeys.Username, Username);
+
+            // pass 'Username' back regardless if the user presses the button
+            // or uses a different method of closing the modal (e.g. Android back button)
+            parameters.Add(NavigationParameterKeys.Username, Username);
+        }
 
         // this is a modal, so we need to close it modally
         parameters.UseModalNavigation = true;
@@ -70,4 +83,13 @@ private async Task Finish()
     }
 
     #endregion Commands
+
+    #region Private methods
+
+    private bool IsValidUsername()
+    {
+        return !string.IsNullOrWhiteSpace(Username);
+    }
+
+    #endregion Private methods
 }

samples/DemoApp/ViewModels/HomeViewModel.cs

@@ -1,6 +1,7 @@
 using CommunityToolkit.Mvvm.ComponentModel;
 using CommunityToolkit.Mvvm.Input;
 using DemoApp.Abstractions;
+using DemoApp.Models;
 using DemoApp.Views;
 
 namespace DemoApp.ViewModels;
@@ -9,7 +10,9 @@ public partial class HomeViewModel : BaseViewModel
 {
     #region Fields
 
-    protected IWeatherService weatherService { get; }
+    private IPreferences preferences { get; }
+
+    private IWeatherService weatherService { get; }
 
     #endregion Fields
 
@@ -27,9 +30,11 @@ public partial class HomeViewModel : BaseViewModel
 
     public HomeViewModel(
         INavigationService navigationService,
+        IPreferences preferences,
         IWeatherService weatherService)
         : base(navigationService)
     {
+        this.preferences = preferences;
         this.weatherService = weatherService;
     }
 
@@ -41,11 +46,14 @@ public override async Task OnNavigatedTo(NavigationParameters parameters)
     {
         await base.OnNavigatedTo(parameters);
 
-        var usernameValue = parameters.GetValue<string>("username");
-
-        if (!string.IsNullOrWhiteSpace(usernameValue))
+        if (parameters.ContainsKey(NavigationParameterKeys.Username))
         {
-            Username = usernameValue;
+            Username = parameters.GetValue<string>(NavigationParameterKeys.Username);
+        }
+        else
+        {
+            // load the username from preferences
+            Username = preferences.Get<string>(PreferenceKeys.Username, default);
         }
 
         CurrentWeatherDescription = weatherService.GetWeatherDescription();
@@ -95,6 +103,9 @@ private async Task GoToTabbedPageDemo()
     [RelayCommand]
     private async Task Logout()
     {
+        // remove the username preference
+        preferences.Remove(PreferenceKeys.Username);
+
         // use the navigate URI syntax to logout with an absolute URI
         await navigationService.Navigate("/LoginPage");
     }

samples/DemoApp/ViewModels/LoginViewModel.cs

@@ -1,5 +1,6 @@
 using CommunityToolkit.Mvvm.ComponentModel;
 using CommunityToolkit.Mvvm.Input;
+using DemoApp.Models;
 using DemoApp.Properties;
 using DemoApp.Views;
 
@@ -9,7 +10,9 @@ public partial class LoginViewModel : BaseViewModel
 {
     #region Fields
 
-    protected IDialogService dialogService { get; }
+    private IDialogService dialogService { get; }
+
+    private IPreferences preferences { get; }
 
     #endregion Fields
 
@@ -27,10 +30,12 @@ public partial class LoginViewModel : BaseViewModel
 
     public LoginViewModel(
         IDialogService dialogService,
-        INavigationService navigationService)
+        INavigationService navigationService,
+        IPreferences preferences)
         : base(navigationService)
     {
         this.dialogService = dialogService;
+        this.preferences = preferences;
     }
 
     #endregion Constructors
@@ -49,9 +54,12 @@ private async Task Login()
             return;
         }
 
+        // save username as a preference
+        preferences.Set(PreferenceKeys.Username, Username);
+
         var navigationParameters = new NavigationParameters
         {
-            { "username", Username },
+            { NavigationParameterKeys.Username, Username },
         };
 
         // after we login, we replace the stack so the user can't go back to the Login page
@@ -73,7 +81,7 @@ private async Task Register()
 
     private bool IsValidLoginForm()
     {
-        if (string.IsNullOrEmpty(Username))
+        if (string.IsNullOrWhiteSpace(Username))
         {
             dialogService.DisplayAlert(
                 Resources.Error,

src/Abstractions/IBurkusMvvmBuilder.cs

@@ -2,5 +2,5 @@
 
 internal interface IBurkusMvvmBuilder
 {
-    Func<INavigationService, Task> onStartFunc { get; set; }
+    Func<INavigationService, IServiceProvider, Task> onStartFunc { get; set; }
 }

src/Builders/InternalBurkusMvvmBuilder.cs

@@ -5,5 +5,5 @@
 /// </summary>
 internal class InternalBurkusMvvmBuilder : BurkusMvvmBuilder, IBurkusMvvmBuilder
 {
-    public Func<INavigationService, Task> onStartFunc { get; set; }
+    public Func<INavigationService, IServiceProvider, Task> onStartFunc { get; set; }
 }

src/Extensions/BurkusMvvmBuilderExtensions.cs

@@ -6,9 +6,9 @@ public static class BurkusMvvmBuilderExtensions
     /// Define where the app should go first when starting. You must navigate to a page when starting.
     /// </summary>
     /// <param name="builder">BurkusMvvmBuilder</param>
-    /// <param name="onStartFunc">Function to perform when starting with access to the <see cref="INavigationService"/></param>
+    /// <param name="onStartFunc">Function to perform when starting with access to <see cref="INavigationService"/> and <see cref="IServiceProvider"/></param>
     /// <returns></returns>
-    public static BurkusMvvmBuilder OnStart(this BurkusMvvmBuilder builder, Func<INavigationService, Task> onStartFunc)
+    public static BurkusMvvmBuilder OnStart(this BurkusMvvmBuilder builder, Func<INavigationService, IServiceProvider, Task> onStartFunc)
     {
         var internalBuilder = builder as InternalBurkusMvvmBuilder;
 
@@ -19,4 +19,26 @@ public static BurkusMvvmBuilder OnStart(this BurkusMvvmBuilder builder, Func<INa
 
         return builder;
     }
+
+    /// <summary>
+    /// Define where the app should go first when starting. You must navigate to a page when starting.
+    /// </summary>
+    /// <param name="builder">BurkusMvvmBuilder</param>
+    /// <param name="onStartFunc">Function to perform when starting with access to <see cref="INavigationService"/>.</param>
+    /// <returns></returns>
+    public static BurkusMvvmBuilder OnStart(this BurkusMvvmBuilder builder, Func<INavigationService, Task> onStartFunc)
+    {
+        return OnStart(builder, (nav, sp) => onStartFunc(nav));
+    }
+
+    /// <summary>
+    /// Define where the app should go first when starting. You must navigate to a page when starting.
+    /// </summary>
+    /// <param name="builder">BurkusMvvmBuilder</param>
+    /// <param name="onStartFunc">Function to perform when starting with access to <see cref="IServiceProvider"/>.</param>
+    /// <returns></returns>
+    public static BurkusMvvmBuilder OnStart(this BurkusMvvmBuilder builder, Func<IServiceProvider, Task> onStartFunc)
+    {
+        return OnStart(builder, (nav, sp) => onStartFunc(sp));
+    }
 }

src/Models/BurkusMvvmApplication.cs

@@ -4,15 +4,16 @@
 {
     protected override Window CreateWindow(IActivationState? activationState)
     {
         Current.MainPage = new NavigationPage();
 
         var burkusMvvmBuilder = ServiceResolver.Resolve<IBurkusMvvmBuilder>();
         var navigationService = ServiceResolver.Resolve<INavigationService>();
+        var serviceProvider = ServiceResolver.GetServiceProvider();
 
         // perform the user's desired initialization logic
         if (burkusMvvmBuilder.onStartFunc != null)
         {
-            burkusMvvmBuilder.onStartFunc.Invoke(navigationService);
+            burkusMvvmBuilder.onStartFunc.Invoke(navigationService, serviceProvider);
         }
 
         return base.CreateWindow(activationState);