Merge pull request #3048 from niimima/master_/feature/gobackto-withou…

…t-popping-each-page

[WIP] Go back to without popping each page

e2e/Maui/MauiModule/ViewModels/ViewModelBase.cs

@@ -29,6 +29,7 @@ protected ViewModelBase(BaseServices baseServices)
         SelectedDialog = AvailableDialogs.FirstOrDefault();
         ShowDialog = new DelegateCommand(OnShowDialogCommand, () => !string.IsNullOrEmpty(SelectedDialog))
             .ObservesProperty(() => SelectedDialog);
+        GoBack = new DelegateCommand<string>(OnGoBack);
     }
 
     public IEnumerable<string> AvailableDialogs { get; }
@@ -52,6 +53,8 @@ public string SelectedDialog
 
     public DelegateCommand ShowDialog { get; }
 
+    public DelegateCommand<string> GoBack { get; }
+
     private void OnNavigateCommandExecuted(string uri)
     {
         Messages.Add($"OnNavigateCommandExecuted: {uri}");
@@ -74,6 +77,12 @@ private void OnShowDialogCommand()
     private void DialogCallback(IDialogResult result) =>
         Messages.Add("Dialog Closed");
 
+    private void OnGoBack(string viewName)
+    {
+        Messages.Add($"On Go Back {viewName}");
+        _navigationService.GoBackAsync(viewName);
+    }
+
     public void Initialize(INavigationParameters parameters)
     {
         Messages.Add("ViewModel Initialized");

e2e/Maui/MauiModule/Views/ViewD.xaml

@@ -7,7 +7,7 @@
              x:DataType="loc:ViewModelBase"
              Title="{Binding Title}"
              BackgroundColor="White">
-  <Grid RowDefinitions="*,Auto,Auto,Auto"
+  <Grid RowDefinitions="*,Auto,Auto,Auto,Auto"
         ColumnDefinitions="*,*">
     <CollectionView ItemsSource="{Binding Messages}"
                     Grid.ColumnSpan="2">
@@ -57,5 +57,11 @@
             Margin="10"
             Grid.Row="3"
             Grid.Column="1"/>
+    <Button Text="Go Back View B"
+            Command="{Binding GoBack}"
+            CommandParameter="ViewB"
+            Margin="10"
+            Grid.Row="4"
+            Grid.Column="0"/>
   </Grid>
-</ContentPage>
+</ContentPage>

src/Maui/Prism.Maui/Navigation/INavigationService.cs

@@ -20,6 +20,14 @@ public interface INavigationService
     /// <returns>If <c>true</c> a go back operation was successful. If <c>false</c> the go back operation failed.</returns>
     Task<INavigationResult> GoBackAsync(INavigationParameters parameters);
 
+    /// <summary>
+    /// Navigates to the most recent entry in the back navigation history for the <paramref name="viewName"/>.
+    /// </summary>
+    /// <param name="viewName">The name of the View to navigate back to</param>
+    /// <param name="parameters">The navigation parameters</param>
+    /// <returns>If <c>true</c> a go back operation was successful. If <c>false</c> the go back operation failed.</returns>
+    Task<INavigationResult> GoBackAsync(string viewName, INavigationParameters parameters);
+
     /// <summary>
     /// When navigating inside a NavigationPage: Pops all but the root Page off the navigation stack
     /// </summary>

src/Maui/Prism.Maui/Navigation/INavigationServiceExtensions.cs

@@ -20,7 +20,7 @@ public static Task<INavigationResult> GoBackToAsync(this INavigationService navi
     /// </summary>
     /// <returns><see cref="INavigationResult"/> indicating whether the request was successful or if there was an encountered <see cref="Exception"/>.</returns>
     public static Task<INavigationResult> GoBackAsync(this INavigationService navigationService) =>
-        navigationService.GoBackAsync(null);
+        navigationService.GoBackAsync(new NavigationParameters());
 
     /// <summary>
     /// Navigates to the most recent entry in the back navigation history by popping the calling Page off the navigation stack.
@@ -33,6 +33,14 @@ public static Task<INavigationResult> GoBackAsync(this INavigationService naviga
         return navigationService.GoBackAsync(GetNavigationParameters(parameters));
     }
 
+    /// <summary>
+    /// Navigates to the most recent entry in the back navigation history for the <paramref name="viewName"/>.
+    /// </summary>
+    /// <param name="navigationService">Service for handling navigation between views</param>
+    /// <param name="viewName">The name of the View to navigate back to</param>
+    /// <returns>If <c>true</c> a go back operation was successful. If <c>false</c> the go back operation failed.</returns>
+    public static Task<INavigationResult> GoBackAsync(this INavigationService navigationService, string viewName) => navigationService.GoBackAsync(viewName, new NavigationParameters());
+
     /// <summary>
     /// When navigating inside a NavigationPage: Pops all but the root Page off the navigation stack
     /// </summary>

src/Maui/Prism.Maui/Navigation/PageNavigationService.cs

@@ -2,6 +2,7 @@
 using System.Web;
 using Prism.Common;
 using Prism.Events;
+using Prism.Extensions;
 using Prism.Mvvm;
 using Application = Microsoft.Maui.Controls.Application;
 using XamlTab = Prism.Navigation.Xaml.TabbedPage;
@@ -192,6 +193,66 @@ private async Task<INavigationResult> GoBackInternalAsync(INavigationParameters
         return Notify(NavigationRequestType.GoBack, parameters, GetGoBackException(page, GetPageFromWindow()));
     }
 
+    /// <inheritdoc />
+    public virtual async Task<INavigationResult> GoBackAsync(string viewName, INavigationParameters parameters)
+    {
+        await _semaphore.WaitAsync();
+        try
+        {
+            if (parameters is null)
+                parameters = new NavigationParameters();
+
+            parameters.GetNavigationParametersInternal().Add(KnownInternalParameters.NavigationMode, NavigationMode.Back);
+
+            var page = GetCurrentPage();
+            var canNavigate = await MvvmHelpers.CanNavigateAsync(page, parameters);
+            if (!canNavigate)
+            {
+                throw new NavigationException(NavigationException.IConfirmNavigationReturnedFalse, page);
+            }
+
+            var pagesToDestroy = page.Navigation.NavigationStack.ToList(); // get all pages to destroy
+            pagesToDestroy.Reverse(); // destroy them in reverse order
+            var goBackPage = pagesToDestroy.FirstOrDefault(p => ViewModelLocator.GetNavigationName(p) == viewName); // find the go back page
+            if (goBackPage is null)
+            {
+                throw new NavigationException(NavigationException.GoBackRequiresNavigationPage);
+            }
+            var index = pagesToDestroy.IndexOf(goBackPage);
+            pagesToDestroy.RemoveRange(index, pagesToDestroy.Count - index); // don't destroy pages from the go back page to the root page
+            var pagesToRemove = pagesToDestroy.Skip(1).ToList(); // exclude the current page from the destroy pages
+
+            bool animated = parameters.ContainsKey(KnownNavigationParameters.Animated) ? parameters.GetValue<bool>(KnownNavigationParameters.Animated) : true;
+            NavigationSource = PageNavigationSource.NavigationService;
+            foreach(var removePage in pagesToRemove)
+            {
+                page.Navigation.RemovePage(removePage);
+            }
+            await page.Navigation.PopAsync(animated);
+            NavigationSource = PageNavigationSource.Device;
+
+            foreach (var destroyPage in pagesToDestroy)
+            {
+                MvvmHelpers.OnNavigatedFrom(destroyPage, parameters);
+                MvvmHelpers.DestroyPage(destroyPage);
+            }
+
+            MvvmHelpers.OnNavigatedTo(goBackPage, parameters);
+
+            return Notify(NavigationRequestType.GoBack, parameters);
+        }
+        catch (Exception ex)
+        {
+            return Notify(NavigationRequestType.GoBack, parameters, ex);
+        }
+        finally
+        {
+            NavigationSource = PageNavigationSource.Device;
+            _semaphore.Release();
+        }
+    }
+
+
     private static Exception GetGoBackException(Page currentPage, IView mainPage)
     {
         if (IsMainPage(currentPage, mainPage))

src/Prism.Core/Navigation/NavigationException.cs

@@ -17,6 +17,11 @@ public class NavigationException : Exception
     /// </summary>
     public const string CannotGoBackFromRoot = "Cannot GoBack from NavigationPage Root.";
 
+    /// <summary>
+    /// The <see cref="NavigationException"/> Message returned when GoBackAsync can only be called when the calling Page has been navigated.
+    /// </summary>
+    public const string GoBackRequiresNavigationPage = "GoBackAsync can only be called when the calling Page has been navigated.";
+
     /// <summary>
     /// The <see cref="NavigationException"/> Message returned when GoBackToRootAsync can only be called when the calling Page is within a NavigationPage.
     /// </summary>

tests/Maui/Prism.DryIoc.Maui.Tests/Fixtures/Navigation/NavigationTests.cs

@@ -294,6 +294,59 @@ public async Task GoBack_Issue2232()
         Assert.IsType<MockViewA>(navigationPage.CurrentPage);
     }
 
+    [Fact]
+    public async Task GoBack_Name_PopsToSpecifiedViewWithoutPoppingEachPage()
+    {
+        var mauiApp = CreateBuilder(prism => prism.CreateWindow("NavigationPage/MockViewA/MockViewB/MockViewC/MockViewD/MockViewE"))
+            .Build();
+        var window = GetWindow(mauiApp);
+
+        Assert.IsAssignableFrom<NavigationPage>(window.Page);
+        var navigationPage = (NavigationPage)window.Page;
+        var withoutPoppingPage = (MockViewD)navigationPage.Navigation.NavigationStack.First(p => ViewModelLocator.GetNavigationName(p) == nameof(MockViewD));
+        var withoutPoppingPageVm = (MockViewModelBase)withoutPoppingPage.BindingContext;
+
+        Assert.IsType<MockViewA>(navigationPage.RootPage);
+        Assert.IsType<MockViewE>(navigationPage.CurrentPage);
+
+        var result = await navigationPage.CurrentPage.GetContainerProvider()
+            .Resolve<INavigationService>()
+            .GoBackAsync("MockViewC");
+
+        Assert.True(result.Success);
+
+        Assert.IsType<MockViewC>(navigationPage.CurrentPage);
+
+        // In the GoBackAsync method, the OnNavigatedTo method is not called for pages that are not popped.
+        Assert.True(withoutPoppingPageVm.Actions.Last() == nameof(MockViewModelBase.OnNavigatedFrom));
+    }
+
+    [Fact]
+    public async Task GoBack_Name_PopsToSpecifiedViewWithoutPoppingEachPageOfLimitation()
+    {
+        var mauiApp = CreateBuilder(prism => prism.CreateWindow("NavigationPage/MockViewA/MockViewA/MockViewB/MockViewC/MockViewD/MockViewE"))
+            .Build();
+        var window = GetWindow(mauiApp);
+
+        Assert.IsAssignableFrom<NavigationPage>(window.Page);
+        var navigationPage = (NavigationPage)window.Page;
+
+        Assert.IsType<MockViewA>(navigationPage.RootPage);
+        Assert.IsType<MockViewE>(navigationPage.CurrentPage);
+
+        var result = await navigationPage.CurrentPage.GetContainerProvider()
+            .Resolve<INavigationService>()
+            .GoBackAsync("MockViewA");
+
+        Assert.True(result.Success);
+
+        Assert.IsType<MockViewA>(navigationPage.CurrentPage);
+
+        // If there are two instances of MockViewA, it will return to the instance closest to the current page.
+        // Therefore, the current modal stack will be in the state of NavigationPage/MockViewA/MockViewA.
+        Assert.Equal(2, navigationPage.Navigation.NavigationStack.Count);
+    }
+
     [Fact]
     public async Task TabbedPage_SelectTabSets_CurrentTab()
     {