[Enhancement] Make it easier to access IDialogService from Singletons

src/Maui/Prism.Maui/Common/MvvmHelpers.cs

@@ -1,5 +1,6 @@
-using System.ComponentModel;
+using System.ComponentModel;
 using System.Reflection;
+using Prism.Dialogs;
 using Prism.Navigation;
 using Prism.Navigation.Regions;
 using Prism.Navigation.Xaml;
@@ -8,9 +9,9 @@
 
 namespace Prism.Common;
 
 public static class MvvmHelpers
 {
     public static void InvokeViewAndViewModelAction<T>(object view, Action<T> action) where T : class
     {
         if (view is T viewAsT)
         {
@@ -31,7 +32,7 @@
         }
     }
 
     public static async Task InvokeViewAndViewModelActionAsync<T>(object view, Func<T, Task> action) where T : class
     {
         if (view is T viewAsT)
         {
@@ -52,7 +53,7 @@
         }
     }
 
     public static void DestroyPage(IView view)
     {
         try
         {
@@ -95,7 +96,7 @@
         }
     }
 
     public static void DestroyWithModalStack(Page page, IList<Page> modalStack)
     {
         foreach (var childPage in modalStack.Reverse())
         {
@@ -104,7 +105,7 @@
         DestroyPage(page);
     }
 
     public static T GetImplementerFromViewOrViewModel<T>(object view)
             where T : class
     {
         if (view is T viewAsT)
@@ -272,27 +273,44 @@
         return EvaluateCurrentPage(page);
     };
 
-    private static Page EvaluateCurrentPage(Page target)
+    private static Page GetTarget(Page target)
     {
-        Page child = null;
+        return target switch
+        {
+            FlyoutPage flyout => GetTarget(flyout.Detail),
+            TabbedPage tabbed => GetTarget(tabbed.CurrentPage),
+            NavigationPage navigation => GetTarget(navigation.CurrentPage),
+            ContentPage page => page,
+            _ => throw new NotSupportedException($"The page type '{target.GetType().FullName}' is not supported.")
+        };
+    }
 
-        if (target is FlyoutPage flyout)
-            child = flyout.Detail;
-        else if (target is TabbedPage tabbed)
-            child = tabbed.CurrentPage;
-        else if (target is NavigationPage np)
-            child = np.Navigation.NavigationStack.Last();
+    private static Page EvaluateCurrentPage(Page target)
+    {
+        Page child = GetTarget(target);
 
-        if (child != null)
+        if (child is not null)
             target = GetOnNavigatedToTargetFromChild(child);
 
         if (target is Page page)
+        {
+            if (target is IDialogContainer)
+            {
+                if (page.Parent is Page parentPage)
+                {
+                    return GetTarget(parentPage);
+                }
+
+                throw new InvalidOperationException("Unable to determine the current page.");
+            }
+
             return page.Parent switch
             {
                 TabbedPage tab when tab.CurrentPage != target => EvaluateCurrentPage(tab.CurrentPage),
                 NavigationPage nav when nav.CurrentPage != target => EvaluateCurrentPage(nav.CurrentPage),
                 _ => target
             };
+        }
 
         return null;
     }

src/Maui/Prism.Maui/Dialogs/DialogService.cs

@@ -1,209 +1,26 @@
-using Prism.Commands;
 using Prism.Common;
-using Prism.Dialogs.Xaml;
-using Prism.Mvvm;
-using Prism.Navigation;
 
 #nullable enable
 namespace Prism.Dialogs;
 
 /// <summary>
-/// Provides the ability to display dialogs from ViewModels.
+/// Provides a default scoped implementation of the <see cref="IDialogService"/>.
 /// </summary>
-public sealed class DialogService : IDialogService
+public sealed class DialogService : DialogServiceBase
 {
-    private readonly IContainerProvider _container;
     private readonly IPageAccessor _pageAccessor;
 
     /// <summary>
     /// Creates a new instance of the <see cref="DialogService"/> for Maui Applications
     /// </summary>
-    /// <param name="container">The <see cref="IContainerProvider"/> that will be used to help resolve the Dialog Views.</param>
     /// <param name="pageAccessor">The <see cref="IPageAccessor"/> used to determine where in the Navigation Stack we need to process the Dialog.</param>
     /// <exception cref="ArgumentNullException">Throws when any constructor arguments are null.</exception>
-    public DialogService(IContainerProvider container, IPageAccessor pageAccessor)
+    public DialogService(IPageAccessor pageAccessor) 
     {
-        ArgumentNullException.ThrowIfNull(container);
         ArgumentNullException.ThrowIfNull(pageAccessor);
-        _container = container;
         _pageAccessor = pageAccessor;
     }
 
     /// <inheritdoc/>
-    public void ShowDialog(string name, IDialogParameters parameters, DialogCallback callback)
-    {
-        IDialogContainer? dialogModal = null;
-        try
-        {
-            parameters = UriParsingHelper.GetSegmentParameters(name, parameters ?? new DialogParameters());
-
-            // This needs to be resolved when called as a Module could load any time
-            // and register new dialogs
-            var registry = _container.Resolve<IDialogViewRegistry>();
-            var view = registry.CreateView(_container, UriParsingHelper.GetSegmentName(name)) as View 
-                ?? throw new ViewCreationException(name, ViewType.Dialog);
-
-            var currentPage = _pageAccessor.Page;
-            dialogModal = _container.Resolve<IDialogContainer>();
-            IDialogContainer.DialogStack.Add(dialogModal);
-            var dialogAware = GetDialogController(view);
-
-            async Task DialogAware_RequestClose(IDialogResult outResult)
-            {
-                bool didCloseDialog = true;
-                try
-                {
-                    var result = await CloseDialogAsync(outResult ?? new DialogResult(), currentPage, dialogModal);
-                    if (result.Exception is DialogException de && de.Message == DialogException.CanCloseIsFalse)
-                    {
-                        didCloseDialog = false;
-                        return;
-                    }
-
-                    await callback.Invoke(result);
-                    GC.Collect();
-                }
-                catch (DialogException dex)
-                {
-                    if (dex.Message == DialogException.CanCloseIsFalse)
-                    {
-                        didCloseDialog = false;
-                        return;
-                    }
-
-                    var result = new DialogResult
-                    {
-                        Exception = dex,
-                        Parameters = parameters,
-                        Result = ButtonResult.None
-                    };
-
-                    if (dex.Message != DialogException.CanCloseIsFalse)
-                    {
-                        await DialogService.InvokeError(callback, dex, parameters);
-                    }
-                }
-                catch (Exception ex)
-                {
-                    await DialogService.InvokeError(callback, ex, parameters);
-                }
-                finally
-                {
-                    if (didCloseDialog && dialogModal is not null)
-                    {
-                        IDialogContainer.DialogStack.Remove(dialogModal);
-                    }
-                }
-            }
-
-            DialogUtilities.InitializeListener(dialogAware, DialogAware_RequestClose);
-
-            dialogAware.OnDialogOpened(parameters);
-
-            if (!parameters.TryGetValue<bool>(KnownDialogParameters.CloseOnBackgroundTapped, out var closeOnBackgroundTapped))
-            {
-                var dialogLayoutCloseOnBackgroundTapped = DialogLayout.GetCloseOnBackgroundTapped(view);
-                if (dialogLayoutCloseOnBackgroundTapped.HasValue)
-                {
-                    closeOnBackgroundTapped = dialogLayoutCloseOnBackgroundTapped.Value;
-                }
-            }
-
-            var dismissCommand = new DelegateCommand(() => dialogAware.RequestClose.Invoke(), dialogAware.CanCloseDialog);
-
-            PageNavigationService.NavigationSource = PageNavigationSource.DialogService;
-            dialogModal.ConfigureLayout(_pageAccessor.Page, view, closeOnBackgroundTapped, dismissCommand, parameters);
-            PageNavigationService.NavigationSource = PageNavigationSource.Device;
-
-            MvvmHelpers.InvokeViewAndViewModelAction<IActiveAware>(currentPage, aa => aa.IsActive = false);
-            MvvmHelpers.InvokeViewAndViewModelAction<IActiveAware>(view, aa => aa.IsActive = true);
-        }
-        catch (Exception ex)
-        {
-            callback.Invoke(ex);
-        }
-    }
-
-    private static async Task InvokeError(DialogCallback callback, Exception exception, IDialogParameters parameters)
-    {
-        var result = new DialogResult 
-        {
-            Parameters = parameters,
-            Exception = exception,
-            Result = ButtonResult.None
-        };
-        await callback.Invoke(result);
-    }
-
-    private static async Task<IDialogResult> CloseDialogAsync(IDialogResult result, Page currentPage, IDialogContainer dialogModal)
-    {
-        try
-        {
-            PageNavigationService.NavigationSource = PageNavigationSource.DialogService;
-
-            result ??= new DialogResult();
-            if (result.Parameters is null)
-            {
-                result = new DialogResult
-                {
-                    Exception = result.Exception,
-                    Parameters = new DialogParameters(),
-                    Result = result.Result
-                };
-            }
-
-            var view = dialogModal.DialogView;
-            var dialogAware = GetDialogController(view);
-
-            if (!dialogAware.CanCloseDialog())
-            {
-                throw new DialogException(DialogException.CanCloseIsFalse);
-            }
-
-            PageNavigationService.NavigationSource = PageNavigationSource.DialogService;
-            await dialogModal.DoPop(currentPage);
-            PageNavigationService.NavigationSource = PageNavigationSource.Device;
-
-            MvvmHelpers.InvokeViewAndViewModelAction<IActiveAware>(view, aa => aa.IsActive = false);
-            MvvmHelpers.InvokeViewAndViewModelAction<IActiveAware>(currentPage, aa => aa.IsActive = true);
-            dialogAware.OnDialogClosed();
-
-            return result;
-        }
-        catch (DialogException)
-        {
-            throw;
-        }
-        catch (Exception ex)
-        {
-            return new DialogResult
-            {
-                Exception = ex,
-                Parameters = result.Parameters,
-                Result = result.Result
-            };
-        }
-        finally
-        {
-            PageNavigationService.NavigationSource = PageNavigationSource.Device;
-        }
-    }
-
-    private static IDialogAware GetDialogController(View view)
-    {
-        if (view is IDialogAware viewAsDialogAware)
-        {
-            return viewAsDialogAware;
-        }
-        else if (view.BindingContext is null)
-        {
-            throw new DialogException(DialogException.NoViewModel);
-        }
-        else if (view.BindingContext is IDialogAware dialogAware)
-        {
-            return dialogAware;
-        }
-
-        throw new DialogException(DialogException.ImplementIDialogAware);
-    }
+    protected override Page? GetCurrentPage() => _pageAccessor.Page;
 }