Postpone popup show until platform is ready (#934)

* If platform is not enabled defer to OnNavigatedTo event

* Sample to prove support for showing Popup in OnAppearing

* Unsubscribe event handlers

* Make use of ContinueWith to avoid awaiting

* Update src/CommunityToolkit.Maui/Views/Popup/PopupExtensions.shared.cs

Co-authored-by: Pedro Jesus <pedrojesus.cefet@gmail.com>

* improved the error handling on TCS

Co-authored-by: Pedro Jesus <pedrojesus.cefet@gmail.com>

samples/CommunityToolkit.Maui.Sample/AppShell.xaml.cs

@@ -114,6 +114,7 @@ public partial class AppShell : Shell
 		CreateViewModelMapping<MultiplePopupPage, MultiplePopupViewModel, ViewsGalleryPage, ViewsGalleryViewModel>(),
 		CreateViewModelMapping<PopupAnchorPage, PopupAnchorViewModel, ViewsGalleryPage, ViewsGalleryViewModel>(),
 		CreateViewModelMapping<PopupPositionPage, PopupPositionViewModel, ViewsGalleryPage, ViewsGalleryViewModel>(),
+		CreateViewModelMapping<ShowPopupInOnAppearingPage, ShowPopupInOnAppearingPageViewModel, ViewsGalleryPage, ViewsGalleryViewModel>(),
 	});
 
 	public AppShell() => InitializeComponent();

samples/CommunityToolkit.Maui.Sample/MauiProgram.cs

@@ -167,6 +167,7 @@ static void RegisterViewsAndViewModels(in IServiceCollection services)
 		services.AddTransientWithShellRoute<MultiplePopupPage, MultiplePopupViewModel>();
 		services.AddTransientWithShellRoute<PopupAnchorPage, PopupAnchorViewModel>();
 		services.AddTransientWithShellRoute<PopupPositionPage, PopupPositionViewModel>();
+		services.AddTransientWithShellRoute<ShowPopupInOnAppearingPage, ShowPopupInOnAppearingPageViewModel>();
 
 		// Add Popups
 		services.AddTransient<CsharpBindingPopup, CsharpBindingPopupViewModel>();

samples/CommunityToolkit.Maui.Sample/Pages/Views/Popup/ShowPopupInOnAppearingPage.xaml

@@ -0,0 +1,16 @@
+<?xml version="1.0" encoding="utf-8" ?>
+<pages:BasePage xmlns="http://schemas.microsoft.com/dotnet/2021/maui"
+                xmlns:x="http://schemas.microsoft.com/winfx/2009/xaml"
+                x:Class="CommunityToolkit.Maui.Sample.Pages.Views.ShowPopupInOnAppearingPage"
+                xmlns:pages="clr-namespace:CommunityToolkit.Maui.Sample.Pages"
+                xmlns:viewModels="clr-namespace:CommunityToolkit.Maui.Sample.ViewModels.Views"
+                Title="ShowPopupInOnAppearingPage"
+                x:TypeArguments="viewModels:ShowPopupInOnAppearingPageViewModel"
+                x:DataType="viewModels:ShowPopupInOnAppearingPageViewModel">
+    <VerticalStackLayout>
+        <Label 
+            Text="Proves that we now support showing a popup before the platform is even ready."
+            VerticalOptions="Center" 
+            HorizontalOptions="Center" />
+    </VerticalStackLayout>
+</pages:BasePage>

samples/CommunityToolkit.Maui.Sample/Pages/Views/Popup/ShowPopupInOnAppearingPage.xaml.cs

@@ -0,0 +1,26 @@
+using CommunityToolkit.Maui.Sample.Models;
+using CommunityToolkit.Maui.Sample.ViewModels.Views;
+using CommunityToolkit.Maui.Views;
+
+namespace CommunityToolkit.Maui.Sample.Pages.Views;
+
+public partial class ShowPopupInOnAppearingPage : BasePage<ShowPopupInOnAppearingPageViewModel>
+{
+	readonly PopupSizeConstants popupSizeConstants;
+
+	public ShowPopupInOnAppearingPage(
+		PopupSizeConstants popupSizeConstants,
+		ShowPopupInOnAppearingPageViewModel showPopupInOnAppearingPageViewModel)
+		: base(showPopupInOnAppearingPageViewModel)
+	{
+		InitializeComponent();
+		this.popupSizeConstants = popupSizeConstants;
+	}
+
+	protected override async void OnAppearing()
+	{
+
+		// Proves that we now support showing a popup before the platform is even ready.
+		var result = await this.ShowPopupAsync(new ReturnResultPopup(popupSizeConstants));
+	}
+}

samples/CommunityToolkit.Maui.Sample/ViewModels/Views/Popup/ShowPopupInOnAppearingPageViewModel.cs

@@ -0,0 +1,5 @@
+namespace CommunityToolkit.Maui.Sample.ViewModels.Views;
+
+public class ShowPopupInOnAppearingPageViewModel : BaseViewModel
+{
+}

samples/CommunityToolkit.Maui.Sample/ViewModels/Views/ViewsGalleryViewModel.cs

@@ -25,6 +25,7 @@ public ViewsGalleryViewModel()
 			SectionModel.Create<MultiplePopupViewModel>("Mutiple Popups Page", Colors.Red, "A page demonstrating multiple different Popups"),
 			SectionModel.Create<PopupPositionViewModel>("Custom Positioning Popup", Colors.Red, "Displays a basic popup anywhere on the screen using VerticalOptions and HorizontalOptions"),
 			SectionModel.Create<PopupAnchorViewModel>("Anchor Popup", Colors.Red, "Popups can be anchored to other view's on the screen"),
+			SectionModel.Create<ShowPopupInOnAppearingPageViewModel>("Show Popup in OnAppearing", Colors.Red, "Proves that we now support showing a popup before the platform is even ready."),
 		})
 	{
 	}

src/CommunityToolkit.Maui/Views/Popup/PopupExtensions.shared.cs

@@ -21,12 +21,21 @@ public static partial class PopupExtensions
 	/// </param>
 	public static void ShowPopup<TPopup>(this Page page, TPopup popup) where TPopup : Popup
 	{
-#if WINDOWS
-		PlatformShowPopup(popup, GetMauiContext(page));
-#else
-		CreatePopup(page, popup);
-#endif
+		if (page.IsPlatformEnabled)
+		{
+			CreateAndShowPopup(page, popup);
+		}
+		else
+		{
+			void handler(object? sender, NavigatedToEventArgs args)
+			{
+				page.NavigatedTo -= handler;
 
+				CreateAndShowPopup(page, popup);
+			}
+
+			page.NavigatedTo += handler;
+		}
 	}
 
 	/// <summary>
@@ -43,13 +52,34 @@ public static void ShowPopup<TPopup>(this Page page, TPopup popup) where TPopup
 	/// </returns>
 	public static Task<object?> ShowPopupAsync<TPopup>(this Page page, TPopup popup) where TPopup : Popup
 	{
-#if WINDOWS
-		return PlatformShowPopupAsync(popup, GetMauiContext(page));
-#else
+		if (page.IsPlatformEnabled)
+		{
+			return CreateAndShowPopupAsync(page, popup);
+		}
+		else
+		{
+			var taskCompletionSource = new TaskCompletionSource<object?>();
 
-		CreatePopup(page, popup);
-		return popup.Result;
-#endif
+			async void handler(object? sender, NavigatedToEventArgs args)
+			{
+				page.NavigatedTo -= handler;
+
+				try
+				{
+					var result = await CreateAndShowPopupAsync(page, popup);
+
+					taskCompletionSource.TrySetResult(result);
+				}
+				catch (Exception ex)
+				{
+					taskCompletionSource.TrySetException(ex);
+				}
+			}
+
+			page.NavigatedTo += handler;
+
+			return taskCompletionSource.Task;
+		}
 	}
 
 	static void CreatePopup(Page page, Popup popup)
@@ -65,4 +95,24 @@ static IMauiContext GetMauiContext(Page page)
 	{
 		return page.Handler?.MauiContext ?? throw new InvalidOperationException("Could not locate MauiContext.");
 	}
+
+	static void CreateAndShowPopup<TPopup>(Page page, TPopup popup) where TPopup : Popup
+	{
+#if WINDOWS
+		PlatformShowPopup(popup, GetMauiContext(page));
+#else
+		CreatePopup(page, popup);
+#endif
+	}
+
+	static Task<object?> CreateAndShowPopupAsync<TPopup>(this Page page, TPopup popup) where TPopup : Popup
+	{
+#if WINDOWS
+		return PlatformShowPopupAsync(popup, GetMauiContext(page));
+#else
+		CreatePopup(page, popup);
+
+		return popup.Result;
+#endif
+	}
 }