feature for Xamarin added ReactiveShell, ReactiveShellContent, Reacti…

…veFlyOut (#2814)

* feature for Xamarin added ReactiveShell, ShellViewModel, ReactiveFlyOut

ReactiveShell can be used when you wish to use a viewmodel on your base
NOTE: Only supports WhenActivated NOT WhenDeactivated due to the Base nature of the Shell component

ShellViewModel is a ViewModel based version of ShellContent

* Updates to resolve queries refactored tests using Xamarin.Forms.Mocks

Rename ShellViewModel to ReactiveShellContent to keep in with other extended elements

* Removed ReactiveMasterDetailPage is obsolete

* throw new NullReferenceException(nameof(Locator.Current)) if Locator.Current is null

src/ReactiveUI.XamForms.Tests/Activation/ActivatingReactivePagesTests.cs

@@ -0,0 +1,146 @@
+// Copyright (c) 2021 .NET Foundation and Contributors. All rights reserved.
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for full license information.
+
+using ReactiveUI.XamForms;
+using ReactiveUI.XamForms.Tests.Activation;
+using ReactiveUI.XamForms.Tests.Activation.Mocks;
+using Splat;
+using Xamarin.Forms;
+using Xunit;
+
+namespace ReactiveUI.Tests
+{
+    /// <summary>
+    /// Tests for activating views.
+    /// </summary>
+    public class ActivatingReactivePagesTests : IClassFixture<ApplicationFixture<App>>
+    {
+        private ApplicationFixture<App> _fixture;
+
+        /// <summary>
+        /// Initializes a new instance of the <see cref="ActivatingReactivePagesTests"/> class.
+        /// </summary>
+        /// <param name="fixture">The fixture.</param>
+        public ActivatingReactivePagesTests(ApplicationFixture<App> fixture)
+        {
+            _fixture = fixture;
+            Locator.CurrentMutable.Register(() => new ActivationForViewFetcher(), typeof(IActivationForViewFetcher));
+            Locator.CurrentMutable.Register<IViewFor<ShellViewModel>>(() => new ShellView());
+            Locator.CurrentMutable.Register<IViewFor<ContentPageViewModel>>(() => new ContentPageView());
+            Locator.CurrentMutable.Register<IViewFor<TabbedPageViewModel>>(() => new TabbedPageView());
+            Locator.CurrentMutable.Register<IViewFor<CarouselPageViewModel>>(() => new CarouselPageView());
+            Locator.CurrentMutable.Register<IViewFor<FlyOutPageViewModel>>(() => new FlyoutPageView());
+            _fixture.ActivateApp(new App());
+        }
+
+        /// <summary>
+        /// Tests to make sure that views generally activate.
+        /// </summary>
+        [Fact]
+        public void ActivatingReactiveShellTest()
+        {
+            var main = _fixture.AppMock!.MainPage as AppShell;
+
+            Assert.Equal(1, main!.ViewModel!.IsActiveCount);
+            Assert.Equal(1, main.IsActiveCount);
+        }
+
+        /// <summary>
+        /// Tests to make sure that views generally activate.
+        /// </summary>
+        [Fact]
+        public void ActivatingReactiveContentPageTest()
+        {
+            var vm = new ContentPageViewModel();
+            var fixture = new ContentPageView
+            {
+                ViewModel = vm
+            };
+
+            // Activate
+            Shell.Current.Navigation.PushAsync(fixture);
+            Assert.Equal(1, fixture.ViewModel.IsActiveCount);
+            Assert.Equal(1, fixture.IsActiveCount);
+
+            // Deactivate
+            Shell.Current.GoToAsync("..");
+            fixture.ViewModel = null;
+            Assert.Equal(0, vm.IsActiveCount);
+            Assert.Equal(0, fixture.IsActiveCount);
+        }
+
+        /// <summary>
+        /// Tests to make sure that views generally activate.
+        /// </summary>
+        [Fact]
+        public void ActivatingReactiveTabbedPageTest()
+        {
+            var vm1 = new TabbedPageViewModel();
+            var fixture1 = new TabbedPageView
+            {
+                ViewModel = vm1
+            };
+
+            // Activate
+            Shell.Current.Navigation.PushAsync(fixture1);
+            Assert.Equal(1, fixture1.ViewModel.IsActiveCount);
+            Assert.Equal(1, fixture1.IsActiveCount);
+
+            // Deactivate
+            Shell.Current.GoToAsync("..");
+            fixture1.ViewModel = null;
+            Assert.Equal(0, vm1.IsActiveCount);
+            Assert.Equal(0, fixture1.IsActiveCount);
+        }
+
+        /// <summary>
+        /// Tests to make sure that views generally activate.
+        /// </summary>
+        [Fact]
+        public void ActivatingReactiveFlyoutPageTest()
+        {
+            var vm3 = new FlyOutPageViewModel();
+            var fixture3 = new FlyoutPageView
+            {
+                ViewModel = vm3
+            };
+
+            // Activate
+            Shell.Current.Navigation.PushAsync(fixture3);
+            Assert.Equal(1, fixture3.ViewModel!.IsActiveCount);
+            Assert.Equal(1, fixture3.IsActiveCount);
+
+            // Deactivate
+            Shell.Current.GoToAsync("..");
+            fixture3.ViewModel = null;
+            Assert.Equal(0, vm3.IsActiveCount);
+            Assert.Equal(0, fixture3.IsActiveCount);
+        }
+
+        /// <summary>
+        /// Tests to make sure that views generally activate.
+        /// </summary>
+        [Fact]
+        public void ActivatingReactiveCarouselPageTest()
+        {
+            var vm4 = new CarouselPageViewModel();
+            var fixture4 = new CarouselPageView
+            {
+                ViewModel = vm4
+            };
+
+            // Activate
+            Shell.Current.Navigation.PushAsync(fixture4);
+            Assert.Equal(1, fixture4.ViewModel!.IsActiveCount);
+            Assert.Equal(1, fixture4.IsActiveCount);
+
+            // Deactivate
+            Shell.Current.GoToAsync("..");
+            fixture4.ViewModel = null;
+            Assert.Equal(0, vm4.IsActiveCount);
+            Assert.Equal(0, fixture4.IsActiveCount);
+        }
+    }
+}

src/ReactiveUI.XamForms.Tests/Activation/Mocks/App.xaml

@@ -0,0 +1,34 @@
+<?xml version="1.0" encoding="utf-8" ?>
+<test:ApplicationMock
+    x:Class="ReactiveUI.XamForms.Tests.Activation.App"
+    xmlns="http://xamarin.com/schemas/2014/forms"
+    xmlns:x="http://schemas.microsoft.com/winfx/2009/xaml"
+    xmlns:test="clr-namespace:ReactiveUI.Tests">
+    <!--
+        Define global resources and styles here, that apply to all pages in your app.
+    -->
+    <Application.Resources>
+        <ResourceDictionary>
+            <Color x:Key="Primary">#2196F3</Color>
+            <Style TargetType="Button">
+                <Setter Property="TextColor" Value="White" />
+                <Setter Property="VisualStateManager.VisualStateGroups">
+                    <VisualStateGroupList>
+                        <VisualStateGroup x:Name="CommonStates">
+                            <VisualState x:Name="Normal">
+                                <VisualState.Setters>
+                                    <Setter Property="BackgroundColor" Value="{StaticResource Primary}" />
+                                </VisualState.Setters>
+                            </VisualState>
+                            <VisualState x:Name="Disabled">
+                                <VisualState.Setters>
+                                    <Setter Property="BackgroundColor" Value="#332196F3" />
+                                </VisualState.Setters>
+                            </VisualState>
+                        </VisualStateGroup>
+                    </VisualStateGroupList>
+                </Setter>
+            </Style>
+        </ResourceDictionary>
+    </Application.Resources>
+</test:ApplicationMock>

src/ReactiveUI.XamForms.Tests/Activation/Mocks/App.xaml.cs

@@ -0,0 +1,57 @@
+// Copyright (c) 2021 .NET Foundation and Contributors. All rights reserved.
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for full license information.
+
+using Xamarin.Forms;
+
+namespace ReactiveUI.XamForms.Tests.Activation
+{
+    /// <summary>
+    /// The App.
+    /// </summary>
+    /// <seealso cref="Xamarin.Forms.Application" />
+    public partial class App
+    {
+        /// <summary>
+        /// Initializes a new instance of the <see cref="App" /> class.
+        /// </summary>
+        /// <param name="page">The page.</param>
+        public App()
+        {
+            InitializeComponent();
+
+            MainPage = new AppShell();
+        }
+
+        /// <summary>
+        /// Application developers override this method to perform actions when the application starts.
+        /// </summary>
+        /// <remarks>
+        /// To be added.
+        /// </remarks>
+        protected override void OnStart()
+        {
+        }
+
+        /// <summary>
+        /// Application developers override this method to perform actions when the application enters the sleeping state.
+        /// </summary>
+        /// <remarks>
+        /// To be added.
+        /// </remarks>
+        protected override void OnSleep()
+        {
+        }
+
+        /// <summary>
+        /// Application developers override this method to perform actions when the application resumes from a sleeping state.
+        /// </summary>
+        /// <remarks>
+        /// To be added.
+        /// </remarks>
+        protected override void OnResume()
+        {
+        }
+    }
+}

src/ReactiveUI.XamForms.Tests/Activation/Mocks/AppShell.xaml

@@ -0,0 +1,39 @@
+<?xml version="1.0" encoding="UTF-8" ?>
+<rxui:ReactiveShell
+    x:Class="ReactiveUI.XamForms.Tests.Activation.AppShell"
+    xmlns="http://xamarin.com/schemas/2014/forms"
+    xmlns:x="http://schemas.microsoft.com/winfx/2009/xaml"
+    xmlns:rxui="clr-namespace:ReactiveUI.XamForms;assembly=ReactiveUI.XamForms"
+    xmlns:vm="clr-namespace:ReactiveUI.XamForms.Tests.Activation"
+    Title="Shell.XamForms.Test"
+    x:TypeArguments="vm:AppShellViewModel">
+
+    <!--
+        The overall app visual hierarchy is defined here, along with navigation.
+
+        https://docs.microsoft.com/xamarin/xamarin-forms/app-fundamentals/shell/
+    -->
+    <Shell.Resources>
+        <ResourceDictionary>
+            <Style x:Key="BaseStyle" TargetType="Element">
+                <Setter Property="Shell.BackgroundColor" Value="{StaticResource Primary}" />
+                <Setter Property="Shell.ForegroundColor" Value="White" />
+                <Setter Property="Shell.TitleColor" Value="White" />
+                <Setter Property="Shell.DisabledColor" Value="#B4FFFFFF" />
+                <Setter Property="Shell.UnselectedColor" Value="#95FFFFFF" />
+                <Setter Property="Shell.TabBarBackgroundColor" Value="{StaticResource Primary}" />
+                <Setter Property="Shell.TabBarForegroundColor" Value="White" />
+                <Setter Property="Shell.TabBarUnselectedColor" Value="#95FFFFFF" />
+                <Setter Property="Shell.TabBarTitleColor" Value="White" />
+            </Style>
+            <Style BasedOn="{StaticResource BaseStyle}" TargetType="TabBar" />
+            <Style BasedOn="{StaticResource BaseStyle}" TargetType="FlyoutItem" />
+        </ResourceDictionary>
+    </Shell.Resources>
+
+    <rxui:ReactiveShellContent Title="Shell" x:TypeArguments="vm:ShellViewModel" />
+    <rxui:ReactiveShellContent Title="Content" x:TypeArguments="vm:ContentPageViewModel" />
+    <rxui:ReactiveShellContent Title="Tabbed" x:TypeArguments="vm:TabbedPageViewModel" />
+    <rxui:ReactiveShellContent Title="Carousel" x:TypeArguments="vm:CarouselPageViewModel" />
+    <rxui:ReactiveShellContent Title="FlyOut" x:TypeArguments="vm:FlyOutPageViewModel" />
+</rxui:ReactiveShell>

src/ReactiveUI.XamForms.Tests/Activation/Mocks/AppShell.xaml.cs

@@ -0,0 +1,35 @@
+// Copyright (c) 2021 .NET Foundation and Contributors. All rights reserved.
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for full license information.
+
+using System.Reactive.Disposables;
+
+namespace ReactiveUI.XamForms.Tests.Activation
+{
+    /// <summary>
+    /// App Shell.
+    /// </summary>
+    /// <seealso cref="Xamarin.Forms.Shell" />
+    public partial class AppShell
+    {
+        /// <summary>
+        /// Initializes a new instance of the <see cref="AppShell"/> class.
+        /// </summary>
+        public AppShell()
+        {
+            InitializeComponent();
+            ViewModel = new();
+            this.WhenActivated(d =>
+            {
+                IsActiveCount++;
+                d(Disposable.Create(() => IsActiveCount--));
+            });
+        }
+
+        /// <summary>
+        /// Gets or sets the active count.
+        /// </summary>
+        public int IsActiveCount { get; set; }
+    }
+}

src/ReactiveUI.XamForms.Tests/Activation/Mocks/AppShellViewModel.cs

@@ -0,0 +1,41 @@
+// Copyright (c) 2021 .NET Foundation and Contributors. All rights reserved.
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for full license information.
+
+using System.Reactive.Disposables;
+
+namespace ReactiveUI.XamForms.Tests.Activation
+{
+    /// <summary>
+    /// Activating View Model2.
+    /// </summary>
+    /// <seealso cref="ReactiveUI.ReactiveObject" />
+    /// <seealso cref="ReactiveUI.IActivatableViewModel" />
+    public class AppShellViewModel : ReactiveObject, IActivatableViewModel
+    {
+        /// <summary>
+        /// Initializes a new instance of the <see cref="AppShellViewModel"/> class.
+        /// </summary>
+        public AppShellViewModel()
+        {
+            Activator = new ViewModelActivator();
+
+            this.WhenActivated(d =>
+            {
+                IsActiveCount++;
+                d(Disposable.Create(() => IsActiveCount--));
+            });
+        }
+
+        /// <summary>
+        /// Gets or sets the Activator which will be used by the View when Activation/Deactivation occurs.
+        /// </summary>
+        public ViewModelActivator Activator { get; protected set; }
+
+        /// <summary>
+        /// Gets or sets the active count.
+        /// </summary>
+        public int IsActiveCount { get; protected set; }
+    }
+}