move DI Configuration to ApplicationServices

Author: christiannagel

Xamarin/BooksAppX/BooksAppX/BooksAppX.Android/BooksAppX.Android.csproj

@@ -53,6 +53,9 @@
     <PackageReference Include="Microsoft.Extensions.Logging">
       <Version>2.0.0</Version>
     </PackageReference>
+    <PackageReference Include="System.Runtime.CompilerServices.Unsafe">
+      <Version>4.3.0</Version>
+    </PackageReference>
     <PackageReference Include="Xamarin.Forms" Version="2.5.0.122203" />
     <PackageReference Include="Xamarin.Android.Support.Design" Version="25.4.0.2" />
     <PackageReference Include="Xamarin.Android.Support.v7.AppCompat" Version="25.4.0.2" />

Xamarin/BooksAppX/BooksAppX/BooksAppX/App.xaml.cs

@@ -15,15 +15,14 @@ public partial class App : Application
         public App()
         {
             InitializeComponent();
-            RegisterServices();
 
             MainPage = new BooksAppX.Views.MainPage();
         }
 
         protected override void OnStart()
         {
             // Handle when your app starts
-            AppServices.GetService<INavigationService>().UseNavigation = true; // always use navigation
+            ApplicationServices.Instance.ServiceProvider.GetService<INavigationService>().UseNavigation = true; // always use navigation
         }
 
         protected override void OnSleep()
@@ -35,22 +34,5 @@ protected override void OnResume()
         {
             // Handle when your app resumes
         }
-
-        private void RegisterServices()
-        {
-            var services = new ServiceCollection();
-            services.AddSingleton<IBooksRepository, BooksSampleRepository>();
-            services.AddSingleton<IItemsService<Book>, BooksService>();
-            services.AddTransient<BooksViewModel>();
-            services.AddTransient<BookDetailViewModel>();
-            services.AddTransient<AboutViewModel>();
-            services.AddSingleton<IMessageService, XamarinMessageService>();
-            services.AddSingleton<INavigationService, XamarinNavigationService>();
-            services.AddSingleton<XamarinInitializeNavigationService>();
-            services.AddLogging();
-            AppServices = services.BuildServiceProvider();
-        }
-
-        public IServiceProvider AppServices { get; private set; }
     }
 }

Xamarin/BooksAppX/BooksAppX/BooksAppX/ApplicationServices.cs

@@ -0,0 +1,43 @@
+using BooksAppX.Services;
+using BooksAppX.ViewModels;
+using BooksLib.Models;
+using BooksLib.Services;
+using BooksLib.ViewModels;
+using Framework.Services;
+using Microsoft.Extensions.DependencyInjection;
+using System;
+
+namespace BooksAppX
+{
+    public class ApplicationServices
+    {
+        private ApplicationServices()
+        {
+            var services = new ServiceCollection();
+            services.AddSingleton<IBooksRepository, BooksSampleRepository>();
+            services.AddSingleton<IItemsService<Book>, BooksService>();
+            services.AddTransient<BooksViewModel>();
+            services.AddTransient<BookDetailViewModel>();
+            services.AddTransient<AboutViewModel>();
+            services.AddSingleton<IMessageService, XamarinMessageService>();
+            services.AddSingleton<INavigationService, XamarinNavigationService>();
+            services.AddSingleton<XamarinInitializeNavigationService>();
+            services.AddLogging();
+            ServiceProvider = services.BuildServiceProvider();
+        }
+
+        private static ApplicationServices _instance;
+        private static object _instanceLock = new object();
+        private static ApplicationServices GetInstance()
+        {
+            lock (_instanceLock)
+            {
+                return _instance ?? (_instance = new ApplicationServices());
+            }
+        }
+        public static ApplicationServices Instance => _instance ?? GetInstance();
+
+        public IServiceProvider ServiceProvider { get; }
+    }
+
+}

Xamarin/BooksAppX/BooksAppX/BooksAppX/BooksAppX.projitems

@@ -15,6 +15,7 @@
     <Compile Include="$(MSBuildThisFileDirectory)App.xaml.cs">
       <DependentUpon>App.xaml</DependentUpon>
     </Compile>
+    <Compile Include="$(MSBuildThisFileDirectory)ApplicationServices.cs" />
     <Compile Include="$(MSBuildThisFileDirectory)Services\XamarinInitializeNavigationService.cs" />
     <Compile Include="$(MSBuildThisFileDirectory)Services\XamarinMessageService.cs" />
     <Compile Include="$(MSBuildThisFileDirectory)Services\XamarinNavigationService.cs" />

Xamarin/BooksAppX/BooksAppX/BooksAppX/Views/AboutPage.xaml.cs

@@ -11,7 +11,7 @@ public partial class AboutPage : ContentPage
         public AboutPage()
         {
             InitializeComponent();
-            ViewModel = (Application.Current as App).AppServices.GetService<AboutViewModel>();
+            ViewModel = ApplicationServices.Instance.ServiceProvider.GetService<AboutViewModel>();
             BindingContext = this;
         }
 

Xamarin/BooksAppX/BooksAppX/BooksAppX/Views/BookDetailPage.xaml.cs

@@ -14,6 +14,6 @@ public BookDetailPage ()
             BindingContext = this;
         }
 
-        public BookDetailViewModel ViewModel { get; } = (Application.Current as App).AppServices.GetService<BookDetailViewModel>();
+        public BookDetailViewModel ViewModel { get; } = ApplicationServices.Instance.ServiceProvider.GetService<BookDetailViewModel>();
     }
 }

Xamarin/BooksAppX/BooksAppX/BooksAppX/Views/BooksPage.xaml.cs

@@ -14,7 +14,7 @@ public BooksPage()
             BindingContext = this;
         }
 
-        public BooksViewModel ViewModel { get; } = (Application.Current as App).AppServices.GetService<BooksViewModel>();
+        public BooksViewModel ViewModel { get; } = ApplicationServices.Instance.ServiceProvider.GetService<BooksViewModel>();
 
         //async void OnItemSelected(object sender, SelectedItemChangedEventArgs args)
         //{

Xamarin/BooksAppX/BooksAppX/BooksAppX/Views/MainPage.xaml.cs

@@ -16,7 +16,7 @@ public MainPage ()
         {
             InitializeComponent();
 
-            (Application.Current as App).AppServices.GetService<XamarinInitializeNavigationService>().SetNavigation(navigationPage.Navigation, PageNames.BooksPage);
+            ApplicationServices.Instance.ServiceProvider.GetService<XamarinInitializeNavigationService>().SetNavigation(navigationPage.Navigation, PageNames.BooksPage);
         }
 
         protected override bool OnBackButtonPressed()
@@ -27,7 +27,7 @@ protected override bool OnBackButtonPressed()
 
         private async void OnBackButtonAsync()
         {
-            await (Application.Current as App).AppServices.GetService<INavigationService>().GoBackAsync();
+            await ApplicationServices.Instance.ServiceProvider.GetService<INavigationService>().GoBackAsync();
         }
     }
 }