Updating all view dispatchers to inherit from async dispatcher

MvvmCross/Base/IMvxMainThreadAsyncDispatcher.cs

@@ -0,0 +1,18 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MS-PL license.
+// See the LICENSE file in the project root for more information.
+
+using System;
+using System.Threading.Tasks;
+
+namespace MvvmCross.Base
+{
+    // Note: The long term goal should be to deprecate IMvxMainThreadDispatcher
+    // As such, even though the implementation of this interface also implements
+    // IMvxMainThreadDispatcher, this interface should not inherit from IMvxMainThreadDispatcher
+    public interface IMvxMainThreadAsyncDispatcher
+    {
+        Task ExecuteOnMainThreadAsync(Action action, bool maskExceptions = true);
+        Task ExecuteOnMainThreadAsync(Func<Task> action, bool maskExceptions = true);
+    }
+}

MvvmCross/Base/IMvxMainThreadDispatcher.cs

@@ -9,12 +9,7 @@ namespace MvvmCross.Base
 {
     public interface IMvxMainThreadDispatcher
     {
+        [Obsolete("Use IMvxMainThreadAsyncDispatcher.ExecuteOnMainThreadAsync instead")]
         bool RequestMainThreadAction(Action action, bool maskExceptions = true);
     }
-
-    public interface IMvxMainThreadAsyncDispatcher
-    {
-        Task<bool> ExecuteOnMainThreadAsync(Action action, bool maskExceptions = true);
-        Task<bool> ExecuteOnMainThreadAsync(Func<Task> action, bool maskExceptions = true);
-    }
 }

MvvmCross/Base/MvxMainThreadAsyncDispatcher.cs

@@ -0,0 +1,43 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MS-PL license.
+// See the LICENSE file in the project root for more information.
+
+using System;
+using System.Threading.Tasks;
+
+namespace MvvmCross.Base
+{
+    public abstract class MvxMainThreadAsyncDispatcher : MvxMainThreadDispatcher, IMvxMainThreadAsyncDispatcher
+    {
+        public Task ExecuteOnMainThreadAsync(Action action, bool maskExceptions = true)
+        {
+            var asyncAction = new Func<Task>(() =>
+            {
+                action();
+                return Task.CompletedTask;
+            });
+            return ExecuteOnMainThreadAsync(asyncAction, maskExceptions);
+        }
+
+        public async Task ExecuteOnMainThreadAsync(Func<Task> action, bool maskExceptions = true)
+        {
+            var completion = new TaskCompletionSource<bool>();
+            var syncAction = new Action(async () =>
+            {
+                await action();
+                completion.SetResult(true);
+            });
+            RequestMainThreadAction(syncAction, maskExceptions);
+
+            // If we're already on main thread, then the action will
+            // have already completed at this point, so can just return
+            if (completion.Task.IsCompleted)
+                return;
+
+            // Make sure we don't introduce weird locking issues  
+            // blocking on the completion source by jumping onto
+            // a new thread to wait
+            await Task.Run(async () => await completion.Task);
+        }
+    }
+}

MvvmCross/Base/MvxMainThreadDispatcher.cs

@@ -4,12 +4,13 @@
 
 using System;
 using System.Reflection;
+using System.Threading.Tasks;
 using MvvmCross.Exceptions;
 using MvvmCross.Logging;
 
 namespace MvvmCross.Base
 {
-    public abstract class MvxMainThreadDispatcher : MvxSingleton<IMvxMainThreadDispatcher>
+    public abstract class MvxMainThreadDispatcher : MvxSingleton<IMvxMainThreadDispatcher>, IMvxMainThreadDispatcher
     {
         protected static void ExceptionMaskedAction(Action action, bool maskExceptions)
         {
@@ -34,5 +35,7 @@ namespace MvvmCross.Base
                     throw exception;
             }
         }
+
+        public abstract bool RequestMainThreadAction(Action action, bool maskExceptions = true);
     }
 }

MvvmCross/Core/MvxSetup.cs

@@ -339,6 +339,7 @@ namespace MvvmCross.Core
         {
             var dispatcher = CreateViewDispatcher();
             Mvx.RegisterSingleton(dispatcher);
+            Mvx.RegisterSingleton<IMvxMainThreadAsyncDispatcher>(dispatcher);
             Mvx.RegisterSingleton<IMvxMainThreadDispatcher>(dispatcher);
         }
 

MvvmCross/Platforms/Android/Views/MvxAndroidMainThreadDispatcher.cs

@@ -10,9 +10,9 @@ using MvvmCross.Base;
 
 namespace MvvmCross.Platforms.Android.Views
 {
-    public class MvxAndroidMainThreadDispatcher : MvxMainThreadDispatcher
+    public class MvxAndroidMainThreadDispatcher : MvxMainThreadAsyncDispatcher
     {
-        public bool RequestMainThreadAction(Action action, bool maskExceptions = true)
+        public override bool RequestMainThreadAction(Action action, bool maskExceptions = true)
         {
             if (Application.SynchronizationContext == SynchronizationContext.Current)
                 action();

MvvmCross/Platforms/Console/Views/MvxConsoleViewDispatcher.cs

@@ -1,4 +1,4 @@
-// Licensed to the .NET Foundation under one or more agreements.
+// Licensed to the .NET Foundation under one or more agreements.
 // The .NET Foundation licenses this file to you under the MS-PL license.
 // See the LICENSE file in the project root for more information.
 
@@ -10,10 +10,10 @@ using MvvmCross.Views;
 namespace MvvmCross.Platforms.Console.Views
 {
     public class MvxConsoleViewDispatcher
-        : MvxMainThreadDispatcher
+        : MvxMainThreadAsyncDispatcher
         , IMvxViewDispatcher
     {
-        public bool RequestMainThreadAction(Action action, bool maskExceptions = true)
+        public override bool RequestMainThreadAction(Action action, bool maskExceptions = true)
         {
             action();
             return true;

MvvmCross/Platforms/Ios/Views/MvxIosUIThreadDispatcher.cs

@@ -11,7 +11,7 @@ using UIKit;
 namespace MvvmCross.Platforms.Ios.Views
 {
     public abstract class MvxIosUIThreadDispatcher
-        : MvxMainThreadDispatcher
+        : MvxMainThreadAsyncDispatcher
     {
         private readonly SynchronizationContext _uiSynchronizationContext;
 
@@ -22,7 +22,7 @@ namespace MvvmCross.Platforms.Ios.Views
                 throw new MvxException("SynchronizationContext must not be null - check to make sure Dispatcher is created on UI thread");
         }
 
-        public bool RequestMainThreadAction(Action action, bool maskExceptions = true)
+        public override bool RequestMainThreadAction(Action action, bool maskExceptions = true)
         {
             if (_uiSynchronizationContext == SynchronizationContext.Current)
                 action();

MvvmCross/Platforms/Mac/Views/MvxMacUIThreadDispatcher.cs

@@ -12,7 +12,7 @@ using MvvmCross.Exceptions;
 namespace MvvmCross.Platforms.Mac.Views
 {
     public abstract class MvxMacUIThreadDispatcher
-        : MvxMainThreadDispatcher
+        : MvxMainThreadAsyncDispatcher
     {
         private readonly SynchronizationContext _uiSynchronizationContext;
 
@@ -23,7 +23,7 @@ namespace MvvmCross.Platforms.Mac.Views
                 throw new MvxException("SynchronizationContext must not be null - check to make sure Dispatcher is created on UI thread");
         }
 
-        public bool RequestMainThreadAction(Action action,
+        public override bool RequestMainThreadAction(Action action,
             bool maskExceptions = true)
         {
             if (_uiSynchronizationContext == SynchronizationContext.Current)

MvvmCross/Platforms/Tvos/Views/MvxTvosUIThreadDispatcher.cs

@@ -11,7 +11,7 @@ using UIKit;
 namespace MvvmCross.Platforms.Tvos.Views
 {
     public abstract class MvxTvosUIThreadDispatcher
-        : MvxMainThreadDispatcher
+        : MvxMainThreadAsyncDispatcher
     {
         private readonly SynchronizationContext _uiSynchronizationContext;
 
@@ -22,7 +22,7 @@ namespace MvvmCross.Platforms.Tvos.Views
                 throw new MvxException("SynchronizationContext must not be null - check to make sure Dispatcher is created on UI thread");
         }
 
-        public bool RequestMainThreadAction(Action action, bool maskExceptions = true)
+        public override bool RequestMainThreadAction(Action action, bool maskExceptions = true)
         {
             if (_uiSynchronizationContext == SynchronizationContext.Current)
                 action();

MvvmCross/Platforms/Uap/Views/MvxWindowsMainThreadDispatcher.cs

@@ -8,7 +8,7 @@ using MvvmCross.Base;
 
 namespace MvvmCross.Platforms.Uap.Views
 {
-    public class MvxWindowsMainThreadDispatcher : MvxMainThreadDispatcher
+    public class MvxWindowsMainThreadDispatcher : MvxMainThreadAsyncDispatcher
     {
         private readonly CoreDispatcher _uiDispatcher;
 
@@ -17,7 +17,7 @@ namespace MvvmCross.Platforms.Uap.Views
             _uiDispatcher = uiDispatcher;
         }
 
-        public bool RequestMainThreadAction(Action action, bool maskExceptions = true)
+        public override bool RequestMainThreadAction(Action action, bool maskExceptions = true)
         {
             if (_uiDispatcher.HasThreadAccess)
             {

MvvmCross/Platforms/Wpf/Views/MvxWpfUIThreadDispatcher.cs

@@ -9,7 +9,7 @@ using MvvmCross.Base;
 namespace MvvmCross.Platforms.Wpf.Views
 {
     public class MvxWpfUIThreadDispatcher
-        : MvxMainThreadDispatcher
+        : MvxMainThreadAsyncDispatcher
     {
         private readonly Dispatcher _dispatcher;
 
@@ -18,7 +18,7 @@ namespace MvvmCross.Platforms.Wpf.Views
             _dispatcher = dispatcher;
         }
 
-        public bool RequestMainThreadAction(Action action, bool maskExceptions = true)
+        public override bool RequestMainThreadAction(Action action, bool maskExceptions = true)
         {
             if (_dispatcher.CheckAccess())
             {

MvvmCross/Views/IMvxViewDispatcher.cs

@@ -7,10 +7,10 @@ using MvvmCross.ViewModels;
 
 namespace MvvmCross.Views
 {
-    public interface IMvxViewDispatcher : IMvxMainThreadDispatcher
+    public interface IMvxViewDispatcher : IMvxMainThreadDispatcher, IMvxMainThreadAsyncDispatcher
     {
         bool ShowViewModel(MvxViewModelRequest request);
 
         bool ChangePresentation(MvxPresentationHint hint);
     }
-}
+}

UnitTests/MvvmCross.UnitTest/Mocks/Dispatchers/CallbackMockMainThreadDispatcher.cs

@@ -8,7 +8,7 @@ using MvvmCross.Base;
 namespace MvvmCross.UnitTest.Mocks.Dispatchers
 {
     public class CallbackMockMainThreadDispatcher
-        : MvxMainThreadDispatcher, IMvxMainThreadDispatcher
+        : MvxMainThreadAsyncDispatcher
     {
         private readonly Func<Action, bool> _callback;
 
@@ -17,7 +17,7 @@ namespace MvvmCross.UnitTest.Mocks.Dispatchers
             _callback = callback;
         }
 
-        public virtual bool RequestMainThreadAction(Action action, 
+        public override bool RequestMainThreadAction(Action action,
                                                     bool maskExceptions = true)
         {
             return _callback(action);

UnitTests/MvvmCross.UnitTest/Mocks/Dispatchers/CountingMockMainThreadDispatcher.cs

@@ -8,11 +8,11 @@ using MvvmCross.Base;
 namespace MvvmCross.UnitTest.Mocks.Dispatchers
 {
     public class CountingMockMainThreadDispatcher
-        : MvxMainThreadDispatcher, IMvxMainThreadDispatcher
+        : MvxMainThreadAsyncDispatcher
     {
         public int Count { get; set; }
 
-        public bool RequestMainThreadAction(Action action, bool maskExceptions = true)
+        public override bool RequestMainThreadAction(Action action, bool maskExceptions = true)
         {
             Count++;
             return true;

UnitTests/MvvmCross.UnitTest/Mocks/Dispatchers/InlineMockMainThreadDispatcher.cs

@@ -8,9 +8,9 @@ using MvvmCross.Base;
 namespace MvvmCross.UnitTest.Mocks.Dispatchers
 {
     public class InlineMockMainThreadDispatcher
-        : MvxMainThreadDispatcher, IMvxMainThreadDispatcher
+        : MvxMainThreadAsyncDispatcher
     {
-        public virtual bool RequestMainThreadAction(Action action, 
+        public override bool RequestMainThreadAction(Action action, 
             bool maskExceptions = true)
         {
             action();

UnitTests/MvvmCross.UnitTest/Mocks/Dispatchers/NavigationMockDispatcher.cs

@@ -5,6 +5,7 @@
 using System;
 using System.Collections.Generic;
 using System.Linq;
+using System.Threading.Tasks;
 using MvvmCross.Base;
 using MvvmCross.Logging;
 using MvvmCross.Tests;
@@ -26,7 +27,7 @@ namespace MvvmCross.UnitTest.Mocks.Dispatchers
             return true;
         }
 
-        public virtual bool ShowViewModel(MvxViewModelRequest request)
+        public virtual Task<bool> ShowViewModel(MvxViewModelRequest request)
         {
             var debugString = $"ShowViewModel: '{request.ViewModelType.Name}' ";
             if (request.ParameterValues != null)
@@ -36,13 +37,13 @@ namespace MvvmCross.UnitTest.Mocks.Dispatchers
             MvxTestLog.Instance.Log(MvxLogLevel.Debug, () => debugString);
 
             Requests.Add(request);
-            return true;
+            return Task.FromResult(true);
         }
 
-        public virtual bool ChangePresentation(MvxPresentationHint hint)
+        public virtual Task<bool> ChangePresentation(MvxPresentationHint hint)
         {
             Hints.Add(hint);
-            return true;
+            return Task.FromResult(true);
         }
 
     }