Implement Next action in android IME (#13222)

* implement Next action in android IME

* Handle UIReturnKeyType.Next on iOS

* Remove NavigationMethod.Directional (do we need focus adorner?)

---------

Co-authored-by: Max Katz <maxkatz6@outlook.com>
Co-authored-by: Julien Lebosquain <julien@lebosquain.net>

samples/MobileSandbox/MainView.xaml

@@ -8,7 +8,7 @@
     <TextBox TextInputOptions.Multiline="True" AcceptsReturn="True" Watermark="Text" Height="200" TextWrapping="Wrap"/>
     <TextBox Watermark="Username" TextInputOptions.ContentType="Email" TextInputOptions.ReturnKeyType="Done" />
     <TextBox Watermark="Password" PasswordChar="*" TextInputOptions.ContentType="Password" />
-    <TextBox Watermark="Pin" PasswordChar="*" TextInputOptions.ContentType="Digits" />
+    <TextBox Watermark="Pin" PasswordChar="*" TextInputOptions.ContentType="Digits" TextInputOptions.ReturnKeyType="Next" />
     <Button Content="Login" Command="{Binding ButtonCommand}" />
   </StackPanel>
 </UserControl>

src/Android/Avalonia.Android/Platform/SkiaPlatform/TopLevelImpl.cs

@@ -624,6 +624,12 @@ namespace Avalonia.Android.Platform.SkiaPlatform
                         _inputMethod.IMM.HideSoftInputFromWindow(_inputMethod.View.WindowToken, HideSoftInputFlags.ImplicitOnly);
                         break;
                     }
+                case ImeAction.Next:
+                    {
+                        FocusManager.GetFocusManager(_toplevel.InputRoot)?
+                            .TryMoveFocus(NavigationDirection.Next);
+                        break;
+                    }
             }
 
             return base.PerformEditorAction(actionCode);

src/Avalonia.Base/Input/FocusManager.cs

@@ -200,6 +200,17 @@ namespace Avalonia.Input
                    // In our unit tests some elements might not have a root. Remove when we migrate to headless tests.
                 ?? (FocusManager?)AvaloniaLocator.Current.GetService<IFocusManager>();
         }
+
+        internal bool TryMoveFocus(NavigationDirection direction)
+        {
+            if (GetFocusedElement() is {} focusedElement
+                && KeyboardNavigationHandler.GetNext(focusedElement, direction) is {} newElement)
+            {
+                return newElement.Focus();
+            }
+
+            return false;
+        }
         
         /// <summary>
         /// Checks if the specified element can be focused.

src/iOS/Avalonia.iOS/TextInputResponder.cs

@@ -182,6 +182,10 @@ partial class AvaloniaView
 
                 switch (ReturnKeyType)
                 {
+                    case UIReturnKeyType.Next:
+                        FocusManager.GetFocusManager(_view._topLevel)?
+                            .TryMoveFocus(NavigationDirection.Next);
+                        break;
                     case UIReturnKeyType.Done:
                     case UIReturnKeyType.Go:
                     case UIReturnKeyType.Send: