Don't focus non-focusable controls.

When navigating `ItemsControl` with keyboard.

src/Avalonia.Controls/ItemsControl.cs

@@ -330,31 +330,34 @@ namespace Avalonia.Controls
         /// <param name="e">The key events.</param>
         protected override void OnKeyDown(KeyEventArgs e)
         {
-            var focus = FocusManager.Instance;
-            var direction = e.Key.ToNavigationDirection();
-            var container = Presenter?.Panel as INavigableContainer;
-
-            if (container == null ||
-                focus.Current == null ||
-                direction == null ||
-                direction.Value.IsTab())
+            if (!e.Handled)
             {
-                return;
-            }
-
-            var current = focus.Current
-                .GetSelfAndVisualAncestors()
-                .OfType<IInputElement>()
-                .FirstOrDefault(x => x.VisualParent == container);
+                var focus = FocusManager.Instance;
+                var direction = e.Key.ToNavigationDirection();
+                var container = Presenter?.Panel as INavigableContainer;
+
+                if (container == null ||
+                    focus.Current == null ||
+                    direction == null ||
+                    direction.Value.IsTab())
+                {
+                    return;
+                }
 
-            if (current != null)
-            {
-                var next = container.GetControl(direction.Value, current);
+                var current = focus.Current
+                    .GetSelfAndVisualAncestors()
+                    .OfType<IInputElement>()
+                    .FirstOrDefault(x => x.VisualParent == container);
 
-                if (next != null)
+                if (current != null)
                 {
-                    focus.Focus(next, NavigationMethod.Directional);
-                    e.Handled = true;
+                    var next = GetNextControl(container, direction.Value, current);
+
+                    if (next != null)
+                    {
+                        focus.Focus(next, NavigationMethod.Directional);
+                        e.Handled = true;
+                    }
                 }
             }
 
@@ -498,5 +501,27 @@ namespace Avalonia.Controls
                 ItemCount = Items.Count();
             }
         }
+
+        protected static IInputElement GetNextControl(
+            INavigableContainer container,
+            NavigationDirection direction,
+            IInputElement from)
+        {
+            IInputElement result;
+
+            while (from != null)
+            {
+                result = container.GetControl(direction, from);
+
+                if (result?.Focusable == true)
+                {
+                    return result;
+                }
+
+                from = result;
+            }
+
+            return null;
+        }
     }
 }

tests/Avalonia.Controls.UnitTests/ItemsControlTests.cs

@@ -11,6 +11,7 @@ using Avalonia.VisualTree;
 using Xunit;
 using System.Collections.ObjectModel;
 using Avalonia.UnitTests;
+using Avalonia.Input;
 
 namespace Avalonia.Controls.UnitTests
 {
@@ -494,6 +495,77 @@ namespace Avalonia.Controls.UnitTests
             Assert.NotNull(NameScope.GetNameScope((TextBlock)container.Child));
         }
 
+        [Fact]
+        public void Focuses_Next_Item_On_Key_Down()
+        {
+            using (UnitTestApplication.Start(TestServices.RealFocus))
+            {
+                var items = new object[]
+                {
+                    new Button(),
+                    new Button(),
+                };
+
+                var target = new ItemsControl
+                {
+                    Template = GetTemplate(),
+                    Items = items,
+                };
+
+                var root = new TestRoot { Child = target };
+
+                target.ApplyTemplate();
+                target.Presenter.ApplyTemplate();
+                target.Presenter.Panel.Children[0].Focus();
+
+                target.RaiseEvent(new KeyEventArgs
+                {
+                    RoutedEvent = InputElement.KeyDownEvent,
+                    Key = Key.Down,
+                });
+
+                Assert.Equal(
+                    target.Presenter.Panel.Children[1],
+                    FocusManager.Instance.Current);
+            }
+        }
+
+        [Fact]
+        public void Does_Not_Focus_Non_Focusable_Item_On_Key_Down()
+        {
+            using (UnitTestApplication.Start(TestServices.RealFocus))
+            {
+                var items = new object[]
+                {
+                    new Button(),
+                    new Button { Focusable = false },
+                    new Button(),
+                };
+
+                var target = new ItemsControl
+                {
+                    Template = GetTemplate(),
+                    Items = items,
+                };
+
+                var root = new TestRoot { Child = target };
+
+                target.ApplyTemplate();
+                target.Presenter.ApplyTemplate();
+                target.Presenter.Panel.Children[0].Focus();
+
+                target.RaiseEvent(new KeyEventArgs
+                {
+                    RoutedEvent = InputElement.KeyDownEvent,
+                    Key = Key.Down,
+                });
+
+                Assert.Equal(
+                    target.Presenter.Panel.Children[2],
+                    FocusManager.Instance.Current);
+            }
+        }
+
         private class Item
         {
             public Item(string value)