[WinRT/UWP] Open Picker dropdown when calling Focus (#762)

1 files changed, 19 insertions, 0 deletions

diff --git a/Xamarin.Forms.Platform.WinRT/PickerRenderer.cs b/Xamarin.Forms.Platform.WinRT/PickerRenderer.cs
index a7aa16f0..d4ee918e 100644
--- a/Xamarin.Forms.Platform.WinRT/PickerRenderer.cs
+++ b/Xamarin.Forms.Platform.WinRT/PickerRenderer.cs
@@ -19,6 +19,7 @@ namespace Xamarin.Forms.Platform.WinRT
 	{
 		bool _isAnimating;
 		Brush _defaultBrush;
+		bool _dropDownWasOpened;
 
 		protected override void Dispose(bool disposing)
 		{
@@ -32,6 +33,7 @@ namespace Xamarin.Forms.Platform.WinRT
 					Control.DropDownClosed -= OnDropDownOpenStateChanged;
 					Control.OpenAnimationCompleted -= ControlOnOpenAnimationCompleted;
 					Control.Loaded -= ControlOnLoaded;
+					Control.GotFocus -= ControlOnGotFocus;
 				}
 			}
 
@@ -51,6 +53,7 @@ namespace Xamarin.Forms.Platform.WinRT
 					Control.OpenAnimationCompleted += ControlOnOpenAnimationCompleted;
 					Control.ClosedAnimationStarted += ControlOnClosedAnimationStarted;
 					Control.Loaded += ControlOnLoaded;
+					Control.GotFocus += ControlOnGotFocus;
 				}
 
 				Control.ItemsSource = ((LockableObservableListWrapper)Element.Items)._list;
@@ -102,6 +105,19 @@ namespace Xamarin.Forms.Platform.WinRT
 			}
 		}
 
+		void ControlOnGotFocus(object sender, RoutedEventArgs routedEventArgs)
+		{
+			// The FormsComboBox is separate from the Popup/dropdown that it uses to select an item,
+			// and the behavior here is changed to be similar to the other platforms where focusing the
+			// Picker opens the dropdown (with the exception where if focus was given via keyboard, such
+			// as tabbing through controls). The _dropDownWasOpened flag is reset to false in the case that
+			// the FormsComboBox regained focus after the dropdown closed.
+			if (!_dropDownWasOpened && Control.FocusState != FocusState.Keyboard)
+				Control.IsDropDownOpen = true;
+			else
+				_dropDownWasOpened = false;
+		}
+
 		void OnControlSelectionChanged(object sender, SelectionChangedEventArgs e)
 		{
 			if (Element != null)
@@ -129,6 +145,9 @@ namespace Xamarin.Forms.Platform.WinRT
 				_isAnimating = false;
 				// and force the final redraw
 				((IVisualElementController)Element)?.InvalidateMeasure(InvalidationTrigger.MeasureChanged);
+
+				// Related to ControlOnGotFocus, _dropDownWasOpened is set to true
+				_dropDownWasOpened = true;
 			}
 		}