Picker Handlers (#433)

* PickerHandlers

* Nullability fixes

* Updated Picker device tests

* New things in the tests!

* Removed unnecessary Android Api level validation

* Added Picker Items null validation in iOS PickerHandler

* Moved Picker Handler tests between different classes

* Renamed NativePicker to MauiPicker

* Removed unused code from iOS PickerExtensions

* Fix build error

* Fix build error

* Remove duplicate class

Co-authored-by: Matthew Leibowitz <mattleibow@live.com>
Co-authored-by: E.Z. Hart <hartez@gmail.com>

src/Compatibility/Core/src/Android/AppCompat/PickerRenderer.cs

@@ -109,6 +109,7 @@ protected override void OnFocusChangeRequested(object sender, VisualElement.Focu
 			}
 		}
 
+		[PortHandler("Partially ported, still missing code related to TitleColor, etc.")]
 		void IPickerRenderer.OnClick()
 		{
 			Picker model = Element;
@@ -168,6 +169,7 @@ protected void UpdateCharacterSpacing()
 			}
 		}
 
+		[PortHandler("Partially ported, still missing code related to TitleColor, etc.")]
 		void UpdatePicker()
 		{
 			UpdatePlaceHolderText();

src/Compatibility/Core/src/iOS/Renderers/PickerRenderer.cs

@@ -11,6 +11,7 @@
 
 namespace Microsoft.Maui.Controls.Compatibility.Platform.iOS
 {
+	[PortHandler]
 	internal class ReadOnlyField : NoCaretField
 	{
 		readonly HashSet<string> enableActions;
@@ -32,6 +33,7 @@ public PickerRenderer()
 
 		}
 
+		[PortHandler]
 		protected override UITextField CreateNativeControl()
 		{
 			return new ReadOnlyField { BorderStyle = UITextBorderStyle.RoundedRect };
@@ -56,6 +58,8 @@ public PickerRendererBase()
 		}
 
 		protected abstract override TControl CreateNativeControl();
+
+		[PortHandler("Partially ported, still missing code related to TitleColor, etc.")]
 		protected override void OnElementChanged(ElementChangedEventArgs<Picker> e)
 		{
 			if (e.OldElement != null)
@@ -231,6 +235,7 @@ protected internal virtual void UpdatePlaceholder()
 		protected virtual void UpdateAttributedPlaceholder(NSAttributedString nsAttributedString) => 
 			Control.AttributedPlaceholder = nsAttributedString;
 
+		[PortHandler]
 		void UpdatePicker()
 		{
 			var selectedIndex = Element.SelectedIndex;
@@ -266,6 +271,7 @@ void UpdatePickerNativeSize(string oldText)
 				((IVisualElementController)Element).NativeSizeChanged();
 		}
 
+		[PortHandler]
 		void UpdatePickerSelectedIndex(int formsIndex)
 		{
 			var source = (PickerSource)_picker.Model;
@@ -334,6 +340,7 @@ protected override void Dispose(bool disposing)
 			base.Dispose(disposing);
 		}
 
+		[PortHandler]
 		class PickerSource : UIPickerViewModel
 		{
 			PickerRendererBase<TControl> _renderer;

src/Controls/samples/Controls.Sample/Pages/MainPage.cs

@@ -1,3 +1,5 @@
+using System;
+using System.Collections.Generic;
 using Maui.Controls.Sample.ViewModel;
 using Microsoft.Extensions.DependencyInjection;
 using Microsoft.Maui;
@@ -113,6 +115,23 @@ void SetupMauiLayout()
 			placeholderSearchBar.Placeholder = "Placeholder";
 			verticalStack.Add(placeholderSearchBar);
 
+
+			var monkeyList = new List<string>
+			{
+				"Baboon",
+				"Capuchin Monkey",
+				"Blue Monkey",
+				"Squirrel Monkey",
+				"Golden Lion Tamarin",
+				"Howler Monkey",
+				"Japanese Macaque"
+			};
+
+			var picker = new Picker { Title = "Select a monkey" };
+
+			picker.ItemsSource = monkeyList;
+			verticalStack.Add(picker);
+
 			verticalStack.Add(new Slider());
 
 			verticalStack.Add(new Stepper());

src/Controls/src/Core/HandlerImpl/Picker.Impl.cs

@@ -0,0 +1,7 @@
+namespace Microsoft.Maui.Controls
+{
+	public partial class Picker : IPicker
+	{
+
+	}
+}

src/Controls/src/Core/Picker.cs

@@ -9,7 +9,7 @@
 
 namespace Microsoft.Maui.Controls
 {
-	public class Picker : View, IFontElement, ITextElement, ITextAlignmentElement, IElementConfiguration<Picker>
+	public partial class Picker : View, IFontElement, ITextElement, ITextAlignmentElement, IElementConfiguration<Picker>
 	{
 		public static readonly BindableProperty TextColorProperty = TextElement.TextColorProperty;
 

src/Core/src/Core/IPicker.cs

@@ -0,0 +1,14 @@
+using System.Collections;
+using System.Collections.Generic;
+
+namespace Microsoft.Maui
+{
+	public interface IPicker : IView
+	{
+		string Title { get; }
+		IList<string> Items { get; }
+		IList ItemsSource { get; }
+		int SelectedIndex { get; set; }
+		object? SelectedItem { get; set; }
+	}
+}

src/Core/src/Handlers/Picker/PickerHandler.Android.cs

@@ -0,0 +1,112 @@
+using System;
+using System.Collections.Specialized;
+using System.Linq;
+using Android.App;
+using AResource = Android.Resource;
+
+namespace Microsoft.Maui.Handlers
+{
+	public partial class PickerHandler : AbstractViewHandler<IPicker, MauiPicker>
+	{
+		AlertDialog? _dialog;
+
+		protected override MauiPicker CreateNativeView() =>
+			new MauiPicker(Context);
+
+		protected override void ConnectHandler(MauiPicker nativeView)
+		{
+			nativeView.FocusChange += OnFocusChange;
+			nativeView.Click += OnClick;
+
+			if (VirtualView != null && VirtualView.Items is INotifyCollectionChanged notifyCollection)
+				notifyCollection.CollectionChanged += OnCollectionChanged;
+
+			base.ConnectHandler(nativeView);
+		}
+
+		protected override void DisconnectHandler(MauiPicker nativeView)
+		{
+			nativeView.FocusChange -= OnFocusChange;
+			nativeView.Click -= OnClick;
+
+			if (VirtualView != null && VirtualView.Items is INotifyCollectionChanged notifyCollection)
+				notifyCollection.CollectionChanged -= OnCollectionChanged;
+
+			base.DisconnectHandler(nativeView);
+		}
+		public static void MapTitle(PickerHandler handler, IPicker picker)
+		{
+			handler.TypedNativeView?.UpdateTitle(picker);
+		}
+
+		public static void MapSelectedIndex(PickerHandler handler, IPicker picker)
+		{
+			handler.TypedNativeView?.UpdateSelectedIndex(picker);
+		}
+
+		void OnFocusChange(object? sender, global::Android.Views.View.FocusChangeEventArgs e)
+		{
+			if (TypedNativeView == null)
+				return;
+
+			if (e.HasFocus)
+			{
+				if (TypedNativeView.Clickable)
+					TypedNativeView.CallOnClick();
+				else
+					OnClick(TypedNativeView, EventArgs.Empty);
+			}
+			else if (_dialog != null)
+			{
+				_dialog.Hide();
+				TypedNativeView.ClearFocus();
+				_dialog = null;
+			}
+		}
+
+		void OnClick(object? sender, EventArgs e)
+		{
+			if (_dialog == null && VirtualView != null)
+			{
+				using (var builder = new AlertDialog.Builder(Context))
+				{
+					builder.SetTitle(VirtualView.Title ?? string.Empty);
+
+					string[] items = VirtualView.Items.ToArray();
+
+					builder.SetItems(items, (s, e) =>
+					{
+						var selectedIndex = e.Which;
+						VirtualView.SelectedIndex = selectedIndex;
+						TypedNativeView?.UpdatePicker(VirtualView);
+					});
+
+					builder.SetNegativeButton(AResource.String.Cancel, (o, args) => { });
+
+					_dialog = builder.Create();
+				}
+
+				if (_dialog == null)
+					return;
+
+				_dialog.SetCanceledOnTouchOutside(true);
+
+				_dialog.DismissEvent += (sender, args) =>
+				{
+					_dialog.Dispose();
+					_dialog = null;
+				};
+
+				_dialog.Show();
+			}
+		}
+
+		void OnCollectionChanged(object? sender, EventArgs e)
+		{
+			if (VirtualView == null || TypedNativeView == null)
+				return;
+
+			TypedNativeView.UpdatePicker(VirtualView);
+		}
+	}
+}

src/Core/src/Handlers/Picker/PickerHandler.Standard.cs

@@ -0,0 +1,12 @@
+using System;
+
+namespace Microsoft.Maui.Handlers
+{
+	public partial class PickerHandler : AbstractViewHandler<IPicker, object>
+	{
+		protected override object CreateNativeView() => throw new NotImplementedException();
+
+		public static void MapTitle(PickerHandler handler, IPicker view) { }
+		public static void MapSelectedIndex(PickerHandler handler, IPicker view) { }
+	}
+}

src/Core/src/Handlers/Picker/PickerHandler.cs

@@ -0,0 +1,21 @@
+namespace Microsoft.Maui.Handlers
+{
+	public partial class PickerHandler
+	{
+		public static PropertyMapper<IPicker, PickerHandler> PickerMapper = new PropertyMapper<IPicker, PickerHandler>(ViewHandler.ViewMapper)
+		{
+			[nameof(IPicker.Title)] = MapTitle,
+			[nameof(IPicker.SelectedIndex)] = MapSelectedIndex
+		};
+
+		public PickerHandler() : base(PickerMapper)
+		{
+
+		}
+
+		public PickerHandler(PropertyMapper mapper) : base(mapper)
+		{
+
+		}
+	}
+}