Fix Bugzilla38723 (#3812)

fixes #2302

Xamarin.Forms.Controls.Issues/Xamarin.Forms.Controls.Issues.Shared/Bugzilla38723.cs

@@ -1,5 +1,4 @@
-using System;
-using Xamarin.Forms.CustomAttributes;
+using Xamarin.Forms.CustomAttributes;
 using Xamarin.Forms.Internals;
 
 #if UITEST
@@ -7,52 +6,60 @@ using Xamarin.UITest;
 using NUnit.Framework;
 #endif
 
-namespace Xamarin.Forms.Controls
+namespace Xamarin.Forms.Controls.Issues
 {
 	[Preserve(AllMembers = true)]
-	[Issue(IssueTracker.Bugzilla, 38723, "Update Content in Picker's SelectedIndexChanged event causes NullReferenceException", PlatformAffected.iOS)]
-	public class Bugzilla38723 : TestContentPage // or TestMasterDetailPage, etc ...
+	[Issue(IssueTracker.Bugzilla, 38723, "Update Content in Picker's SelectedIndexChanged event causes NullReferenceException", PlatformAffected.All)]
+	public class Bugzilla38723 : TestContentPage
 	{
-		Picker _datePicker;
-		Label _dateLabel;
-
 		protected override void Init()
 		{
-			_datePicker = new Picker
+			var label = new Label
 			{
-				//HorizontalOptions = LayoutOptions.FillAndExpand,
-				VerticalOptions = LayoutOptions.Center,
-				Title = "Pick a Date",
-			};
-			_datePicker.SelectedIndexChanged += DatePickerSelected;
-
-			for (var i = 0; i < 7; i++)
-			{
-				_datePicker.Items.Add(DateTime.Now.AddDays(i).ToString("dd, MMM, yyyy(dddd)"));
-			}
-
-			var stackLayout = new StackLayout
-			{
-				Padding = new Thickness(10, 10)
+				Text = "NoSelected"
 			};
 
-			_dateLabel = new Label
+			var picker = new Picker
 			{
-				HorizontalOptions = LayoutOptions.StartAndExpand,
-				VerticalOptions = LayoutOptions.Center,
-				Text = "Placeholder"
+				Title = "Options",
+				ItemsSource = new[] { "option1", "option2", "option3" }
 			};
 
-			stackLayout.Children.Add(_datePicker);
-			stackLayout.Children.Add(_dateLabel);
-			// Update current page's UI would cause NullReferenceException
-			Content = stackLayout;
+			picker.SelectedIndexChanged += (sender, args) =>
+			{
+				label.Text = "Selected";
+				Content = label;
+			};
+
+			var button = new Button
+			{
+				Text = "SELECT"
+			};
+
+			button.Clicked += (sender, args) =>
+			{
+				picker.SelectedIndex = 0;
+			};
+
+			Content = new StackLayout
+			{
+				Children =
+				{
+					label,
+					picker,
+					button
+				}
+			};
 		}
 
-		void DatePickerSelected(object sender, EventArgs args)
+#if UITEST
+		[Test]
+		public void Bugzilla38723Test()
 		{
-			_dateLabel.Text = args.ToString();
-			Content = _dateLabel;
+			RunningApp.Tap(q => q.Marked("SELECT"));
+			RunningApp.WaitForElement(q => q.Marked("Selected"));
+			RunningApp.WaitForNoElement(q => q.Marked("SELECT"));
 		}
+#endif
 	}
 }