From 6cd45c96518d2273607544889c3a6ac4dcaece21 Mon Sep 17 00:00:00 2001
From: Shane Neuville <shneuvil@microsoft.com>
Date: Tue, 4 Jun 2024 05:09:37 -0500
Subject: [PATCH] Reset opacity when view is being reused

---
 .../Tests/Issues/Issue19955.cs                | 25 +++++
 .../tests/TestCases/Issues/Issue19955.cs      | 91 +++++++++++++++++++
 .../Navigation/NavigationViewFragment.cs      |  4 +
 3 files changed, 120 insertions(+)
 create mode 100644 src/Controls/tests/TestCases.Shared.Tests/Tests/Issues/Issue19955.cs
 create mode 100644 src/Controls/tests/TestCases/Issues/Issue19955.cs

diff --git a/src/Controls/tests/TestCases.Shared.Tests/Tests/Issues/Issue19955.cs b/src/Controls/tests/TestCases.Shared.Tests/Tests/Issues/Issue19955.cs
new file mode 100644
index 000000000000..5b4e0aa3e2b4
--- /dev/null
+++ b/src/Controls/tests/TestCases.Shared.Tests/Tests/Issues/Issue19955.cs
@@ -0,0 +1,25 @@
+using System.Drawing;
+using NUnit.Framework;
+using UITest.Appium;
+using UITest.Core;
+using OpenQA.Selenium.Interactions;
+using NUnit.Framework.Legacy;
+
+namespace Microsoft.Maui.TestCases.Tests.Issues;
+public class Issue19955: _IssuesUITest
+{
+    public Issue19955(TestDevice device) : base(device) { }
+
+    public override string Issue => "Navigating Back to FlyoutPage Renders Blank Page";
+
+    [Test]
+	[Category(UITestCategories.FlyoutPage)]
+	public void NavigatingBackToFlyoutPageRendersBlankPage()
+    {
+		App.WaitForElement("NavigateToSecondPageButton");
+        App.Tap("NavigateToSecondPageButton");
+        App.WaitForElement("NavigateBackToFirstPageButton");
+        App.Tap("NavigateBackToFirstPageButton");
+		App.WaitForElement("NavigateToSecondPageButton");
+    }
+}
\ No newline at end of file
diff --git a/src/Controls/tests/TestCases/Issues/Issue19955.cs b/src/Controls/tests/TestCases/Issues/Issue19955.cs
new file mode 100644
index 000000000000..53cfc0dcff9e
--- /dev/null
+++ b/src/Controls/tests/TestCases/Issues/Issue19955.cs
@@ -0,0 +1,91 @@
+using System;
+using System.Diagnostics;
+using Microsoft.Maui.Controls;
+
+namespace Maui.Controls.Sample.Issues
+{
+	[Issue(IssueTracker.Github, 19955, "Navigating Back to FlyoutPage Renders Blank Page")]
+	public class Issue19955 : NavigationPage
+	{
+		public Issue19955() : base(new MainFlyout())
+		{
+
+		}
+
+		public partial class MainFlyout : FlyoutPage
+		{
+			public MainFlyout()
+			{
+				Flyout = new MainFlyoutMenu();
+				Detail = new MarkerNavigationPage();
+			}
+
+			class MarkerNavigationPage : NavigationPage
+			{
+				public MarkerNavigationPage() : base(new FirstPage())
+				{
+				}
+			}	
+			
+			class MarkerNavigationPage2 : NavigationPage
+			{
+				public MarkerNavigationPage2() : base(new FirstPage())
+				{
+				}
+			}
+		}
+
+		public partial class MainFlyoutMenu : ContentPage
+		{
+			public MainFlyoutMenu()
+			{
+				Title = "MainFlyoutMenu";
+				Content = new VerticalStackLayout(){
+					new Label()
+					{
+						Text = "I'm the Flyout Page"
+					}
+				};
+			}
+		}
+
+		public partial class FirstPage : ContentPage
+		{
+			public FirstPage()
+			{
+				Content = new VerticalStackLayout(){
+					new Button(){
+						Text = "Navigate to Second page",
+						Command = new Command(Button_Clicked),
+						AutomationId = "NavigateToSecondPageButton"
+					},
+				};
+			}
+
+			async void Button_Clicked()
+			{
+				await Application.Current.MainPage.Navigation.PushAsync(new SecondPage());
+			}
+		}
+
+		public partial class SecondPage : ContentPage
+		{
+			public SecondPage()
+			{
+				Content = new VerticalStackLayout()
+				{
+					new Button(){
+						Text = "Navigate back to first page",
+						Command = new Command(Button_Clicked),
+						AutomationId = "NavigateBackToFirstPageButton"
+					}	
+				};
+			}
+
+			async void Button_Clicked()
+			{
+				await Application.Current.MainPage.Navigation.PopAsync();
+			}
+		}
+	}
+}
\ No newline at end of file
diff --git a/src/Core/src/Platform/Android/Navigation/NavigationViewFragment.cs b/src/Core/src/Platform/Android/Navigation/NavigationViewFragment.cs
index 97a25c1e7954..0a47dbc7e1a5 100644
--- a/src/Core/src/Platform/Android/Navigation/NavigationViewFragment.cs
+++ b/src/Core/src/Platform/Android/Navigation/NavigationViewFragment.cs
@@ -58,6 +58,10 @@ public override AView OnCreateView(LayoutInflater inflater, ViewGroup? container
 					.CurrentPage
 					.ToPlatform(NavigationManager.MauiContext, RequireContext(), inflater, ChildFragmentManager);
 
+			// This shouldn't typically happen, but if a previous animation hasn't finished from a navigation that was interrupted
+			// the opacity of the view will be set to 0. This will reset it to 1.
+			NavigationManager.CurrentPage?.Handler?.UpdateValue(nameof(IView.Opacity));
+
 			_currentView.RemoveFromParent();
 
 			return _currentView;