[Android] Fix bug. Children pages in NavigationPage were got appearing events even if they were not latest in navigation stack

Xamarin.Forms.Controls.Issues/Xamarin.Forms.Controls.Issues.Shared/Bugzilla52458.cs

@@ -0,0 +1,185 @@
+using System;
+using System.Linq;
+using Xamarin.Forms.CustomAttributes;
+using Xamarin.Forms.Internals;
+#if UITEST
+using NUnit.Framework;
+#endif
+
+
+namespace Xamarin.Forms.Controls.Issues
+{
+	[Preserve(AllMembers = true)]
+	[Issue(IssueTracker.Bugzilla, 52458, "Children pages in NavigationPage were got `appearing events` even if they were not latest in navigation stack", NavigationBehavior.PushModalAsync)]
+	public class Bugzilla52458 : TestPage
+	{
+		NavigationPage _navPage;
+		ContentPage _page2, _page3;
+		Label _checkIsAppearingLabel;
+
+		IPageController PageController => this;
+
+		protected override void Init()
+		{
+			NavigationPage navPage;
+			ContentPage appearingPage, page2, page3;
+
+			var appearingLabel = new Label
+			{
+				AutomationId = "checkIsAppearingLabel",
+				Text = false.ToString()
+			};
+
+			appearingPage = new ContentPage
+			{
+				Content = new StackLayout
+				{
+					Children =
+					{
+						new Button
+						{
+							BackgroundColor = Color.Red,
+							Text = "NavigateToPage2",
+							Command = new Command(NavigateToPage2)
+						}
+					}
+				}
+			};
+			page2 = new ContentPage
+			{
+				Content = new StackLayout
+				{
+					Children =
+					{
+						new StackLayout()
+						{
+							Orientation = StackOrientation.Horizontal,
+							Children =
+							{
+								new Label
+								{
+									Text = "First page is appeared: "
+								},
+								appearingLabel
+							}
+						},
+						new Button
+						{
+							Text = "SetPage3",
+							Command = new Command(SetPage3)
+						}
+					}
+				}
+			};
+			page3 = new ContentPage
+			{
+				Content = new StackLayout
+				{
+					Children =
+					{
+						new Button
+						{
+							Text = "RevertToNavigationPage",
+							Command = new Command(SetNavigationPage)
+						}
+					}
+				}
+			};
+
+			appearingPage.Appearing += OnAppearingFirstPage;
+			appearingPage.Disappearing += OnDisappearingFirstPage;
+
+			navPage = new NavigationPage(appearingPage);
+
+			_navPage = navPage;
+			_checkIsAppearingLabel = appearingLabel;
+			_page2 = page2;
+			_page3 = page3;
+
+			SetPage(navPage);
+		}
+
+		void OnAppearingFirstPage(object sender, EventArgs e)
+		{
+			Device.StartTimer(TimeSpan.FromMilliseconds(50), () =>
+			{
+				var currentPage = _navPage.CurrentPage;
+
+				_checkIsAppearingLabel.Text = true.ToString();
+
+				if (currentPage != sender)
+				{
+					//throw new Exception("Page cannot get appearing event if it is not last in NavigationStack");
+				}
+
+				return false;
+			});
+		}
+
+		void OnDisappearingFirstPage(object sender, EventArgs e)
+		{
+			_checkIsAppearingLabel.Text = false.ToString();
+		}
+
+		void SetNavigationPage()
+		{
+			SetPage(_navPage);
+		}
+
+		void NavigateToPage2()
+		{
+			if (_navPage.CurrentPage != _page2)
+				_navPage.PushAsync(_page2);
+		}
+
+		void SetPage3()
+		{
+			SetPage(_page3);
+		}
+
+		void SetPage(Page page)
+		{
+			if (PageController.InternalChildren.Count > 0)
+				PageController.InternalChildren.Remove(PageController.InternalChildren.First());
+			PageController.InternalChildren.Add(page);
+		}
+
+		protected override bool OnBackButtonPressed()
+		{
+			var currentPage = (Page)PageController.InternalChildren.FirstOrDefault();
+			var currentPageResult = currentPage?.SendBackButtonPressed();
+
+			if (currentPageResult != null && currentPageResult.Value)
+			{
+				return true;
+			}
+
+			return base.OnBackButtonPressed();
+		}
+
+#if UITEST
+
+		[Test]
+		public void NavigationAppearingTest()
+		{
+			var app = RunningApp;
+			app.WaitForElement(x => x.Text("NavigateToPage2"));
+			app.Tap(x => x.Text("NavigateToPage2"));
+			app.WaitForElement(x => x.Text("SetPage3"));
+			app.Tap(x => x.Text("SetPage3"));
+			app.WaitForElement(x => x.Text("RevertToNavigationPage"));
+			app.Tap(x => x.Text("RevertToNavigationPage"));
+			app.WaitForElement(x => x.Marked("checkIsAppearingLabel"));
+
+			var checkIsAppearingLabel = app.Query(x => x.Marked("checkIsAppearingLabel")).First();
+
+			Assert.IsFalse(string.Equals(checkIsAppearingLabel.Text, true.ToString()), "Page cannot get appearing event if it is not last in NavigationStack");
+
+			app.Back();
+		}
+
+#endif
+
+
+	}
+}

Xamarin.Forms.Controls.Issues/Xamarin.Forms.Controls.Issues.Shared/Xamarin.Forms.Controls.Issues.Shared.projitems

@@ -251,6 +251,7 @@
     <Compile Include="$(MSBuildThisFileDirectory)Bugzilla39829.cs" />
     <Compile Include="$(MSBuildThisFileDirectory)Bugzilla39458.cs" />
     <Compile Include="$(MSBuildThisFileDirectory)Bugzilla39853.cs" />
+    <Compile Include="$(MSBuildThisFileDirectory)Bugzilla52458.cs" />
     <Compile Include="$(MSBuildThisFileDirectory)PlatformSpecifics_iOSTranslucentNavBarX.xaml.cs">
       <DependentUpon>PlatformSpecifics_iOSTranslucentNavBarX.xaml</DependentUpon>
       <SubType>Code</SubType>

Xamarin.Forms.Platform.Android/AppCompat/NavigationPageRenderer.cs

@@ -267,11 +267,7 @@ protected override void OnElementChanged(ElementChangedEventArgs<NavigationPage>
 				navController.InsertPageBeforeRequested += OnInsertPageBeforeRequested;
 				navController.RemovePageRequested += OnRemovePageRequested;
 
-				// If there is already stuff on the stack we need to push it
-				foreach (Page page in navController.Pages)
-				{
-					PushViewAsync(page, false);
-				}
+				InsertPages(navController.Pages);
 			}
 		}
 
@@ -589,6 +585,46 @@ void SetupToolbar()
 			_toolbar = bar;
 		}
 
+		void InsertPages(IEnumerable<Page> pages)
+		{
+			_fragmentStack.Clear();
+
+			if (pages == null)
+				return;
+
+			var pagesCount = pages.Count();
+
+			for (int i = 0; i < pagesCount; i++)
+			{
+				var page = pages.ElementAt(i);
+				Fragment fragment = GetFragment(page, false, false);
+				_fragmentStack.Add(fragment);
+
+				if (i == pagesCount - 1)
+				{
+					((Platform)Element.Platform).NavAnimationInProgress = true;
+					FragmentTransaction transaction = FragmentManager.BeginTransaction();
+
+					Current = page;
+
+					transaction.DisallowAddToBackStack();
+					transaction.Add(Id, fragment);
+					transaction.Show(fragment);
+					transaction.CommitAllowingStateLoss();
+
+					Device.StartTimer(TimeSpan.FromMilliseconds(1), () =>
+					{
+						fragment.UserVisibleHint = true;
+						UpdateToolbar();
+						return false;
+					});
+
+					Context.HideKeyboard(this);
+					((Platform)Element.Platform).NavAnimationInProgress = false;
+				}
+			}
+		}
+
 		Task<bool> SwitchContentAsync(Page page, bool animated, bool removed = false, bool popToRoot = false)
 		{
 			var tcs = new TaskCompletionSource<bool>();