[A] Check Visibility for tab's page appearing (#963)

Xamarin.Forms.Controls.Issues/Xamarin.Forms.Controls.Issues.Shared/Bugzilla52419.cs

@@ -0,0 +1,112 @@
+using Xamarin.Forms.CustomAttributes;
+using Xamarin.Forms.Internals;
+using System;
+
+#if UITEST
+using Xamarin.UITest;
+using NUnit.Framework;
+#endif
+
+namespace Xamarin.Forms.Controls.Issues
+{
+	[Preserve(AllMembers = true)]
+	[Issue(IssueTracker.Bugzilla, 52419, "[A] OnAppearing called for previous pages in a tab's navigation when switching active tabs", PlatformAffected.Android)]
+	public class Bugzilla52419 : TestTabbedPage
+	{
+		protected override void Init()
+		{
+			var nav1 = new NavigationPage { Title = "Tab Page 1" };
+			nav1.PushAsync(new Bugzilla52419Page1());
+			var nav2 = new NavigationPage { Title = "Tab Page 2" };
+			nav2.PushAsync(new Bugzilla52419Page2());
+			Children.Add(nav1);
+			Children.Add(nav2);
+		}
+
+#if UITEST
+
+#if __ANDROID__
+		[Test]
+		public void Bugzilla52419Test()
+		{
+			RunningApp.WaitForElement(q => q.Marked("Push new page"));
+			RunningApp.Tap(q => q.Marked("Push new page"));
+			RunningApp.WaitForElement(q => q.Marked("Push new page"));
+			RunningApp.Tap(q => q.Marked("Push new page"));
+			RunningApp.WaitForElement(q => q.Marked("Push new page"));
+			RunningApp.Tap(q => q.Marked("Push new page"));
+			RunningApp.Tap(q => q.Marked("Tab Page 2"));
+			RunningApp.Tap(q => q.Marked("Tab Page 1"));
+			RunningApp.Tap(q => q.Marked("Tab Page 2"));
+			RunningApp.Tap(q => q.Marked("Tab Page 1"));
+			RunningApp.Back();
+			RunningApp.WaitForElement(q => q.Marked("AppearanceLabel"));
+			var label = RunningApp.Query(q => q.Marked("AppearanceLabel"))[0];
+			Assert.AreEqual("Times Appeared: 2", label.Text);
+		}
+#endif
+
+#endif
+	}
+
+	class Bugzilla52419Page1 : ContentPage
+	{
+		public Label _timesAppeared { get; set; }
+		int _count;
+
+		string _guid = Guid.NewGuid().ToString();
+		public Bugzilla52419Page1()
+		{
+			_timesAppeared = new Label
+			{
+				Text = "Times Appeared: " + _count.ToString(),
+				AutomationId = "AppearanceLabel"
+			};
+			Content = new StackLayout
+			{
+				Children =
+					{
+						new Label
+						{
+							Text = "Page Guid: " + _guid
+						},
+						_timesAppeared,
+						new Label
+						{
+							Text = "Click the button a couple times, switch to the second tab, and then back to the first. The Appearing event (which increase the counter) should only occur for the visible first tab."
+						},
+						new Button
+						{
+							Text = "Push new page",
+							Command = new Command(() => Navigation.PushAsync(new Bugzilla52419Page1()))
+						}
+					}
+			};
+			Appearing += OnAppearing;
+		}
+
+		void OnAppearing(object sender, EventArgs e)
+		{
+			_count++;
+			_timesAppeared.Text = "Times Appeared: " + _count.ToString();
+		}
+	}
+
+	class Bugzilla52419Page2 : ContentPage
+	{
+		public Bugzilla52419Page2()
+		{
+			Title = "Tab Page 2";
+			Content = new StackLayout
+			{
+				Children =
+				{
+					new Label
+					{
+						Text = "Other content"
+					}
+				}
+			};
+		}
+	}
+}

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

@@ -165,6 +165,7 @@
     <Compile Include="$(MSBuildThisFileDirectory)Bugzilla45215.cs" />
     <Compile Include="$(MSBuildThisFileDirectory)Bugzilla44500.cs" />
     <Compile Include="$(MSBuildThisFileDirectory)Bugzilla47548.cs" />
+    <Compile Include="$(MSBuildThisFileDirectory)Bugzilla52419.cs" />
     <Compile Include="$(MSBuildThisFileDirectory)Bugzilla53834.cs" />
     <Compile Include="$(MSBuildThisFileDirectory)Bugzilla51536.cs" />
     <Compile Include="$(MSBuildThisFileDirectory)Bugzilla44940.cs" />

Xamarin.Forms.Platform.Android/Renderers/PageRenderer.cs

@@ -26,7 +26,7 @@ namespace Xamarin.Forms.Platform.Android
 		{
 			base.OnAttachedToWindow();
 			var pageContainer = Parent as PageContainer;
-			if (pageContainer != null && pageContainer.IsInFragment)
+			if (pageContainer != null && (pageContainer.IsInFragment || pageContainer.Visibility == ViewStates.Gone))
 				return;
 			PageController.SendAppearing();
 		}