[Android App Compat] Can opt out of sending Appearing/Disappearing events on Resume/Pause (#450)

* Add reproduction for 40722

* [Core] Add Android AppCompat PS props ...

... to disable sending Disappearing/Appearing events on Pause/Resume
respectively.

* [Android] Allow user to disable Pause/Resume evts

* Revise repro to use new PS option

* Update docs

2 files changed, 69 insertions, 0 deletions

diff --git a/Xamarin.Forms.Controls.Issues/Xamarin.Forms.Controls.Issues.Shared/Bugzilla40722.cs b/Xamarin.Forms.Controls.Issues/Xamarin.Forms.Controls.Issues.Shared/Bugzilla40722.cs
new file mode 100644
index 00000000..1ce0482f
--- /dev/null
+++ b/Xamarin.Forms.Controls.Issues/Xamarin.Forms.Controls.Issues.Shared/Bugzilla40722.cs
@@ -0,0 +1,68 @@
+using Xamarin.Forms.CustomAttributes;
+using Xamarin.Forms.Internals;
+using Xamarin.Forms.PlatformConfiguration;
+using Xamarin.Forms.PlatformConfiguration.AndroidSpecific.AppCompat;
+
+namespace Xamarin.Forms.Controls
+{
+	[Preserve(AllMembers = true)]
+	[Issue(IssueTracker.Bugzilla, 40722, "Using FormsAppCompatActivity calls OnDisappearing on device sleep")]
+	public class Bugzilla40722 : TestContentPage
+	{
+		const string ButtonText_Disable = "Disable Pause/Resume events";
+		const string ButtonText_Enable = "Enable Pause/Resume events";
+		const string Instructions_Disabled = "Sleep the device, then wake it. If \"Disappearing!\" and/or \"Appearing!\" is displayed on this screen, this test has failed.";
+		const string Instructions_Enabled = "Sleep the device, then wake it. If \"Disappearing!\" and/or \"Appearing!\" is NOT displayed on this screen, this test has failed.";
+
+		Label _Target = new Label();
+		bool _sendEvents = true;
+
+		protected override void Init()
+		{
+			ToggleEvents(_sendEvents);
+
+			var instructions = new Label
+			{
+				Text = Instructions_Enabled
+			};
+
+			var button = new Button
+			{
+				Text = ButtonText_Disable
+			};
+
+			button.Clicked += (sender, e) =>
+			{
+				_sendEvents = !_sendEvents;
+				ToggleEvents(_sendEvents);
+				button.Text = _sendEvents ? ButtonText_Disable : ButtonText_Enable;
+				instructions.Text = _sendEvents ? Instructions_Enabled : Instructions_Disabled;
+				_Target.Text = "";
+			};
+
+			Content = new StackLayout { Children = { instructions, button, _Target } };
+		}
+
+
+		protected override void OnAppearing()
+		{
+			base.OnAppearing();
+
+			_Target.Text += "\r\nAppearing!";
+		}
+
+		protected override void OnDisappearing()
+		{
+			base.OnDisappearing();
+
+			_Target.Text += "\r\nDisappearing!";
+		}
+
+		void ToggleEvents(bool value)
+		{
+			Application.Current.On<Android>()
+							.SendDisappearingEventOnPause(value)
+							.SendAppearingEventOnResume(value);
+		}
+	}
+}
\ No newline at end of file
diff --git a/Xamarin.Forms.Controls.Issues/Xamarin.Forms.Controls.Issues.Shared/Xamarin.Forms.Controls.Issues.Shared.projitems b/Xamarin.Forms.Controls.Issues/Xamarin.Forms.Controls.Issues.Shared/Xamarin.Forms.Controls.Issues.Shared.projitems
index 5e9e9034..224ef47a 100644
--- a/Xamarin.Forms.Controls.Issues/Xamarin.Forms.Controls.Issues.Shared/Xamarin.Forms.Controls.Issues.Shared.projitems
+++ b/Xamarin.Forms.Controls.Issues/Xamarin.Forms.Controls.Issues.Shared/Xamarin.Forms.Controls.Issues.Shared.projitems
@@ -189,6 +189,7 @@
     <Compile Include="$(MSBuildThisFileDirectory)Bugzilla43161.cs" />
     <Compile Include="$(MSBuildThisFileDirectory)Bugzilla39768.cs" />
     <Compile Include="$(MSBuildThisFileDirectory)Bugzilla41271.cs" />
+    <Compile Include="$(MSBuildThisFileDirectory)Bugzilla40722.cs" />
     <Compile Include="$(MSBuildThisFileDirectory)Bugzilla41153.cs" />
     <Compile Include="$(MSBuildThisFileDirectory)Bugzilla44129.cs" />
     <Compile Include="$(MSBuildThisFileDirectory)_Template.cs" />