iOS13 Fix Modal lifecycle

Xamarin.Forms.Controls.Issues/Xamarin.Forms.Controls.Issues.Shared/Issue7878.cs

@@ -0,0 +1,86 @@
+using System;
+using Xamarin.Forms.CustomAttributes;
+using Xamarin.Forms.Internals;
+using Xamarin.Forms.PlatformConfiguration;
+using Xamarin.Forms.PlatformConfiguration.iOSSpecific;
+
+namespace Xamarin.Forms.Controls.Issues
+{
+	[Preserve(AllMembers = true)]
+	[Issue(IssueTracker.Github, 7878, "Page not popped on iOS 13 FormSheet swipe down", PlatformAffected.iOS)]
+	public class Issue7878 : TestContentPage
+	{
+		protected override void Init()
+		{
+			var label = new Label
+			{
+				Text = "Both modals should behave the same. With the FormSheet when swiping down the modal should be dismissed properly. And for both modals the Appearing event on this page should be called. If so, this tests succeeded."
+			};
+
+			var modalButtonFormSheet = new Button
+			{
+				Text = "Show Modal FormSheet"
+			};
+
+			modalButtonFormSheet.Clicked += Button_Clicked_FormSheet;
+
+			var modalButton = new Button
+			{
+				Text = "Show Modal Full Screen"
+			};
+
+			modalButton.Clicked += Button_Clicked;
+
+			var stackLayout = new StackLayout
+			{
+				HorizontalOptions = LayoutOptions.Center,
+				VerticalOptions = LayoutOptions.Center,
+				Children = {
+					modalButton, modalButtonFormSheet
+				}
+			};
+
+			Content = stackLayout;
+		}
+
+		protected override void OnAppearing()
+		{
+			base.OnAppearing();
+
+			DisplayAlert("I have appeared!", "👋", "OK");
+		}
+
+		void Button_Clicked(object sender, EventArgs e)
+		{
+			Navigation.PushModalAsync(new ModalPage(false));
+		}
+
+		void Button_Clicked_FormSheet(object sender, EventArgs e)
+		{
+			Navigation.PushModalAsync(new ModalPage(true));
+		}
+
+		class ModalPage : ContentPage
+		{
+			public ModalPage(bool isFormSheet)
+			{
+				if (isFormSheet)
+					On<iOS>().SetModalPresentationStyle(UIModalPresentationStyle.FormSheet);
+
+				var button = new Button
+				{
+					Text = "Pressing this raises the popped event, swiping down as well!",
+					HorizontalOptions = LayoutOptions.Center,
+					VerticalOptions = LayoutOptions.Center
+				};
+
+				button.Clicked += (o, a) =>
+				{
+					Navigation.PopModalAsync();
+				};
+
+				Content = button;
+			}
+		}
+	}
+}

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

@@ -1233,6 +1233,7 @@
     <Compile Include="$(MSBuildThisFileDirectory)Issue7283.cs" />
     <Compile Include="$(MSBuildThisFileDirectory)Issue1658.cs" />
     <Compile Include="$(MSBuildThisFileDirectory)Issue5395.cs" />
+    <Compile Include="$(MSBuildThisFileDirectory)Issue7878.cs" />
     <Compile Include="$(MSBuildThisFileDirectory)Issue6663.cs" />
     <Compile Include="$(MSBuildThisFileDirectory)Issue8004.cs" />
     <Compile Include="$(MSBuildThisFileDirectory)Issue7886.xaml.cs">
@@ -1726,33 +1727,35 @@
     </EmbeddedResource>
   </ItemGroup>
   <ItemGroup>
-    <EmbeddedResource Include="$(MSBuildThisFileDirectory)Issue7593.xaml">
+    <EmbeddedResource Include="$(MSBuildThisFileDirectory)Issue7789.xaml">
       <SubType>Designer</SubType>
       <Generator>MSBuild:UpdateDesignTimeXaml</Generator>
     </EmbeddedResource>
   </ItemGroup>
   <ItemGroup>
-    <EmbeddedResource Include="$(MSBuildThisFileDirectory)Issue7792.xaml">
+    <EmbeddedResource Include="$(MSBuildThisFileDirectory)Issue7865.xaml">
       <SubType>Designer</SubType>
       <Generator>MSBuild:UpdateDesignTimeXaml</Generator>
     </EmbeddedResource>
-    <EmbeddedResource Include="$(MSBuildThisFileDirectory)Issue7758.xaml">
+  </ItemGroup>
+  <ItemGroup>
+    <EmbeddedResource Include="$(MSBuildThisFileDirectory)Issue7593.xaml">
       <SubType>Designer</SubType>
       <Generator>MSBuild:UpdateDesignTimeXaml</Generator>
     </EmbeddedResource>
   </ItemGroup>
   <ItemGroup>
-    <EmbeddedResource Include="$(MSBuildThisFileDirectory)Issue7789.xaml">
+    <EmbeddedResource Include="$(MSBuildThisFileDirectory)Issue7792.xaml">
       <SubType>Designer</SubType>
       <Generator>MSBuild:UpdateDesignTimeXaml</Generator>
     </EmbeddedResource>
-  </ItemGroup>
-  <ItemGroup>
-    <EmbeddedResource Include="$(MSBuildThisFileDirectory)Issue7817.xaml">
+    <EmbeddedResource Include="$(MSBuildThisFileDirectory)Issue7758.xaml">
       <SubType>Designer</SubType>
       <Generator>MSBuild:UpdateDesignTimeXaml</Generator>
     </EmbeddedResource>
-    <EmbeddedResource Include="$(MSBuildThisFileDirectory)Issue7865.xaml">
+  </ItemGroup>
+  <ItemGroup>
+    <EmbeddedResource Include="$(MSBuildThisFileDirectory)Issue7817.xaml">
       <SubType>Designer</SubType>
       <Generator>MSBuild:UpdateDesignTimeXaml</Generator>
     </EmbeddedResource>

Xamarin.Forms.Core/PlatformConfiguration/iOSSpecific/UIModalPresentationStyle.cs

@@ -3,6 +3,7 @@
 	public enum UIModalPresentationStyle
 	{
 		FullScreen,
-		FormSheet
+		FormSheet,
+		Automatic
 	}
 }

Xamarin.Forms.Platform.iOS/Extensions/Extensions.cs

@@ -84,6 +84,10 @@ internal static UIModalPresentationStyle ToNativeModalPresentationStyle(this Pla
 					return UIModalPresentationStyle.FormSheet;
 				case PlatformConfiguration.iOSSpecific.UIModalPresentationStyle.FullScreen:
 					return UIModalPresentationStyle.FullScreen;
+#if __XCODE11__
+				case PlatformConfiguration.iOSSpecific.UIModalPresentationStyle.Automatic:
+					return UIModalPresentationStyle.Automatic;
+#endif
 				default:
 					throw new ArgumentOutOfRangeException(nameof(style));
 			}

Xamarin.Forms.Platform.iOS/ModalWrapper.cs

@@ -2,10 +2,12 @@
 using System.Linq;
 using Xamarin.Forms.PlatformConfiguration.iOSSpecific;
 using UIKit;
+using Foundation;
+using System.Threading.Tasks;
 
 namespace Xamarin.Forms.Platform.iOS
 {
-	internal class ModalWrapper : UIViewController
+	internal class ModalWrapper : UIViewController, IUIAdaptivePresentationControllerDelegate
 	{
 		IVisualElementRenderer _modal;
 
@@ -14,17 +16,37 @@ internal ModalWrapper(IVisualElementRenderer modal)
 			_modal = modal;
 
 			var elementConfiguration = modal.Element as IElementConfiguration<Page>;
-			var modalPresentationStyle = elementConfiguration?.On<PlatformConfiguration.iOS>()?.ModalPresentationStyle() ?? PlatformConfiguration.iOSSpecific.UIModalPresentationStyle.FullScreen;
-			ModalPresentationStyle = modalPresentationStyle.ToNativeModalPresentationStyle();
+			if (elementConfiguration?.On<PlatformConfiguration.iOS>()?.ModalPresentationStyle() is PlatformConfiguration.iOSSpecific.UIModalPresentationStyle style)
+			{
+				var result = style.ToNativeModalPresentationStyle();
+#if __XCODE11__
+				if (!Forms.IsiOS13OrNewer && result == UIKit.UIModalPresentationStyle.Automatic)
+				{
+					result = UIKit.UIModalPresentationStyle.FullScreen;
+				}
+#endif
+
+				ModalPresentationStyle = result;
+			}
 
 			View.BackgroundColor = UIColor.White;
 			View.AddSubview(modal.ViewController.View);
 			TransitioningDelegate = modal.ViewController.TransitioningDelegate;
 			AddChildViewController(modal.ViewController);
 
 			modal.ViewController.DidMoveToParentViewController(this);
+#if __XCODE11__
+			if (Forms.IsiOS13OrNewer)
+				PresentationController.Delegate = this;
+#endif
 		}
-
+#if __XCODE11__
+		[Export("presentationControllerDidDismiss:")]
+		public async void DidDismiss(UIPresentationController presentationController)
+		{
+			await Application.Current.NavigationProxy.PopModalAsync(false);
+		}
+#endif
 		public override void DismissViewController(bool animated, Action completionHandler)
 		{
 			if (PresentedViewController == null)

Xamarin.Forms.Platform.iOS/PageExtensions.cs

@@ -1,5 +1,6 @@
 using System;
 using UIKit;
+using System.Linq;
 
 namespace Xamarin.Forms
 {
@@ -39,5 +40,17 @@ public static UIViewController CreateViewController(this ContentPage page)
 		{
 			return Xamarin.Forms.PageExtensions.CreateViewController(page);
 		}
+
+		internal static Page GetCurrentPage(this Page currentPage)
+		{
+			if (currentPage.NavigationProxy.ModalStack.LastOrDefault() is Page modal)
+				return modal;
+			else if (currentPage is MasterDetailPage mdp)
+				return GetCurrentPage(mdp.Detail);
+			else if (currentPage is IPageContainer<Page> pc)
+				return GetCurrentPage(pc.CurrentPage);
+			else
+				return currentPage;
+		}
 	}
 }

Xamarin.Forms.Platform.iOS/Platform.cs

@@ -8,6 +8,7 @@
 using UIKit;
 using Xamarin.Forms.Internals;
 using RectangleF = CoreGraphics.CGRect;
+using Xamarin.Forms.PlatformConfiguration.iOSSpecific;
 
 namespace Xamarin.Forms.Platform.iOS
 {
@@ -126,6 +127,9 @@ async Task<Page> INavigation.PopModalAsync(bool animated)
 
 			modal.DisposeModalAndChildRenderers();
 
+			if (!IsModalPresentedFullScreen(modal))
+				Page.GetCurrentPage()?.SendAppearing();
+
 			return modal;
 		}
 
@@ -158,6 +162,34 @@ Task INavigation.PushModalAsync(Page modal, bool animated)
 		{
 			EndEditing();
 
+
+			var elementConfiguration = modal as IElementConfiguration<Page>;
+
+			var presentationStyle = elementConfiguration?.On<PlatformConfiguration.iOS>()?.ModalPresentationStyle().ToNativeModalPresentationStyle();
+
+			bool shouldFire = true;
+
+			if (Forms.IsiOS13OrNewer)
+			{
+				if (presentationStyle == UIKit.UIModalPresentationStyle.FullScreen)
+					shouldFire = false; // This is mainly for backwards compatibility
+			}
+			else
+			{
+				// While the above IsiOS13OrNewer will always be false if __XCODE11__ is true
+				// the UIModalPresentationStyle.Automatic is the only Xcode 11 API
+				// for readability I decided to only take this part out
+#if __XCODE11__
+				if (presentationStyle == UIKit.UIModalPresentationStyle.Automatic)
+					shouldFire = false;
+#endif
+				if (presentationStyle == UIKit.UIModalPresentationStyle.FullScreen)
+					shouldFire = false; // This is mainly for backwards compatibility
+			}
+
+			if (_appeared && shouldFire)
+				Page.GetCurrentPage()?.SendDisappearing();
+
 			_modals.Add(modal);
 
 #pragma warning disable CS0618 // Type or member is obsolete
@@ -614,6 +646,13 @@ internal void SubscribeToAlertsAndActionSheets()
 			});
 		}
 
+		static bool IsModalPresentedFullScreen(Page modal)
+		{
+			var elementConfiguration = modal as IElementConfiguration<Page>;
+			var presentationStyle = elementConfiguration?.On<PlatformConfiguration.iOS>()?.ModalPresentationStyle();
+			return presentationStyle != null && presentationStyle == PlatformConfiguration.iOSSpecific.UIModalPresentationStyle.FullScreen;
+		}
+
 		internal void UnsubscribeFromAlertsAndActionsSheets()
 		{
 			MessagingCenter.Unsubscribe<Page, ActionSheetArguments>(this, Page.ActionSheetSignalName);