From 7c72459b29c517fbbce38c14ddeca8c891d31477 Mon Sep 17 00:00:00 2001
From: Kevin Petit <kevin.petit@outlook.com>
Date: Mon, 18 Feb 2019 12:24:26 +0100
Subject: [PATCH] [Android] Fix ObjectDisposedException on
 MasterDetailPageRenderer update (#4955)

* Android - MasterDetailPageRenderer - Fix ObjectDisposedException on update.

* Fix update call to master.

* Move checks inside update methods.
Add HandleMasterPropertyChanged handler unsubscribing.
---
 .../AppCompat/MasterDetailPageRenderer.cs          | 31 +++++++++++++---------
 .../Renderers/MasterDetailRenderer.cs              | 24 ++++++++++++-----
 2 files changed, 35 insertions(+), 20 deletions(-)

diff --git a/Xamarin.Forms.Platform.Android/AppCompat/MasterDetailPageRenderer.cs b/Xamarin.Forms.Platform.Android/AppCompat/MasterDetailPageRenderer.cs
index 99b6e7b..45b3764 100644
--- a/Xamarin.Forms.Platform.Android/AppCompat/MasterDetailPageRenderer.cs
+++ b/Xamarin.Forms.Platform.Android/AppCompat/MasterDetailPageRenderer.cs
@@ -1,4 +1,3 @@
-
 using System;
 using System.ComponentModel;
 using System.Threading.Tasks;
@@ -227,6 +226,9 @@ namespace Xamarin.Forms.Platform.Android.AppCompat
 
 				if (_masterLayout != null)
 				{
+					if (_masterLayout.ChildView != null)
+						_masterLayout.ChildView.PropertyChanged -= HandleMasterPropertyChanged;
+
 					RemoveView(_masterLayout);
 					_masterLayout.Dispose();
 					_masterLayout = null;
@@ -387,10 +389,14 @@ namespace Xamarin.Forms.Platform.Android.AppCompat
 			if (_detailLayout.ChildView == null)
 				Update();
 			else
-				new Handler(Looper.MainLooper).Post(() => Update());
+				// Queue up disposal of the previous renderers after the current layout updates have finished
+				new Handler(Looper.MainLooper).Post(Update);
 
 			void Update()
 			{
+				if (_detailLayout == null || _detailLayout.IsDisposed())
+					return;
+
 				Context.HideKeyboard(this);
 				_detailLayout.ChildView = Element.Detail;
 			}
@@ -412,26 +418,25 @@ namespace Xamarin.Forms.Platform.Android.AppCompat
 
 		void UpdateMaster()
 		{
-
 			if (_masterLayout.ChildView == null)
-				new Handler(Looper.MainLooper).Post(() => Update());
-			else
 				Update();
+			else
+				// Queue up disposal of the previous renderers after the current layout updates have finished
+				new Handler(Looper.MainLooper).Post(Update);
 
 			void Update()
 			{
-				Android.MasterDetailContainer masterContainer = _masterLayout;
-				if (masterContainer == null)
+				if (_masterLayout == null || _masterLayout.IsDisposed())
 					return;
 
-				if (masterContainer.ChildView != null)
-					masterContainer.ChildView.PropertyChanged -= HandleMasterPropertyChanged;
+				if (_masterLayout.ChildView != null)
+					_masterLayout.ChildView.PropertyChanged -= HandleMasterPropertyChanged;
 
-				masterContainer.ChildView = Element.Master;
-				if (Element.Master != null)
-					Element.Master.PropertyChanged += HandleMasterPropertyChanged;
-			}
+				_masterLayout.ChildView = Element.Master;
 
+				if (_masterLayout.ChildView != null)
+					_masterLayout.ChildView.PropertyChanged += HandleMasterPropertyChanged;
+			}
 		}
 
 		void UpdateSplitViewLayout()
diff --git a/Xamarin.Forms.Platform.Android/Renderers/MasterDetailRenderer.cs b/Xamarin.Forms.Platform.Android/Renderers/MasterDetailRenderer.cs
index ca66733..234b32b 100644
--- a/Xamarin.Forms.Platform.Android/Renderers/MasterDetailRenderer.cs
+++ b/Xamarin.Forms.Platform.Android/Renderers/MasterDetailRenderer.cs
@@ -6,7 +6,6 @@ using Android.Content;
 using Android.Support.V4.Widget;
 using Android.Views;
 using AView = Android.Views.View;
-using AColor = Android.Graphics.Drawables.ColorDrawable;
 using Android.OS;
 using Xamarin.Forms.Platform.Android.FastRenderers;
 
@@ -168,7 +167,7 @@ namespace Xamarin.Forms.Platform.Android
 				element.SendViewInitialized(this);
 
 			if (element != null && !string.IsNullOrEmpty(element.AutomationId))
-					SetAutomationId(element.AutomationId);
+				SetAutomationId(element.AutomationId);
 
 			SetContentDescription();
 		}
@@ -209,6 +208,9 @@ namespace Xamarin.Forms.Platform.Android
 
 				if (_masterLayout != null)
 				{
+					if (_masterLayout.ChildView != null)
+						_masterLayout.ChildView.PropertyChanged -= HandleMasterPropertyChanged;
+
 					_masterLayout.Dispose();
 					_masterLayout = null;
 				}
@@ -361,10 +363,13 @@ namespace Xamarin.Forms.Platform.Android
 				Update();
 			else
 				// Queue up disposal of the previous renderers after the current layout updates have finished
-				new Handler(Looper.MainLooper).Post(() => Update());
+				new Handler(Looper.MainLooper).Post(Update);
 
 			void Update()
 			{
+				if (_detailLayout == null || _detailLayout.IsDisposed())
+					return;
+
 				Context.HideKeyboard(this);
 				_detailLayout.ChildView = _page.Detail;
 			}
@@ -384,15 +389,20 @@ namespace Xamarin.Forms.Platform.Android
 				Update();
 			else
 				// Queue up disposal of the previous renderers after the current layout updates have finished
-				new Handler(Looper.MainLooper).Post(() => Update());
+				new Handler(Looper.MainLooper).Post(Update);
 
 			void Update()
 			{
-				if (_masterLayout != null && _masterLayout.ChildView != null)
+				if (_masterLayout == null || _masterLayout.IsDisposed())
+					return;
+
+				if (_masterLayout.ChildView != null)
 					_masterLayout.ChildView.PropertyChanged -= HandleMasterPropertyChanged;
+
 				_masterLayout.ChildView = _page.Master;
-				if (_page.Master != null)
-					_page.Master.PropertyChanged += HandleMasterPropertyChanged;
+
+				if (_masterLayout.ChildView != null)
+					_masterLayout.ChildView.PropertyChanged += HandleMasterPropertyChanged;
 			}
 		}
 
-- 
2.7.4