[Android] Add disposed check to MasterDetailPageRenderer (#6354)

* [Android] Add disposed check to MasterDetailPageRenderer

Co-Authored-By: Felipe Silveira <transis2@users.noreply.github.com>

* Fix dispose pattern

a la #6305

* apply same set of changes to NavigationPageRenderer

fixes #3489
closes #4586

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

@@ -207,10 +207,13 @@ namespace Xamarin.Forms.Platform.Android.AppCompat
 
 		protected override void Dispose(bool disposing)
 		{
-			if (disposing && !_disposed)
+			if (_disposed)
-			{
+				return;
-				_disposed = true;
 
+			_disposed = true;
+
+			if (disposing)
+			{
 				if (_tracker != null)
 				{
 					_tracker.Dispose();
@@ -236,7 +239,8 @@ namespace Xamarin.Forms.Platform.Android.AppCompat
 
 				Device.Info.PropertyChanged -= DeviceInfoPropertyChanged;
 
-				RemoveDrawerListener(this);
+				if (!this.IsDisposed())
+					RemoveDrawerListener(this);
 
 				if (Element != null)
 				{

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

@@ -161,10 +161,13 @@ namespace Xamarin.Forms.Platform.Android.AppCompat
 
 		protected override void Dispose(bool disposing)
 		{
-			if (disposing && !_disposed)
+			if (_disposed)
-			{
+				return;
-				_disposed = true;
 
+			_disposed = true;
+
+			if (disposing)
+			{
 				if (_titleViewRenderer != null)
 				{
 					Android.Platform.ClearRenderer(_titleViewRenderer.View);
@@ -196,7 +199,7 @@ namespace Xamarin.Forms.Platform.Android.AppCompat
 					_toolbar = null;
 				}
 
-				if (_drawerLayout != null && _drawerListener != null)
+				if (_drawerLayout.IsAlive() && _drawerListener.IsAlive())
 				{
 					_drawerLayout.RemoveDrawerListener(_drawerListener);
 				}

Xamarin.Forms.Platform.Android/Extensions/JavaObjectExtensions.cs

@@ -8,5 +8,12 @@ namespace Xamarin.Forms.Platform.Android
 		{
 			return obj.Handle == IntPtr.Zero;
 		}
+		public static bool IsAlive(this Java.Lang.Object obj)
+		{
+			if (obj == null)
+				return false;
+
+			return !obj.IsDisposed();
+		}
 	}
 }