From 7483a995854d1f39443541314f34e27bb9fee144 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Javier=20Su=C3=A1rez?= <javiersuarezruiz@hotmail.com>
Date: Thu, 10 Sep 2020 14:05:40 +0200
Subject: [PATCH] Fixed ScrollView Visibility on Android (#10659) fixes #8015
 fixes #9103

Co-authored-by: Samantha Houts <samhouts@users.noreply.github.com>
---
 .../GalleryPages/ScrollGallery.cs             | 154 ++++++++++--------
 .../Renderers/ScrollViewRenderer.cs           |   4 +-
 .../Resources/values/attrs.xml                |   4 +
 .../Resources/values/styles.xml               |   9 +-
 4 files changed, 97 insertions(+), 74 deletions(-)

diff --git a/Xamarin.Forms.Controls/GalleryPages/ScrollGallery.cs b/Xamarin.Forms.Controls/GalleryPages/ScrollGallery.cs
index 2416317dc..380e53eea 100644
--- a/Xamarin.Forms.Controls/GalleryPages/ScrollGallery.cs
+++ b/Xamarin.Forms.Controls/GalleryPages/ScrollGallery.cs
@@ -11,112 +11,121 @@ namespace Xamarin.Forms.Controls
 		readonly ScrollView _scrollview;
 		readonly StackLayout _stack;
 		ScrollOrientation _orientation;
-		List<Button> _buttons = new List<Button> ();
+		List<Button> _buttons = new List<Button>();
 		Button _toNavigateTo;
-		public ScrollGallery (ScrollOrientation orientation = ScrollOrientation.Vertical)
+		public ScrollGallery(ScrollOrientation orientation = ScrollOrientation.Vertical)
 		{
 			_orientation = orientation;
-			var root = new Grid ();
-			root.RowDefinitions.Add (new RowDefinition () { Height = GridLength.Auto });
-			root.RowDefinitions.Add (new RowDefinition () { Height = GridLength.Auto });
-			root.RowDefinitions.Add (new RowDefinition () { Height = GridLength.Auto });
-			root.RowDefinitions.Add (new RowDefinition ());
+			var root = new Grid();
+			root.RowDefinitions.Add(new RowDefinition() { Height = GridLength.Auto });
+			root.RowDefinitions.Add(new RowDefinition() { Height = GridLength.Auto });
+			root.RowDefinitions.Add(new RowDefinition() { Height = GridLength.Auto });
+			root.RowDefinitions.Add(new RowDefinition() { Height = GridLength.Auto });
+			root.RowDefinitions.Add(new RowDefinition());
 
 			var btnStack1 = new StackLayout { Orientation = StackOrientation.Horizontal };
-			var btnStack = new StackLayout { Orientation = StackOrientation.Horizontal };
+			var btnStack2 = new StackLayout { Orientation = StackOrientation.Horizontal };
+			var btnStack3 = new StackLayout { Orientation = StackOrientation.Horizontal };
+
 			var btn = new Button { Text = "Scroll to 100" };
 			var btn4 = new Button { Text = "Scroll to 100 no anim" };
 			var btn1 = new Button { Text = "Start" };
 			var btn2 = new Button { Text = "Center" };
 			var btn3 = new Button { Text = "End" };
-			var btn7 = new Button { Text = "Toggle Scroll Bar Visibility" };
-			var btn6 = new Button { Text = "MakeVisible", HorizontalOptions= LayoutOptions.CenterAndExpand, BackgroundColor = Color.Accent };
-			var btn8 = new Button { Text = "Toggle Orientation" };
-			var btn9 = new Button { Text = "Default Scroll Bar Visibility" };
+			var btn7 = new Button { Text = "Toggle Scroll Bar Visibility", WidthRequest = 120 };
+			var btn6 = new Button { Text = "MakeVisible", HorizontalOptions = LayoutOptions.CenterAndExpand, BackgroundColor = Color.Accent };
+			var btn8 = new Button { Text = "Toggle Orientation", WidthRequest = 120 };
+			var btn9 = new Button { Text = "Default Scroll Bar Visibility", WidthRequest = 120 };
 
 			var labelStack = new StackLayout { Orientation = StackOrientation.Horizontal };
-			var label = new Label { Text = string.Format ("X: {0}, Y: {1}", 0, 0) };
+			var label = new Label { Text = string.Format("X: {0}, Y: {1}", 0, 0) };
 			var scrollStatusLabel = new Label { Text = string.Empty };
-			
-			root.Children.Add (labelStack);
-			root.Children.Add (btnStack);
-			root.Children.Add (btnStack1);
 
-			btnStack.Children.Add (btn1);
-			btnStack.Children.Add (btn2);
-			btnStack.Children.Add (btn3);
-			btnStack.Children.Add(btn7);
-			btnStack.Children.Add(btn9);
-			btnStack.Children.Add(btn8);
+			root.Children.Add(labelStack);
+			root.Children.Add(btnStack1);
+			root.Children.Add(btnStack2);
+			root.Children.Add(btnStack3);
 
-			btnStack1.Children.Add (btn);
-			btnStack1.Children.Add (btn4);
+			btnStack1.Children.Add(btn1);
+			btnStack1.Children.Add(btn2);
+			btnStack1.Children.Add(btn3);
+
+			btnStack2.Children.Add(btn);
+			btnStack2.Children.Add(btn4);
+
+			btnStack3.Children.Add(btn7);
+			btnStack3.Children.Add(btn9);
+			btnStack3.Children.Add(btn8);
 
 			labelStack.Children.Add(label);
 			labelStack.Children.Add(scrollStatusLabel);
 
-			Grid.SetRow (btnStack, 1);
-			Grid.SetRow (btnStack1, 2);
-		
-			var grid = new Grid ();
-			grid.RowDefinitions.Add (new RowDefinition { Height = GridLength.Auto });
-			grid.RowDefinitions.Add (new RowDefinition ());
-			_stack = new StackLayout ();
-			Grid.SetRow (_stack, 1);
-			grid.Children.Add (btn6);
-			grid.Children.Add (_stack);
-			_scrollview = new ScrollView {
-				AutomationId="thescroller",
+			Grid.SetRow(btnStack1, 1);
+			Grid.SetRow(btnStack2, 2);
+			Grid.SetRow(btnStack3, 3);
+
+			var grid = new Grid();
+			grid.RowDefinitions.Add(new RowDefinition { Height = GridLength.Auto });
+			grid.RowDefinitions.Add(new RowDefinition());
+			_stack = new StackLayout();
+			Grid.SetRow(_stack, 1);
+			grid.Children.Add(btn6);
+			grid.Children.Add(_stack);
+			_scrollview = new ScrollView
+			{
+				AutomationId = "thescroller",
 				BackgroundColor = Color.Aqua,
 				Content = grid
 			};
-			root.Children.Add (_scrollview);
-			Grid.SetRow (_scrollview, 3);
+			root.Children.Add(_scrollview);
+			Grid.SetRow(_scrollview, 4);
 
-			_scrollview.Scrolled+= (object sender, ScrolledEventArgs e) => {
-				label.Text = string.Format ("X: {0}, Y: {1}", e.ScrollX, e.ScrollY);
+			_scrollview.Scrolled += (object sender, ScrolledEventArgs e) => {
+				label.Text = string.Format("X: {0}, Y: {1}", e.ScrollX, e.ScrollY);
 			};
 
 			btn.Clicked += async (object sender, EventArgs e) => {
 				scrollStatusLabel.Text = "scrolling";
-				switch (orientation) {
+				switch (orientation)
+				{
 					case ScrollOrientation.Horizontal:
-						await _scrollview.ScrollToAsync (100, 0, true);
+						await _scrollview.ScrollToAsync(100, 0, true);
 						break;
 					case ScrollOrientation.Vertical:
-						await _scrollview.ScrollToAsync (0, 100, true);
+						await _scrollview.ScrollToAsync(0, 100, true);
 						break;
 					case ScrollOrientation.Both:
-						await _scrollview.ScrollToAsync (100, 100, true);
+						await _scrollview.ScrollToAsync(100, 100, true);
 						break;
 				}
 				scrollStatusLabel.Text = "completed";
 			};
 			btn4.Clicked += async (object sender, EventArgs e) => {
-				switch (orientation) {
+				switch (orientation)
+				{
 					case ScrollOrientation.Horizontal:
-						await _scrollview.ScrollToAsync (100, 0, false);
+						await _scrollview.ScrollToAsync(100, 0, false);
 						break;
 					case ScrollOrientation.Vertical:
-						await _scrollview.ScrollToAsync (0, 100, false);
+						await _scrollview.ScrollToAsync(0, 100, false);
 						break;
 					case ScrollOrientation.Both:
-						await _scrollview.ScrollToAsync (100, 100, true);
+						await _scrollview.ScrollToAsync(100, 100, true);
 						break;
 				}
 			};
 
 			btn1.Clicked += async (object sender, EventArgs e) => {
-				await _scrollview.ScrollToAsync (_toNavigateTo, ScrollToPosition.Start, true);
+				await _scrollview.ScrollToAsync(_toNavigateTo, ScrollToPosition.Start, true);
 			};
 			btn2.Clicked += async (object sender, EventArgs e) => {
-				await _scrollview.ScrollToAsync (_toNavigateTo, ScrollToPosition.Center, true);
+				await _scrollview.ScrollToAsync(_toNavigateTo, ScrollToPosition.Center, true);
 			};
 			btn3.Clicked += async (object sender, EventArgs e) => {
-				await _scrollview.ScrollToAsync (_toNavigateTo, ScrollToPosition.End, true);
+				await _scrollview.ScrollToAsync(_toNavigateTo, ScrollToPosition.End, true);
 			};
 			btn6.Clicked += async (object sender, EventArgs e) => {
-				await _scrollview.ScrollToAsync (_toNavigateTo, ScrollToPosition.MakeVisible, true);
+				await _scrollview.ScrollToAsync(_toNavigateTo, ScrollToPosition.MakeVisible, true);
 			};
 			btn7.Clicked += (object sender, EventArgs e) =>
 			{
@@ -151,34 +160,38 @@ namespace Xamarin.Forms.Controls
 				_scrollview.HorizontalScrollBarVisibility = ScrollBarVisibility.Default;
 			};
 
-			_stack.Padding = new Size (20, 60);
+			_stack.Padding = new Size(20, 60);
 
-			PopulateStack (_stack);
+			PopulateStack(_stack);
 
 			_scrollview.Orientation = _orientation;
 
-			if (orientation == ScrollOrientation.Horizontal || orientation == ScrollOrientation.Both) {
+			if (orientation == ScrollOrientation.Horizontal || orientation == ScrollOrientation.Both)
+			{
 				_stack.Orientation = StackOrientation.Horizontal;
 			}
 
-			if (orientation == ScrollOrientation.Both) {
-				var stack2 = new StackLayout ();
-				PopulateStack (stack2);
-				_stack.Children.Add (stack2);
+			if (orientation == ScrollOrientation.Both)
+			{
+				var stack2 = new StackLayout();
+				PopulateStack(stack2);
+				_stack.Children.Add(stack2);
 			}
 
 			Content = root;
 		}
 
-		void PopulateStack (StackLayout stack)
+		void PopulateStack(StackLayout stack)
 		{
-			for (int i = 0; i < 100; i++) {
+			for (int i = 0; i < 100; i++)
+			{
 
-				var newButton = new Button { Text = "Foo Bar", AutomationId =string.Format ("btn_{0}", i) };
+				var newButton = new Button { Text = "Foo Bar", AutomationId = string.Format("btn_{0}", i) };
 				if (i == 49)
 					newButton.Text = "the before";
 
-				if (i == 50) {
+				if (i == 50)
+				{
 					newButton.Text = "the scrollto button";
 					newButton.BackgroundColor = Color.Yellow;
 					newButton.TextColor = Color.Black;
@@ -186,18 +199,19 @@ namespace Xamarin.Forms.Controls
 				}
 				if (i == 51)
 					newButton.Text = "the after";
-				if (i == 53) {
+				if (i == 53)
+				{
 					newButton.Text = "the make visible from start";
 					newButton.Clicked += async (object sender, EventArgs e) => {
-						await _scrollview.ScrollToAsync (_toNavigateTo, ScrollToPosition.MakeVisible, true);
+						await _scrollview.ScrollToAsync(_toNavigateTo, ScrollToPosition.MakeVisible, true);
 					};
 				}
 
-				_buttons.Add (newButton);
-				stack.Children.Add (newButton);
+				_buttons.Add(newButton);
+				stack.Children.Add(newButton);
 			}
 
-			stack.Children.Add (new Button { Text = "Foo Bottom" });
+			stack.Children.Add(new Button { Text = "Foo Bottom" });
 		}
 	}
-}
+}
\ No newline at end of file
diff --git a/Xamarin.Forms.Platform.Android/Renderers/ScrollViewRenderer.cs b/Xamarin.Forms.Platform.Android/Renderers/ScrollViewRenderer.cs
index f6d0721d9..55fc21097 100644
--- a/Xamarin.Forms.Platform.Android/Renderers/ScrollViewRenderer.cs
+++ b/Xamarin.Forms.Platform.Android/Renderers/ScrollViewRenderer.cs
@@ -32,7 +32,9 @@ namespace Xamarin.Forms.Platform.Android
 		LayoutDirection _prevLayoutDirection = LayoutDirection.Ltr;
 		bool _checkedForRtlScroll = false;
 
-		public ScrollViewRenderer(Context context) : base(context)
+		public ScrollViewRenderer(Context context) : base(
+			new ContextThemeWrapper(context, Resource.Style.scrollViewTheme), null,
+			Resource.Attribute.scrollViewStyle)
 		{
 		}
 
diff --git a/Xamarin.Forms.Platform.Android/Resources/values/attrs.xml b/Xamarin.Forms.Platform.Android/Resources/values/attrs.xml
index c9ed5bdc0..dd99e3768 100644
--- a/Xamarin.Forms.Platform.Android/Resources/values/attrs.xml
+++ b/Xamarin.Forms.Platform.Android/Resources/values/attrs.xml
@@ -10,4 +10,8 @@
     <attr name="collectionViewStyle" format="reference"/>
   </declare-styleable>
 
+  <declare-styleable name="ScrollViewRendererTheme">
+    <attr name="scrollViewStyle" format="reference"/>
+  </declare-styleable>
+
 </resources>
\ No newline at end of file
diff --git a/Xamarin.Forms.Platform.Android/Resources/values/styles.xml b/Xamarin.Forms.Platform.Android/Resources/values/styles.xml
index 56c3051b2..9047d995c 100644
--- a/Xamarin.Forms.Platform.Android/Resources/values/styles.xml
+++ b/Xamarin.Forms.Platform.Android/Resources/values/styles.xml
@@ -12,13 +12,16 @@
     attribute defined in attrs.xml), we can apply the collectionViewScrollBars style explicitly to the renderer we are
     creating (and avoid forcing every child control to have scrollbars).
   -->
-  
-  <style name="collectionViewScrollBars">
+  <style name="scrollViewScrollBars">
     <item name="android:scrollbars">vertical|horizontal</item>
   </style>
   
   <style name="collectionViewTheme">
-    <item name="collectionViewStyle">@style/collectionViewScrollBars</item>
+    <item name="collectionViewStyle">@style/scrollViewScrollBars</item>
+  </style>
+  
+  <style name="scrollViewTheme">
+    <item name="scrollViewStyle">@style/scrollViewScrollBars</item>
   </style>
 
   <style name="MainTheme" parent="MainTheme.Base">