Fix TextColor null reset to restore platform defaults on iOS and Android

src/Controls/tests/TestCases.HostApp/Issues/Issue35513.cs

@@ -0,0 +1,96 @@
+namespace Maui.Controls.Sample.Issues;
+
+[Issue(IssueTracker.Github, 35513, "Button TextColor does not restore to platform default when reset to null after dynamic update", PlatformAffected.Android | PlatformAffected.iOS | PlatformAffected.macOS)]
+public class Issue35513 : ContentPage
+{
+	Button _sampleButton;
+	Label _sampleLabel;
+	Entry _sampleEntry;
+	Editor _sampleEditor;
+	RadioButton _sampleRadioButton;
+	Picker _samplePicker;
+
+	public Issue35513()
+	{
+		_sampleButton = new Button
+		{
+			Text = "Button Control"
+		};
+
+		_sampleLabel = new Label
+		{
+			Text = "Label Control"
+		};
+
+		_sampleEntry = new Entry
+		{
+			Text = "Entry Control"
+		};
+
+		_sampleEditor = new Editor
+		{
+			Text = "Editor Control",
+			AutoSize = EditorAutoSizeOption.TextChanges
+		};
+
+		_sampleRadioButton = new RadioButton
+		{
+			Content = "RadioButton Control"
+		};
+
+		_samplePicker = new Picker
+		{
+			Title = "Picker Control"
+		};
+		_samplePicker.Items.Add("First Option");
+		_samplePicker.Items.Add("Second Option");
+		_samplePicker.SelectedIndex = 0;
+
+
+		Content = new ScrollView
+		{
+			Content = new VerticalStackLayout
+			{
+				Padding = new Thickness(24),
+				Spacing = 14,
+				Children =
+				{
+					_sampleButton,
+					_sampleLabel,
+					_sampleEntry,
+					_sampleEditor,
+					_sampleRadioButton,
+					_samplePicker,
+					new Button
+					{
+						Text = "Set Text Color",
+						AutomationId = "SetTextColorButton",
+						Command = new Command(() =>
+						{
+							_sampleButton.TextColor = Colors.Orange;
+							_sampleLabel.TextColor = Colors.Orange;
+							_sampleEntry.TextColor = Colors.Orange;
+							_sampleEditor.TextColor = Colors.Orange;
+							_sampleRadioButton.TextColor = Colors.Orange;
+							_samplePicker.TextColor = Colors.Orange;
+						})
+					},
+					new Button
+					{
+						Text = "Reset Text Color",
+						AutomationId = "ResetTextColorButton",
+						Command = new Command(() =>
+						{
+							_sampleButton.TextColor = null;
+							_sampleLabel.TextColor = null;
+							_sampleEntry.TextColor = null;
+							_sampleEditor.TextColor = null;
+							_sampleRadioButton.TextColor = null;
+							_samplePicker.TextColor = null;
+						})
+					}
+				}
+			}
+		};
+	}
+}

src/Controls/tests/TestCases.Shared.Tests/Tests/Issues/Issue35513.cs

@@ -0,0 +1,31 @@
+using NUnit.Framework;
+using UITest.Appium;
+using UITest.Core;
+
+namespace Microsoft.Maui.TestCases.Tests.Issues;
+
+public class Issue35513 : _IssuesUITest
+{
+	public Issue35513(TestDevice device) : base(device) { }
+
+	public override string Issue => "Button TextColor does not restore to platform default when reset to null after dynamic update";
+
+	[Test, Order(1)]
+	[Category(UITestCategories.Button)]
+	public void TextViewBasedControlsTextColorUpdates()
+	{
+		App.WaitForElement("SetTextColorButton");
+		App.Tap("SetTextColorButton");
+		VerifyScreenshot("AfterSetTextColorOnTextViewBasedControls");
+	}
+
+	[Test, Order(2)]
+	[Category(UITestCategories.Button)]
+	public void TextViewBasedControlsRestoreDefaultAfterResetToNull()
+	{
+		App.WaitForElement("SetTextColorButton");
+		App.Tap("SetTextColorButton");
+		App.Tap("ResetTextColorButton");
+		VerifyScreenshot("AfterResetTextColorToNullOnTextViewBasedControls");
+	}
+}

src/Core/src/Platform/Android/TextViewExtensions.cs

@@ -1,6 +1,7 @@
 using System;
 using System.Net;
 using System.Runtime.CompilerServices;
+using Android.Content.Res;
 using Android.Graphics;
 using Android.Text;
 using Android.Views;
@@ -14,6 +15,7 @@ namespace Microsoft.Maui.Platform
 	public static class TextViewExtensions
 	{
 		static readonly ConditionalWeakTable<TextView, StrongBox<int>> s_htmlGenerations = new();
+		static readonly ConditionalWeakTable<TextView, ColorStateList> defaultTextColors = new();
 
 		public static void UpdateTextPlainText(this TextView textView, IText label)
 		{
@@ -58,8 +60,20 @@ public static void UpdateTextColor(this TextView textView, ITextStyle textStyle)
 		{
 			var textColor = textStyle.TextColor;
 
-			if (textColor != null)
-				textView.SetTextColor(textColor.ToPlatform());
+			// Cache the original themed TextColors the first time this control is updated.
+			if (textView.TextColors is ColorStateList currentColors)
+			{
+				defaultTextColors.GetValue(textView, _ => currentColors);
+			}
+
+			if (textColor is null)
+			{
+				var defaultColors = defaultTextColors.TryGetValue(textView, out var cached) ? cached : null;
+				textView.SetTextColor(defaultColors);
+				return;
+			}
+
+			textView.SetTextColor(textColor.ToPlatform());
 		}
 
 		public static void UpdateFont(this TextView textView, ITextStyle textStyle, IFontManager fontManager)

src/Core/src/Platform/iOS/ButtonExtensions.cs

@@ -42,7 +42,6 @@ public static void UpdateTextColor(this UIButton platformButton, ITextStyle butt
 					platformButton.SetTitleColor(null, UIControlState.Disabled);
 					platformButton.TintColor = window.TintColor;
 				}
-
 				return;
 			}