[Android] Fix Entry/Editor crash when setting Text in TextChanged event handler

src/Controls/tests/TestCases.HostApp/Issues/Issue32004.xaml

@@ -0,0 +1,20 @@
+<?xml version="1.0" encoding="utf-8" ?>
+<ContentPage xmlns="http://schemas.microsoft.com/dotnet/2021/maui"
+             xmlns:x="http://schemas.microsoft.com/winfx/2009/xaml"
+             x:Class="Maui.Controls.Sample.Issues.Issue32004">
+    <VerticalStackLayout Padding="20" Spacing="10">
+        <Label Text="Test Entry TextChanged crash" FontSize="18" FontAttributes="Bold"/>
+        <Label Text="1. Delete all text from the entry below" />
+        <Label Text="2. App should not crash" />
+
+        <Entry x:Name="CartonsEntry" 
+               Text="0" 
+               Keyboard="Numeric" 
+               TextChanged="Quantity_TextChanged"
+               AutomationId="TestEntry" />
+
+        <Label x:Name="StatusLabel" 
+               Text="Status: Ready" 
+               AutomationId="StatusLabel" />
+    </VerticalStackLayout>
+</ContentPage>

src/Controls/tests/TestCases.HostApp/Issues/Issue32004.xaml.cs

@@ -0,0 +1,26 @@
+namespace Maui.Controls.Sample.Issues;
+
+[Issue(IssueTracker.Github, 32004, "Entry crashes when setting Text in TextChanged event handler", PlatformAffected.Android)]
+public partial class Issue32004 : ContentPage
+{
+	public Issue32004()
+	{
+		InitializeComponent();
+	}
+
+	private void Quantity_TextChanged(object sender, TextChangedEventArgs e)
+	{
+		// This reproduces the crash: when text is cleared (empty/null),
+		// setting the Text property causes a re-entrant TextWatcher callback
+		// while EmojiCompat is processing, leading to "end should be < than charSequence length" crash
+		if (string.IsNullOrEmpty(e.NewTextValue))
+		{
+			((Entry)sender).Text = "0";
+			StatusLabel.Text = "Status: Reset to 0";
+		}
+		else
+		{
+			StatusLabel.Text = $"Status: Text is '{e.NewTextValue}'";
+		}
+	}
+}

src/Controls/tests/TestCases.Shared.Tests/Tests/Issues/Issue32004.cs

@@ -0,0 +1,42 @@
+#if ANDROID
+using System.Threading.Tasks;
+using NUnit.Framework;
+using UITest.Appium;
+using UITest.Core;
+
+namespace Microsoft.Maui.TestCases.Tests.Issues
+{
+	public class Issue32004 : _IssuesUITest
+	{
+		public Issue32004(TestDevice testDevice) : base(testDevice)
+		{
+		}
+
+		public override string Issue => "Entry crashes when setting Text in TextChanged event handler";
+
+		[Test]
+		[Category(UITestCategories.Entry)]
+		public void EntryDoesNotCrashWhenSettingTextInTextChangedEvent()
+		{
+			// Wait for the entry to be visible
+			App.WaitForElement("TestEntry");
+
+			// Clear the entry text - this should trigger the TextChanged event
+			// which will set Text to "0", previously causing a crash
+			App.ClearText("TestEntry");
+
+			// Wait a moment for the deferred text update to complete
+			Task.Delay(100).Wait();
+
+			// If we reach here without crashing, the fix is working
+			// Verify that the status label updated
+			var statusText = App.WaitForElement("StatusLabel").GetText();
+			Assert.That(statusText, Does.Contain("Reset to 0"));
+
+			// Verify the entry text was set to "0"
+			var entryText = App.WaitForElement("TestEntry").GetText();
+			Assert.That(entryText, Is.EqualTo("0"));
+		}
+	}
+}
+#endif

src/Core/src/Handlers/Editor/EditorHandler.Android.cs

@@ -63,8 +63,29 @@ protected override void DisconnectHandler(AppCompatEditText platformView)
 		public static void MapBackground(IEditorHandler handler, IEditor editor) =>
 			handler.PlatformView?.UpdateBackground(editor);
 
-		public static void MapText(IEditorHandler handler, IEditor editor) =>
-			handler.PlatformView?.UpdateText(editor);
+		public static void MapText(IEditorHandler handler, IEditor editor)
+		{
+			if (handler.PlatformView == null)
+				return;
+
+			// If we're in the middle of processing a text change from the platform,
+			// we need to be careful about how we update the text to avoid re-entering
+			// TextWatcher callbacks while EmojiCompat is processing.
+			// This prevents "end should be < than charSequence length" crash.
+			if (handler is EditorHandler editorHandler && editorHandler.DataFlowDirection == DataFlowDirection.FromPlatform)
+			{
+				// When updating from platform, defer the update to avoid re-entrance
+				handler.PlatformView.PostDelayed(() =>
+				{
+					if (handler.PlatformView != null)
+						handler.PlatformView.UpdateText(editor);
+				}, 10);
+			}
+			else
+			{
+				handler.PlatformView.UpdateText(editor);
+			}
+		}
 
 		public static void MapTextColor(IEditorHandler handler, IEditor editor) =>
 			handler.PlatformView?.UpdateTextColor(editor);

src/Core/src/Handlers/Entry/EntryHandler.Android.cs

@@ -77,8 +77,29 @@ void OnViewAttachedToWindow(object? sender, ViewAttachedToWindowEventArgs e)
 		public static void MapBackground(IEntryHandler handler, IEntry entry) =>
 			handler.PlatformView?.UpdateBackground(entry);
 
-		public static void MapText(IEntryHandler handler, IEntry entry) =>
-			handler.PlatformView?.UpdateText(entry);
+		public static void MapText(IEntryHandler handler, IEntry entry)
+		{
+			if (handler.PlatformView == null)
+				return;
+
+			// If we're in the middle of processing a text change from the platform,
+			// we need to be careful about how we update the text to avoid re-entering
+			// TextWatcher callbacks while EmojiCompat is processing.
+			// This prevents "end should be < than charSequence length" crash.
+			if (handler is EntryHandler entryHandler && entryHandler.DataFlowDirection == DataFlowDirection.FromPlatform)
+			{
+				// When updating from platform, defer the update to avoid re-entrance
+				handler.PlatformView.PostDelayed(() =>
+				{
+					if (handler.PlatformView != null)
+						handler.PlatformView.UpdateText(entry);
+				}, 10);
+			}
+			else
+			{
+				handler.PlatformView.UpdateText(entry);
+			}
+		}
 
 		public static void MapTextColor(IEntryHandler handler, IEntry entry)
 		{