Implement MaxLength property in EntryHandlers

src/Compatibility/Core/src/Android/Renderers/EntryRenderer.cs

@@ -366,6 +366,7 @@ void OnKeyboardBackPressed(object sender, EventArgs eventArgs)
 			Control?.ClearFocus();
 		}
 
+		[PortHandler]
 		void UpdateMaxLength()
 		{
 			var currentFilters = new List<IInputFilter>(EditText?.GetFilters() ?? new IInputFilter[0]);

src/Compatibility/Core/src/iOS/Renderers/EntryRenderer.cs

@@ -388,6 +388,7 @@ void UpdateCharacterSpacing()
 				UpdateAttributedPlaceholder(placeHolder);
 		}
 
+		[PortHandler]
 		void UpdateMaxLength()
 		{
 			var currentControlText = Control.Text;
@@ -396,6 +397,7 @@ void UpdateMaxLength()
 				Control.Text = currentControlText.Substring(0, Element.MaxLength);
 		}
 
+		[PortHandler]
 		bool ShouldChangeCharacters(UITextField textField, NSRange range, string replacementString)
 		{
 			var newLength = textField?.Text?.Length + replacementString?.Length - range.Length;

src/Controls/samples/Controls.Sample/Pages/MainPage.cs

@@ -98,6 +98,7 @@ void SetupMauiLayout()
 			verticalStack.Add(new Entry { IsTextPredictionEnabled = false });
 			verticalStack.Add(new Entry { Placeholder = "This should be placeholder text" });
 			verticalStack.Add(new Entry { Text = "This should be read only property", IsReadOnly = true });
+			verticalStack.Add(new Entry { MaxLength = 5, Placeholder = "MaxLength text" });
 
 			verticalStack.Add(new ProgressBar { Progress = 0.5 });
 			verticalStack.Add(new ProgressBar { Progress = 0.5, BackgroundColor = Color.LightCoral });

src/Core/src/Core/ITextInput.cs

@@ -14,5 +14,10 @@ public interface ITextInput : IText, IPlaceholder
 		/// Gets a value indicating whether or not the view is read-only.
 		/// </summary>
 		bool IsReadOnly { get; }
+
+		/// <summary>
+		/// Gets the maximum allowed length of input.
+		/// </summary>
+		int MaxLength { get; }
 	}
 }

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

@@ -60,6 +60,11 @@ public static void MapIsTextPredictionEnabled(EntryHandler handler, IEntry entry
 			handler.TypedNativeView?.UpdateIsTextPredictionEnabled(entry);
 		}
 
+		public static void MapMaxLength(EntryHandler handler, IEntry entry)
+		{
+			handler.TypedNativeView?.UpdateMaxLength(entry);
+		}
+
 		public static void MapPlaceholder(EntryHandler handler, IEntry entry)
 		{
 			handler.TypedNativeView?.UpdatePlaceholder(entry);

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

@@ -11,6 +11,7 @@ public static void MapTextColor(IViewHandler handler, IEntry entry) { }
 		public static void MapIsPassword(IViewHandler handler, IEntry entry) { }
 		public static void MapHorizontalTextAlignment(IViewHandler handler, IEntry entry) { }
 		public static void MapIsTextPredictionEnabled(IViewHandler handler, IEntry entry) { }
+		public static void MapMaxLength(IViewHandler handler, IEntry entry) { }
 		public static void MapPlaceholder(IViewHandler handler, IEntry entry) { }
 		public static void MapIsReadOnly(IViewHandler handler, IEntry entry) { }
 		public static void MapFont(IViewHandler handler, IEntry entry) { }

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

@@ -9,6 +9,7 @@ public partial class EntryHandler
 			[nameof(IEntry.IsPassword)] = MapIsPassword,
 			[nameof(IEntry.HorizontalTextAlignment)] = MapHorizontalTextAlignment,
 			[nameof(IEntry.IsTextPredictionEnabled)] = MapIsTextPredictionEnabled,
+			[nameof(IEntry.MaxLength)] = MapMaxLength,
 			[nameof(IEntry.Placeholder)] = MapPlaceholder,
 			[nameof(IEntry.IsReadOnly)] = MapIsReadOnly,
 			[nameof(IEntry.Font)] = MapFont,

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

@@ -1,4 +1,5 @@
 using System;
+using Foundation;
 using Microsoft.Extensions.DependencyInjection;
 using Microsoft.Maui.Platform.iOS;
 using UIKit;
@@ -25,13 +26,15 @@ protected override void ConnectHandler(MauiTextField nativeView)
 			nativeView.EditingChanged += OnEditingChanged;
 			nativeView.EditingDidEnd += OnEditingEnded;
 			nativeView.TextPropertySet += OnTextPropertySet;
+			nativeView.ShouldChangeCharacters += OnShouldChangeCharacters;
 		}
 
 		protected override void DisconnectHandler(MauiTextField nativeView)
 		{
 			nativeView.EditingChanged -= OnEditingChanged;
 			nativeView.EditingDidEnd -= OnEditingEnded;
 			nativeView.TextPropertySet -= OnTextPropertySet;
+			nativeView.ShouldChangeCharacters -= OnShouldChangeCharacters;
 		}
 
 		protected override void SetupDefaults(MauiTextField nativeView)
@@ -45,6 +48,9 @@ public override Size GetDesiredSize(double widthConstraint, double heightConstra
 		public static void MapText(EntryHandler handler, IEntry entry)
 		{
 			handler.TypedNativeView?.UpdateText(entry);
+
+			// Any text update requires that we update any attributed string formatting
+			MapFormatting(handler, entry);
 		}
 
 		public static void MapTextColor(EntryHandler handler, IEntry entry)
@@ -67,6 +73,11 @@ public static void MapIsTextPredictionEnabled(EntryHandler handler, IEntry entry
 			handler.TypedNativeView?.UpdateIsTextPredictionEnabled(entry);
 		}
 
+		public static void MapMaxLength(EntryHandler handler, IEntry entry)
+		{
+			handler.TypedNativeView?.UpdateMaxLength(entry);
+		}
+
 		public static void MapPlaceholder(EntryHandler handler, IEntry entry)
 		{
 			handler.TypedNativeView?.UpdatePlaceholder(entry);
@@ -82,6 +93,27 @@ public static void MapReturnType(EntryHandler handler, IEntry entry)
 			handler.TypedNativeView?.UpdateReturnType(entry);
 		}
 
+		public static void MapFont(EntryHandler handler, IEntry entry)
+		{
+			_ = handler.Services ?? throw new InvalidOperationException($"{nameof(Services)} should have been set by base class.");
+
+			var fontManager = handler.Services.GetRequiredService<IFontManager>();
+
+			handler.TypedNativeView?.UpdateFont(entry, fontManager);
+		}
+
+		public static void MapFormatting(EntryHandler handler, IEntry entry)
+		{
+			handler.TypedNativeView?.UpdateMaxLength(entry);
+
+			// Update all of the attributed text formatting properties
+			handler.TypedNativeView?.UpdateCharacterSpacing(entry);
+
+			// Setting any of those may have removed text alignment settings,
+			// so we need to make sure those are applied, too
+			handler.TypedNativeView?.UpdateHorizontalTextAlignment(entry);
+		}
+
 		void OnEditingChanged(object? sender, EventArgs e) => OnTextChanged();
 
 		void OnEditingEnded(object? sender, EventArgs e) => OnTextChanged();
@@ -101,13 +133,23 @@ void OnTextChanged()
 				VirtualView.Text = nativeText;
 		}
 
-		public static void MapFont(EntryHandler handler, IEntry entry)
+		bool OnShouldChangeCharacters(UITextField textField, NSRange range, string replacementString)
 		{
-			_ = handler.Services ?? throw new InvalidOperationException($"{nameof(Services)} should have been set by base class.");
+			var currLength = textField?.Text?.Length ?? 0;
 
-			var fontManager = handler.Services.GetRequiredService<IFontManager>();
+			// fix a crash on undo
+			if (range.Length + range.Location > currLength)
+				return false;
 
-			handler.TypedNativeView?.UpdateFont(entry, fontManager);
+			if (VirtualView == null || TypedNativeView == null)
+				return false;
+
+			var addLength = replacementString?.Length ?? 0;
+			var remLength = range.Length;
+
+			var newLength = currLength + addLength - remLength;
+
+			return newLength <= VirtualView.MaxLength;
 		}
 	}
 }

src/Core/src/Platform/Android/EditTextExtensions.cs

@@ -1,4 +1,5 @@
-using Android.Content.Res;
+using System.Collections.Generic;
+using Android.Content.Res;
 using Android.Text;
 using Android.Util;
 using AndroidX.AppCompat.Widget;
@@ -76,9 +77,27 @@ public static void UpdateIsTextPredictionEnabled(this AppCompatEditText editText
 		public static void UpdateIsTextPredictionEnabled(this AppCompatEditText editText, IEditor editor)
 		{
 			if (editor.IsTextPredictionEnabled)
-				return;
+				editText.InputType &= ~InputTypes.TextFlagNoSuggestions;
+			else
+				editText.InputType |= InputTypes.TextFlagNoSuggestions;
+		}
+
+		public static void UpdateMaxLength(this AppCompatEditText editText, IEntry entry)
+		{
+			var currentFilters = new List<IInputFilter>(editText?.GetFilters() ?? new IInputFilter[0]);
+
+			for (var i = 0; i < currentFilters.Count; i++)
+			{
+				if (currentFilters[i] is InputFilterLengthFilter)
+				{
+					currentFilters.RemoveAt(i);
+					break;
+				}
+			}
+
+			currentFilters.Add(new InputFilterLengthFilter(entry.MaxLength));
 
-			editText.InputType |= InputTypes.TextFlagNoSuggestions;
+			editText?.SetFilters(currentFilters.ToArray());
 		}
 
 		public static void UpdatePlaceholder(this AppCompatEditText editText, IEntry entry)

src/Core/src/Platform/iOS/TextFieldExtensions.cs

@@ -54,6 +54,14 @@ public static void UpdateIsTextPredictionEnabled(this UITextField textField, IEn
 				textField.AutocorrectionType = UITextAutocorrectionType.No;
 		}
 
+		public static void UpdateMaxLength(this UITextField textField, IEntry entry)
+		{
+			var currentControlText = textField.Text;
+
+			if (currentControlText?.Length > entry.MaxLength)
+				textField.Text = currentControlText.Substring(0, entry.MaxLength);
+		}
+
 		public static void UpdatePlaceholder(this UITextField textField, IEntry entry)
 		{
 			textField.Placeholder = entry.Placeholder;

src/Core/tests/DeviceTests/Handlers/Editor/EditorHandlerTests.cs

@@ -55,5 +55,22 @@ public async Task IsTextPredictionEnabledCorrectly(bool isEnabled)
 
 			await ValidatePropertyInitValue(editor, () => editor.IsTextPredictionEnabled, GetNativeIsTextPredictionEnabled, isEnabled);
 		}
+
+		[Theory(DisplayName = "IsTextPredictionEnabled Updates Correctly")]
+		[InlineData(true, true)]
+		[InlineData(true, false)]
+		[InlineData(false, true)]
+		[InlineData(false, false)]
+		public async Task IsTextPredictionEnabledUpdatesCorrectly(bool setValue, bool unsetValue)
+		{
+			var editor = new EditorStub();
+
+			await ValidatePropertyUpdatesValue(
+				editor,
+				nameof(IEditor.IsTextPredictionEnabled),
+				GetNativeIsTextPredictionEnabled,
+				setValue,
+				unsetValue);
+		}
 	}
 }

src/Core/tests/DeviceTests/Handlers/Entry/EntryHandlerTests.cs

@@ -1,5 +1,4 @@
-using System;
-using System.Threading.Tasks;
+using System.Threading.Tasks;
 using Microsoft.Maui.DeviceTests.Stubs;
 using Microsoft.Maui.Handlers;
 using Xunit;
@@ -237,5 +236,53 @@ public async Task TextChangedEventsFireCorrectly(string initialText, string newT
 			else
 				Assert.Equal(0, eventFiredCount);
 		}
+
+		[Theory(DisplayName = "MaxLength Initializes Correctly")]
+		[InlineData(2)]
+		[InlineData(5)]
+		[InlineData(8)]
+		[InlineData(10)]
+		public async Task MaxLengthInitializesCorrectly(int maxLength)
+		{
+			const string text = "Lorem ipsum dolor sit amet";
+			var expectedText = text.Substring(0, maxLength);
+
+			var entry = new EntryStub()
+			{
+				MaxLength = maxLength,
+				Text = text
+			};
+
+			var nativeText = await GetValueAsync(entry, GetNativeText);
+
+			Assert.Equal(expectedText, nativeText);
+			Assert.Equal(expectedText, entry.Text);
+		}
+
+		[Theory(DisplayName = "MaxLength Clips Native Text Correctly")]
+		[InlineData(2)]
+		[InlineData(5)]
+		[InlineData(8)]
+		[InlineData(10)]
+		public async Task MaxLengthClipsNativeTextCorrectly(int maxLength)
+		{
+			const string text = "Lorem ipsum dolor sit amet";
+			var expectedText = text.Substring(0, maxLength);
+
+			var entry = new EntryStub()
+			{
+				MaxLength = maxLength,
+			};
+
+			var nativeText = await GetValueAsync(entry, handler =>
+			{
+				entry.Text = text;
+
+				return GetNativeText(handler);
+			});
+
+			Assert.Equal(expectedText, nativeText);
+			Assert.Equal(expectedText, entry.Text);
+		}
 	}
-}
+}

src/Core/tests/DeviceTests/Handlers/Entry/EntryHandlerTests.iOS.cs

@@ -85,7 +85,6 @@ public async Task ReturnTypeInitializesCorrectly()
 			Assert.Equal(expectedValue, values.NativeViewValue);
 		}
 
-
 		UITextField GetNativeEntry(EntryHandler entryHandler) =>
 			(UITextField)entryHandler.View;
 

src/Core/tests/DeviceTests/Stubs/EntryStub.cs

@@ -26,6 +26,8 @@ public string Text
 
 		public Font Font { get; set; }
 
+		public int MaxLength { get; set; } = int.MaxValue;
+
 		public TextAlignment HorizontalTextAlignment { get; set; }
 
 		public ReturnType ReturnType { get; set; }