Cross platform CheckBox control using unicode signs, with some bindable properties

An Example Usage of cross platform checkbox

... 	
	var checkBox = new CheckBox();
	MainPage = new ContentPage() {
		Content = checkBox
	};
... 

CheckBox.cs

using System;
using Xamarin.Forms;

namespace F4M.Framework.Xma.Controls {

	/// <summary>
	/// The check box checked event args.
	/// </summary>
	public class CheckboxChangedEventArgs : EventArgs {
		/// <summary>
		/// Initializes a new instance of the <see cref="CheckboxChangedEventArgs"/> class.
		/// </summary>
		/// <param name="item">The Item. Use this as a tag</param>
		/// <param name="isChecked">if set to <c>true</c> [new value].</param>
		public CheckboxChangedEventArgs(object item, bool isChecked) {
			IsChecked = isChecked;
			Item = item;
		}

		/// <summary>
		/// Gets the Item. Use it to reference anything you want. Works like a Tag
		/// </summary>
		/// <value>
		/// The Item.
		/// </value>
		public object Item { get; private set; }

		/// <summary>
		/// Gets a value indicating whether this instance is checked.
		/// </summary>
		/// <value>
		/// <c>true</c> if this instance is checked; otherwise, <c>false</c>.
		/// </value>
		public bool IsChecked { get; private set; }
	}

	/// <summary>
	/// A typical checkbox control
	/// </summary>
	/// <remarks>
	/// If you want to use this control in XAML, you have to define the namespace first.
	/// <example>
	/// Example page definition
	/// <code lang="xml">
	/// <![CDATA[
	/// <ContentPage xmlns="http://xamarin.com/schemas/2014/forms"
	///		xmlns:x="http://schemas.microsoft.com/winfx/2009/xaml"
	///		x:Class="F4M.AdapterDemo.Views.CheckboxSampleView"
	///		xmlns:controls="clr-namespace:F4M.Framework.Xma.Controls;assembly=F4M.Framework.Xma">
	///		<StackLayout>
	///			<controls:Item IsChecked="true"/>
	///		</StackLayout>
	/// </ContentPage>
	/// ]]>
	/// </code>
	/// </example>
	/// </remarks>
	public class CheckBox : ContentView {
		private Label _checkboxControl;
		private readonly string _checkOff;
		private readonly string _checkOn;
		
		#region IsChecked		
		/// <summary>
		/// Occurs when control gets [checked].
		/// </summary>
		public event EventHandler<CheckboxChangedEventArgs> Checked;

		/// <summary>
		/// Gets or sets a value indicating whether this instance is checked.
		/// </summary>
		/// <value>
		/// <c>true</c> if this instance is checked; otherwise, <c>false</c>.
		/// </value>
		public bool IsChecked {
			get { return (bool)GetValue(IsCheckedProperty); }
			set { SetValue(IsCheckedProperty, value); }
		}

		/// <summary>
		/// The is checked property
		/// </summary>
		public static BindableProperty IsCheckedProperty = BindableProperty.Create<CheckBox, bool>(
			o => o.IsChecked, 
			default(bool),
			propertyChanged: OnIsCheckedPropertyChanged);

		/// <summary>
		/// Called when [IsChecked] property changed.
		/// </summary>
		/// <param name="sender">The sender.</param>
		/// <param name="oldValue">if set to <c>true</c> [old value].</param>
		/// <param name="newValue">if set to <c>true</c> [new value].</param>
		private static void OnIsCheckedPropertyChanged(BindableObject sender, bool oldValue, bool newValue) {
			var checkBox = (CheckBox)sender;
			var doCheck = newValue;
			if (doCheck) {
				checkBox.TransitionToChecked();
			} else {
				checkBox.TransitionToUnchecked();
			}

			if (checkBox.Checked != null) {
				checkBox.Checked(checkBox, new CheckboxChangedEventArgs(checkBox.Item, doCheck));
			}
		}

		#endregion

		#region Item

		/// <summary>
		/// Gets or sets the item. Use this like a tag if you want to bind additional data
		/// </summary>
		/// <value>
		/// The item.
		/// </value>
		public object Item {
			get { return GetValue(ItemProperty); }
			set { SetValue(ItemProperty, value); }
		}

		/// <summary>
		/// The item property
		/// </summary>
		public static BindableProperty ItemProperty = BindableProperty.Create<CheckBox, object>(
			o => o.Item,
			default(object),
			propertyChanged: OnItemPropertyChanged);

		/// <summary>
		/// Called when [Item] property changed.
		/// </summary>
		/// <param name="sender">The sender.</param>
		/// <param name="oldvalue">The old value.</param>
		/// <param name="newvalue">The new value.</param>
		private static void OnItemPropertyChanged(BindableObject sender, object oldvalue, object newvalue) {
		}

		#endregion

		#region FontSize

		/// <summary>
		/// Gets or sets the size of the font.
		/// </summary>
		/// <value>
		/// The size of the font.
		/// </value>
		public double FontSize {
			get { return (double)GetValue(FontSizeProperty); }
			set { SetValue(FontSizeProperty, value); }
		}

		/// <summary>
		/// The font size property
		/// </summary>
		public static BindableProperty FontSizeProperty = BindableProperty.Create<CheckBox, double>(o => o.FontSize, -1.0, propertyChanged: OnFontSizePropertyChanged);

		/// <summary>
		/// Called when [FontSize] property changed.
		/// </summary>
		/// <param name="sender">The sender.</param>
		/// <param name="oldvalue">The old value.</param>
		/// <param name="newvalue">The new value.</param>
		private static void OnFontSizePropertyChanged(BindableObject sender, double oldvalue, double newvalue) {
			var checkBox = (CheckBox) sender;
			checkBox._checkboxControl.FontSize = newvalue;
		}

		#endregion

		private void TransitionToChecked() {
			_checkboxControl.Text = _checkOn;
		}

		private void TransitionToUnchecked() {
			_checkboxControl.Text = _checkOff;
		}

		/// <summary>
		/// Initialize a new instance of <see cref="CheckBox"/>.
		/// </summary>
		public CheckBox() {
			_checkOn = GetCheckOnSymbol();
			_checkOff = GetCheckOffSymbol();
			InitCheckboxControl();
			SetupView();
			RegisterGestureRecognizers();
		}

		private string GetCheckOffSymbol() {
			var result = "unknownCheckboxOffSymbol";
			Device.OnPlatform(
				Android: () => { result = "\u25FB"; },
				Default: () => { result = "\u2610"; }
			);

			return result;
		}

		private string GetCheckOnSymbol() {
			var result = "unknownCheckboxOffSymbol";
			Device.OnPlatform(
				Android: () => { result = "\u25FC"; },
				Default: () => { result = "\u2611"; }
			);

			return result;
		}

		private void InitCheckboxControl() {
			_checkboxControl = new Label { Text = IsChecked ? _checkOn : _checkOff };
		}

		private void SetupView() {
			Content = _checkboxControl;
		}

		private void RegisterGestureRecognizers() {
			var tabGesture = new TapGestureRecognizer();
			tabGesture.Command = new Command(ToggleCheckbox);
			_checkboxControl.GestureRecognizers.Add(tabGesture);
		}

		private void ToggleCheckbox() {
			IsChecked = !IsChecked;
		}
	}
}