Nullable DatePicker Xamarin - Update from jrgcubano

APPNullableDatePicker.cs

using System;
using System.Collections.Generic;
using System.Text;
using Xamarin.Forms;

namespace NullableDateAPP.Controls
{
    public class NullableDatePicker : DatePicker
    {
        public NullableDatePicker() : base()
        {


        }

        /// <summary>
        /// The font property
        /// </summary>
        public static readonly BindableProperty FontProperty =
            BindableProperty.Create("Font", typeof(Font), typeof(NullableDatePicker), new Font());

        /// <summary>
        /// The NullableDate property
        /// </summary>
        public static readonly BindableProperty NullableDateProperty =
            BindableProperty.Create("NullableDate", typeof(DateTime?), typeof(NullableDatePicker), null, BindingMode.TwoWay);

        /// <summary>
        /// The XAlign property
        /// </summary>
        public static readonly BindableProperty XAlignProperty =
            BindableProperty.Create("XAlign", typeof(TextAlignment), typeof(NullableDatePicker),
            TextAlignment.Start);

        /// <summary>
        /// The HasBorder property
        /// </summary>
        public static readonly BindableProperty HasBorderProperty =
            BindableProperty.Create("HasBorder", typeof(bool), typeof(NullableDatePicker), true);

        /// <summary>
        /// The Placeholder property
        /// </summary>
        public static readonly BindableProperty PlaceholderProperty =
            BindableProperty.Create("Placeholder", typeof(string), typeof(NullableDatePicker), string.Empty, BindingMode.OneWay);

        /// <summary>
        /// The PlaceholderTextColor property
        /// </summary>
        public static readonly BindableProperty PlaceholderTextColorProperty =
            BindableProperty.Create("PlaceholderTextColor", typeof(Color), typeof(NullableDatePicker), Color.Default);


        /// <summary>
        /// Gets or sets the Font
        /// </summary>
        public Font Font
        {
            get { return (Font)GetValue(FontProperty); }
            set { SetValue(FontProperty, value); }
        }

        /// <summary>
        /// Get or sets the NullableDate
        /// </summary>
        public DateTime? NullableDate
        {
            get { return (DateTime?)GetValue(NullableDateProperty); }
            set
            {
                if (value != NullableDate)
                {
                    SetValue(NullableDateProperty, value);
                    UpdateDate();
                }
            }
        }

        /// <summary>
        /// Gets or sets the X alignment of the text
        /// </summary>
        public TextAlignment XAlign
        {
            get { return (TextAlignment)GetValue(XAlignProperty); }
            set { SetValue(XAlignProperty, value); }
        }


        /// <summary>
        /// Gets or sets if the border should be shown or not
        /// </summary>
        public bool HasBorder
        {
            get { return (bool)GetValue(HasBorderProperty); }
            set { SetValue(HasBorderProperty, value); }
        }

        /// <summary>
        /// Get or sets the PlaceHolder
        /// </summary>
        public string Placeholder
        {
            get { return (string)GetValue(PlaceholderProperty); }
            set { SetValue(PlaceholderProperty, value); }
        }

        /// <summary>
        /// Sets color for placeholder text
        /// </summary>
        public Color PlaceholderTextColor
        {
            get { return (Color)GetValue(PlaceholderTextColorProperty); }
            set { SetValue(PlaceholderTextColorProperty, value); }
        }

        protected override void OnBindingContextChanged()
        {
            base.OnBindingContextChanged();
            UpdateDate();
        }

        protected override void OnPropertyChanged(string propertyName = null)
        {
            base.OnPropertyChanged(propertyName);

            if (propertyName == DateProperty.PropertyName)
            {
                NullableDate = Date;
            }

            if (propertyName == NullableDateProperty.PropertyName)
            {
                if (NullableDate.HasValue)
                {
                    Date = NullableDate.Value;
                    OnPropertyChanged(DateProperty.PropertyName);
                }
            }
        }

        private void UpdateDate()
        {
            if (NullableDate.HasValue)
            {
                Date = NullableDate.Value;
            }
            else
            {
                Date = DateTime.Today;
            }
        }
    }
}

CheckColorExtensions.cs

using UIKit;
using Xamarin.Forms;

namespace NullableDateAPP.iOS.Extensions
{
    /// <summary>
    /// Color extensions
    /// </summary>
    public static class CheckColorExtensions
    {
        internal static readonly UIColor SeventyPercentGrey = new UIColor(0.7f, 0.7f, 0.7f, 1);

        public static bool IsDefault(this Color color) => Color.Default == color;
    }
}

DroidNullableDatePickerRenderer.cs

using Android.Views; 
using System.ComponentModel;
using Xamarin.Forms;
using Xamarin.Forms.Platform.Android;
using NullableDateAPP.Droid.Renderer;
using Android.Content;
using NullableDateAPP.Controls;
using System;
using Android.App;
using System.Globalization;

[assembly: ExportRenderer(typeof(NullableDatePicker), typeof(NullableDatePickerRenderer))]
namespace NullableDateAPP.Droid.Renderer
{
    public class NullableDatePickerRenderer : DatePickerRenderer
    {
        public NullableDatePickerRenderer(Context context): base(context)
        { 
        }

        
        protected override DatePickerDialog CreateDatePickerDialog(int year, int month, int day)
        {
            var dialog = base.CreateDatePickerDialog(year, month, day); 
            //capture OK click
            dialog.DateSet += Dialog_DateSet;
            return dialog;
        }

        private void Dialog_DateSet(object sender, DatePickerDialog.DateSetEventArgs e)
        {
            var view = (NullableDatePicker)Element;
            view.NullableDate = view.Date; 
        }

        protected override void OnElementChanged(ElementChangedEventArgs<DatePicker> e)
        {
            base.OnElementChanged(e);

            //Remove line under input
            Control?.SetBackgroundColor(Android.Graphics.Color.Transparent);

            var view = Element as NullableDatePicker;

            if (view != null)
            {
                SetFont(view);
                SetTextAlignment(view);
                // SetBorder(view);
                SetNullableText(view);
                SetPlaceholder(view);
                SetPlaceholderTextColor(view);
            }

        }

        protected override void OnElementPropertyChanged(object sender, PropertyChangedEventArgs e)
        {
            base.OnElementPropertyChanged(sender, e);

            var view = (NullableDatePicker)Element;

            if (e.PropertyName == NullableDatePicker.FontProperty.PropertyName)
                SetFont(view);
            else if (e.PropertyName == NullableDatePicker.XAlignProperty.PropertyName)
                SetTextAlignment(view);
            // else if (e.PropertyName == NullableDatePicker.HasBorderProperty.PropertyName)
            //  SetBorder(view);
            else if (e.PropertyName == NullableDatePicker.NullableDateProperty.PropertyName)
                SetNullableText(view);
            else if (e.PropertyName == NullableDatePicker.PlaceholderProperty.PropertyName)
                SetPlaceholder(view);
            else if (e.PropertyName == NullableDatePicker.PlaceholderTextColorProperty.PropertyName)
                SetPlaceholderTextColor(view);

        }

        /// <summary>
        /// Sets the text alignment.
        /// </summary>
        /// <param name="view">The view.</param>
        private void SetTextAlignment(NullableDatePicker view)
        {
            switch (view.XAlign)
            {
                case Xamarin.Forms.TextAlignment.Center:
                    Control.Gravity = GravityFlags.CenterHorizontal;
                    break;
                case Xamarin.Forms.TextAlignment.End:
                    Control.Gravity = GravityFlags.End;
                    break;
                case Xamarin.Forms.TextAlignment.Start:
                    Control.Gravity = GravityFlags.Start;
                    break;
            }
        }

        /// <summary>
        /// Sets the font.
        /// </summary>
        /// <param name="view">The view.</param>
        private void SetFont(NullableDatePicker view)
        {
            if (view.Font != Font.Default)
            {
                Control.TextSize = view.Font.ToScaledPixel();
                //Control.Typeface = view.Font.ToExtendedTypeface(Context);
            }
        }

        /// <summary>
        /// Set text based on nullable value
        /// </summary>
        /// <param name="view"></param>
        private void SetNullableText(NullableDatePicker view)
        {
            if (view.NullableDate == null)
                Control.Text = string.Empty;
        }

        /// <summary>
        /// Set the placeholder
        /// </summary>
        /// <param name="view"></param>
        private void SetPlaceholder(NullableDatePicker view)
        {
            Control.Hint = view.Placeholder;
        }

        /// <summary>
        /// Sets the color of the placeholder text.
        /// </summary>
        /// <param name="view">The view.</param>
        private void SetPlaceholderTextColor(NullableDatePicker view)
        {
            if (view.PlaceholderTextColor != Color.Default)
            {
                Control.SetHintTextColor(view.PlaceholderTextColor.ToAndroid());
            }
        }
    }
}

IOsNullableDatePickerRenderer.cs

using Xamarin.Forms.Platform.iOS;
using Xamarin.Forms; 
using System.ComponentModel;
using UIKit; 
using Foundation;
using System;
using CoreGraphics;
using NullableDateAPP.Controls;
using NullableDateAPP.iOS.Renderer;
using NullableDateAPP.iOS.Extensions;

[assembly: ExportRenderer(typeof(NullableDatePicker), typeof(NullableDatePickerRenderer))]
namespace NullableDateAPP.iOS.Renderer
{
    public class NullableDatePickerRenderer : DatePickerRenderer
    {
        protected override void OnElementChanged(ElementChangedEventArgs<DatePicker> e)
        {
            base.OnElementChanged(e);

            var view = Element as NullableDatePicker;
              
            if (view != null)
            {
                SetFont(view);
                SetTextAlignment(view);
                SetBorder(view);
                SetNullableText(view);
                SetPlaceholderTextColor(view);

                ResizeHeight();
            }
        }

         
        protected override void OnElementPropertyChanged(object sender, PropertyChangedEventArgs e)
        {
            base.OnElementPropertyChanged(sender, e);

            var view = (NullableDatePicker)Element;

            if (e.PropertyName == NullableDatePicker.FontProperty.PropertyName)
                SetFont(view);
            else if (e.PropertyName == NullableDatePicker.XAlignProperty.PropertyName)
                SetTextAlignment(view);
            else if (e.PropertyName == NullableDatePicker.HasBorderProperty.PropertyName)
                SetBorder(view);
            else if (e.PropertyName == NullableDatePicker.NullableDateProperty.PropertyName)
                SetNullableText(view);
            else if (e.PropertyName == NullableDatePicker.PlaceholderTextColorProperty.PropertyName)
                SetPlaceholderTextColor(view);

            ResizeHeight();
        }

        /// <summary>
        /// Sets the text alignment.
        /// </summary>
        /// <param name="view">The view.</param>
        private void SetTextAlignment(NullableDatePicker view)
        {
            switch (view.XAlign)
            {
                case TextAlignment.Center:
                    Control.TextAlignment = UITextAlignment.Center;
                    break;
                case TextAlignment.End:
                    Control.TextAlignment = UITextAlignment.Right;
                    break;
                case TextAlignment.Start:
                    Control.TextAlignment = UITextAlignment.Left;
                    break;
            }
        }

        /// <summary>
        /// Sets the font.
        /// </summary>
        /// <param name="view">The view.</param>
        private void SetFont(NullableDatePicker view)
        {
            UIFont uiFont;
            if (view.Font != Font.Default && (uiFont = view.Font.ToUIFont()) != null)
                Control.Font = uiFont;
            else if (view.Font == Font.Default)
                Control.Font = UIFont.SystemFontOfSize(17f);
        }

        /// <summary>
        /// Sets the border.
        /// </summary>
        /// <param name="view">The view.</param>
        private void SetBorder(NullableDatePicker view)
        {
            Control.BorderStyle = view.HasBorder ? UITextBorderStyle.RoundedRect : UITextBorderStyle.None;
        }

        /// <summary>
        /// Set text based on nullable value
        /// </summary>
        /// <param name="view"></param>
        private void SetNullableText(NullableDatePicker view)
        {
            if (view.NullableDate == null)
                Control.Text = string.Empty;
        }

        /// <summary>
        /// Resizes the height.
        /// </summary>
        private void ResizeHeight()
        {
            if (Element.HeightRequest >= 0) return;

            var height = Math.Max(Bounds.Height,
                new UITextField { Font = Control.Font }.IntrinsicContentSize.Height) * 2;

            Control.Frame = new CGRect(0.0f, 0.0f, (nfloat)Element.Width, (nfloat)height);

            Element.HeightRequest = height;
        }

        /// <summary>
        /// Sets the color of the placeholder text.
        /// </summary>
        /// <param name="view">The view.</param>
        private void SetPlaceholderTextColor(NullableDatePicker view)
        {
            if (!string.IsNullOrEmpty(view.Placeholder))
            {
                var foregroundUIColor = view.PlaceholderTextColor.ToUIColor(CheckColorExtensions.SeventyPercentGrey);
                var backgroundUIColor = view.BackgroundColor.ToUIColor();
                var targetFont = Control.Font;
                Control.AttributedPlaceholder = new NSAttributedString(view.Placeholder, targetFont, foregroundUIColor, backgroundUIColor);
            }
        }
    }
}