Customise "Done" button in Forms picker with an Effect

PickerTunerEffect.Droid.cs

using System;
using Xamarin.Forms;
using Xamarin.Forms.Platform.Android;
using System.Reflection;
using Android.Views;
using Android.App;
using static Android.Views.View;
using Android.Content;
using PickerTest.Droid;

[assembly:ResolutionGroupName("Xamarin")]
[assembly:ExportEffect(typeof(PickerTunerEffect), "PickerTunerEffect")]
namespace PickerTest.Droid
{
	public class PickerTunerEffect : PlatformEffect
	{
		public PickerTunerEffect()
		{
		}

		public IntPtr Handle => throw new NotImplementedException();

		public void Dispose()
		{
		}

		public void OnClick(Android.Views.View v)
		{
			
		}

		protected override void OnAttached()
		{
			Control.SetOnClickListener(new CustomPickerListener(Container));
		}

		protected override void OnDetached()
		{
		}

		class CustomPickerListener : Java.Lang.Object, IOnClickListener
		{
			public CustomPickerListener(ViewGroup renderer)
			{
				_renderer = renderer;
			}

			ViewGroup _renderer;

			public void OnClick(global::Android.Views.View v)
			{
				if (_renderer == null)
				{
					return;
				}

				var dynClickHandler = _renderer.GetType().GetMethod("OnClick", BindingFlags.NonPublic | BindingFlags.Instance);
				dynClickHandler.Invoke(_renderer, null);

				var field = typeof(Xamarin.Forms.Platform.Android.AppCompat.PickerRenderer).GetField("_dialog", BindingFlags.NonPublic | BindingFlags.GetField | BindingFlags.Instance);
				var alertDialog = field.GetValue(_renderer) as AlertDialog;
				var btn = alertDialog.GetButton((int)DialogButtonType.Negative);
				btn.Text = "Custom Title!";	
			}
		}
	}
}

PickerTunerEffect.iOS.cs

using System;
using PickerTest.iOS;
using UIKit;
using Xamarin.Forms;
using Xamarin.Forms.Platform.iOS;

[assembly:ResolutionGroupName("Xamarin")]
[assembly:ExportEffect(typeof(PickerTunerEffect), "PickerTunerEffect")]
namespace PickerTest.iOS
{
	public class PickerTunerEffect : PlatformEffect
	{
		public PickerTunerEffect()
		{
		}

		UIToolbar _toolbar;
		UIBarButtonItem _doneBtn;

		protected override void OnAttached()
		{
			var textField = Control;
			_toolbar = textField.InputAccessoryView as UIToolbar;
			_doneBtn = _toolbar.Items[1];
			_toolbar.SetItems(new UIBarButtonItem[] {
				new UIBarButtonItem(UIBarButtonSystemItem.FlexibleSpace),
				new UIBarButtonItem("Custom Title!", UIBarButtonItemStyle.Done, HandleButtonClicked)
			}, false);
		}

		protected override void OnDetached()
		{
			_toolbar.Items = new UIBarButtonItem[] { };
			_toolbar = null;
			_doneBtn = null;
		}

		void HandleButtonClicked(object sender, EventArgs e)
		{
			UIApplication.SharedApplication.SendAction(_doneBtn.Action, _doneBtn.Target, sender: null, forEvent: null);
		}
	}
}