Xamarin.Forms custom side menu

MainPage.xaml

<?xml version="1.0" encoding="utf-8" ?>
<ContentPage
    x:Class="SideMenuTest.MainPage"
    xmlns="http://xamarin.com/schemas/2014/forms"
    xmlns:x="http://schemas.microsoft.com/winfx/2009/xaml">

    <AbsoluteLayout>
        <StackLayout
            AbsoluteLayout.LayoutBounds="0,0,1,1"
            AbsoluteLayout.LayoutFlags="All"
            Background="Blue">
            <Label
                FontSize="Large"
                Text="12345678901234567890"
                TextColor="White" />
        </StackLayout>

        <BoxView
            AbsoluteLayout.LayoutBounds="0,0,AutoSize,1"
            AbsoluteLayout.LayoutFlags="XProportional,YProportional,HeightProportional"
            Opacity="0"
            WidthRequest="16">
            <BoxView.GestureRecognizers>
                <PanGestureRecognizer PanUpdated="Anchor_OnPanUpdated" />
            </BoxView.GestureRecognizers>
        </BoxView>

        <StackLayout
            x:Name="SideMenu"
            AbsoluteLayout.LayoutBounds="-240,0,AutoSize,1"
            AbsoluteLayout.LayoutFlags="YProportional,HeightProportional"
            Background="Green"
            WidthRequest="240">
            <StackLayout.GestureRecognizers>
                <PanGestureRecognizer PanUpdated="SideMenu_OnPanUpdated" />
            </StackLayout.GestureRecognizers>
        </StackLayout>

    </AbsoluteLayout>

</ContentPage>

MainPage.xaml.cs

namespace SideMenuTest
{
    using System;

    using Xamarin.Forms;

    public partial class MainPage
    {
        public MainPage()
        {
            InitializeComponent();
        }

        private bool showSideMenu;
        private double lastPosition;

        private void Anchor_OnPanUpdated(object sender, PanUpdatedEventArgs e)
        {
            if (e.StatusType == GestureStatus.Started)
            {
                ViewExtensions.CancelAnimations(SideMenu);

                var rect = AbsoluteLayout.GetLayoutBounds(SideMenu);
                showSideMenu = rect.X > -SideMenu.Width;
                lastPosition = rect.X;
            }
            else if (e.StatusType == GestureStatus.Running)
            {
                var rect = AbsoluteLayout.GetLayoutBounds(SideMenu);
                rect.X = Math.Max(Math.Min(0, e.TotalX - SideMenu.Width), -SideMenu.Width);
                AbsoluteLayout.SetLayoutBounds(SideMenu, rect);

                if (rect.X > lastPosition)
                {
                    showSideMenu = true;
                }
                else if (rect.X < lastPosition)
                {
                    showSideMenu = false;
                }
                lastPosition = rect.X;
            }
            else if (e.StatusType == GestureStatus.Completed)
            {
                var rect = AbsoluteLayout.GetLayoutBounds(SideMenu);
                var pos = showSideMenu ? 0 : -SideMenu.Width;
                var length = (uint)(250 * Math.Abs(pos - rect.X) / SideMenu.Width);

                SideMenu.Animate("Slide", x =>
                {
                    rect.X = x;
                    AbsoluteLayout.SetLayoutBounds(SideMenu, rect);
                }, rect.X, pos, length: length);
            }
        }

        private void SideMenu_OnPanUpdated(object sender, PanUpdatedEventArgs e)
        {
            if (e.StatusType == GestureStatus.Started)
            {
                ViewExtensions.CancelAnimations(SideMenu);

                var rect = AbsoluteLayout.GetLayoutBounds(SideMenu);
                showSideMenu = rect.X > -SideMenu.Width;
                lastPosition = rect.X;
            }
            else if (e.StatusType == GestureStatus.Running)
            {
                var rect = AbsoluteLayout.GetLayoutBounds(SideMenu);
                rect.X = Math.Max(Math.Min(0, rect.X + e.TotalX), -SideMenu.Width);
                AbsoluteLayout.SetLayoutBounds(SideMenu, rect);

                if (rect.X > lastPosition)
                {
                    showSideMenu = true;
                }
                else if (rect.X < lastPosition)
                {
                    showSideMenu = false;
                }
                lastPosition = rect.X;
            }
            else if (e.StatusType == GestureStatus.Completed)
            {
                var rect = AbsoluteLayout.GetLayoutBounds(SideMenu);
                var pos = showSideMenu ? 0 : -SideMenu.Width;
                var length = (uint)(250 * Math.Abs(pos - rect.X) / SideMenu.Width);

                SideMenu.Animate("Slide", x =>
                {
                    rect.X = x;
                    AbsoluteLayout.SetLayoutBounds(SideMenu, rect);
                }, rect.X, pos, length: length);
            }
        }
    }
}