MainActivity.cs

using System;

using Android.App;
using Android.Content;
using Android.Content.PM;
using Android.Runtime;
using Android.Views;
using Android.Widget;
using Android.OS;
using Android.Webkit;
using Xam.Plugin.WebView.Droid;

namespace SampleApp.Droid
{
    [Activity(Label = "SampleApp", Icon = "@drawable/icon", Theme = "@style/MainTheme", MainLauncher = true, ConfigurationChanges = ConfigChanges.ScreenSize | ConfigChanges.Orientation)]
    public class MainActivity : global::Xamarin.Forms.Platform.Android.FormsAppCompatActivity, IMainActivityWithStarting
    {
        protected override void OnCreate(Bundle bundle)
        {
            TabLayoutResource = Resource.Layout.Tabbar;
            ToolbarResource = Resource.Layout.Toolbar;

            base.OnCreate(bundle);
            
            FormsWebViewRenderer.Initialize();

            global::Xamarin.Forms.Forms.Init(this, bundle);
            LoadApplication(new App());
        }

        private Action<int, Result, Intent> _resultCallback;
        public void StartActivity(Intent intent, int requestCode, Action<int, Result, Intent> resultCallback)
        {
            _resultCallback = resultCallback;
            StartActivityForResult(intent, requestCode);
        }
        protected override void OnActivityResult(int requestCode, Result resultCode, Intent data)
        {
            base.OnActivityResult(requestCode, resultCode, data);
            if (_resultCallback != null)
            {
                _resultCallback(requestCode, resultCode, data);
                _resultCallback = null;
            }
        }
    }
}