MonoGame_AdMobCrash_Activity1.cs

using Android.App;
using Android.Content.PM;
using Android.Gms.Ads;
using Android.OS;
using Android.Views;
using System;

namespace AdMobTest
{
    [Activity(Label = "AdMobTest"
        , MainLauncher = true
        , Icon = "@drawable/icon"
        , Theme = "@style/Theme.Splash"
        , AlwaysRetainTaskState = true
        , LaunchMode = Android.Content.PM.LaunchMode.SingleInstance
        , ScreenOrientation = ScreenOrientation.FullUser
        , ConfigurationChanges = ConfigChanges.Orientation | ConfigChanges.Keyboard | ConfigChanges.KeyboardHidden | ConfigChanges.ScreenSize)]
    public class Activity1 : Microsoft.Xna.Framework.AndroidGameActivity, IAdProvider
    {
        private InterstitialAd _ad;

        protected override void OnCreate(Bundle bundle)
        {
            base.OnCreate(bundle);

            CreateAndLoadAd();

            var g = new Game1(this);
            SetContentView((View)g.Services.GetService(typeof(View)));
            g.Run();
        }

        private void CreateAndLoadAd()
        {
            _ad = new InterstitialAd(this);
            // Obtain an ad unit id and replace the string below with it, then uncomment :)
            //string adUnitID = "<< YOUR AD UNIT ID >>";
            _ad.AdUnitId = adUnitID;

            if (_ad.AdListener != null)
            {
                _ad.AdListener.Dispose();
                _ad.AdListener = null;
            }

            var listener = new MyAdListener();
            listener.AdLoaded += (sender, e) =>
            {
                this.AdReady = true;
                System.Diagnostics.Debug.WriteLine("*** Ad loaded and ready.");
            };

            listener.AdClosed += (sender, e) => RequestAndLoadAd();
            _ad.AdListener = listener;

            RequestAndLoadAd();
        }

        private void RequestAndLoadAd()
        {
            this.AdReady = false;
            System.Diagnostics.Debug.WriteLine("*** Requesting and loading new ad.");
            var requestBuilder = new AdRequest.Builder().AddTestDevice(AdRequest.DeviceIdEmulator);
            var request = requestBuilder.Build();

            _ad.LoadAd(request);
        }

        public void ShowAd()
        {
            System.Diagnostics.Debug.WriteLine("*** ShowAd called.");
            if (_ad != null && _ad.IsLoaded == true)
            {
                _ad.Show();
            }
        }

        public bool AdReady { get; private set; } = false;
    }

    public class MyAdListener : AdListener
    {
        public event EventHandler AdLoaded;
        public event EventHandler AdClosed;

        public override void OnAdLoaded()
        {
            base.OnAdLoaded();

            if (this.AdLoaded != null)
                this.AdLoaded(this, new EventArgs());
        }

        public override void OnAdClosed()
        {
            base.OnAdClosed();

            if (this.AdClosed != null)
                this.AdClosed(this, new EventArgs());
        }
    }
}