TypeInitializationException when running Admob Banner Ads on IPhone, works fine on Simulator Xamarin.Forms ios

Question

We are building a Xamarin.Forms Application and have Admob Ads in it. The Ads works fine on Simulator but gives a TypeInitializationException on IPhone 6s ios 13. The error is -

{System.TypeInitializationException: The type initializer for 'Google.MobileAds.AdSizeCons' threw an exception. ---> System.NullReferenceException: Object reference not set to an instance of an object. at Google.MobileAds.AdSizeCons.get_Banner () <0x114527170 + 0x00030> in <62f0bd410ddd4c31bdeb77ff27efb070>:0 at Google.MobileAds.AdSizeCons..cctor () <0x114526c60 + 0x00000> in <62f0bd410ddd4c31bdeb77ff27efb070>:0 --- End of inner exception stack trace ---

My code for Ads is -

AdView.cs

  public class AdMobBannerAd : View
    {
       
    }

CustomRenderer.cs

[assembly: ExportRenderer(typeof(AdMobBannerAd), typeof(AdMobViewRenderer))]

namespace Excercise.iOS.Renderers {

[Protocol]
public class AdMobViewRenderer : ViewRenderer<AdMobBannerAd, BannerView>
{
  
    string bannerId = "ca-app-pub-3940256099942544/2934735716";  // test ad id
    BannerView adView;
   // AdSize size = AdSize.SmartBanner;
    bool viewOnScreen;

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

        if (e.NewElement == null)
            return;

        if (e.OldElement == null)
        {
            adView = new BannerView(AdSizeCons.SmartBannerPortrait)
            //    adView = new BannerView()
            {
                AdUnitId = bannerId,
                RootViewController = GetRootViewController()
            };

            //adView.AdSize = AdSizeCons.SmartBannerPortrait
            //    ;
            adView.AdReceived += (sender, args) =>
            {
                if (!viewOnScreen) this.AddSubview(adView);
                viewOnScreen = true;
            };

            var request = Request.GetDefaultRequest();
            request.TestDevices = new[] { "xxxxxxx" };
            //   request.TestDevices =[];
            adView.LoadRequest(request);
            base.SetNativeControl(adView);
        }


    }

        private UIViewController GetRootViewController()
        {
            foreach (UIWindow window in UIApplication.SharedApplication.Windows)
            {
                if (window.RootViewController != null)
                {
                    return window.RootViewController;
                }
            }

            return null;
        }

AppDelegate.cs

  public override bool FinishedLaunching(UIApplication app, NSDictionary options)
    {
        try
        {

            global::Xamarin.Forms.Forms.Init();

            MobileAds.Configure("ca-app-pub-xxxxxxxxxxxx~xxxxxx");

            App.ScreenHeight = (int)UIScreen.MainScreen.Bounds.Height;
            App.ScreenWidth = (int)UIScreen.MainScreen.Bounds.Width;
           
            LoadApplication(new App());
        }
        catch(Exception ex)
        {
            string str = ex.Message;
        }
        return base.FinishedLaunching(app, options);
    }

Has anyone come across the same issue? Please help!

Thank you!

Answer 1

Change the order of: ... global::Xamarin.Forms.Forms.Init();

MobileAds.Configure("ca-app-pub-xxxxxxxxxxxx~xxxxxx"); ...

MobileAds need to come first.