Recently, I spent some time banging my head against the wall attempting to figure out how to add AdMob ads to my app. I read through all of the existing recommended blog posts and articles on the subject. I delved into stack overflow. I even perused the official documentation.

I decided that I needed to simplify and see if I could get it working in a sample app; then move it to my full app. (Spoiler alert I succeeded.)

I am sharing what worked for me.

I created an AdMob account at https://admob.google.com/home/

I set up an and App. For more information, see https://support.google.com/admob/answer/9989980?visit_id=637411851150652490-2677892110&rd=1.

I created an Add Unit. For more information, see https://support.google.com/admob/answer/6128738?visit_id=637411851150652490-2677892110&rd=1.

NOTE: You get both an App ID, created when you set up the app, and an Ad Unit ID, created when you create an Add Unit. I failed to Grok the difference, as well as where and when they important. The App ID is as you might surmise and application level identifier. You set it once for the entire app. In my case, I set in the AdroidManifest, but you can also set set it in code during the start up of your app. The Ad Unit ID is the identifier for a specific instance of an Ad at specified location if your UI. If I understand the AdMob documentation correctly, you can use multiple Ad Unit IDs in the same app.

I created a Blank Android Mobile App called AdMobSample.

I selected the "Blank" template to create what Microsoft calls an "empty app". In reality, it creates a simple single page app the is useful when you are trying out new techniques. At this time, I am only interested in Android apps so I made sure to uncheck iOS which is typically checked by default.

I used NuGet to add the Xamarin.GooglePlayServices.Ads plug-in to the app.

Note: I initially made the mistake of installing it for all the projects in the app. This caused the plug-in to fail to install with an error message that the plug-in is not compatible with .NET 2.0.

In the MainActivity.cs file of the Android Project, I added a using statement to reference Ads namespace:

using Android.Gms.Ads;

In the OnCreate method, I initialized the ads by calling MobileAds.Initialize:

base.OnCreate(savedInstanceState);

MobileAds.Initialize(ApplicationContext);
Xamarin.Essentials.Platform.Init(this, savedInstanceState);
global::Xamarin.Forms.Forms.Init(this, savedInstanceState);
LoadApplication(new App());

I modified the AndroidManifest.xml file located in the Properties folder of the Android project to specify the App ID for the app:

<?xml version="1.0" encoding="utf-8"?>
<manifest xmlns:android="http://schemas.android.com/apk/res/android" android:versionCode="1" android:versionName="1.0" package="com.companyname.admobsample">
    <uses-sdk android:minSdkVersion="21" android:targetSdkVersion="28" />
    <application android:label="AdMobSample.Android" android:theme="@style/MainTheme">
      <activity android:name="com.google.android.gms.ads.AdActivity" android:configChanges="keyboard|keyboardHidden|orientation|screenLayout|uiMode|screenSize|smallestScreenSize" android:theme="@android:style/Theme.Translucent" />
	  <!-- Set set this to YOUR APP ID-->
      <meta-data android:name="com.google.android.gms.ads.APPLICATION_ID" android:value="ca-app-pub-xxxxxxxxxxxxxxxx~yyyyyyyyyy" />
      <meta-data android:name="com.google.android.gms.ads.AD_MANAGER_APP" android:value="true" />
    </application>
    <uses-permission android:name="android.permission.ACCESS_NETWORK_STATE" />
</manifest>

To display the ad I had to add a view in the shared project. For more information on implementing a view, see Implementing a View.

In the shared project I added AdMobView.cs:

using Xamarin.Forms;

namespace AdMobSample.controls
{
	public class AdMobView : View
	{
		public static readonly BindableProperty AdUnitIdProperty = BindableProperty.Create(
				   nameof(AdUnitId),
				   typeof(string),
				   typeof(AdMobView),
				   string.Empty);

		public string AdUnitId
		{
			get => (string)GetValue(AdUnitIdProperty);
			set => SetValue(AdUnitIdProperty, value);
		}
	}
}

To create the view for Android I had to a custom view renderer. After the view is created you call SetNativeControl() to display it. For more information on view renderers, see .

In Android project I added AdMobViewRenderer.cs:

using System.ComponentModel;
using AdMobSample.controls;
using AdMobSample.Droid;
using Android.Content;
using Android.Gms.Ads;
using Android.Widget;
using Xamarin.Forms;
using Xamarin.Forms.Platform.Android;

[assembly: ExportRenderer(typeof(AdMobView), typeof(AdMobViewRenderer))]
namespace AdMobSample.Droid
{
	public class AdMobViewRenderer : ViewRenderer<AdMobView, AdView>
	{
		public AdMobViewRenderer(Context context) : base(context) { }

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

			if (e.NewElement != null && Control == null)
			{
				SetNativeControl(CreateAdView());
			}
		}

		protected override void OnElementPropertyChanged(object sender, PropertyChangedEventArgs e)
		{
			base.OnElementPropertyChanged(sender, e);

			if (e.PropertyName == nameof(AdView.AdUnitId))
				Control.AdUnitId = Element.AdUnitId;
		}

		
		private AdView CreateAdView()
		{
			var adView = new AdView(Context)
			{
				AdSize = AdSize.SmartBanner,
				AdUnitId = Element.AdUnitId
			};

			adView.LayoutParameters = new LinearLayout.LayoutParams(LayoutParams.MatchParent, LayoutParams.MatchParent);

			adView.LoadAd(new AdRequest
							.Builder()
							.Build());

			return adView;
		}
	}
}

Finally, I modified the MainPage.xaml by adding a reference to the view xmlns:local="clr-namespace:AdMobSample.controls" and I added the control in a stacklayout as follows <local:AdMobView AdUnitId="ca-app-pub-3940256099942544/6300978111" WidthRequest="320" HeightRequest="50"/>:

<?xml version="1.0" encoding="utf-8" ?>
<ContentPage xmlns="http://xamarin.com/schemas/2014/forms"
             xmlns:local="clr-namespace:AdMobSample.controls"
             xmlns:x="http://schemas.microsoft.com/winfx/2009/xaml"
             x:Class="AdMobSample.MainPage">
    <StackLayout>
        <Label Text="Display an Admob Banner!" 
           HorizontalOptions="Center"
           VerticalOptions="CenterAndExpand" />
        <!-- Place the Admob controls here -->
        <local:AdMobView AdUnitId="ca-app-pub-3940256099942544/6300978111" WidthRequest="320" HeightRequest="50"/>
    </StackLayout>
</ContentPage>

This displays a test ad using the Google supplied Test Ad Unit ID ca-app-pub-3940256099942544/6300978111. For more information on test ad units, see Test Ads.

Note: If you do not specify a width and Height request the ad does not display.