How to integrate Admob into Unity Android Build

I am using MacOS Mavericks, Unity 5 Personal Edition and GooglePlayService Rev 23 and Eclipse Juno.
For integrating Admob into Unity iOS see this post.

Download Unity plugin from here:

https://github.com/googleads/googleads-mobile-plugins/releases

At time of writing the latest  is Google Mobile Ads Unity Plugin v2.2

Download it and import to unity after creating a Plugins folder in Assets.

Insert the necessary code to call your Admob Banner and Interstitial ads. For me I wrote a custom script called AdsController.cs:

using UnityEngine;
using System.Collections;
using GoogleMobileAds.Api;
using System;  // For EventArgs

public class AdsController : MonoBehaviour {
   

    InterstitialAd interstitial;
    BannerView bannerView;

    void Start () {

        //------ Banner Ad -------
        // Create a 320x50 banner at the top of the screen.
        // Put your Admob banner ad id here
        bannerView = new BannerView(
            "ca-app-pub-xxxxxxxxxxxxxxxx/xxxxxxxxxx", AdSize.SmartBanner, AdPosition.Top);
        // Create ad request
        AdRequest request = new AdRequest.Builder().Build();
        // Load the banner with the request.
        bannerView.LoadAd(request);        

        bannerView.Show();

        //---- Interstitial Ad -----
        // Initialize an InterstitialAd.
        // Put your admob interstitial ad id here:
        interstitial = new InterstitialAd("ca-app-pub-xxxxxxxxxxxxxxxx/xxxxxxxxxx");

        //Add callback for when ad is loaded
        interstitial.AdLoaded += HandleAdLoaded;

        // Create an ad request.
        AdRequest requestInterstitial = new AdRequest.Builder().Build();
        // Load the interstitial with the request.
        interstitial.LoadAd(requestInterstitial);
    }
    
   

    public void HandleAdLoaded(object sender, EventArgs args) {
        
        interstitial.Show ();
    }

  
    void OnDestroy(){
        if (interstitial!=null) {
            interstitial.AdLoaded -= HandleAdLoaded;
            interstitial.Destroy ();
        }
        if(bannerView!=null){
            bannerView.Destroy ();
        }
    }

}

Put the script above in Game Over scene, or, Level Cleared scene. So that when the scene loads, the banner and interstitial ads get called and shown at the same time.

Open Eclipse Android SDK Manager and download the latest Google Play Service SDK:

Then copy and paste the google-play-services_lib folder located at ANDROID_SDK_LOCATION/extras/google/google_play_services/libproject,  into the Plugins/Android folder of your project as shown circled in red below:

Then modify the AndroidManifest.xml file shown above circled in green as follows:

<?xml version="1.0" encoding="utf-8"?>
<manifest xmlns:android="http://schemas.android.com/apk/res/android" android:installLocation="auto" 
package="com.site.myappname" android:versionName="1.0" android:versionCode="1">
  <supports-screens android:smallScreens="true" android:normalScreens="true" android:largeScreens="true" 
  android:xlargeScreens="true" android:anyDensity="true" />
  
  <!-- Google Mobile Ads Permissions -->
    <uses-permission android:name="android.permission.INTERNET" />
    <uses-permission android:name="android.permission.ACCESS_NETWORK_STATE" />
    
  <application android:icon="@drawable/app_icon" android:label="@string/app_name" android:debuggable="false">
    <!-- meta-data tag for Google Play services -->
    <meta-data android:name="com.google.android.gms.version" android:value="@integer/google_play_services_version"/>
    <activity android:name="com.unity3d.player.UnityPlayerProxyActivity" android:label="@string/app_name" 
    android:configChanges="fontScale|keyboard|keyboardHidden|locale|mnc|mcc|navigation|orientation|screenLayout|screenSize|smallestScreenSize|uiMode|touchscreen" >
    <meta-data android:name="unityplayer.ForwardNativeEventsToDalvik" android:value="true" />
      <intent-filter>
        <action android:name="android.intent.action.MAIN" />
        <category android:name="android.intent.category.LAUNCHER" />
      </intent-filter>
    </activity>
    <activity android:name="com.unity3d.player.UnityPlayerActivity" android:label="@string/app_name" android:configChanges="fontScale|keyboard|keyboardHidden|locale|mnc|mcc|navigation|orientation|screenLayout|screenSize|smallestScreenSize|uiMode|touchscreen" >
    </activity>
    <activity android:name="com.unity3d.player.UnityPlayerNativeActivity" android:label="@string/app_name" android:configChanges="fontScale|keyboard|keyboardHidden|locale|mnc|mcc|navigation|orientation|screenLayout|screenSize|smallestScreenSize|uiMode|touchscreen" >
      <meta-data android:name="unityplayer.ForwardNativeEventsToDalvik" android:value="true" />
      <meta-data android:name="android.app.lib_name" android:value="unity" />
    </activity>
    <activity android:name="com.unity3d.player.VideoPlayer" android:label="@string/app_name" android:configChanges="fontScale|keyboard|keyboardHidden|locale|mnc|mcc|navigation|orientation|screenLayout|screenSize|smallestScreenSize|uiMode|touchscreen" >
    </activity>
   
  </application>
  <uses-feature android:glEsVersion="0x00020000" />
  <uses-sdk android:minSdkVersion="9" android:targetSdkVersion="19" />
</manifest>

Make sure you do not add the Ads Activity because it is already included in the GooglePlayService Lib manifest file and will be merged with AndroidManifest.xml above during build.

Next, build the Unity Android .apk file  with the player setttings shown here (on right side of screen):

Transfer the apk to your android phone/tablet and run.