<uses-permission android:name="android.permission.ACCESS_NETWORK_STATE" />

<uses-permission android:name="android.permission.INTERNET" /> 

<application

        android:allowBackup="true"

        android:icon="@drawable/ic_launcher"

        android:label="@string/app_name"

        android:theme="@style/AppTheme" >

        <meta-data

        android:name="com.google.android.gms.version"

        android:value="@integer/google_play_services_version"/>

....

<activity

            android:name="com.google.android.gms.ads.AdActivity"

 android:configChanges="keyboard|keyboardHidden|orientation|screenLayout|uiMode|screenSize|smallestScreenSize" />

 <com.google.android.gms.ads.AdView 

          xmlns:ads="http://schemas.android.com/apk/res-auto"

    android:id="@+id/mainAd"

    android:layout_width="fill_parent"

    android:layout_height="0dp"

    android:layout_weight="1"

    ads:adUnitId="ca-app-pub-xxxxxxxxxx" //애드몹사이트에서 추가한 광고 ID를 적어준다.

    ads:adSize="BANNER"

    android:layout_gravity="bottom"

    android:gravity="bottom"

    android:orientation="horizontal"

    /> 

import com.google.android.gms.ads.AdRequest;

import com.google.android.gms.ads.AdView;

import com.google.android.gms.ads.InterstitialAd;

InterstitialAd interstitial;

private AdView adView;

void Start () {

    interstitial = new InterstitialAd(this);

        interstitial.setAdUnitId("ca-app-pub-xxxxxxxxxx"); //애드몹사이트에서 추가한 광고 ID를 적어준다.

        // Create an empty ad request.

        AdRequest request = new AdRequest.Builder().build();

        // Load the Ads with the request.

        interstitial.loadAd(request); //전면광고로 할 경우 필요함. 

      //Adview를 생성합니다. 

        adView = (AdView)findViewById(R.id.mainAd);

        AdRequest adRequest = new AdRequest.Builder()

                            //.addTestDevice("B3EEABB8EE11C2BE770B684D95219ECB") //TestDevice인 경우 필요함.

        .build();

        adView.loadAd(adRequest);

    } 

전면 광고 인 경우

interstitial.show(); //이렇게 하면 전면광고로 표시됨.