1. Poner el codigo en el evento OnCreate

com.google.android.gms.ads.MobileAds.initialize(this, "ca-app-pub-1306351702834787~5573843465");

com.google.android.gms.ads.AdView adView = new com.google.android.gms.ads.AdView(this);

adView.setAdSize(com.google.android.gms.ads.AdSize.SMART_BANNER);

adView.setAdUnitId("ca-app-pub-1306351702834787/2651386401");

linear6.addView(adView);


adView.loadAd(new com.google.android.gms.ads.AdRequest.Builder().build());


adView.setAdListener(new com.google.android.gms.ads.AdListener() {

@Override

public void onAdLoaded() {}

@Override

public void onAdFailedToLoad(int errorCode) {

showMessage(String.valueOf(errorCode));}
@Override

public void onAdOpened() {}

@Override

public void onAdClicked() {}

@Override

public void onAdLeftApplication() {}

@Override

public void onAdClosed() {}

});