Banner Adview

// XML................

<?xml version="1.0" encoding="utf-8"?>


<RelativeLayout
    xmlns:android="http://schemas.android.com/apk/res/android"
    android:layout_width="wrap_content"
    android:layout_height="wrap_content"
    xmlns:ads="http://schemas.android.com/apk/res-auto">

    <com.google.android.gms.ads.AdView
        android:id="@+id/webAdView"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_centerHorizontal="true"
        android:layout_alignParentBottom="true"
        ads:adSize="SMART_BANNER"
        ads:adUnitId="@string/banner_ad_unit_id">
    </com.google.android.gms.ads.AdView>


</RelativeLayout>


//JAVA......................
 MobileAds.initialize(this,getString(R.string.app_ad_id));
            AdView adView = findViewById(R.id.webAdView);
            AdRequest adRequest = new AdRequest.Builder().build();
            adView.loadAd(adRequest);