<LinearLayout
            android:id="@+id/admob_layout"
            android:layout_width="match_parent"
            android:layout_height="wrap_content"
            android:layout_alignParentBottom="true"
            android:gravity="center"
            android:visibility="visible" >

            <com.google.android.gms.ads.AdView
                android:id="@+id/adView"
                android:layout_width="match_parent"
                android:layout_height="wrap_content"
                ads:adSize="SMART_BANNER"
                ads:adUnitId="@string/ad_unit_id" />
        </LinearLayout>