In Android Studio there is a activity called Scrolling activity.It has scrolling feature.If you want to add banner ad under that scrolling activity,you have to do some steps.In this post we are going to show above steps.




Step 1 : go to build.gradle file and add ,
               implementation 'com.google.android.gms:play-services-ads:15.0.1'


Step 2: connect internet connection with app.For that go t0 AndroidManifest.xml file and under package add,
  package="com.a7saturnapps.firstaid.firstaidsinhala">

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

Step 3: Now you have to add Ad code.for that firstly you have to add Newly Scrolling activity to Android Studio.For that go to,
  Under java folder right click com........... and New > Activity >  Scrolling Activity
Let's say you scrolling activity name is Banner_Ad

After adding it go to,
 activity_banner_ad.xml and change the code like below code.That's all.replace your adUnitiID.

xml version="1.0" encoding="utf-8"?>RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android" xmlns:app="http://schemas.android.com/apk/res-auto" xmlns:tools="http://schemas.android.com/tools" android:layout_width="match_parent" android:layout_height="match_parent" android:fitsSystemWindows="true" tools:context=".Banner_Ad">
android.support.design.widget.CoordinatorLayout android:layout_width="match_parent" android:layout_height="match_parent" android:layout_above="@+id/adView">
android.support.design.widget.AppBarLayout android:id="@+id/app_bar" android:layout_width="match_parent" android:layout_height="180dp" android:fitsSystemWindows="true" android:theme="@style/AppTheme.AppBarOverlay">
android.support.design.widget.CollapsingToolbarLayout android:id="@+id/toolbar_layout" android:layout_width="match_parent" android:layout_height="match_parent" android:fitsSystemWindows="true" app:contentScrim="?attr/colorPrimary" app:layout_scrollFlags="scroll|exitUntilCollapsed" app:toolbarId="@+id/toolbar">
android.support.v7.widget.Toolbar android:id="@+id/toolbar" android:layout_width="match_parent" android:layout_height="?attr/actionBarSize" app:layout_collapseMode="pin" app:popupTheme="@style/AppTheme.PopupOverlay" />
android.support.design.widget.CollapsingToolbarLayout>
android.support.design.widget.AppBarLayout>
include layout="@layout/content_banner__ad" />
android.support.design.widget.CoordinatorLayout>
com.google.android.gms.ads.AdView android:id="@+id/adView" android:layout_width="match_parent" android:layout_height="wrap_content" android:layout_alignParentBottom="true" android:layout_centerHorizontal="true" app:adSize="BANNER" app:adUnitId="ca-app-pub-3940256099942544/6300978111" />
RelativeLayout>

Also you can change adsize name to BANNER or SMART_BANNER
 more details here :
https://developers.google.com/mobile-ads-sdk/docs/adx/android/banner