I set this code in /res/layout/activity_main.xml

 <LinearLayout
    android:id="@+id/banner_container"
    android:layout_width="match_parent"
    android:layout_height="wrap_content"
    android:layout_alignParentBottom="true"
    android:orientation="vertical"
    app:layout_constraintBottom_toBottomOf="parent"/>

And I also set in java class

private AdView adView;

@Override
public void onCreate(Bundle savedInstanceState) {

adView = new AdView(this, "my_ads_code", AdSize.BANNER_HEIGHT_50);
LinearLayout adContainer = (LinearLayout) findViewById(R.id.banner_container);
adContainer.addView(adView);
adView.loadAd();

I use these codes in MainActivity. How do I use these banner ads in the second activity?