Admob banner not showing Android

问题:

My admob banner in my app is not showing. It's just a white space, I have added parts to all manifest, xml and java files. Anyone can spot any errors within my xml?

Thanks for any help.

<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
xmlns:app="http://schemas.android.com/apk/res-auto"
android:layout_width="match_parent"
android:layout_height="match_parent"
xmlns:fab="http://schemas.android.com/apk/res-auto"
xmlns:tools="http://schemas.android.com/tools"
xmlns:ads="http://schemas.android.com/apk/res-auto"
tools:context=".ScrollingActivity">

<ListView
    android:id="@+id/list"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:dividerHeight="1dp"
    android:divider="#9E9E9E"
    android:layout_above="@+id/fab" />

<com.melnykov.fab.FloatingActionButton
    android:id="@+id/fab"
    android:layout_width="wrap_content"
    android:layout_height="wrap_content"
    android:scaleType="center"
    fab:fab_colorNormal="@color/primary"
    fab:fab_colorPressed="@color/primary_pressed"
    android:src="@mipmap/ic_pause_black_24dp"
    android:layout_alignParentBottom="true"
    android:layout_alignParentRight="true"
    android:layout_alignParentEnd="true"
    android:layout_marginRight="20dp"
    android:layout_marginBottom="20dp" />

<com.google.android.gms.ads.AdView
    android:id="@+id/adView"
    android:layout_width="wrap_content"
    android:layout_height="wrap_content"
    ads:adSize="BANNER"
    ads:adUnitId="@string/banner_home_footer"
    android:layout_alignParentBottom="true"
    android:layout_alignParentLeft="true"
    android:layout_alignParentStart="true">
</com.google.android.gms.ads.AdView>