Android Not enough space to show ad - admob

Question

I know there are lots of answers to this question and I have already tried most of the solutions and couldn't get a solution at this point.

I am trying to show an ad on my Android Activity and I keep getting this message

Not enough space to show ad. Needs 480x75 pixels, but only has 480x0 pixels.

My XML file for the activity is as follows:

<android.support.v4.widget.DrawerLayout xmlns:android="http://schemas.android.com/apk/res/android"
android:id="@+id/drawer_layout"
android:layout_width="match_parent"
android:layout_height="match_parent" >

<LinearLayout
    android:id="@+id/content_layout"
    android:layout_width="match_parent"
    android:layout_height="wrap_content"
    android:orientation="vertical" >

        <FrameLayout
            android:id="@+id/content_frame"
            android:layout_width="match_parent"
            android:layout_height="wrap_content"
            android:layout_gravity="top" />

        <com.google.android.gms.ads.AdView
            xmlns:ads="http://schemas.android.com/apk/res-auto"
            android:id="@+id/adView"
            android:layout_width="match_parent"
            android:layout_height="wrap_content"
            ads:adUnitId="***"
            ads:adSize="BANNER"/>

    </LinearLayout>    

<ListView
    android:id="@+id/listview_drawer"
    android:layout_width="240dp"
    android:layout_height="match_parent"
    android:layout_gravity="start"
    android:background="#111"
    android:choiceMode="singleChoice"
    android:divider="@android:color/transparent"
    android:dividerHeight="0dp" />
</android.support.v4.widget.DrawerLayout>

And I am creating it with:

adView = (AdView) findViewById(R.id.adView);

    AdRequest adRequest = new AdRequest.Builder()
    .addTestDevice("my_device_id")
    .build();
    adView.loadAd(adRequest);

I can't seem to have it shown on my screen. Can someone help me with this?

Thanks in advance!

UPDATE

I managed to do it using a RelativeLayout and this is how i did it:

<RelativeLayout
    android:id="@+id/content_layout"
    android:layout_width="match_parent"
    android:layout_height="wrap_content"
    android:orientation="vertical" >

        <FrameLayout
            android:id="@+id/content_frame"
            android:layout_width="match_parent"
            android:layout_height="wrap_content"
            android:layout_above="@+id/adView" />

        <com.google.android.gms.ads.AdView
            xmlns:ads="http://schemas.android.com/apk/res-auto"
            android:id="@+id/adView"
            android:layout_width="match_parent"
            android:layout_height="50dp"
            android:layout_alignParentBottom="true"
            android:layout_alignParentLeft="true"
            app:adSize="BANNER"
            app:adUnitId="****" >
        </com.google.android.gms.ads.AdView>

    </RelativeLayout>