More complete sample from here and here.
Or you can check out my layout sample. p.s no need to put API key in the map view.
<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
android:orientation="vertical"
android:layout_width="match_parent"
android:layout_height="match_parent">
<com.google.android.gms.maps.MapView
android:id="@+id/map_view"
android:layout_width="match_parent"
android:layout_height="match_parent"
android:layout_weight="2"
/>
<ListView android:id="@+id/nearby_lv"
android:layout_width="match_parent"
android:layout_height="match_parent"
android:background="@color/white"
android:layout_weight="1"
/>
</LinearLayout>