@Asahi pretty much hit the nail on the head, but I just wanted to add a bit of XML for anyone maybe floating in here later via google:
<ListView android:id="@+id/MyListView"
android:layout_height="match_parent"
android:layout_width="match_parent"
android:divider="@android:color/transparent"
android:dividerHeight="10.0sp"/>
For some reason, values such as “10”, “10.0”, and “10sp” all are rejected by Android for the dividerHeight
value. It wants a floating point number and a unit, such as “10.0sp”. As @Goofyahead notes, you can also use display-independent pixels for this value (ie, “10dp”).