Instead of a shape, you could try a View
:
<View
android:layout_width="1dp"
android:layout_height="match_parent"
android:background="#FF0000FF" />
I have only used this for horizontal lines, but I would think it would work for vertical lines as well.
Use:
<View
android:layout_width="match_parent"
android:layout_height="1dp"
android:background="#FF0000FF" />
for a horizontal line.