No line numbers in Eclipse or Android Studio XML editor

Question

When editing XML files in the editor for Eclipse, line numbers are not displayed.

Use case:

I create a layout with many views, one of these lacks android:layout_

Answer 1

To make the line numbers always show for Android Studio:

File > Settings > Editor > Appearance then click the "Show line numbers" box.

The accepted answer works, but it will only make the line numbers visible on the active editor.