Android-Studio to show XML code instead of design

Solution 1:

Newer (I guess 2.x+) versions of Android Studio have this option in the main settings:

Open the settings with one of the following actions:

Press Ctrl+Alt+S.
On the main menu, choose File | Settings for Windows and Linux or IntelliJ IDEA | Preferences for OS X
Press Ctrl+Shift+A, type settings and press Enter.

Then navigate to the following sub-menu:

Editor -> Layout Editor -> "Prefer XML editor"

Screenshot of the Preferences

This has been added in the newest release of Android Studio (0.8.12).

default to xml editor

Other features of the new release can be found here.