Enable multi-user support in the Android emulator

Android 4.2 (API 17) offers multi-user support for tablet sharing. To add a user on a physical tablet running 4.2 or later, go to Settings | Users. You can also do this in an emulator, but you first have to set an emulator property as follows:

1. Create a new AVD based on a tablet (say, the Nexus 7 device definition in the latest ADT) with API 17.
2. Start the emulator
3. Run these adb commands:

> adb shell setprop fw.max_users 4
> adb shell stop
> adb shell start

You can now add a user in the emulator. To see the new user bubble on the lock screen, press F7. You may have to press it twice for the slide lock to become active.