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Along with the release of the new Nexus 4 smartphone and Nexus 10 tablet on Tuesday and the rollout of updates to Android 4.2 to several existing Nexus devices, Google has also pushed the source code for the new Jelly Bean flavour of its mobile operating system to the Android Open Source Project (AOSP). In a post on the Android Developers Blog, the company detailed the features in the latest Android version, which also brings with it a new SDK revision (API level 17).
New features in Android 4.2 include increased performance for the platform's Renderscript 3D graphics API, the ability to modify widgets so that they can be placed on a device's lock screen, and improved internationalisation support. Some Android 4.2 devices can also drive more than one external screen and have the ability to target different content at each screen separately. Until now, Android was only able to mirror the contents of the main display on external screens.
The Nexus 10 tablet also includes a multi-user mode as part of Android 4.2; this introduces the ability to use several accounts on a single physical device. Applications are managed separately for each user, but if two users install the same app, it will only be downloaded to the device once and only takes the space of one installed copy; however, settings and user data are kept separately for each user. The account that is created first is regarded as the owner of the tablet and is the only one that can reset the device to factory settings or enable developer features such as USB debugging.
In testing the multi-account capabilities, The H's associates at Heise Mobil found that enabling USB debugging brings with it some risks however. It enables anyone to access the contents of all user accounts on the tablet by plugging it into a computer and browsing the filesystem hierarchy. The same thing can be done with single-user Android devices as well, but it is something to keep in mind when thinking about using a multi-user Android tablet to store confidential data. To implement this support for multiple user accounts, Android uses symlinks to create virtual SD card directories for each user.
Android 4.2 factory images for Nexus devices (including the Galaxy Nexus) are now available from Google's Android Developers web site; however, the company has confirmed that the Nexus S smartphone and Motorola Xoom tablet will not receive the update. Source code for Android 4.2 is available from AOSP.