Domo Arigato Mr Androidato—An Introduction to the New Google Mobile Linux Framework, Android

All your phones, are belong to Google—a brief overview of Android, the new software stack created by Google for the Open Handset Alliance.

The Open Handset Alliance (OHA) is an industry trade group comprising more than 30 technology and mobile companies. The focus of the OHA is to accelerate innovation in the mobile application and hardware space and to provide consumers with a more comprehensive and inexpensive mobile device experience. Android is a new, mobile application development framework developed by Google for the OHA that represents part of a greater promise from OHA members to make the open platform an industry success.

Along Came an Android

In addition to announcing its intent to bid on the C Block of the 700MHz wireless spectrum recently, Google continues to lead the charge to ensure that the FCC mandates the spectrum be open for all mobile devices and all operating systems. These two points are partly why the Android announcement is so important. Imagine using your phone as you do now, but with the option to modify it like you do your desktop computer. With Android, you will be able to tweak a subset of software on your phone to your liking—more so than merely changing the background, selecting a ring tone or downloading carrier-sanctioned software. If this idea becomes a reality, it might herald the beginning of a new era of personal computing and possibly even foster the creation of a new generation of small mobile phone companies and software vendors. Without waxing too philosophically on the benefits of an open spectrum, open devices, open software and open access, let's get to the meat of the problem, or shall we say, the logic of the Android.

The Meat

The key features of the Android Software Development Kit (SDK) include an application framework, a memory-optimized runtime environment named Dalvik (so called because of one of the main engineer's affinity for the Icelandic town), an integrated browser based on WebKit, a custom 2-D graphics library, a 3-D graphics library based on OpenGL ES 1.0, structured data storage through SQLite, support for a variety of media formats (MPEG-4, H.264, MP3, AAC, AMR, JPG, PNG and GIF), and hardware-dependent support for a multitude of components (GSM, Bluetooth, EDGE, 3G, Wi-Fi, camera, GPS, compass and accelerometer). All of this functionality is accessible through the Eclipse IDE or on its own through the user's own Java environment. The platform also includes an emulator, debugging utilities, memory and performance profiling tools, and the source code for a set of example programs.

Figure 1. Browsing the Linux Journal Web site using the WebKit-based browser on the Android emulator. This particular screenshot highlights the built-in zoom feature that enables you to see a full-size view of a Web site.

Figure 2. Using the built-in Maps feature to find my hometown in Ohio. The maps feature works similarly to the one found on the Internet—first providing a world view, then allowing you to pick a particular region and keep zooming until you reach the magnification limit or are satisfied with what you see.

So Many Layers, So Little Time

The Android framework consists of four layers, as shown in Figure 3. At the top of the stack is the aptly named Applications layer, so called because it is where finished applications are assembled and situated in the framework. The second is the Application Framework layer, where the building blocks of each application are created using the underlying system libraries and associated application code. Next comes the Library and Runtime layer where core system libraries, Google Java libraries and the Dalvik virtual machine reside. The fourth and final layer is the Kernel layer, where Linux (version 2.6.x) communicates with the underlying hardware.

Figure 3. Hierarchical View of the Android Framework

Table 1. How the Android Framework Compares to Existing Mobile Frameworks

License(s) Apache2 (mirrored GPLv2.0/LGPL components)GPLv2.0 (kernel)/proprietaryMany free and open-source licensesGPLv2.0/LGPLv2.1GPLv2.0 (Community Edition)
SDK (price)Eclipse plugin or standalone (free)Eclipse plugin (Community Edition, free)VistaMax or Laika (some parts require a device)OpenEmbedded (free)Qt Tools (Community Edition, free)
Sign-up RequiredNoYesDepends (OS requires valid device ID)NoYes (Community Edition, free)
Primary UIJavaQtGTK+GTK+Qt
Primary Application Language(s)Java (underlying libraries C/C++)Java ME/C++Languages with GTK+ bindingsLanguages with GTK+ bindingsLanguages with Qt bindings
Preferred SimulatorAndroid emulatorMotoDev emulator/Java ME emulatorQEMUQEMU (and others)Greenphone emulator (QEMU)
Primary Devices Unknown (probably OHA devices) Most Motorola mobile devices Nokia N Series (and others) Neo1973 Neo1973 (Greenphone discontinued)
Licensing Free (some services cost extra) Free (some services cost extra) Free (device required for some OS bits) Free Free (noncommercial only)