Dr. Dobb's Journal - September 2008 - (Page 40)

d09thom_p3ds 7/14/08 9:31 AM Page 40 State of the Art by Tom Thompson The Android Mobile Phone Platform Google’s play to change the face of mobile phones Tom is the head of Proactive Support for embedded products at Freescale Semiconductor. He has written documentation of demo programs for several mobile APIs. He can be reached at tom_thompson@lycos.com. “I have always wished that my computer would be as easy to use as my telephone. My wish has come true. I no longer know how to use my telephone.” —Bjarne Stroustrup At 25 years of age, you might think that the mobile phone has grown up. However, it’s about to undergo some dramatic changes—a delayed adolescence, if you will. Specifically, its software is about to undergo an overhaul. New, upstart players in the market want to revamp its entire software stack, with attention on its UI. Such changes will be welcomed by mobile phone users, because—as Bjarne Stroustrup attests—many of these devices have uniformly awful UIs. It’s not altruism on these companies’ part that motivates this effort, but a lucrative market of more than a billion subscribers that’s growing rapidly. With the launch of its iPhone in 2007, Apple quickstarted the mobile phone’s makeover. While the existing players—Nokia’s Symbian, Sun’s Java Micro Edition (Java ME, formerly known as “Java 2 Micro Edition,” or J2ME), and Microsoft’s Windows Mobile—aren’t standing still, such a disruptive change also provides an opportunity for new players to enter the field. Google has done just that with Android, its own mobile phone platform (code .google.com/android). Android uses Java and its application frameworks are Java-based, which offers the intriguing possibility of porting field-tested Java ME applications to it. Figure 1 shows the Android software stack. At the stack’s bottom and closest to the silicon, a Linux 2.6 kernel provides preemptive multitasking and system services such as threads, networking services, plus memory and process management. It manages all low-level drivers and acts as a Hardware Abstraction Layer (HAL). Any low-level device accesses should be handled through the Android frameworks and not Linux command-line utilities. Above the kernel is the Android runtime and support libraries layer. The runtime consists of the Dalvik Virtual Machine (DVM) and core libraries. The DVM is a bytecode interpreter that provides device independence for Android applications, similar in purpose to Java ME’s JVM. Like the JVM, Google’s DVM is optimized for embedded systems. For example, it uses register-based calls and storage, reducing the overhead incurred using stack operations. Furthermore, the core libraries that implement Java capabilities are written in native code. Importantly, a device can execute multiple instances of the DVM, with each running an Android This Is the Droid You’re Looking For Android is a mobile phone stack developed by Google for the Open Handset Alliance (www.openhandsetalliance.com). Android is open source, and draws on open-source projects such as Linux, WebKit, SQLite, and FreeType to implement its core services. 40 Dr. Dobb’s Journal l www.ddj.com l September 2008 http://code.google.com/android http://code.google.com/android http://www.openhandsetalliance.com http://www.openhandsetalliance.com http://www.ddj.com

Table of Contents Feed for the Digital Edition of Dr. Dobb's Journal - September 2008

Dr. Dobb's Journal - September 2008 Contents Friday Night Fish Fry Alia Vox Developer Diaries Developer’s Notebook A Conversation With Erik Demaine Application Lifecycle Management Meets Model-Driven Development Building a Robust Development Environment Real Users Really Matter Matching Wildcards: An Algorithm The Android Mobile Phone Platform Managing Application Thread Use Signalling Integer Overflows in Java .NET Development & the IBM WebSphere Portal Server The Agile Edge Effective Concurrency Swaine’s Flames

Dr. Dobb's Journal - September 2008

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