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Unlocking Android was put out by Manning Publications on 28 May 2009, under the ISBN 978-1933988672. It was authored by W. Frank Ableson, Charlie Collins, and Robi Sen — all of whom have extensive experience in developing mobile software applications. The publisher's Web page makes available author biographies, descriptions of the book, all its ancillary parts (the foreword, preface, acknowledgments, table of contents, and index), a white paper on Android (oddly termed a "green paper"), and two sample chapters ("Targeting Android" and "Intents and services"). There is a link to download the source code from the Google Code site, organized by chapter. The Manning site also hosts a forum, where readers and the authors can discuss the book. As of this writing, there are 42 threads, comprising 120 messages. Lastly, the site has links to order both the print and electronic versions of the book. Note that purchasing the former automatically entitles one to a copy of the latter. Manning appears to be pioneering this approach to making e-books more readily available to customers, since every print copy now contains an insert with a list of codes that can be used to download a PDF copy of the book.

The book is ostensibly intended for Android beginners, even though it does contain enough detailed information to serve as a partial reference for more experienced developers. It is organized in a logical fashion, in three parts, starting with an overview of Android itself, both the technology and the organization behind it. Then the reader is introduced to the Android programming environment, along with its many components and capabilities. The book concludes with tutorial chapters that step the reader through creating a sample Android application and more. The material covers Android SDK 1.x. Since Android programs are written in Java, any reader fluent in that language will have a much easier time absorbing the ideas. However, the authors state that even non-Java programmers should be able to follow the examples, as long as they have knowledge of similar languages, such as C, C++, or C#. However, even a cursory glance at the code, by such a reader, would prove that Java knowledge is essential.

The first chapter — oddly named "Targeting Android" — introduces the platform, the organizations behind it, the mobile market as a whole, Android's features, how it differs from featured phones and smartphones, its open-source licenses, platform components, libraries, service managers, programming environment, and virtual terminal. Be warned that Figure 1.1 could be confusing to some readers, because it shows the layers of technology that compose the Android platform, but pictures them on the front of a mobile phone, showing a keypad, which makes the layers appear to be part of the actual user interface; the phone should be removed from the illustration, in a future edition. The chapter goes on to discuss booting and activating Android, as well as how to map applications to processes. Some readers anxious to get to the technical nitty-gritty, may become impatient when reading the first portion of this chapter, because it largely consists of introductory material. Yet this context can be helpful and interesting to people unfamiliar with the mobile phone market. (Articles and tutorials aimed at new mobile application developers, oftentimes assume that said developers are already extremely familiar with the rapidly changing mobile market.) In the later portion of the chapter, readers are shown a handful of code snippets, with some explanation as to what they are doing and how. In reading this material, the reader could be easily overwhelmed with all of the new terminology. One can only hope that the authors were not thinking that the typical reader would understand all of what is discussed, or be able to do anything with it. A canonical "Hello, world" program or something similar — with an explanation as to how to execute it — would have been a far more gentle introduction. By the way, the first few code snippets are poorly indented, and some of the method names are italicized, while others are not — with no mention as to what this might signify, either in the chapter or in the earlier "Code Conventions" section.

In Chapter 2, the reader is introduced to the key tools for basic Android development, including the SDK, Eclipse, and the Android Emulator. An example application — a tip calculator — is developed, step by step, to illustrate those tools. Clearly, this tutorial information should have been presented before the second section of the previous chapter. It nonetheless serves as a valuable introduction to programming Android. Incidentally, Figure 2.1 labels the development environment as being located on a laptop, incorrectly suggesting that desktop computers are not equally usable platforms. Later, when the authors suggest that readers add the Android SDK tools directory to their system search path, they specify only the release-independent directory (containing adb, for instance), and not the release-specific paths (containing aapt, which is the first tool discussed); readers presumably should add both. Also, the authors should specify which release to use, 1.1 or 1.5. The reader eventually is told how to run a sample application — and not a moment too soon, because at that point the reader is already 15 percent of the way into the book. To reach that point, she must wade through more introductory material than was needed, in addition to discussions of network speed and latency, command line tools, DDMS, Java packages, and other information. All of this could and should be covered later, when it would be much more meaningful, and the reader would have greater motivation to learn it, having seen an Android application running (if only in the emulator).

Part 2 forms the bulk of the book, consisting of nine chapters devoted to the essential aspects of Android application development: user interfaces, including the Activity class, views, resource types, and manifest files; Intent classes, broadcast receivers, task services, and inter-process communications; data storage and retrieval, including user preferences, files stored on the local system and on SD cards, databases, and the ContentProvider class; networking, including client/server interaction, HTTP, and Web services such as SOAP; telephony, including how to receive and initiate calls and SMS messages; notifications and alarms; generating graphics and animation; multimedia, including audio and video, utilizing the OpenCORE technology; location-based applications, using a variety of tools, including Google Earth's KML. All of these chapters make use of example applications, with annotated source code and screenshots of the applications running in the Android emulator.

The third and final part of the book comprises two chapters, each of which extends the core concepts of Android development. Chapter 12 steps the reader through the creation of a substantial application, named "Field Service Application," designed for mobile technicians who provide support services for customers of contracted clients. The application is designed to be used by both the technician and his home office to assign and manage job orders, capture customer signatures of completed jobs, order replacement parts, and receive navigation assistance. The final chapter, "Hacking Android," explores Android's utilization of Linux, the C programming language, and the SQLite database — as well as how the Android developer can access these capabilities under the hood.

Appendix A explains how to install the Eclipse integrated development environment (IDE), the Android software development kit (SDK), and the ADT plug-in for Eclipse. Readers who do not already have those components installed on their computers, may want to first read the appendix and follow the procedures. Note, however, that the procedures given in section A.4, for installing the ADT plug-in, are already out of date — namely, for Eclipse version 3.3. In addition, the URL given by the authors ("https://dl-sll.google.com/android/eclipse") is invalid, because it is missing the trailing directory slash, which is necessary for it to work within Eclipse. (This points up the importance of including root directories in URLs, despite their common absence, because even though Web browsers will automatically correct this upon receiving an error message from the server, Eclipse evidently does not.) The online Android installation instructions are much more useful, because they also include the latest version of Eclipse, 3.4.

As is to be expected with the first edition of any detailed computer programming book, this one contains some errata — for instance, in the first portion of the book alone: "Android[']s" (page xxii, twice), "Webkit" (page 7, in the caption), "SQLite[,] an" (page 11), and "byte code[s]" (page 13). Also, terms such as "Internet" and "Web" are in all-lowercase, throughout the book, even though they are proper names. (In our world of instant messaging and Twitter, grammatical degeneration continues apace.) For any reader who wishes to follow along and implement the sample projects, possibly the most disappointing decision by the authors was that of offering the sample code not as a single archive file, or even individual archive files for each of the 13 chapters. Instead, the reader must tediously click through multiple layers of directories, just to get the code displayed in a browser, one file at a time. Readers are advised to employee a Web copying utility, which, given a starting URL, will try to download all of the linked pages, recursively, and store those Web pages and other Web elements on their own computer (even localizing links, to retain working navigation in the saved pages).

Yet by far the biggest problem with this book, is that while it claims to be an introductory text, suitable for someone completely unfamiliar with Android, it does not bring the newcomer up to speed at a reasonable pace for learning. Instead, it presents a large number of code snippets and tools to the reader, without adequate explanation for the beginner to truly understand what is happening. This pattern begins even in the first chapter, which is sorely lacking a tutorial on how to execute the sample code — to better understand it and perhaps modify it (a practice that most programmers find quite valuable for assimilating a new technology). On page 23 is a frustratingly brief sidebar on testing the receipt of an SMS message, that is far from adequate for the reader anxious to begin testing out this new material. The second chapter continues this unfortunate tendency of describing tools prior to giving the reader enough information to run those tools themselves in the same manner, and see the same results. For instance, on page 41, the authors show how to use the adb tool to connect to a running emulator session, but at that point the reader has no such sessions running. (Sometimes the authors of programming books understand the material quite well, but neglect to view it from the perspective of someone who does not yet have that understanding.)

While more appropriate for intermediate Android developers than claimed, Unlocking Android contains a wealth of information to help Java programmers begin developing mobile applications for Google's new platform, with numerous code snippets and screenshots.

Michael J. Ross is a freelance Web developer and writer.

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