INTRODUCTION
I FIRST STARTED PLAYING WITH THE ANDROID SDK before it was officially released as version 1.0. Back then, the tools were unpolished, the APIs in the SDK were unstable, and the documentation was sparse. Fast-forward three and a half years, Android is now a formidable mobile operating system, with a following no less impressive than the iPhone. Having gone through all the growing pains of Android, I think now is the best time to start learning about Android programming — the APIs have stabilized, and the tools have improved. One challenge remains, however: Getting started is still an elusive goal for many. What’s more, Google has recently released their latest version of the Android SDK — 4.0, a unified mobile OS for both smartphones and tablets. The Android 4.0 SDK includes several new features for tablet developers, and understanding all these new features requires some effort on the part of beginners.
It was with this challenge in mind that I was motivated to write this book, one that could benefit beginning Android programmers and enable them to write progressively more sophisticated applications.
As a book written to help jump-start beginning Android developers, it covers the necessary topics in a linear manner so that you can build on your knowledge without being overwhelmed by the details. I adopt the philosophy that the best way to learn is by doing — hence, the numerous Try It Out sections in each chapter, which first show you how to build something and then explain how everything works. I have also taken this opportunity to further improve the previous edition of this book, addressing feedback from readers and adding additional topics that are important to beginning Android developers.
Although Android programming is a huge topic, my aim for this book is threefold: to get you started with the fundamentals, to help you understand the underlying architecture of the SDK, and to appreciate why things are done in certain ways. It is beyond the scope of any book to cover everything under the sun related to Android programming, but I am confident that after reading this book (and doing the exercises), you will be well equipped to tackle your next Android programming challenge.
WHO THIS BOOK IS FOR
This book is targeted for the beginning Android developer who wants to start developing applications using Google’s Android SDK. To truly benefit from this book, you should have some background in programming and at least be familiar with object-oriented programming concepts. If you are totally new to Java — the language used for Android development — you might want to take a programming course in Java programming first, or grab one of many good books on Java programming. In my experience, if you already know C# or VB.NET, learning Java is not too much of an effort; you should be comfortable just following along with the Try It Outs.
For those totally new to programming, I know the lure of developing mobile apps and making some money is tempting. However, before attempting to try out the examples in this book, I think a better starting point would be to learn the basics of programming first.
NOTE All the examples discussed in this book were written and tested using version 4.0 of the Android SDK. While every effort is made to ensure that all the tools used in this book are the latest, it is always possible that by the time you read this book, a newer version of the tools may be available. If so, some of the instructions and/or screenshots may differ slightly. However, any variations should be manageable.
WHAT THIS BOOK COVERS
This book covers the fundamentals of Android programming using the Android SDK. It is divided into 12 chapters and three appendixes.
Chapter 1: Getting Started with Android Programming covers the basics of the Android OS and its current state. You will learn about the features of Android devices, as well as some of the popular devices on the market. You will also learn how to download and install all the required tools to develop Android applications and then test them on the Android emulator.
Chapter 2: Activities, Fragments, and Intents gets you acquainted with these three fundamental concepts in Android programming. Activities and fragments are the building blocks of an Android application. You will learn how to link activities together to form a complete Android application using intents, one of the unique characteristics of the Android OS.
Chapter 3: Getting to Know the Android User Interface covers the various components that make up the UI of an Android application. You will learn about the various layouts you can use to build the UI of your application, and the numerous events that are associated with the UI when users interact with the application.
Chapter 4: Designing Your User Interface with Views walks you through the various basic views you can use to build your Android UI. You will learn three main groups of views: basic views, picker views, and list views. You will also learn about the specialized fragments available in Android 3.0 and 4.0.
Chapter 5: Displaying Pictures and Menus with Views continues the exploration of views. Here, you will learn how to display images using the various image views, as well as display options and context menus in your application. This chapter ends with some additional cool views that you can use to spice up your application.
Chapter 6: Data Persistence shows you how to save, or store, data in your Android application. In addition to learning the various techniques to store user data, you will also learn file manipulation and how to save files onto internal and external storage (SD card). In addition, you will learn how to create and use a SQLite database in your Android application.
Chapter 7: Content Providers discusses how data can be shared among different applications on an Android device. You will learn how to use a content provider and then build one yourself.
Chapter 8: Messaging explores two of the most interesting topics in mobile programming — sending SMS messages and e-mail. You will learn how to programmatically send and receive SMS and e-mail messages, and how to intercept incoming SMS messages so that the built-in Messaging application will not be able to receive any messages.
Chapter 9: Location-Based Services demonstrates how to build a location-based service application using Google Maps. You will also learn how to obtain geographical location data and then display the location on the map.
Chapter 10: Networking explores how to connect to web servers to download data. You will see how XML and JSON web services can be consumed in an Android application. This chapter also explains sockets programming, and you will learn how to build a chat client in Android.
Chapter 11: Developing Android Services demonstrates how you can write applications using services. Services are background applications that run without a UI. You will learn how to run your services asynchronously on a separate thread, and how your activities can communicate with them.
Chapter 12: Publishing Android Applications discusses the various ways you can publish your Android applications when you are ready. You will also learn about the necessary steps to publishing and selling your applications on the Android Market.
Appendix A: Using Eclipse for Android Development provides a brief overview of the many features in Eclipse.
Appendix B: Using the Android Emulator provides some tips and tricks on using the Android emulator for testing your applications.
Appendix C: Answers to Exercises contains the solutions to the end-of-chapter exercises found in every chapter.
HOW THIS BOOK IS STRUCTURED
This book breaks down the task of learning Android programming into several smaller chunks, enabling you to digest each topic before delving into a more advanced one.
If you are a total beginner to Android programming, start with Chapter 1 first. Once you have familiarized yourself with the basics, head over to the appendixes to read more about Eclipse and the Android emulator. When you are ready, continue with Chapter 2 and gradually move into more advanced topics.
A feature of this book is that all the code samples in each chapter are independent of those discussed in previous chapters. This gives you the flexibility to dive into the topics that interest you and start working on the Try It Out projects.
WHAT YOU NEED TO USE THIS BOOK
All the examples in this book run on the Android emulator (which is included as part of the Android SDK). However, to get the most out of this book, having a real Android device would be useful (though not absolutely necessary).
CONVENTIONS
To help you get the most from the text and keep track of what’s happening, a number of conventions are used throughout the book.
TRY IT OUT: These Are Exercises or Examples for You to Follow
The Try It Out sections appear once or more per chapter. These are exercises to work through as you follow the related discussion in the text.
1. They consist of a set of numbered steps.
2. Follow the steps with your copy of the project files.
How It Works
After each Try It Out, the code you’ve typed is explained in detail.
As for other conventions in the text:
- New terms and important words are highlighted in italics when first introduced.
- Keyboard combinations are treated like this: Ctrl+R.
- Filenames, URLs, and code within the text are treated like so: persistence.properties.
- Code is presented in two different ways:
We use a monofont type with no highlighting for most code examples.
We use bolding to emphasize code that is of particular importance in the present context.
NOTE Notes, tips, hints, tricks, and asides to the current discussion look like this.
SOURCE CODE
As you work through the examples in this book, you may choose either to type in all the code manually or to use the source code files that accompany the book. All the source code used in this book is available for download at www.wrox.com. When at the site, simply locate the book’s title (use the Search box or one of the title lists) and click the Download Code link on the book’s detail page to obtain all the source code for the book.
You’ll find the filename of the project you need in a CodeNote such as this at the beginning of the Try it Out features:
code snippet filename
After you download the code, just decompress it with your favorite compression tool. Alternatively, go to the main Wrox code download page at www.wrox.com/dynamic/books/download.aspx to see the code available for this book and for all other Wrox books.
NOTE Because many books have similar titles, you may find it easiest to search by ISBN; this book’s ISBN is 978-1-118-19954-1.
ERRATA
We make every effort to ensure that there are no errors in the text or in the code. However, no one is perfect, and mistakes do occur. If you find an error in one of our books, such as a spelling mistake or faulty piece of code, we would be very grateful for your feedback. By sending in errata, you may save another reader hours of frustration and at the same time help us provide even higher-quality information.
To find the errata page for this book, go to www.wrox.com and locate the title using the Search box or one of the title lists. Then, on the book details page, click the Book Errata link. On this page, you can view all errata that has been submitted for this book and posted by Wrox editors.
NOTE A complete book list, including links to each book’s errata, is also available at www.wrox.com/misc-pages/booklist.shtml.
If you don’t spot “your” error on the Book Errata page, go to www.wrox.com/contact/techsupport.shtml and complete the form there to send us the error you have found. We’ll check the information and, if appropriate, post a message to the book’s errata page and fix the problem in subsequent editions of the book.
P2P.WROX.COM
For author and peer discussion, join the P2P forums at p2p.wrox.com. The forums are a web-based system for you to post messages relating to Wrox books and related technologies and to interact with other readers and technology users. The forums offer a subscription feature to e-mail you topics of interest of your choosing when new posts are made to the forums. Wrox authors, editors, other industry experts, and your fellow readers are present on these forums.
At p2p.wrox.com, you will find a number of different forums that will help you not only as you read this book but also as you develop your own applications. To join the forums, just follow these steps:
1. Go to p2p.wrox.com and click the Register link.
2. Read the terms of use and click Agree.
3. Complete the required information to join as well as any optional information you want to provide and click Submit.
4. You will receive an e-mail with information describing how to verify your account and complete the joining process.
NOTE You can read messages in the forums without joining P2P, but in order to post your own messages, you must join.
After you join, you can post new messages and respond to messages that other users post. You can read messages at any time on the web. If you want to have new messages from a particular forum e-mailed to you, click the Subscribe to This Forum icon by the forum name in the forum listing.
For more information about how to use the Wrox P2P, be sure to read the P2P FAQs for answers to questions about how the forum software works, as well as many common questions specific to P2P and Wrox books. To read the FAQs, click the FAQ link on any P2P page.