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1714 android recipes

ord for the book, and
for making the intial introductions between myself and the team here at Apress. Finally, I send a
huge thank you to the team that Apress brought together to work with Jeff and me and make the
book the best it could possibly be: Steve Anglin, Corbin Collins, Tom Welsh, Paul Connolly, and
everyone else. Without your time and effort, this project would not even exist.
—Dave Smith
I thank Steve Anglin for contacting me to write this book, Corbin Collins for guiding me through
the various aspects of this project, Tom Welsh for helping me with the development of my
chapters, and Paul Connolly for his diligence in catching various flaws that would otherwise have
made it into this book. I also thank my coauthor Dave Smith for making a fantastic contribution
to this book.
—Jeff Friesen

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Preface
Welcome to Android Recipes!
If you are reading this book, you probably don’t need to be told of the immense opportunity
that mobile devices represent for software developers and users. In recent years, Android has

become one of the top mobile platforms for device users. This means that you, as a developer,
must know how to harness Android so you can stay connected to this market and the potential
that it offers. But any new platform brings with it uncertainty about best practices or solutions to
common needs and problems.
What we aim to do with Android Recipes is give you the tools to write applications for the
Android platform through direct e×amples targeted at the specific problems you are trying to
solve. This book is not a deep dive into the Android SDK, NDK, or any of the other tools. We don’t
weigh you down with all the details and theory behind the curtain. That’s not to say that those
details aren’t interesting or important. You should take the time to learn them, as they may save
you from making future mistakes. However, more often than not they are simply a distraction
when you are just looking for a solution to an immediate problem.
This book is not meant to teach you Java programming or even the building blocks of an
Android application. You won’t find many basic recipes in this book (such as how to display te×t
with Te×tView, for instance), as we feel these are tasks easily remembered once learned. Instead,
we set out to address tasks that developers, once comfortable with Android, need to do often, but
that are too comple× to remember or accomplish with a few lines of code.
Treat Android Recipes as a reference to consult, a resource-filled cookbook that you can
always open to find the pragmatic advice you need to get the job done quickly and well.

What Will You Find in the Book?
Although this book is not a beginner’s guide to Android, Chapter 1 offers an overview of those
Android fundamentals that are necessary for understanding the rest of the book’s content.
Chapter 1 also shows you how to set up your environment so that you can develop Android apps.
Specifically, it shows you how to install the Android SDK and Eclipse with the ADT Plugin.
As you become a seasoned Android app developer, you’re going to want to save time by not
reinventing the wheel. Instead, you’ll want to create and use your own libraries of reusable code,
or use the libraries that others have created. Chapter 7 shows you how to create and use your own
library code in the form of JAR-based libraries and Android library projects. In addition to
creating your own libraries, we’ll introduce a couple of Java libraries outside the Android SDK
that your applications can make use of.
In the intervening chapters, we dive into using the Android SDK to solve real problems. You
will learn tricks for effectively creating a user interface that runs well across device boundaries.
You will become a master of incorporating the collection of hardware (radios, sensors, and
cameras) that makes mobile devices such a unique platform. We’ll even discuss how to make the
system work for you, integrating with the services and applications provided by Google and the

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■ PREFACE

various device manufacturers. Along the way, you’ll be introduced to some tools developed by
the community to help making development and testing of your applications easier.
Are you interested in scripting languages (such as Python or Ruby)? If so, you'll want to check
out Appendix A, which introduces you to Scripting Layer for Android. This special app lets you
install scripting language interpreters and scripts on a device, and then run these scripts, which
can speed up development.
Performance matters if you want your apps to succeed. Most of the time, this isn't a problem
because (as of version 2.2) Android's Dalvik virtual machine features a Just-In-Time compiler that
compiles Dalvik bytecode to the device's native code. However, if this isn’t enough, you’ll need to
leverage the Android NDK to boost performance. Appendix B offers you an introduction to the
NDK and demonstrates its usefulness in the context of an OpenGL example.
When creating apps, you need to ensure that they are performant, responsive, and seamless.
Apps that perform well drain less power from the battery, responsive apps avoid the dreaded
Application Not Responding dialog box, and seamless apps interact properly with other apps so as
not to annoy or confuse the user. Additionally, when you publish your app to Google’s Android
Market, you don’t want the app to be visible to incompatible devices. Instead, you want Android
Market to filter your app so that users of these incompatible devices cannot download (or even see)
the app. Appendix C rounds out the book by offering you guidelines for creating performant,
responsive, and seamless apps; and for taking advantage of filtering so that an app can be
downloaded (from Android Market) only by those users whose devices are compatible with the app.

Keep a Level Eye on the Target
Throughout the book, you will see that we have marked most recipes with the minimum API
Level that is required to support it. Most of the recipes in this book are marked API Level 1,
meaning that the code used can be run in applications targeting any version of Android since 1.0.
However, where necessary we make use of APIs introduced in later versions. Pay close attention
to the API Level marking of each recipe to ensure that you are not using code that doesn’t match
up with the version of Android your application is targeted to support.

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