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Android Native Development Kit Cookbook.pdf

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Published: 2018-03-17 Author:Bieber 27 Browses


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书名: Android Native Development Kit Cookbook

作者: Feipeng Liu

副书名: A step-by-step tutorial with more than 60 concise recipes on Android NDK development skills

出版日期: March 2013

页数: 346

ISBN: 978-1-84969-150-5

Extracting password :687a49e74611bd09


Android Native
Development Kit
Cookbook
A step-by-step tutorial with more than 60 concise recipes
on Android NDK development skills
Feipeng Liu
BIRMINGHAM - MUMBAI
Android Native Development Kit Cookbook
Copyright © 2013 Packt Publishing
All rights reserved. No part of this book may be reproduced, stored in a retrieval system, or
transmitted in any form or by any means, without the prior written permission of the publisher,
except in the case of brief quotations embedded in critical articles or reviews.
Every effort has been made in the preparation of this book to ensure the accuracy of the
information presented. However, the information contained in this book is sold without
warranty, either express or implied. Neither the author, nor Packt Publishing, and its dealers
and distributors will be held liable for any damages caused or alleged to be caused directly or
indirectly by this book.
Packt Publishing has endeavored to provide trademark information about all of the companies
and products mentioned in this book by the appropriate use of capitals. However, Packt
Publishing cannot guarantee the accuracy of this information.
First published: March 2013
Production Reference: 1140313
Published by Packt Publishing Ltd.
Livery Place
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Birmingham B3 2PB, UK.
ISBN 978-1-84969-150-5
www.packtpub.com
Cover Image by Artie Ng (artherng@yahoo.com.au)
Credits
Author
Feipeng Liu
Reviewers
Roger Belk
Frank Grützmacher
Sylvain Ratabouil
Acquisition Editor
Martin Bell
Commissioning Editor
Shreerang Deshpande
Lead Technical Editor
Mayur Hule
Technical Editors
Lubna Shaikh
Worrell Lewis
Project Coordinator
Leena Purkait
Proofreader
Aaron Nash
Indexer
Monica Ajmera Mehta
Graphics
Aditi Gajjar
Valentina D'silva
Production Coordinator
Shantanu Zagade
Cover Work
Shantanu Zagade
About the Author
Feipeng Liu is a technology enthusiast who is focused on multimedia systems and
applications. He started mobile applications development in 2008 on Windows Mobile.
Since Feb 2010, he has been developing apps for Android with NDK. His Android apps have
been used by many users. One of his apps, video converter Android, has reached one
million downloads within 10 months. Feipeng received his B.ENG in Electrical and Electronic
Engineering degree from Nanyang Technological University, and Master of Computing degree
in the Department of Computer Science from National University of Singapore.
I would like to thank Shreerang Deshpande for offering me the opportunity
to author this book and for helping me throughout the writing, and Leena
Purkait for keeping track of its progress and coordination, Mayur Hule,
Lubna Shaikh, and Worrell Lewis for editing the book drafts! I would like to
express my gratitude to other Packt Publishing staff who helped with the
book! My grateful thanks are also extended to Roger, Frank and Sylvain,
who offered great suggestions during the review.
I also would like to thank Assoc. Prof. Wei Tsang Ooi in National University of
Singapore, the supervisor of my master project. A lot of stuff in this book is
based on the things I learnt during the project.
Last but not least, I would like to thank my parents Zhulan Shen and Yi Liu,
and Ms. Yang Xiaoqing for the support and understanding during the writing
of the book.
About the Reviewers
Roger Belk is a 45-year-old self-taught Android developer with 20 + apps in Google’s
Play Store under the developer name BigTexApps. He started out using Google’s & MIT’s
App Inventor and then after two years of learning to use AI, he taught himself to use Java to
build Android apps. He has reviewed two other books, Google App Inventor, Ralph Roberts,
Packt Publishing (ISBN 978-1-84969-212-0) and Android 3.0 Animation, Alex Shaw, Packt
Publishing (ISBN 978-1-84951-528-3).
Frank Grützmacher spent some years in the research of distributed electronic design
tools and worked for several German blue chip companies such as Deutsche Post and AEG.
He was involved in Android platform extensions for a mobile manufacturer. Therefore, on
one hand he knows how to build large enterprise apps and on the other hand how to make
Android system apps.
He is currently working for the IT daughter of the largest German Telco company.
In the past, he has reviewed Corba- and Java-related books for American and
German publishers.
Sylvain Ratabouil
technologies. He worked in the space industry and got involved in aeronautic projects
at Valtech, where he is now taking part in the digital revolution.
As a technology lover, he is passionate about mobile technologies and cannot live or sleep
anymore without his Android smart phone.
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
Preface 1
Chapter 1: Hello NDK 7
Introduction 7
Setting up an Android NDK development environment in Windows 8
Setting up an Android NDK development environment in Ubuntu Linux 16
Setting up an Android NDK development environment in Mac OS 19
Updating Android NDK 20
Writing a Hello NDK program 22
Chapter 2: Java Native Interface 27
Introduction 28
Loading native libraries and registering native methods 29
Passing parameters and receiving returns in primitive types 34
Manipulating strings in JNI 39
Managing references in JNI 43
Manipulating classes in JNI 50
Manipulating objects in JNI 53
Manipulating arrays in JNI 57
 
Calling static and instance methods from the native code 67
 
Checking errors and handling exceptions in JNI 76
Integrating assembly code in JNI 80
Chapter 3: Build and Debug NDK Applications 83
Introduction 83
Building an Android NDK application at the command line 84
Building an Android NDK application in Eclipse 94
Building an Android NDK application for different ABIs 97
Building Android NDK applications for different CPU features 102
ii
Table of Contents
Debugging an Android NDK application with logging messages 106
Debugging an Android NDK application with CheckJNI 110
Debugging an Android NDK application with NDK GDB 113
Debugging an Android NDK application with CGDB 116
Debugging an Android NDK application in Eclipse 119
Chapter 4: Android NDK OpenGL ES API 123
Introduction 123
Drawing 2D Graphics and applying transforms with the OpenGL ES 1.x API 127
Drawing 3D graphics and lighting up the scene with the OpenGL ES 1.x API 133
Mapping texture to 3D objects with the OpenGL ES 1.x API 140
Drawing 3D graphics with the OpenGL ES 2.0 API 145
Displaying graphics with EGL 152
Chapter 5: Android Native Application API 159
Introduction 159
Creating a native activity with the native_activity.h interface 161
Creating a native activity with the Android native app glue 166
Managing native windows at Android NDK 174
Detecting and handling input events at Android NDK 178
Accessing sensors at Android NDK 181
Managing assets at Android NDK 186
Chapter 6: Android NDK Multithreading 191
Introduction 191
Creating and terminating native threads at Android NDK 192
Synchronizing native threads with mutex at Android NDK 195
Synchronizing native threads with conditional variables at Android NDK 200
Synchronizing native threads with reader/writer locks at Android NDK 206
Synchronizing native threads with semaphore at Android NDK 212
Scheduling native threads at Android NDK 217
Managing data for native threads at Android NDK 228
Chapter 7: Other Android NDK API 233
Introduction 233
Programming with the jnigraphics library in Android NDK 234
Programming with the dynamic linker library in Android NDK 238
Programming with the zlib compression library in Android NDK 241
Programming audio with the OpenSL ES audio library in Android NDK 247
Programming with the OpenMAX AL multimedia library in Android NDK 259
iii
Table of Contents
Chapter 8: Porting and Using the Existing Libraries with Android NDK 265
Introduction 265
Porting a library as a shared library module with the Android NDK
build system 266
Porting a library as a static library module with the Android NDK
build system 271
Porting a library with its existing build system using the
Android NDK toolchain 275
Using a library as a prebuilt library 280
Using a library in multiple projects with import-module 282
 
Chapter 9: Porting an Existing Application to Android with NDK 293
Introduction 293
Porting a command-line executable to Android with an NDK build system 294
Porting a command-line executable to Android with an NDK
standalone compiler 298
Adding GUI to a ported Android app 305
Using background threads at porting 310
Index 319
iv
Table of Contents
Preface

The total number of apps in Google Play is expected to reach 1,000,000 in mid 2013. Most
of the Android apps are written in Java with Android Software Development Kit (SDK). Many
developers only write Android code in Java even though they are experienced with C/C++,
without realizing what a powerful tool they are giving up.
Android Native Development Kit (NDK) was released in 2009 to help developers write and
port native code. It offers a set of cross-compiling tools and a few libraries. Programming in
NDK offers two main advantages. Firstly, you can optimize your apps in native code and boost
performance. Secondly, you can reuse a large number of existing C/C++ code. Android Native
Development Kit is a practical guide to help you write Android native code with NDK. We will
start with the basics such as Java Native Interface (JNI), and build and debug a native app
(chapter 1 to 3). We will then explore various libraries provided by NDK, including OpenGL ES,
Native Application API, OpenSL ES, OpenMAX AL, and so on (Chapters 4 to 7). After that,
we will discuss porting existing applications and libraries to Android with NDK (Chapters 8
and 9). Finally, we will demonstrate how to write multimedia apps and games with NDK
(Bonus chapters 1 and 2).
What this book covers
Chapter 1, Hello NDK, covers how to set up an Android NDK development environment in
Windows, Linux, and MacOS. We will write a "Hello NDK" application at the end of the chapter.
Chapter 2, Java Native Interface, describes the usage of JNI in detail. We will call native
methods from the Java code and vice versa.
Chapter 3, Build and Debug NDK Applications, demonstrates building native code from a
command line and Eclipse IDE. We will also look at debugging native code with gdb, cgdb,
eclipse, and so on.
Chapter 4, Android NDK OpenGL ES API, illustrates OpenGL ES 1.x and 2.0 APIs. We will cover
2D drawing, 3D graphics, texture mapping, EGL, and so on.
Preface
2
Chapter 5, Android Native Application API, discusses Android native application APIs, including
managing native windows, accessing sensors, handling input events, managing assets, and
so on. We will see how to write a pure native app in this chapter.
Chapter 6, Android NDK Multithreading, depicts Android multithreading API. We will cover
creating and terminating native threads, various thread synchronization techniques
(mutex, conditional variables, semaphore, and reader/writer lock), thread scheduling,
and thread data management.
Chapter 7, Other Android NDK API, discusses a few more Android libraries, including
jnigraphics, the dynamic linker library, the zlib compression library, the OpenSL
ES library, and the OpenMAX AL library.
Chapter 8, Porting and Using Existing Libraries with Android NDK, describes various
techniques of porting and using existing C/C++ libraries with NDK. We will port the boost
library at the end of the chapter.
Chapter 9, Porting Existing Applications to Android with NDK, provides a step-by-step guide
for porting an existing application to Android with NDK. We use an open source image resizing
program as an example.
Bonus Chapter 1, Developing Multimedia Applications with NDK, demonstrates how to write
multimedia applications with the ffmpeg library. We will port the ffmpeg library and use the
library APIs to write a frame grabber application.
Bonus Chapter 2, Developing Games with NDK, discusses writing games with NDK. We will
port the Wolfenstein 3D game to show how to set up game display, add game control, and
enable audio effects for a game.
You can download the bonus chapters from http://www.packtpub.com/sites/default/
files/downloads/Developing_Multimedia_Applications_with_NDK.pdf and
http://www.packtpub.com/sites/default/files/downloads/Developing_
Games_with_NDK.pdf.

A computer with Windows, Ubuntu Linux, or MacOS installed is necessary (Linux or MacOS is

Android development. Therefore, it is recommended to have an Android device.
The book assumes a basic understanding of C and C++ programming languages. You should
also be familiar with Java and Android SDK.
Note that the sample code of this book is based on Android ndk r8 unless otherwise stated,
since it is the latest version of NDK at the time of writing. By the time the book is published,
there should be newer versions. The code should also run on any newer versions. Therefore
we can install NDK r8 or later.
Preface
3

The book is written for anyone who is interested in writing native code for Android. The
chapters are arranged from basic to intermediate to advanced, and they are relatively
independent. Readers who are new to NDK are recommended to read from the beginning to


Conventions

information. Here are some examples of these styles, and an explanation of their meaning.
Code words in text are shown as follows: "Windows NDK comes with a new ndk-build.cmd
build script."
A block of code is set as follows:
#include <string.h>
#include <jni.h>
Java_cookbook_chapter1_HelloNDKActivity_naGetHelloNDKStr(JNIEnv* pEnv,
jobject pObj)
{
return (*pEnv)->NewStringUTF(pEnv, "Hello NDK!");
}
When we wish to draw your attention to a particular part of a code block, the relevant lines or
items are set in bold:
LOCAL_PATH := $(call my-dir)
include $(CLEAR_VARS)
LOCAL_MODULE := framegrabber
LOCAL_SRC_FILES := framegrabber.c
#LOCAL_CFLAGS := -DANDROID_BUILD
LOCAL_LDLIBS := -llog -ljnigraphics -lz
LOCAL_STATIC_LIBRARIES := libavformat_static libavcodec_static
libswscale_static libavutil_static
include $(BUILD_SHARED_LIBRARY)
$(call import-module,ffmpeg-1.0.1/android/armv5te)
Any command-line input or output is written as follows:
$sudo update-java-alternatives -s <java name>
Preface
4
New terms and important words are shown in bold. Words that you see on the screen, in
menus or dialog boxes for example, appear in the text like this: "Go to Control Panel | System
and Security | System | Advanced system settings."
Warnings or important notes appear in a box like this.
Tips and tricks appear like this.

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Preface
5
Errata
Although we have taken every care to ensure the accuracy of our content, mistakes do

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1
Hello NDK
In this chapter, we will cover the following recipes:
f Setting up an Android NDK development environment in Windows
f Setting up an Android NDK development environment in Ubuntu Linux
f Setting up an Android NDK development environment in Mac OS
f Updating Android NDK
f Writing a Hello NDK program
Introduction
Android NDK is a toolset that allows developers to implement a part of or an entire Android
application in a native language, such as C, C++, and assembly. Before we start our journey
to NDK, it is important to understand the advantages of NDK.
First of all, NDK may improve application performance. This is usually true for many
processor-bound applications. Many multimedia applications and video games use
native code for processor-intensive tasks.
The performance improvements can come from three sources. Firstly, the native code is
compiled to a binary code and run directly on OS, while Java code is translated into Java
byte-code and interpreted by Dalvik Virtual Machine (VM). At Android 2.2 or higher,
a Just-In-Time (JIT) compiler is added to Dalvik VM to analyze and optimize the Java
byte-code while the program is running (for example, JIT can compile a part of the
byte-code to binary code before its execution). But in many cases, native code still
runs faster than Java code.
Hello NDK
8
Java code is run by Dalvik VM on Android. Dalvik VM is specially designed
for systems with constrained hardware resources (memory space, processor
speed, and so on).
The second source for performance improvements at NDK is that native code allows
developers to make use of some processor features that are not accessible at Android SDK,
such as NEON, a Single Instruction Multiple Data (SIMD) technology, allowing multiple
data elements to be processed in parallel. One particular coding task example is the color
conversion for a video frame or a photo. Suppose we are to convert a photo of 1920x1280
pixels from the RGB color space to the YCbCr color space. The naive approach is to apply a
conversion formula to every pixel (that is, over two million pixels). With NEON, we can process
multiple pixels at one time to reduce the processing time.
The third aspect is that we can optimize the critical code at an assembly level, which is a
common practice in desktop software development.
The advantages of using native code do not come free. Calling JNI
methods introduces extra work for the Dalvik VM and since the code is
compiled, no runtime optimization can be applied. In fact, developing in
NDK doesn't guarantee a performance improvement and can actually
harm performance at times. Therefore, we only stated that it may
improve the app's performance.
The second advantage of NDK is that it allows the porting of existing C and C++ code to

share code between Android and non-Android projects.
Before we decide to use NDK for an Android app, it is good to know that NDK will not

prefers programming in C or C++ over Java. NDK cannot access lots of APIs available in
the Android SDK directly, and developing in NDK will always introduce extra complexity
into your application.
With the understanding of the pros and cons of NDK, we can start our journey to Android NDK.
This chapter will cover how to set up Android NDK development in Windows, Ubuntu Linux, and
Mac OS. For developers who have set up an Android NDK development environment before, a
recipe with detailed steps of how to update an NDK development environment is provided.
At the end of the chapter, we will write a Hello NDK program with the environment setup.
Setting up an Android NDK development
environment in Windows
In this recipe, we will explore how to set up an Android NDK development environment
in Windows.
Chapter 1
9
Getting ready
Check the Windows edition and system type. An Android development environment can be set
up on Windows XP 32-bit, Windows Vista 32- or 64-bit, and Windows 7 32- or 64-bit.
Android development requires Java JDK 6 or above to be installed. Follow these steps to

1. Go to the Oracle Java JDK web page at http://www.oracle.com/technetwork/
java/javase/downloads/index.html, and choose JDK6 or above for your
platform to download.
2. Double-click on the downloaded executable, and click through the installation wizard

3. Go to Control Panel | System and Security | System | Advanced system settings.
A System Properties window will pop up.
4. Click on the Environment Variables button in the Advanced tab; another
Environment Variables window will pop up.
5. Under System variables, click on New to add a variable with the name as
JAVA_HOME and value as the path of the JDK installation root directory.
This is shown as follows:
Hello NDK
10
6. Under System variablesPATH (or Path) environment variable.
Insert %JAVA_HOME%\bin; at the beginning of the value. If no PATH or Path
variable exists, create a new variable with the value set to %JAVA_HOME%\bin.
Click on OK all the way through to dismiss all windows.
7. 
console, and enter javac -version
Java version in the output.
Cygwin is a Linux-like environment for Windows to run software available on Linux. Android
NDK development requires Cygwin 1.7 or higher installed to execute some Linux programs;
for example, the GNU make.
Since NDK r7, the Windows NDK comes with a new ndk-build.cmd build script, which uses
NDK's prebuilt binaries for GNU make, awk, and other tools. Therefore Cygwin is not required
for building NDK programs with ndk-build.cmd. However, it is recommended that you
still install Cygwin, because ndk-build.cmd is an experimental feature and Cygwin is still
needed by the debugging script ndk-gdb.
Follow these steps to install Cygwin:
1. Go to http://cygwin.com/install.html to download setup.exe for Cygwin.
Double-click on it after the download is complete in order to start the installation.
2. Click on Next, then select Install from Internet. Keep clicking on Next until you see
the Available Download Sites list. Select the site that is close to your location, then
click on Next:
Chapter 1
11
3. Look for GNU make under Devel, ensure it is version 3.81 or later, and gawk under
Base. Alternatively, you can search for make and gawk using the Search box. Make
sure both GNU make and gawk are selected to install, then click on Next. The

Eclipse is a powerful software Integrated Development Environment (IDE) with an
extensible plugin system. It is the recommended IDE to develop Android apps. Go to
http://www.eclipse.org/downloads/, and download the Eclipse Classic or
will be ready
for use. Note that Android development requires Eclipse 3.6.2 (Helios) or greater.
The Android developer website provides an Android Developer Tools bundle
at http://developer.android.com/sdk/index.html. It includes
the Eclipse IDE with the ADT plugin, and the Android SDK. We can download
this bundle and skip the SDK installation described in steps 1 to 10 of the
following How to do it... section.
Hello NDK
12
How to do it…
The following steps show you how to set up an Android NDK development environment in

if SDK is already set up.
1. Start Eclipse. Select Help | Install New Software, and a window titled Install will
pop up.
2. Click on the Add… button at the top-right will corner, and another window titled
Add Repository will pop up.
3. In the Add Repository window, enter ADT for Name and
https://dl-ssl.google.com/android/eclipse/ for Location.
Then click on OK.
4. It may take a few seconds for Eclipse to load the software items from the ADT
website. After loading, select Developer Tools and NDK Plugins, then click on
Next to proceed:
5. In the next window, a list of tools to be installed will be shown. Simply click on Next.
Read and accept all the license agreements, then click on Finish.
6. Eclipse as prompted.
7. Download Android SDK from
http://developer.android.com/sdk/index.html.
8. 
the installation.
9. In Eclipse, select Window | Preferences to open the Preferences window. Select
Android from the left panel, then click on Browse to locate the Android SDK root
directory. Click on Apply, and then OK.
Chapter 1
13
10. Start Android SDK Manager at the Android SDK installation root directory. Select
Android SDK Tools, Android SDK Platform-tools, at least one Android platform (the
latest is preferred), System Image, SDK Samples, and Android Support. Then click
on Install. in the next window, read and accept all the license agreements, then click
on Install:
11. Go to http://developer.android.com/tools/sdk/ndk/index.html to

Downloading the example code
You can download the example code files for all Packt books you have
purchased from your account at http://www.packtpub.com. If you
purchased this book elsewhere, you can visit http://www.packtpub.
com/support and register to have the files e-mailed directly to you.
Hello NDK
14
12. Open Cygwin.bat under the cygwin root directory. It contains the following
content by default:
@echo off
C:
chdir C:\cygwin\bin
bash --login -i
13. Add the following content after @echo off before C:
set IS_UNIX=
set JAVA_HOME=<JDK path>
set PATH=<SDK path>\tools;<NDK path>
set ANDROID_NDK_ROOT=/cygdrive/<NDK path>
Progra~1 is
the short name for the Program Files folder:
set IS_UNIX=
set JAVA_HOME=c:/Progra~1/Java/jdk1.7.0_05
set PATH=C:/Users/Administrator/AppData/Local/Android/android-sdk/
tools;C:/Users/Administrator/Downloads/android-ndk-r8-windows/
android-ndk-r8
set ANDROID_NDK_ROOT=/cygdrive/c/Users/Administrator/Downloads/
android-ndk-r8-windows/android-ndk-r8
14. Start Cygwin by double-clicking on cygwin.bat, then go to the samples/hello-jni
directory in NDK. Type the command ndk-build. If the build is successful, it proves
that the NDK environment is set up correctly:
15. In Eclipse, select Window | Preferences to open the Preferences window. Click on
Android from the left panel, and select NDK from the drop-down list. Click on Browse
to locate the Android NDK root directory. Click on OK to dismiss the pop-up window.
This enables us to build and debug Android NDK applications with the Eclipse
NDK plugin:
Chapter 1
15
How it works…

development environment.

make it more convenient to use.
Cygwin is not required for Android SDK development, but is essential for NDK development
because NDK uses some Linux tools that depend on Cygwin.
NDK plugin in ADT: NDK plugin for Eclipse is available in Android Development Tools (ADT),
which allows us to build and debug Android NDK applications easily.
The NDK plugin is only available for ADT 20.0.0 or later, which was
released on June 2012. You may want to update your Eclipse ADT in
order to use the NDK plugin.
There's more…
We installed Eclipse IDE as a part of our development environment. Eclipse is the
recommended IDE for developing Android applications, and it comes with lots of useful
tools and utilities to help our development. However, it is not a compulsory component
of the development environment.
Hello NDK
16
Setting up an Android NDK development
environment in Ubuntu Linux
This recipe depicts how to set up an Android NDK development environment in Ubuntu Linux.
Getting ready
Check your Ubuntu version and make sure it is version 8.04 or later.
GNU C Library (glibc) 2.7 or above is required. It is usually installed with Linux by default.
Two simple methods can check the version of glibc:
1. Start a terminal, and enter ldd --version. This will print the version of ldd
and glibc:
2. We can execute the library as an application. Start a terminal, locate the library
location, and then enter the following command:
<glibc library location>/<glibc library>.
The following output will be displayed:
3. We need to enable 32-bit application execution if we are using a 64-bit machine.
Start a terminal, and enter the following command:
sudo apt-get install ia32-libs
Chapter 1
17
4. Install JDK 6 or above. At a terminal, enter the command sudo apt-get install
openjdk-6-jdk, or alternatively we can enter sudo apt-get install sun-
java6-jdk. After installation, we need to add the JDK path to the PATH
environment variable by adding the following lines to ~/.bashrc:
export JDK_PATH=/usr/local/jdk1.7.0/bin
export PATH=$PATH:$JDK_PATH
We will use Eclipse as our IDE. Please refer to the Setting up an Android NDK development
environment in Windows recipe for instructions.
How to do it…
The following steps indicate the procedure of setting up an Android NDK development
environment on Ubuntu Linux:
1. Follow steps 1 to 6 of the Setting up an Android NDK development environment in
Windows recipe to install the ADT plugin for Eclipse.
2. Download Android SDK from http://developer.android.com/sdk/index.
html, then extract the downloaded package.
3. Append the following lines to ~/.bashrc:
export ANDROID_SDK=<path to Android SDK directory>
export PATH=$PATH:$ ANDROID_SDK/tools:$ANDROID_SDK/platform-tools
4. Follow steps 9 and 10 of the Setting up an Android NDK development environment
in Windows
additional packages.
5. Download the latest version of Android NDK from http://developer.android.
com/tools/sdk/ndk/index.html
6. Change the lines that you appended to ~/.bashrc in step 3:
export ANDROID_SDK=<path to Android SDK directory>
export ANDROID_NDK=<path to Android NDK directory>
export PATH=$PATH:$ANDROID_SDK/tools:$ANDROID_SDK/platform-
tools:$ANDROID_NDK
Hello NDK
18
7. Start a new terminal, then go to the samples/hello-jni directory in NDK.
Type the command ndk-build. If the build is successful, it proves that the
NDK environment is set up correctly:
How it works…

so that the tools can be accessed without referring to the SDK and NDK directories.
The .bashrcwhen you start a new terminal.
The export commands appended the Android SDK and NDK directory locations to the
environment variable PATH. Therefore, every time a new bash shell starts, PATH is set
properly for SDK and NDK tools.
There's more…
The following are a few more tips on setting up an NDK development environment:
f : We append to the SDK and NDK paths to the PATH
environment variable at ~/.bashrc


as follows:
For C shell (csh), the startup file to use is ~/.cshrc.
For ksh, the startup file to use can be obtained using the command
echo $ENV.
For sh, the startup file to use is ~/.profile. The user needs to log out of
the current session and log in again for it to take effect.
f Switch JDK: In Android development, we can either use Oracle Java JDK or OpenJDK.
In case we run into issues with any one of the JDKs, we can switch to another Java
JDK, if we have installed both of them.
To check which JDK the system is currently using, use the following command:
$update-java-alternatives -l
To switch between two JDKs, use the following command:
$sudo update-java-alternatives -s <java name>
Chapter 1
19
The following is an example for switching to Oracle JDK 1.6.0:
$sudo update-java-alternatives -s java-1.6.0-sun
Setting up an Android NDK development
environment in Mac OS
This recipe describes how to set up an Android NDK development environment in Mac OS.
Getting ready
Android development requires Mac OS X 10.5.8 or higher, and it works on the x86 architecture
only. Ensure that your machine meets these requirements before getting started.
Register an Apple developer account, then go to https://developer.apple.com/xcode/
to download Xcode, which contains a lot of developer tools, including the make utility required
for Android NDK development. After the download is complete, run the installation package and
make sure that the UNIX Development option is selected for installation.
As usual, Java JDK 6 or above is required. Mac OS X usually ships with a full JDK. We can
verify that your machine has the required version by using the following command:
$javac -version
How to do it…
Setting up an Android NDK development environment on Mac OS X is similar to setting it up
on Ubuntu Linux. The following steps explain how we can do this:
1. Follow steps 1 to 6 of the Setting up an Android NDK development environment in
Windows recipe to install the ADT plugin for Eclipse.
2. Download Android SDK from http://developer.android.com/sdk/index.
html, then extract the downloaded package.
3. Append the following lines to ~/.profile
Save the changes and log out of the current session:
export ANDROID_SDK=<path to Android SDK directory>
export PATH=$PATH:$ ANDROID_SDK/tools:$ANDROID_SDK/platform-tools
4. In Eclipse, select Eclipse | Preferences to open the Preferences window. Select
Android from the left panel, then click on Browse to locate the Android SDK root
directory. Click on Apply, and then OK.
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