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Reuse existing C code with the Android NDK

Learn how to use the Android Native Developer's Kit

Frank Ableson, Entrepreneur, Navitend
W. Frank Ableson is an entrepreneur living in northern New Jersey with his wife Nikki and their children. His professional interests include mobile software and embedded design. He is the author of Unlocking Android (Manning Publications, 2009) and Android in Action (Manning Publications, 2011) and he is the mobile editor for Linux Magazine.

Summary:  The Android Software Developer Kit (SDK) used by the majority of Android application developers requires the use of the Java™ programming language. However, there is a large body of C language code available online. The Android Native Developer Kit (NDK) permits an Android developer to reuse existing C source code within an Android application. In this tutorial, you will create an image processing application in the Java programming language that uses C code to perform basic image processing operations.

Date:  12 Apr 2011
Level:  Intermediate
PDF:  A4 and Letter (773 KB | 42 pages)Get Adobe® Reader®

Activity:  41458 views
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Before you start

One of the motivations for exploring the NDK in the first place is the opportunity to leverage open source projects, many of which are written in C. After completing this tutorial, you will have learned how to create a Java Native Interface (JNI) library, written in C and compiled with the Native Development Kit (NDK), and incorporate the library into an Android application written in the Java language. The application demonstrates how to perform basic image processing operations against raw image data. You will also learn how to extend the Eclipse build environment to integrate an NDK project into an Android SDK project file. From this foundation, you will be better equipped to port existing open source code to the Android platform.

About this tutorial

This tutorial introduces the Android NDK within the Eclipse environment. The NDK is used to add functionality to an Android application using the C programming language. The tutorial begins with a high-level look at the NDK and its common usage scenarios. From there, the topic of image processing is introduced, followed by an introduction and demonstration of this tutorial's application: IBM Photo Phun. This application is a mix of SDK-based Java code and NDK-compiled C code. The tutorial moves on to introduce the Java Native Interface (JNI), which is the technology of interest when working with the NDK. A look ahead to the completed project's source files provides a roadmap for the application constructed here. Then, in a step-by-step manner, you will construct this application. The Java class and C source files are explained. To conclude, the Eclipse build environment is customized to integrate the NDK tool chain directly into the easy-to-use Eclipse build process.

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Prerequisites

To follow this tutorial, you should be comfortable constructing Android applications with the Android SDK and have a basic familiarity with the C programming language. In addition, you will need the following:

  • Eclipse and Android Developer Tools (ADT) — Primary code editor, Java Compiler, and Android Development Tools Plug-in
  • Android Software Developer Kit (SDK)
  • Android Native Developer Kit (NDK)
  • PNG Image — Image used for testing image processing operations

I created the code samples for this tutorial on a MacBook Pro with Eclipse V3.4.2 and Android SDK V8, which supports the Android release labeled 2.2 (Froyo). The NDK release used in this tutorial is r4b. The code requires version r4b or later because the image handling capabilities of the Android NDK are not available in prior releases of the NDK.

See Resources for links to these tools.

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TutorialTitle=Reuse existing C code with the Android NDK
publish-date=04122011
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