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Download Android 1.5 NDK, Release 1

June 2009

The Android NDK is a companion tool to the Android SDK that lets Androidapplication developers build performance-critical portions of their apps innative code. It is designed for use only in conjunction with theAndroid SDK, so if you have not already installed the Android 1.5 SDK, please doso before downloading the NDK. Also, please read What is theAndroid NDK? to get an understanding of what the NDK offers and whether itwill be useful to you.

Select the download package that is appropriate for your developmentcomputer.

Platform Package Size MD5 Checksum
Windows android-ndk-1.5_r1-windows.zip 22500667 bytes e5c53915903d8b81f3e2ea422e2e2717
Mac OS X (intel) android-ndk-1.5_r1-darwin-x86.zip 17215303 bytes 1931f0e182798a4c98924fd87380b5b8
Linux 32/64-bit (x86) android-ndk-1.5_r1-linux-x86.zip 16025885 bytes 80a4e14704ca84c21bf1824cb25fbd8b

What is the Android NDK?

The Android NDK provides tools that allow Android application developersto embed components that make use of native code in their Android applications.

Android applications run in the Dalvik virtual machine. The NDK allowsdevelopers to implement parts of their applications using native-code languagessuch as C and C++. This can provide benefits to certain classes of applications,in the form of reuse of existing code and in some cases increased speed.

The NDK provides:

  • A set of tools and build files used to generate native code libraries from Cand C++ sources
  • A way to embed the corresponding native libraries into application packagefiles (.apks) that can be deployed on Android devices
  • A set of native system headers and libraries that will be supported in allfuture versions of the Android platform, starting from Android 1.5
  • Documentation, samples, and tutorials

This release of the NDK supports the ARMv5TE machine instruction setand provides stable headers for libc (the C library), libm (the Math library),the JNI interface, and other libraries.

The NDK will not benefit most applications. As a developer, you will needto balance its benefits against its drawbacks; notably, using native code doesnot result in an automatic performance increase, but does always increaseapplication complexity. Typical good candidates for the NDK are self-contained,CPU-intensive operations that don't allocate much memory, such as signal processing,physics simulation, and so on. Simply re-coding a method to run in C usually doesnot result in a large performance increase. The NDK can, however, can bean effective way to reuse a large corpus of existing C/C++ code.

Please note that the NDK does not enable you to develop native-onlyapplications. Android's primary runtime remains the Dalvik virtual machine.

Contents of the NDK

Development tools

The NDK includes a set of cross-toolchains (compilers, linkers, etc..) thatcan generate native ARM binaries on Linux, OS X, and Windows (with Cygwin)platforms.

It provides a set of system headers for stable native APIs that areguaranteed to be supported in all later releases of the platform:

  • libc (C library) headers
  • libm (math library) headers
  • JNI interface headers
  • libz (Zlib compression) headers
  • liblog (Android logging) header
  • A Minimal set of headers for C++ support

The NDK also provides a build system that lets you work efficiently with yoursources, without having to handle the toolchain/platform/CPU/ABI details. Youcreate very short build files to describe which sources to compile and whichAndroid application will use them — the build system compiles the sourcesand places the shared libraries directly in your application project.

Important: With the exception of thelibraries listed above, native system libraries in the Android 1.5 platform arenot stable and may change in future platform versions.Your applications should only make use of the stable native systemlibraries provided in this NDK.

Documentation

The NDK package includes a set of documentation that describes thecapabilities of the NDK and how to use it to create shared libraries for yourAndroid applications. In this release, the documentation is provided only in thedownloadable NDK package. You can find the documentation in the<ndk>/docs/ directory. Included are these files:

  • INSTALL.TXT — describes how to install the NDK and configure it foryour host system
  • OVERVIEW.TXT — provides an overview of the NDK capabilities andusage
  • ANDROID-MK.TXT — describes the use of the Android.mk file, whichdefines the native sources you want to compile
  • APPLICATION-MK.TXT — describes the use of the Application.mk file,which describes the native sources required by your Android application
  • HOWTO.TXT — information about common tasks associated with NDKdevelopment.
  • SYSTEM-ISSUES.TXT — known issues in the Android system imagesthat you should be aware of, if you are developing using the NDK.
  • STABLE-APIS.TXT — a complete list of the stable APIs exposedby headers in the NDK.

Additionally, the package includes detailed information about the "bionic"C library provided with the Android platform that you should be aware of, if youare developing using the NDK. You can find the documentation in the<ndk>/docs/system/libc/ directory:

  • OVERVIEW.TXT — provides an overview of the "bionic" C library and thefeatures it offers.

Sample applications

The NDK includes two sample Android applications that illustrate how to usenative code in your Android applications:

  • hello-jni — A simple application that loads a string froma native method implemented in a shared library and then displays it in theapplication UI.
  • two-libs — A simple application that loads a sharedlibrary dynamically and calls a native method provided by the library. In thiscase, the method is implemented in a static library that is imported by theshared library.

For more information, see Using the SampleApplications.

System and Software Requirements

The sections below describe the system and software requirements for usingthe Android NDK, as well as platform compatibility considerations that affectappplications using libraries produced with the NDK.

The Android SDK

  • A complete Android SDK installation (including all dependencies) isrequired.
  • Android 1.5 SDK or later version is required.

Supported operating systems

  • Windows XP (32-bit) or Vista (32- or 64-bit)
  • Mac OS X 10.4.8 or later (x86 only)
  • Linux (32- or 64-bit, tested on Linux Ubuntu Dapper Drake)

Required development tools

  • For all development platforms, GNU Make 3.81 or later is required. Earlierversions of GNU Make might work but have not been tested.
  • For Windows, a recent release of Cygwin, including both the gmake and gccpackages, is required.

Android platform compatibility

  • The native libraries created by the Android NDK can only be used ondevices running the Android 1.5 platform version or later. This is due totoolchain and ABI related changes that make the native libraries incompatiblewith 1.0 and 1.1 system images.
  • For this reason, you should use native libraries produced with the NDK inapplications that are deployable to devices running the Android 1.5 platformversion or later. To ensure compatibility, an application using a native libraryproduced with the NDK must declare a elementin its manifest file, with the attributeandroid:minSdkVersion="3".

Installing the NDK

Installing the NDK on your development computer is straightforward andinvolves extracting the NDK from its download package and running a host-setupscript.

Before you get started make sure that you have downloaded the latest Android SDK and upgraded your applicationsand environment as needed. The NDK will not work with older versions of theAndroid SDK. Also, take a moment to review the Systemand Software Requirements for the NDK, if you haven't already.

To install the NDK, follow these steps:

  1. From the table at the top of this page, select the NDK package that isappropriate for your development computer and download the package.
  2. Uncompress the NDK download package using tools available on your computer.When uncompressed, the NDK files are contained in a directory calledandroid-ndk-. You can rename the NDK directory ifnecessary and you can move it to any location on your computer. Thisdocumentation refers to the NDK directory as <ndk>.
  3. Open a terminal, change to the NDK directory, and run the host-setup script.The script sets up your environment and generates a host configuration file usedlater, when building your shared libraries. The path to the host-setup scriptis:

    <ndk>/build/host-setup.sh

    If the script completes successfully, it prints a "Host setup complete."message. If it fails, it prints instructions that you can follow to correct anyproblems.

Once you have run the host-setup script, you are ready start working with theNDK.

Getting Started with the NDK

Once you've installed the NDK successfully, take a few minutes to read thedocumentation included in the NDK. You can find the documentation in the<ndk>/docs/ directory. In particular, please read theOVERVIEW.TXT document completely, so that you understand the intent of the NDKand how to use it.

Here's the general outline of how you work with the NDK tools:

  1. Place your native sources under<ndk>/sources//.... If you want, you can placea symlink to your sources, rather than the sources themselves. The sources youreference here are not strictly associated with a specific shared library orAndroid application. Instead, they are accessible to any build configuration andcan be used to produce any number of shared libraries that can be used by anyAndroid application.
  2. Create <ndk>/sources//Android.mk todescribe your native sources to the NDK build system
  3. Create <ndk>/apps//Application.mk todescribe your Android application and native sources it needs to the NDK buildsystem. This file sets up the link between an Android SDK application projectand any number of shared libraries defined in the<ndk>/sources/ folder and it specifies the path to theapplication project that will receive the shared library built from thesources.
  4. Build your native code by running this make command from the top-level NDKdirectory:

    $ make APP=

    The build tools copy the stripped, shared libraries needed by yourapplication to the proper location in the application's project directory.

  5. Finally, compile your application using the SDK tools in the usual way. TheSDK build tools will package the shared libraries in the application'sdeployable .apk file.

For complete information on all of the steps listed above, please see thedocumentation included with the NDK package.

Using the Sample Applications

The NDK includes two sample applications that illustrate how to use nativecode in your Android applications:

  • hello-jni — A simple application that loads a string froma native method implemented in a shared library and then displays it in theapplication UI.
  • two-libs — A simple application that loads a sharedlibrary dynamically and calls a native method provided by the library. In thiscase, the method is implemented in a static library imported by the sharedlibrary.

For each sample, the NDK includes an Android application project, as well asthe corresponding C source code and the necessary Android.mk and Application.mkfiles. The application projects are provided in<ndk>/apps//project/ and the C source foreach application is provided in<ndk>/sources/samples//.

Once you have installed the NDK, you can build the shared libraries from theNDK by using these commands from the root of the NDK directory:

  • $ make APP=hello-jni — compiles<ndk>/sources/samples/hello-jni/hello-jni.c and outputs ashared library to<ndk>/apps/hello-jni/project/libs/armeabi/libhello-jni.so.
  • $ make APP=two-libs — compiles<ndk>/sources/samples/two-libs/second.c andfirst.c and outputs a shared library to<ndk>/apps/two-libs/project/libs/armeabi/libtwolib-second.so.

Next, build the sample Android applications that use the sharedlibraries:

  • If you are developing in Eclipse with ADT, use the New Project Wizard tocreate a new Android project for each sample, using the "Import from ExistingSource" option and importing the source from<ndk>/apps//project/. Then, set up an AVD, ifnecessary, and build/run the application in the emulator. For more informationabout creating a new Android project in Eclipse, see Developing inEclipse.
  • If you are developing with Ant, use the android tool to createthe build file for each of the sample projects at<ndk>/apps//project/. Then set up an AVD, ifnecessary, build your project in the usual way, and run it in the emulator.For more information, see Developing in OtherIDEs.

Discussion Forum and Mailing List

If you have questions about the NDK or would like to read or contribute todiscussions about it, please visit the android-ndk group andmailing list.

Except as noted, this content is licensed under Creative Commons Attribution 2.5. For details and restrictions, see the Content License.
10-25 08:37
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