What is the Android NDK?

The Android NDK is a toolset that lets you embed components that make use of native code in your Android applications.

Android applications run in the Dalvik virtual machine. The NDK allows you to implement parts of your applications using native-code languages such 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 C and C++ sources

A way to embed the corresponding native libraries into an application package file (.apk) that can be deployed on Android devices

A set of native system headers and libraries that will be supported in all future versions of the Android platform, starting from Android 1.5

Documentation, samples, and tutorials

The latest release of the NDK supports these ARM instruction sets:

ARMv\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0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(including Thumb-1 instructions)

ARMv7-A (including Thumb-2 and VFPv3-D16 instructions, with optional support for NEON/VFPv3-D32 instructions)

Future releases of the NDK will also support:

x86 instructions (see CPU-ARCH-ABIS.TXT for more information)

ARMv5TE machine code will run on all ARM-based Android devices. ARMv7-A will run only on devices such as the Verizon Droid or Google Nexus One that have a compatible CPU. The main difference between the two instruction sets is that ARMv7-A supports hardware FPU, Thumb-2, and NEON instructions. You can target either or both of the instruction sets — ARMv5TE is the default, but switching to ARMv7-A is as easy as adding a single line to the application's Application.mk file, without needing to change anything else in the file. You can also build for both architectures at the same time and have everything stored in the final .apk. For complete information is provided in the CPU-ARCH-ABIS.TXT in the NDK package.

The NDK provides stable headers for libc (the C library), libm (the Math library), OpenGL ES (3D graphics library), the JNI interface, and other libraries, as listed in the section below.

The NDK will not benefit most applications. As a developer, you will need to balance its benefits against its drawbacks; notably, using native code does not result in an automatic performance increase, but does always increase application complexity. Typical good candidates for the 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0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0 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 does not result in a large performance increase. The NDK can, however, can be an effective way to reuse a large corpus of existing C/C++ code.

Please note that the NDK does not enable you to develop native-only applications. 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..) that can 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 are guaranteed 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

OpenGL ES 1.1 and OpenGL ES 2.0 (3D graphics libraries) headers

libjnigraphics (Pixel buffer access) header (for Android 2.2 and above).

A Minimal set of headers for C++ support

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

Important: With the exception of the libraries listed above, native system libraries in the Android platform are not stable and may change in future platform versions. Your applications should only make use of the stable native system libraries provided in this NDK.

Documentation

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

INSTALL.TXT — describes how to install the NDK and configure it for your host system

OVERVIEW.TXT — provides an overview of the NDK capabilities and usage

ANDROID-MK.TXT — describes the use of the Android.mk file, which defines 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 NDK development.

SYSTEM-ISSUES.TXT — known issues in the Android system images that you should be aware of, if you are developing using the NDK.

STABLE-APIS.TXT — a complete list of the stable APIs exposed by headers in the NDK.

CPU-ARCH-ABIS.TXT — a description of supported CPU architectures and how to target them.

CPU-FEATURES.TXT — a description of the cpufeatures static library that lets your application code detect the target device's CPU family and the optional features at runtime.

CPU-ARM-NEON.TXT — a description of how to build with optional ARM NEON / VFPv3-D32 instructions.

CHANGES.TXT — a complete list of changes to the NDK across all releases.

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

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

Sample applications

The NDK includes sample Android applications that illustrate how to use native code in your Android applications. For more information, see Using the Sample Applications.

System and Software Requirements

The sections below describe the system and software requirements for using the Android NDK, as well as platform compatibility considerations that \0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0affect appplications using libraries produced with the NDK.

The Android SDK

A complete Android SDK installation (including all dependencies) is required.

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. Earlier versions of GNU Make might work but have not been tested.

A recent version of awk (either GNU Awk or Nawk) is also required.

For Windows, Cygwin 1.7 or higher is required. The NDK will not work with Cygwin 1.5 installations.

Android platform compatibility

The native libraries created by the Android NDK can only be used on devices running the Android 1.5 platform version or later. This is due to toolchain and ABI related changes that make the native libraries incompatible with 1.0 and 1.1 system images.

For this reason, you should use native libraries produced with the NDK in applications that are deployable to devices running the Android 1.5 platform version or later.

To ensure compatibility, an application using a native library produced with the NDK must declare a element in its manifest file, with an android:minSdkVersion attribute value of "3" or higher. For example:

...

...

If you use this NDK to create a native library that uses the OpenGL ES APIs, the application containing the library can be deployed only to devices running the minimum platform versions described in the table below. To ensure compatibility, make sure that your application declares the proper android:minSdkVersion attribute value, as given in the table.

OpenGL ES Version Used Compatible Android Platform(s) Required uses-sdk Attribute

OpenGL ES 1.1 Android 1.6 and higher android:minSdkVersion="4"

OpenGL ES 2.0 Android 2.0 and higher android:minSdkVersion="5"

For more information about API Level and its relationship to Android platform versions, see Android API Levels.

Additionally, an application using the OpenGL ES APIs should declare a element in its manifest, with an android:glEsVersion attribute that specifies the minimum OpenGl ES version required by the application. This ensures that Android Market will show your application only to users whose devices are capable of supporting your application. For example:

...

...

For more information, see the documentation.

If you use this NDK to create a native library that uses the API to access Android Bitmap pixel buffers, the application containing the library can be deployed only to devices running Android 2.2 (API level 8) or higher. To ensure compatibility, make sure that your application declares attribute value in its manifest.

Installing the NDK

Installing the NDK on your development computer is straightforward and involves extracting the NDK from its download package. Unlike previous releases, there is no need to run a host-setup script.

Before you get started make sure that you have downloaded the latest Android SDK and upgraded your applications and environment as needed. The NDK will not work with older ve\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0rsions of the Android SDK. Also, take a moment to review the System and Software Requirements for the NDK, if you haven't already.

To install the NDK, follow these steps:

From the table at the top of this page, select the NDK package that is appropriate for your development computer and download the package.

Uncompress the NDK download package using tools available on your computer. When uncompressed, the NDK files are contained in a directory called android-ndk-. You can rename the NDK directory if necessary and you can move it to any location on your computer. This documentation refers to the NDK directory as .

You are now ready start working with the NDK.

Getting Started with the NDK

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

If you used a previous version of the NDK, take a moment to review the list of NDK changes in the CHANGES.TXT document.

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

Place your native sources under /jni/...

Create 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to describe your native sources to the NDK build system

Optional: Create /jni/Application.mk.

Build your native code by running the 'ndk-build' script from your projet's directory. It is located in the top-level NDK directory:

$ cd

$ /ndk-build

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

Finally, compile your application using the SDK tools in the usual way. The SDK build tools will package the shared libraries in the application's deployable .apk file.

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

Using the Sample Applications

The NDK includes sample applications that illustrate how to use native code in your Android applications:

hello-jni — a simple application that loads a string from a native method implemented in a shared library and then displays it in the application UI.

two-libs — a simple application that loads a shared library dynamically and calls a native method provided by the library. In this case, the method is implemented in a static library imported by the shared library.

san-angeles — a simple application that renders 3D graphics through the native OpenGL ES APIs, while managing activity lifecycle with a GLSurfaceView object.

hello-gl2 — a simple application that renders a triangle using OpenGL ES 2.0 vertex and fragment shaders.

hello-neon — a simple application that shows how to use the cpufeatures library to check CPU capabilities at runtime, then use NEON intrinsics if supported by the CPU. Specifically, the application implements two versions of a tiny benchmark for a FIR filter loop, a C version and a NEON-optimized version for devices that support it.

bitmap-plasma — a simple application that demonstrates how to access the pixel buffers of Android Bitmap objects from native code, and uses this to generate an old-school "plasma" effect.

For each sample, the NDK includes the corresponding C source code and the necessary Android.mk and Application.mk files. There are located under /samples// and their source code can be found under /samples//jni/.

You can build the shared libraries for the sample apps by going into /samples// then calling the ndk-build command. The generated shared libraries will be located under /samples//libs/armeabi/ for (ARMv5TE machine code) and/or /samples//libs/armeabi-v7a/ for (ARMv7 machine code).

Next, build the sample Android applications that use the shared libraries:

If you are developing in Eclipse with ADT, use the New Project Wizard to create a new Android project for each sample, using the "Import from Existing Source" option and importing the source from /apps//project/. Then, set up an AVD, if necessary, and build/run the application in the emulator. For more information about creating a new Android project in Eclipse, see Developing in Eclipse.

If you are developing with Ant, use the android tool to create the build file for each of the sample projects at /apps//project/. Then set up an AVD, if necessary, build your project in the usual way, and run it in the emulator. For more information, see Developing in Other IDEs.

웹문서를 자동으로 좀 그럴싸하게 넣도록 수정해봐야지 이건 영아니다; 가독성 0;;

OpenCV in Android

Using OpenCV in Android. This tutorial is tested under Ubuntu 10.04 + Android SDKr05 + Android NDKr03.

Preparing the development environment

Download and install Android SDK. Details can be found here

Download eclipse and install the ADT plugin. Details can be found here

Download Androdi NDK. This tool is used to cross compile OpenCV source code to Android. Currently (NDK r3) only C is fully supported, so I can only use OpenCV 1.1 under Android. The laterst version of OpenCV uses lots of STL functions. :(

Download OpenCV source code

Download the source code here. The source code in cxcore and cv directories are based on OpenCV 1.1pre version. I only change less than 10 lines to make it pass the compilation. I do not include highgui because there are too much work to cross compile libraries like IJG. I provide two simple functions in cvjni.cpp to set and get images between JVM and native environment.

Test the code

Create a new Android project in eclipse. For example, called testOpenCV.

In the root directory of the project, create a new folder called jni and extract all files in android_opencv.tar.gz to this folder.

Change to the Android NDK directory and run

./build/host-setup.sh

This will tell you whether your system is ready to cross compile the source code. If there is no error, switch to apps directory and create a new folder called opencv and move the Application.mk from the jni folder to opencv.

Modify the Application.mk file to make sure APP_BUILD_SCRIPT and APP_PROJECT_PATH point to the correct file and path.

Go back to the Android NDK directory and run

make APP=opencv

This step may take serveral minutes. Be patient.

Now let's write a simple app to test whether OpenCV work. When I created the project, I use the namespace edu.stanford.zixuanpc. If you are using other namespace, you need to change the function name in cvjni and run make again. In this simple app, we would like to use the camera to take an image and extract SURF features from this image and show the results.

I have three java files which can be downloaded here. They are a little bit long so I do not want to paste the source code here. The general idea is that I use the intent to start the camera or gallery activities to get the image and send this image to OpenCV. After OpenCV finishes extracting SURF features, it send the processed image back to JVM. The interface between JVM and OpenCV is pretty simple: setSourceImage and getSourceImage.

OpenCV.java

package edu.stanford.zixuanpc;

public class OpenCV {

static{

System.loadLibrary("opencv");

}

public native boolean setSourceImage(int[] pixels, int width, int height);

public native byte[] getSourceImage();

public native void extractSURFFeature();

}

And here is the code how we use these two functions:

Code snippet in testOpenCVActivity.java

Bitmap bitmap = BitmapFactory.decodeFile(mCurrentImagePath);

int width = bitmap.getWidth();

int height = bitmap.getHeight();

int[] pixels = new int[width * height];

bitmap.getPixels(pixels, 0, width, 0, 0, width, height);

opencv.setSourceImage(pixels, width, height);

opencv.extractSURFFeature();

byte[] imageData = opencv.getSourceImage();

bitmap = BitmapFactory.decodeByteArray(imageData, 0,

imageData.length);

mImageView.setImageBitmap(bitmap);

You can use other OpenCV functions supported in 1.1.

출처 : http://www.stanford.edu/~zxwang/android_opencv.html

원래는 Silverlight UI 붙이는 거였지만 ㅋㅋ

왠일인지 놋북에선 GG라서 ㅠ

그냥 내일 할일을 오늘하고 오늘할일을 내일 하는 swap 연산을 수행 ㅋ

1. insertNDepthTweet(string rootScreenName, int depth, int max){}

2. 겹치는 트윗은 넣지 않는다.