What is the 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. Applications that use native activities must be run on Android 2.3 or later.
• Documentation, samples, and tutorials

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

• ARMv5TE (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.HTML 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. Complete information is provided in the CPU-ARCH-ABIS.HTML 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 Development Tools section.