am 8acb68e9: Merge "Doc Change: Docs for NDK r4." into froyo

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page.title=Android NDK

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<div class="toggleable open">

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Android NDK, Revision 4</a> <em>(May 2010)</em>

  <div class="toggleme">

<dl>

<dt>General notes:</dt>

<dd>

<ul>

<li>Provides a simplified build system through the new <code>ndk-build</code> build

command. </li>

<li>Adds support for easy native debugging of generated machine code through the new

<code>ndk-gdb</code> command.</li>

<li>Adds a new Android-specific ABI for ARM-based CPU architectures,

<code>armeabi-v7a</code>. The new ABI extends the existing <code>armeabi</code>

ABI to include these CPU instruction set extensions:

<ul>

<li>Thumb-2 instructions</li>

<li>VFP hardware FPU instructions (VFPv3-D16)</li>

<li>Optional support for ARM Advanced SIMD (NEON) GCC intrinsics and VFPv3-D32.

Supported by devices such as Verizon Droid, Google Nexus One, and others.</li>

</ul>

<li>Adds a new <code>cpufeatures</code> static library (with sources) that lets

your app detect the host device's CPU features at runtime. Specifically,

applications can check for ARMv7-A support, as well as VFPv3-D32 and NEON

support, then provide separate code paths as needed.</li>

<li>Adds a sample application, <code>hello-neon</code>, that illustrates how to 

use the <code>cpufeatures</code> library to check CPU features and then provide

an optimized code path using NEON instrinsics, if 

supported by the CPU.</li>

<li>Lets you generate machine code for either or both of the instruction sets

supported by the NDK. For example, you can build for both ARMv5 and ARMv7-A

architectures at the same time and have everything stored to your application's

final <code>.apk</code>.</li>

<li>To ensure that your applications are available to users only if their

devices are capable of running them, Android Market now filters applications

based on the instruction set information included in your application — no

action is needed on your part to enable the filtering. Additionally, the Android

system itself also checks your application at install time and allows the

installation to continue only if the application provides a library that is

compiled for the device's CPU architecture.</li>

<li>Adds support for Android 2.2, including a new stable API for accessing

the pixel buffers of {@link android.graphics.Bitmap} objects from native

code.</li>

</ul>

</dd>

</dl>

</div>

</div>

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Android NDK, Revision 3</a> <em>(March 2010)</em>

  <div class="toggleme">

<ul>

<li>A set of tools and build files used to generate native code libraries from C

and C++ sources</li>

<li>A way to embed the corresponding native libraries into application package

files (.apks) that can be deployed on Android devices</li>

<li>A way to embed the corresponding native libraries into an application package

file (<code>.apk</code>) that can be deployed on Android devices</li>

<li>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 </li>

<li>Documentation, samples, and tutorials</li>

</ul>

<p>This release of the NDK supports the ARMv5TE machine instruction set and

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.</p>

<p>The latest release of the NDK supports these ARM instruction sets:</p>

<ul>

<li>ARMv5TE (including Thumb-1 instructions)</li>

<li>ARMv7-A (including Thumb-2 and VFPv3-D16 instructions, with 

optional support for NEON/VFPv3-D32 instructions)</li>

</ul>

<p>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 <code>.apk</code>. Complete information is provided in the

CPU-ARCH-ABIS.TXT in the NDK package. </p>

<p>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.</p>

<p>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 

<li>libz (Zlib compression) headers</li>

<li>liblog (Android logging) header</li>

<li>OpenGL ES 1.1 and OpenGL ES 2.0 (3D graphics libraries) headers</li>

<li>libjnigraphics (Pixel buffer access) header (for Android 2.2 and above).</li> 

<li>A Minimal set of headers for C++ support</li>

</ul>

by headers in the NDK.</li>

<li>CPU-ARCH-ABIS.TXT &mdash; a description of supported CPU architectures 

and how to target them. </li>

<li>CPU-FEATURES.TXT &mdash; a description of the <code>cpufeatures</code>

static library that lets your application code detect the target device's 

CPU family and the optional features at runtime. 	</li>

<li>CPU-ARM-NEON.TXT &mdash; a description of how to build with optional

ARM NEON / VFPv3-D32 instructions. </li>

<li>CHANGES.TXT &mdash; a complete list of changes to the NDK across all 

releases.</li>

</ul>

<ul>

  <li>For all development platforms, GNU Make 3.81 or later is required. Earlier

versions of GNU Make might work but have not been tested.</li>

  <li>For Windows, a recent release of <a

href="http://www.cygwin.com">Cygwin</a> is required. </li>

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

  <li>For Windows, <a

href="http://www.cygwin.com">Cygwin</a> 1.7 or higher is required. The NDK 

will <em>not</em> work with Cygwin 1.5 installations.</li>

</ul>

<h4>Android platform compatibility</h4>

&lt;/manifest&gt;</pre>

</li>

<li>Additionally, if you use this NDK to create a native library that uses the

<li>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

<p>For more information about API Level and its relationship to Android

platform versions, see <a href="{@docRoot}guide/appendix/api-levels.html">

Android API Levels</a>.</p></li>

<li>Additionally, an application using the OpenGL ES APIs should declare a

<code>&lt;uses-feature&gt;</code> element in its manifest, with an

<code>android:glEsVersion</code> 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: 

<pre style="margin:1em;">&lt;manifest&gt;

  ...

<!-- Declare that the application uses the OpenGL ES 2.0 API and is designed

     to run only on devices that support OpenGL ES 2.0 or higher. -->

  <uses-feature android:glEsVersion="0x00020000" />

  ...

&lt;/manifest&gt;</pre>

<p>For more information, see the <a

href="{@docRoot}guide/topics/manifest/uses-feature-element.html"><code>&lt;uses-feature&gt;</code></a>

documentation.</p></li>

<li>If you use this NDK to create a native library that uses the API to access

Android {@link android.graphics.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 <code>&lt;uses-sdk android:minSdkVersion="8" /&gt;</code>attribute

value in its manifest.</li>

</ul>

<h2 id="installing">Installing the NDK</h2>

<p>Installing the NDK on your development computer is straightforward and

involves extracting the NDK from its download package and running a host-setup

script. </p>

involves extracting the NDK from its download package. Unlike previous releases,

there is no need to run a host-setup script.</p>

<p>Before you get started make sure that you have downloaded the latest <a

href="{@docRoot}sdk/index.html">Android SDK</a> and upgraded your applications

<code>android-ndk-&lt;version&gt;</code>. 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 <code>&lt;ndk&gt;</code>.  </li>

<li>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 used

later, when building your shared libraries. The path to the host-setup script

is:

<p><code>&lt;ndk&gt;/build/host-setup.sh</code></p>

<p>If the script completes successfully, it prints a "Host setup complete."

message. If it fails, it prints instructions that you can follow to correct any

problems. </p>

</li>

</ol>

<p>Once you have run the host-setup script, you are ready start working with the

NDK. </p>

<p>You are now ready start working with the NDK. </p>

<h2 id="gettingstarted">Getting Started with the NDK</h2>

<code>&lt;project&gt;/jni/...</code></li>

<li>Create <code>&lt;project&gt;/jni/Android.mk</code> to

describe your native sources to the NDK build system</li>

<li>Create <code>&lt;ndk&gt;/apps/&lt;my_app&gt;/Application.mk</code> to

describe your Android application and native sources it needs to the NDK build

system. This file sets up the link between an Android SDK application project

and any number of shared libraries defined in the

<code>&lt;project&gt;/jni/</code> folder and it specifies the path to the

application project that will receive the shared library built from the

sources.</li>

<li>Build your native code by running this make command from the top-level NDK

directory:

<p><code>$ make APP=&lt;my_app&gt;</code></p>

<li>Optional: Create <code>&lt;project&gt;/jni/Application.mk</code>.</li>

<li>Build your native code by running the 'ndk-build' script from your projet's directory.

It is located in the top-level NDK directory:

<p><pre>

$ cd <project>

$ <ndk>/ndk-build

</pre></p>

<p>The build tools copy the stripped, shared libraries needed by your

application to the proper location in the application's project directory.</p>

<li>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. </p></li>

deployable <code>.apk</code> file. </p></li>

</ol>

<h2 id="samples">Using the Sample Applications</h2>

<p>The NDK includes four sample applications that illustrate how to use native

<p>The NDK includes sample applications that illustrate how to use native

code in your Android applications:</p>

<ul>

with a {@link android.opengl.GLSurfaceView} object. </li>

<li><code>hello-gl2</code> &mdash; a simple application that renders a triangle

using OpenGL ES 2.0 vertex and fragment shaders.</li>

<li><code>hello-neon</code> &mdash; a simple application that shows how to use

the <code>cpufeatures</code> 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.</li>

<li><code>bitmap-plasma</code> &mdash; a simple application that demonstrates

how to access the pixel buffers of Android {@link android.graphics.Bitmap}

objects from native code, and uses this to generate an old-school "plasma"

effect. </li>

</ul>

<p>For each sample, the NDK includes an Android application project, as well as

the corresponding C source code and the necessary Android.mk and Application.mk

files. The application projects are provided in

<code>&lt;ndk&gt;/apps/&lt;app_name&gt;/project/</code> and the C source for

each application is provided in

<code>&lt;ndk&gt;/apps/&lt;app_name&gt;/project/jni/</code>.</p>

<p>For each sample, the NDK includes the corresponding C source code and the

necessary Android.mk and Application.mk files. There are  located under 

<code>&lt;ndk&gt;/samples/&lt;name&gt;/</code> and their source code can be found under

<code>&lt;ndk&gt;/samples/&lt;name&gt;/jni/</code>. </p>

<p>Once you have installed the NDK and run <code>$ build/host-setup.sh</code> from

the root of the NDK directory, you can build the shared libraries for the

sample apps by using these commands:</p>

<ul>

<li><code>$ make APP=hello-jni</code> &mdash; compiles

<code>hello-jni.c</code> and outputs a shared library to

<code>&lt;ndk&gt;/apps/hello-jni/project/libs/armeabi/libhello-jni.so</code>.

</li>

<li><code>$ make APP=two-libs</code> &mdash; compiles

<code>first.c</code> and <code>second.c</code> and outputs a shared library to

<code>&lt;ndk&gt;/apps/two-libs/project/libs/armeabi/libtwolib-second.so</code>.

</li>

<li><code>$ make APP=san-angeles</code> &mdash; compiles

<code>importgl.c</code>, <code>demo.c</code>,and <code>app-android.c</code> and 

outputs a shared library to <code>&lt;ndk&gt;/apps/san-angeles/project/libs/armeabi/libsangeles.so</code>.

</li>

<li><code>$ make APP=hello-gl2</code> &mdash; compiles

<code>gl_code.cpp</code> and outputs a shared library to 

<code>&lt;ndk&gt;/apps/hello-gl2/project/libs/armeabi/libgl2jni.so</code>.

</li>

</ul>

<p>You can build the shared libraries for the sample apps by going into <code>&lt;ndk&gt;/samples/&lt;name&gt;/</code>

then calling the <code>ndk-build</code> command. The generated shared libraries will be located under

<code>&lt;ndk&gt;/samples/&lt;name&gt;/libs/armeabi/</code> for (ARMv5TE machine code) and/or

<code>&lt;ndk&gt;/samples/&lt;name&gt;/libs/armeabi-v7a/</code> for (ARMv7 machine code).

</p>

<p>Next, build the sample Android applications that use the shared

libraries:</p>

mailing list.</p>

      <span style="display:none" class="zh-TW"></span>

    </h2>

    <ul>

      <li><a href="<?cs var:toroot ?>sdk/ndk/index.html">Android NDK, r3</a>

      <li><a href="<?cs var:toroot ?>sdk/ndk/index.html">Android NDK, r4</a>

      <span class="new">new!</span></li>

    </ul>

  </li>