android_frameworks_base/docs/html/sdk/ndk/index.jd

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page.title=Android NDK
@jd:body

<h2 id="notes">Revisions</h2>

<p>The sections below provide information and notes about successive releases of
the NDK, as denoted by revision number. </p>

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<div class="toggleable open">
    <a href="#"
         onclick="return toggleDiv(this)"><img src="{@docRoot}assets/images/triangle-opened.png"
         class="toggle-img"
         height="9px"
         width="9px" /> Android NDK, Revision 5</a> <em>(November 2010)</em>

    <div class="toggleme">
      <dl>
        <dt>NDK r5 notes:</dt>

        <dd>
          <p>The r5 release of the NDK includes many new APIs, many of which are introduced to
          support native game development and applications that require similar requirements. Most
          notably, native activities are now supported, which allow you to write an application
          entirely with native code. For detailed information describing the changes in this
          release, read the CHANGES.HTML document included in the downloaded NDK package.</p>
        </dd>
      </dl>

      <dl>
        <dt>General notes:</dt>

        <dd>
          <ul>
          
            <li>A new toolchain (based on GCC 4.4.3), which generates better code, and can also now
be used as a standalone cross-compiler, for people who want to build their stuff with
<code>./configure &amp;&amp; make</code>. See
docs/STANDALONE-TOOLCHAIN.html for the details. The binaries for GCC 4.4.0 are still provided,
but the 4.2.1 binaries were removed.</li>

            <li>Support for prebuilt static and shared libraries (docs/PREBUILTS.html), module
exports and imports to make sharing and reuse of third-party modules much easier
(docs/IMPORT-MODULE.html explains why).</li>

            <li>A C++ STL implementation (based on STLport) is now provided as a helper module. It
can be used either as a static or shared library (details and usage exemple under
sources/android/stlport/README). <strong>Note:</strong> For now, C++ Exceptions and RTTI are still
not supported.</li>

            <li>Improvements to the <code>cpufeatures</code> helper library to deal with buggy
kernel that incorrectly report they run on an ARMv7 CPU (while the device really is an ARMv6). We
recommend developers that use it to simply rebuild their applications to benefit from it, then
upload to Market.</li>

            <li>Adds support for native activities, which allows you to write completely native
            applications.</li>

            <li>Adds an EGL library that lets you create and manage OpenGL ES textures and
            services.</li>

            <li>Adds native support for the following:

              <ul>
                <li>Input subsystem (such as the keyboard and touch screen)</li>

                <li>Window and surface subsystem</li>

                <li>Audio APIs based on the OpenSL ES standard that support playback and recording
                as well as control over platform audio effects</li>

                <li>Event loop APIs to wait for things such as input and sensor events</li>

                <li>Access to assets packaged in the <code>.apk</code></li>

                <li>Access to sensor data (accelerometer, compass, gyroscope, etc.)</li>
              </ul>
            </li>

            <li>New sample applications, <code>native-plasma</code> and
              <code>native-activity</code>, to demonstrate how to write a native activity.</li>
            
            <li>Plus many bugfixes and other small improvements; see docs/CHANGES.html for a more
detailed list of changes.</li>
          </ul>
        </dd>
      </dl>
    </div>
  </div>

  <div class="toggleable closed">
    <a href="#"
         onclick="return toggleDiv(this)"><img src="{@docRoot}assets/images/triangle-closed.png"
         class="toggle-img"
         height="9px"
         width="9px" /> Android NDK, Revision 4b</a> <em>(June 2010)</em>

    <div class="toggleme">
      <dl>
        <dt>NDK r4b notes:</dt>

        <dd>
          <p>Includes fixes for several issues in the NDK build and debugging scripts &mdash; if
          you are using NDK r4, we recommend downloading the NDK r4b build. For detailed
          information describing the changes in this release, read the CHANGES.TXT document
          included in the downloaded NDK package.</p>
        </dd>
      </dl>

      <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 on production
            devices 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 by Motorola, Google Nexus One, and
                others.</li>
              </ul>
            </li>

            <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 &mdash; 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>

  <div class="toggleable closed">
    <a href="#"
         onclick="return toggleDiv(this)"><img src="{@docRoot}assets/images/triangle-closed.png"
         class="toggle-img"
         height="9px"
         width="9px" /> Android NDK, Revision 3</a> <em>(March 2010)</em>

    <div class="toggleme">
      <dl>
        <dt>General notes:</dt>

        <dd>
          <ul>
            <li>Adds OpenGL ES 2.0 native library support.</li>

            <li>Adds a sample application,<code>hello-gl2</code>, that illustrates the use of
            OpenGL ES 2.0 vertex and fragment shaders.</li>

            <li>The toolchain binaries have been refreshed for this release with GCC 4.4.0, which
            should generate slightly more compact and efficient machine code than the previous one
            (4.2.1). The NDK also still provides the 4.2.1 binaries, which you can optionally use
            to build your machine code.</li>
          </ul>
        </dd>
      </dl>
    </div>
  </div>

  <div class="toggleable closed">
    <a href="#"
         onclick="return toggleDiv(this)"><img src="{@docRoot}assets/images/triangle-closed.png"
         class="toggle-img"
         height="9px"
         width="9px" /> Android NDK, Revision 2</a> <em>(September 2009)</em>

    <div class="toggleme">
      <p>Originally released as "Android 1.6 NDK, Release 1".</p>

      <dl>
        <dt>General notes:</dt>

        <dd>
          <ul>
            <li>Adds OpenGL ES 1.1 native library support.</li>

            <li>Adds a sample application, <code>san-angeles</code>, that renders 3D graphics
            through the native OpenGL ES APIs, while managing activity lifecycle with a {@link
            android.opengl.GLSurfaceView} object.</li>
          </ul>
        </dd>
      </dl>
    </div>
  </div>

  <div class="toggleable closed">
    <a href="#"
         onclick="return toggleDiv(this)"><img src="{@docRoot}assets/images/triangle-closed.png"
         class="toggle-img"
         height="9px"
         width="9px" /> Android NDK, Revision 1</a> <em>(June 2009)</em>

    <div class="toggleme">
      <p>Originally released as "Android 1.5 NDK, Release 1".</p>

      <dl>
        <dt>General notes:</dt>

        <dd>
          <ul>
            <li>Includes compiler support (GCC) for ARMv5TE instructions, including Thumb-1
            instructions.</li>

            <li>Includes system headers for stable native APIs, documentation, and sample
            applications.</li>
          </ul>
        </dd>
      </dl>
    </div>
  </div>
  
  <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. 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 and environment as
  needed. The NDK will not work with older versions of the Android SDK. Also, take a moment to
  review the <a href="{@docRoot}sdk/ndk/reqs.html">System and Software Requirements</a> for the
  NDK, if you haven't already.</p>

  <p>To install the NDK, follow these steps:</p>

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

    <li>Uncompress the NDK download package using tools available on your computer. When
    uncompressed, the NDK files are contained in a directory called
    <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>
  </ol>

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

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

  <p>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 <code>&lt;ndk&gt;/docs/</code>
  directory. In particular, please read the OVERVIEW.HTML document completely, so that you
  understand the intent of the NDK and how to use it.</p>

  <p>If you used a previous version of the NDK, take a moment to review the list of NDK changes in
  the CHANGES.HTML document.</p>

  <p>Here's the general outline of how you work with the NDK tools:</p>

  <ol>
    <li>Place your native sources under <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>Optional: Create <code>&lt;project&gt;/jni/Application.mk</code>.</li>

    <li>Build your native code by running the 'ndk-build' script from your project's directory. It
    is located in the top-level NDK directory:
      <pre class="no-pretty-print">
cd &lt;project&gt;
&lt;ndk&gt;/ndk-build
</pre>

      <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>

    <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 <code>.apk</code> file.</li>
  </ol>

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

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

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

  <ul>
    <li><code>hello-jni</code> &mdash; a simple application that loads a string from a native
    method implemented in a shared library and then displays it in the application UI.</li>

    <li><code>two-libs</code> &mdash; 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.</li>

    <li><code>san-angeles</code> &mdash; a simple application that renders 3D graphics through the
    native OpenGL ES APIs, while managing activity lifecycle 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>

    <li><code>native-activity</code> &mdash; a simple application that demonstrates how to use the
    native-app-glue static library to create a native activity</li>

    <li><code>native-plasma</code> &mdash; a version of bitmap-plasma implemented with a native
    activity.</li>
  </ul>

  <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>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>

  <ul>
    <li>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 <code>&lt;ndk&gt;/apps/&lt;app_name&gt;/project/</code>. 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 <a href=
    "{@docRoot}guide/developing/eclipse-adt.html">Developing in Eclipse</a>.</li>

    <li>If you are developing with Ant, use the <code>android</code> tool to create the build file
    for each of the sample projects at <code>&lt;ndk&gt;/apps/&lt;app_name&gt;/project/</code>.
    Then set up an AVD, if necessary, build your project in the usual way, and run it in the
    emulator. For more information, see <a href=
    "{@docRoot}guide/developing/other-ide.html">Developing in Other IDEs</a>.</li>
  </ul>

  <h3 id="hello-jni">Exploring the hello-jni Sample</h3>

  <p>The hello-jni sample is a simple demonstration on how to use JNI from an Android application.
  The HelloJni activity receives a string from a simple C function and displays it in a
  TextView.</p>

  <p>The main components of the sample include:</p>

  <ul>
    <li>The familiar basic structure of an Android application (an <code>AndroidManifest.xml</code>
    file, a <code>src/</code> and <code>res</code> directories, and a main activity)</li>

    <li>A <code>jni/</code> directory that includes the implemented source file for the native code
    as well as the Android.mk file</li>

    <li>A <code>tests/</code> directory that contains unit test code.</li>
  </ul>

  <ol>
    <li>Create a new project in Eclipse from the existing sample source or use the
    <code>android</code> tool to update the project so it generates a build.xml file that you can
    use to build the sample.

      <ul>
        <li>In Eclipse:

          <ol type="a">
            <li>Click <strong>File &gt; New Android Project...</strong></li>

            <li>Select the <strong>Create project from existing source</strong> radio button.</li>

            <li>Select any API level above Android 1.5.</li>

            <li>In the <strong>Location</strong> field, click <strong>Browse...</strong> and select
            the <code>&lt;ndk-root&gt;/samples/hello-jni</code> directory.</li>

            <li>Click <strong>Finish</strong>.</li>
          </ol>
        </li>

        <li>On the command line:

          <ol type="a">
            <li>Change to the <code>&lt;ndk-root&gt;/samples/hello-jni</code> directory.</li>

            <li>Run the following command to generate a build.xml file:
              <pre class="no-pretty-print">
android update project -p . -s
</pre>
            </li>
          </ol>
        </li>
      </ul>
    </li>

    <li>Compile the native code using the <code>ndk-build</code> command.
      <pre class="no-pretty-print">
cd &lt;ndk-root&gt;/samples/hello-jni
&lt;ndk_root&gt;/ndk-build
</pre>
    </li>

    <li>Build and install the application as you would a normal Android application. If you are
    using Eclipse, run the application to build and install it on a device. If you are using Ant,
    run the following commands from the project directory:
      <pre class="no-pretty-print">
ant debug
adb install bin/HelloJni-debug.apk
</pre>
    </li>
  </ol>

  <p>When you run the application on the device, the string <code>Hello JNI</code> should appear on
  your device. You can explore the rest of the samples that are located in the
  <code>&lt;ndk-root&gt;/samples</code> directory for more examples on how to use the JNI.</p>

  <h3 id="native-activity">Exploring the native-activity Sample Application</h3>

  <p>The native-activity sample provided with the Android NDK demonstrates how to use the
  android_native_app_glue static library. This static library makes creating a native activity
  easier by providing you with an implementation that handles your callbacks in another thread, so
  you do not have to worry about them blocking your main UI thread. The main parts of the sample
  are described below:</p>

  <ul>
    <li>The familiar basic structure of an Android application (an <code>AndroidManifest.xml</code>
    file, a <code>src/</code> and <code>res</code> directories). The AndroidManifest.xml declares
    that the application is native and specifies the .so file of the native activity. See {@link
    android.app.NativeActivity} for the source or see the
    <code>&lt;ndk_root&gt;/platforms/samples/native-activity/AndroidManifest.xml</code> file.</li>

    <li>A <code>jni/</code> directory contains the native activity, main.c, which uses the
    <code>android_native_app_glue.h</code> interface to implement the activity. The Android.mk that
    describes the native module to the build system also exists here.</li>
  </ul>

  <p>To build this sample application:</p>

  <ol>
    <li>Create a new project in Eclipse from the existing sample source or use the
    <code>android</code> tool to update the project so it generates a build.xml file that you can
    use to build the sample.

      <ul>
        <li>In Eclipse:

          <ol type="a">
            <li>Click <strong>File &gt; New Android Project...</strong></li>

            <li>Select the <strong>Create project from existing source</strong> radio button.</li>

            <li>Select any API level above Android 2.3.</li>

            <li>In the <strong>Location</strong> field, click <strong>Browse...</strong> and select
            the <code>&lt;ndk-root&gt;/samples/native-activity</code> directory.</li>

            <li>Click <strong>Finish</strong>.</li>
          </ol>
        </li>

        <li>On the command line:

          <ol type="a">
            <li>Change to the <code>&lt;ndk-root&gt;/samples/native-activity</code> directory.</li>

            <li>Run the following command to generate a build.xml file:
              <pre class="no-pretty-print">
android update project -p . -s
</pre>
            </li>
          </ol>
        </li>
      </ul>
    </li>

    <li>Compile the native code using the <code>ndk-build</code> command.
      <pre class="no-pretty-print">
cd &lt;ndk-root&gt;/platforms/samples/android-9/samples/native-activity
&lt;ndk_root&gt;/ndk-build
</pre>
    </li>

    <li>Build and install the application as you would a normal Android application. If you are
    using Eclipse, run the application to build and install it on a device. If you are using Ant,
    run the following commands in the project directory, then run the application on the device:
      <pre class="no-pretty-print">
ant debug
adb install bin/NativeActivity-debug.apk
</pre>
    </li>
  </ol>
  
  <h2 id="forum">Discussion Forum and Mailing List</h2>

  <p>If you have questions about the NDK or would like to read or contribute to discussions about
  it, please visit the <a href="http://groups.google.com/group/android-ndk">android-ndk</a> group
  and mailing list.</p>