Merge "Doc change: updating ndk download and overview page" into gingerbread

         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>

      <p>This release of the NDK includes many new APIs, most of which are introduced to

         support the development of games and similar applications that make extensive use

         of native code. Using the APIs, developers have direct native access to events, audio,

         graphics and window management, assets, and storage. Developers can also implement the

         Android application lifecycle in native code with help from the new

         {@link android.app.NativeActivity} class. For detailed information describing the changes in this

         release, read the CHANGES.HTML document included in the downloaded NDK package.

      </p>

      <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 support for native activities, which allows you to implement the

            Android application lifecycle in native code.</li>

            <li>Adds native support for the following:

              <ul>

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

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

                <li>Event loop APIs to wait for things such as input and sensor events.</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 assets packaged in an <code>.apk</code> file.</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>Includes 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>Plus many bugfixes and other small improvements; see docs/CHANGES.html for a more

            <li>Adds support for prebuilt static and shared libraries (docs/PREBUILTS.html) and module

            exports and imports to make sharing and reuse of third-party modules much easier

            (docs/IMPORT-MODULE.html explains why).</li>

            <li>Provides a default C++ STL implementation (based on STLport) as a helper module. It can be used either

            as a static or shared library (details and usage examples are in sources/android/stlport/README). Prebuilt

            binaries for STLport (static or shared) and GNU libstdc++ (static only) are also provided if you choose to

            compile against those libraries instead of the default C++ STL implementation. 

            C++ Exceptions and RTTI are not supported in the default STL implementation. For more information, see

            docs/CPLUSPLUS-SUPPORT.HTML.</li>

            <li>Includes improvements to the <code>cpufeatures</code> helper library that improves reporting

            of the CPU type (some devices previously reported ARMv7 CPU when the device really was an ARMv6). We

            recommend developers that use this library to rebuild their applications then

            upload to Market to benefit from the improvements.</li>

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

              services.</li>

            <li>Adds new sample applications, <code>native-plasma</code> and <code>native-activity</code>, 

            to demonstrate how to write a native activity.</li>

            <li>Includes many bugfixes and other small improvements; see docs/CHANGES.html for a more

              detailed list of changes.</li>

          </ul>

        </dd>

  <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>

  NDK from its download package.</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>

  needed. The NDK is compatible with older platform versions but not older versions of the SDK tools.

  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>

    <code>&lt;ndk&gt;</code>.</li>

  </ol>

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

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

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

    <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 <project>

      <pre class="no-pretty-print">cd &lt;project&gt;

<ndk>/ndk-build

</pre>

  <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 <ndk-root>/samples/hello-jni

<ndk_root>/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 <ndk-root>/platforms/samples/android-9/samples/native-activity

<ndk_root>/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>

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

  Android applications. For more information, see <a href=

  "{@docRoot}sdk/ndk/overview.html#samples">Sample Applications</a>.</p>

  <h2 id="forum">Discussion Forum and Mailing List</h2>