cherry pick Change-Id: I183ff47e59617b2c17a92b876ca8c8bcc9b45262

</li>

</ol>

<h2>See also</h2>

<ol>

  <li><a

href="{@docRoot}sdk/compatibility-library.html">Compatibility Library</a></li>

  <li><a href="http://code.google.com/p/iosched/">Google I/O App source code</a></li>

</ol>

</div>

</div>

application will look and feel consistent with the system and other applications when it is

enabled.</p>

    <p>Additionally, when an activity uses the holographic theme, the system enables the <a

href="{@docRoot}guide/topics/ui/actionbar.html">Action Bar</a> for the activity. The Action Bar

href="{@docRoot}guide/topics/ui/actionbar.html">Action Bar</a> for the activity and removes the

Options Menu button in the system bar. The Action Bar

replaces the traditional title bar at the top of the activity window and provides the user access to

the activity's Options Menu.</p>

      </li>

<h2 id="Upgrading">Upgrading or Developing a New App for Tablets</h2>

<div class="sidebox-wrapper">

<div class="sidebox">

  <h3>Use new APIs and remain backward-compatible</h3>

  <h3>Use the Compatibility Library to remain backward-compatible</h3>

<p>It is possible for you to upgrade your application with some new

APIs <em>and</em> remain compatible with older versions of Android. Usually, this requires that you

use techniques such as reflection to check for the availability of certain APIs at runtime. However,

to help you add features from Android 3.0 without requiring you to change your <a

href="{@docRoot}guide/topics/manifest/uses-sdk-element.html#min">{@code android:minSdkVersion}</a>

or build target, we're providing a static library called the "Android Compatibility package"

or build target, we're providing a static library called the <a

href="{@docRoot}sdk/compatibility-library.html">Compatibility Library</a>

(downloadable from the AVD and SDK Manager).</p>

<p>This library includes APIs for <a

href="{@docRoot}guide/topics/fundamentals/fragments.html">fragments</a>, <a

href="{@docRoot}guide/topics/fundamentals/loaders.html">loaders</a>, and some updated classes. By

simply adding this library to your Android project, you can use these APIs in your application and

remain compatible with Android 1.6. For more information, see the blog post, <a

href="http://android-developers.blogspot.com/2011/03/fragments-for-all.html">Fragments for

All</a>.</p>

remain compatible with Android 1.6. For information about how to get the library and start

using it in your application, see the <a

href="{@docRoot}sdk/compatibility-library.html">Compatibility Library</a> document.</p>

</div>

</div>

href="{@docRoot}sdk/android-3.0.html">Android 3.0 Platform</a> document.</p>

<h3>Look at some samples</h3>

<p>Many of the new features and APIs that are described above and in the <a

page.title=Compatibility Library

@jd:body

<div id="qv-wrapper">

<div id="qv">

<h2>In this document</h2>

<ol>

  <li><a href="#Notes">Revisions</a></li>

  <li><a href="#Installing">Installing the Compatibility Library</a></li>

  <li><a href="#SettingUp">Setting Up a Project to Use the Library</a></li>

  <li><a href="#Using">Using Some of the Library APIs</a></li>

  <li><a href="#Samples">Samples</a></li>

</ol>

<h2>See also</h2>

<ol>

  <li><a

href="{@docRoot}guide/practices/optimizing-for-3.0.html">Optimizing Apps for Android 3.0</a></li>

  <li><a href="http://code.google.com/p/iosched/">Google I/O App source code</a></li>

</ol>

</div>

</div>

<p><em>Minimum API level supported:</em> <b>4</b></p>

<p>The Compatibility Library is a static library you can add to your Android application in order to

use APIs not available in older versions of the Android platform. The primary goal of the library is

to provide APIs introduced in Andriod 3.0 for older versions of Android so that all applications can

use them.</p>

<p>If you're not able to use APIs introduced in Android 3.0 directly, because you want to remain

backward-compatible, the Compatibility Library provides your application access to self-contained

versions of some of the latest APIs that you can use with older versions of Android. Most

importantly, the library provides implementations of the {@link android.app.Fragment} and {@link

android.content.Loader} APIs, so you can use them in a way that's compatible with devices running

Android 1.6 (API level 4) and higher. Thus, you can more easily create a single APK that supports a

majority of devices and provide larger devices (such as tablets) a fully optimized experience by

using <a href="{@docRoot}guide/topics/fundamentals/fragments.html">Fragments</a> in your activity

design.</p>

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

<p>The sections below provide notes about successive releases of

the Compatibility Library, as denoted by revision number.</p>

<div class="toggle-content open">

  <p><a href="#" onclick="return toggleContent(this)">

    <img src="{@docRoot}assets/images/triangle-opened.png" class="toggle-content-img" />

    Compatibility Library, revision 2 (May 2011)

  </a></p>

  <div class="toggle-content-toggleme" style="padding-left:2em"> 

    <dl>

    <dt>Changes:</dt>

    <dd>

      <ul>

        <li>Support for fragment animations.</li>

        <li>Fix {@code Fragment.onActivityResult()} bug.</li>

      </ul>

    </dd>

    </dl>

  </div>

</div>

<div class="toggle-content closed">

  <p><a href="#" onclick="return toggleContent(this)">

    <img src="{@docRoot}assets/images/triangle-closed.png" class="toggle-content-img" />

    Compatibility Library, revision 1 (March 2011)

  </a></p>

  <div class="toggle-content-toggleme" style="padding-left:2em"> 

      <p>Initial release of the library.</p>

  </div>

</div>

<h2 id="Installing">Installing the Compatibility Library</h2>

<p>The Compatibility Library is provided as a downloadable package from the Android SDK and AVD

Manager. To install the library:</p>

<ol>

  <li>Launch the SDK and AVD Manager. 

    <p>From Eclipse, you can select <strong>Window</strong>

&gt; <strong>Android SDK and AVD Manager</strong>. Or, launch {@code SDK Manager.exe} from

the {@code <sdk>/} directory (on Windows only) or {@code android} from the {@code

&lt;sdk&gt;/tools/} directory.</p></li>

  <li>Expand the Android Repository, check <strong>Android Compatibility package</strong>

and click <strong>Install selected</strong>.</li>

  <li>Proceed to install the package.</li>

</ol>

<p>When done, all files (including source code, samples, and the {@code .jar} file) are saved

into the <code>&lt;sdk&gt;/extras/android/compatibility/</code> directory. The next directory

name is {@code v4}, which indicates the lowest compatible version for the library within. That

is, the code in {@code v4/} supports API level 4 and above. (There may be future libraries that

have a different minimum version, so they will be saved alongside this one.)</p>

<h2 id="SettingUp">Setting Up a Project to Use the Library</h2>

<p>To add the Compatibility Library to your Android project:</p>

<ol>

  <li>In your Android project, create a directory named {@code libs} at the root of your

project (next to {@code src/}, {@code res/}, etc.)</li>

  <li>Navigate to {@code &lt;sdk&gt;/extras/android/compatibility/v4/}.</li>

  <li>Copy the {@code android-support-v4.jar} file into your project {@code libs/} directory.</li>

  <li>Add the JAR to your project build path. In Eclipse, right-click the JAR file in the

Package Explorer, select <strong>Build Path</strong> &gt; <strong>Add to Build Path</strong>.

You should then see the JAR file appear in a new directory called Referenced Libraries.</li>

</ol>

<p>Your application is now ready to use fragments, loaders and other APIs from the library. All the

provided APIs are in the {@code android.support.v4} package.</p>

<p class="warning"><strong>Warning:</strong> Be certain that you not confuse the standard

{@code android} packages with those in {@code android.support.v4}. Some code completion tools might

get this wrong, especially if you're building against recent versions of the platform. To be safe,

keep your build target set to the same version as you have defined for your <a

href="{@docRoot}guide/topics/manifest/uses-sdk-element.html#min">{@code android:minSdkVersion}</a>

and double check the import statements for classes that are duplicated in the Compatibility

Library, such as {@code SimpleCursorAdapter}.</p>

<h2 id="Using">Using Some of the Library APIs</h2>

<p>The Compatibility Library provides access to several classes introduced with Android 3.0, plus

some updated version of existing classes. Some of the most useful and notable classes in the

library are:</p>

<ul>

  <li>{@link android.app.Fragment}</li>

  <li>{@link android.app.FragmentManager}</li>

  <li>{@link android.app.FragmentTransaction}</li>

  <li>{@link android.app.ListFragment}</li>

  <li>{@link android.app.DialogFragment}</li>

  <li>{@link android.app.LoaderManager}</li>

  <li>{@link android.content.Loader}</li>

  <li>{@link android.content.AsyncTaskLoader}</li>

  <li>{@link android.content.CursorLoader}</li>

</ul>

<p>For each of the classes above (and others not listed), the APIs work almost exactly the same

as the counterparts in the latest version of the Android platform. Thus, you can usually refer to

the latest reference documentation for information about the supported APIs. There are some

differences, however. Most notably:</p>

<ul>

  <li>When creating an activity to use fragments, you must declare your activity to extend the

{@code FragmentActivity} class (instead of the traditional {@link android.app.Activity}

class).</li>

  <li>To manage your fragments and loaders, you must use the methods {@code

FragmentActivity.getSupportFragmentManager()} and {@code

FragmentActivity.getSupportLoaderManager()} (instead of the {@link

android.app.Activity#getFragmentManager()} and {@link android.app.Activity#getLoaderManager()}

methods).</li>

  <li>The {@link android.app.ActionBar} is <strong>not supported</strong> by the library.

However, when creating your <a href="{@docRoot}guide/topics/ui/menus.html#options-menu">Options

Menu</a>, you can declare which items should be added to the Action Bar when it's available (on

Android 3.0 or later). You can do so with the {@code MenuCompat.setShowAsAction()} method. For

example:

<pre>

public boolean onCreateOptionsMenu(Menu menu) {

    MenuInflater inflater = getMenuInflater();

    inflater.inflate(R.menu.options, menu);

    MenuCompat.setShowAsAction(menu.findItem(R.id.action_search), 1);

    return true;

}

</pre>

</li>

</ul>

<p>The Compatibility Library currently does not provide reference documentation for the included

APIs. To generate your own set, using the {@code javadoc} tool, perform the

following from a command line:</p>

<pre class="no-pretty-print">

cd <sdk>/extras/android/compatibility/v4/

mkdir docs

javadoc -sourcepath src/java/ -subpackages android.support.v4 -d docs

</pre>

<p>Open the {@code docs/index.html} file to begin browsing the generated documentation.</p>

<div class="note"><p><strong>Tip:</strong> To enable the Holographic theme on devices

running Android 3.0 or higher, declare in your manifest file that your application targets

API level 11. For example:</p>

<pre>

<uses-sdk android:minSdkVersion="4" android:targetSdkVersion="11" />

</pre>

<p>This way, your application automatically receives the Holographic theme and the Action Bar for 

each activity when running on Android 3.0 and higher.</p>

</div>

<p>For more information about how you can optimize your application for the latest

Android-powered devices, read <a href="{@docRoot}guide/practices/optimizing-for-3.0.html">Optimizing

Apps for Android 3.0</a>.</p>

<h2 id="Samples">Samples</h2>

<p>If you want to see some sample code that uses the Compatibility Library, take a look at the

<a href="{@docRoot}resources/samples/ApiDemos/src/com/example/android/apis/support/index.html">API

Demos</a> sample code that's included with the Samples package you can download from the AVD and SDK

Manager.</p>

<p>Additionally, the <a href="http://code.google.com/p/iosched/">Google I/O App</a> is a complete

application that uses the library to provide a single APK for both handsets and tablets and also

demonstrates some of Android's best practices in Android UI design.</p>

      <li><a href="<?cs var:toroot ?>sdk/tools-notes.html">SDK Tools, r11</a> <span

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

      <li><a href="<?cs var:toroot ?>sdk/win-usb.html">Google USB Driver, r4</a></li>

      <li><a href="<?cs var:toroot ?>sdk/compatibility-library.html">Compatibility Library, r2</a> <span

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

    </ul>

  </li>

  <li>