docs/html/sdk/android-4.0.jd

page.title=Android 4.0 Platform
sdk.platform.version=4.0
sdk.platform.apiLevel=14
@jd:body

<div id="qv-wrapper">
<div id="qv">

<h2>In this document</h2>
<ol>
  <li><a href="#relnotes">Revisions</a></li>
  <li><a href="#api">API Overview</a></li>
  <li><a href="#Honeycomb">Previous APIs</a></li>
  <li><a href="#api-level">API Level</a></li>
  <li><a href="#apps">Built-in Applications</a></li>
  <li><a href="#locs">Locales</a></li>
  <li><a href="#skins">Emulator Skins</a></li>
</ol>

<h2>Reference</h2>
<ol>
<li><a
href="{@docRoot}sdk/api_diff/14/changes.html">API
Differences Report &raquo;</a> </li>
</ol>

</div>
</div>


<p><em>API Level:</em>&nbsp;<strong>{@sdkPlatformApiLevel}</strong></p>

<p>Android 4.0 is a major platform release that adds a variety of new features for users and app
developers. Besides all the new features and APIs discussed below, Android 4.0 is an important
platform release because it brings the extensive set of APIs and Holographic themes from Android 3.x
to smaller screens. As an app developer, you now have a single platform and unified API framework
that enables you to develop and publish your application with a single APK that provides an
optimized user experience for handsets, tablets, and more, when running the same version of
Android&mdash;Android 4.0 (API level 14) or greater. </p>

<p>The Android {@sdkPlatformVersion} platform is available as a
downloadable component for the Android SDK so you can begin developing and testing your
applications on Android 4.0 with the Android emulator. The downloadable platform includes
an Android library and system image, as well as a set of emulator skins and
more. The downloadable platform does not include any external libraries.</p>

<p>To start developing or testing against Android {@sdkPlatformVersion},
use the Android SDK Manager to download the platform into your SDK. For more
information, see <a href="{@docRoot}sdk/adding-components.html">Adding SDK
Components</a>. If you are new to Android, <a
href="{@docRoot}sdk/index.html">download the SDK Starter Package</a> first.</p>

<p class="note"><strong>Reminder:</strong> If you've already published an
Android application, please test your application on Android {@sdkPlatformVersion} as
soon as possible to be sure your application provides the best
experience possible on the latest Android-powered devices.</p>

<p>For a high-level overview of the new user and developer features in Android 4.0, see the
<a href="http://developer.android.com/sdk/android-4.0-highlights.html">Platform Highlights</a>.</p>



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

<p>To determine what revision of the Android {@sdkPlatformVersion} platform you
have installed, refer to the "Installed Packages" listing in the Android SDK Manager.</p>

<p class="caution"><strong>Important:</strong> To download the new Android
4.0 system components from the Android SDK Manager, you must first update the
SDK tools to revision 14 or later and restart the Android SDK Manager. If you do not,
the Android 4.0 system components will not be available for download.</p>

<div class="toggle-content opened" style="padding-left:1em;">

  <p><a href="#" onclick="return toggleContent(this)">
    <img src="{@docRoot}assets/images/triangle-opened.png"
class="toggle-content-img" alt="" />
    Android {@sdkPlatformVersion}, Revision 2</a> <em>(December 2011)</em>
  </a></p>

  <div class="toggle-content-toggleme" style="padding-left:2em;">
    <p>Maintenance update. The system version is 4.0.2.</p>
    <dl>
      <dt>Dependencies:</dt>
      <dd>SDK Tools r14 or higher is required.</dd>
    </dl>
  </div>
</div>

<div class="toggle-content closed" style="padding-left:1em;">

  <p><a href="#" onclick="return toggleContent(this)">
    <img src="{@docRoot}assets/images/triangle-closed.png"
class="toggle-content-img" alt="" />
    Android {@sdkPlatformVersion}, Revision 1</a> <em>(October 2011)</em>
  </a></p>

  <div class="toggle-content-toggleme" style="padding-left:2em;">
    <p>Initial release. The system version is 4.0.1.</p>
    <dl>
      <dt>Dependencies:</dt>
      <dd>SDK Tools r14 or higher is required.</dd>
    </dl>
  </div>
</div>


<h2 id="api">API Overview</h2>

<p>The sections below provide a technical overview of new APIs in Android 4.0.</p>

<div class="toggle-content closed" style="padding-left:1em;">

  <p><a href="#" onclick="return toggleContent(this)">
    <img src="{@docRoot}assets/images/triangle-closed.png"
class="toggle-content-img" alt="" />
    <strong>Table of Contents</strong>
  </a></p>

  <div class="toggle-content-toggleme" style="padding-left:2em;">
    <ol class="toc" style="margin-left:-1em">
      <li><a href="#Contacts">Social APIs in Contacts Provider</a></li>
      <li><a href="#Calendar">Calendar Provider</a></li>
      <li><a href="#Voicemail">Voicemail Provider</a></li>
      <li><a href="#Multimedia">Multimedia</a></li>
      <li><a href="#Camera">Camera</a></li>
      <li><a href="#AndroidBeam">Android Beam (NDEF Push with NFC)</a></li>
      <li><a href="#WiFiDirect">Wi-Fi Direct</a></li>
      <li><a href="#Bluetooth">Bluetooth Health Devices</a></li>
      <li><a href="#A11y">Accessibility</a></li>
      <li><a href="#SpellChecker">Spell Checker Services</a></li>
      <li><a href="#TTS">Text-to-speech Engines</a></li>
      <li><a href="#NetworkUsage">Network Usage</a></li>
      <li><a href="#RenderScript">RenderScript</a></li>
      <li><a href="#Enterprise">Enterprise</a></li>
      <li><a href="#Sensors">Device Sensors</a></li>
      <li><a href="#ActionBar">Action Bar</a></li>
      <li><a href="#UI">User Interface and Views</a></li>
      <li><a href="#Input">Input Framework</a></li>
      <li><a href="#Properties">Properties</a></li>
      <li><a href="#HwAccel">Hardware Acceleration</a></li>
      <li><a href="#Jni">JNI Changes</a></li>
      <li><a href="#WebKit">WebKit</a></li>
      <li><a href="#Permissions">Permissions</a></li>
      <li><a href="#DeviceFeatures">Device Features</a></li>
    </ol>
  </div>
</div>





<h3 id="Contacts">Social APIs in Contacts Provider</h3>

<p>The contact APIs defined by the {@link android.provider.ContactsContract} provider have been
extended to support new social-oriented features such as a personal profile for the device owner and
the ability for users to invite individual contacts to social networks that are installed on the
device.</p>


<h4>User Profile</h4>

<p>Android now includes a personal profile that represents the device owner, as defined by the
{@link android.provider.ContactsContract.Profile} table.  Social apps that maintain a user identity 
can contribute to the user's profile data by creating a new {@link
android.provider.ContactsContract.RawContacts} entry within the {@link
android.provider.ContactsContract.Profile}. That is, raw contacts that represent the device user do
not belong in the traditional raw contacts table defined by the {@link
android.provider.ContactsContract.RawContacts} Uri; instead, you must add a profile raw contact in
the table at {@link android.provider.ContactsContract.Profile#CONTENT_RAW_CONTACTS_URI}. Raw
contacts in this table are then aggregated into the single user-visible profile labeled "Me".</p>

<p>Adding a new raw contact for the profile requires the {@link
android.Manifest.permission#WRITE_PROFILE} permission. Likewise, in order to read from the profile
table, you must request the {@link android.Manifest.permission#READ_PROFILE} permission. However,
most apps should not need to read the user profile, even when contributing data to the
profile. Reading the user profile is a sensitive permission and you should expect users to be
skeptical of apps that request it.</p>


<h4>Invite Intent</h4>

<p>The {@link android.provider.ContactsContract.Intents#INVITE_CONTACT} intent action allows an app
to invoke an action that indicates the user wants to add a contact to a social network. The app
receiving the app uses it to invite the specified contact to that
social network. Most apps will be on the receiving-end of this operation. For example, the
built-in People app invokes the invite intent when the user selects "Add connection" for a specific
social app that's listed in a person's contact details.</p> 

<p>To make your app visible as in the "Add connection" list, your app must provide a sync adapter to
sync contact information from your social network. You must then indicate to the system that your
app responds to the {@link android.provider.ContactsContract.Intents#INVITE_CONTACT} intent by
adding the {@code inviteContactActivity} attribute to your app’s sync configuration file, with a
fully-qualified name of the activity that the system should start when sending the invite intent.
The activity that starts can then retrieve the URI for the contact in question from the intent’s
data and perform the necessary work to invite that contact to the network or add the person to the
user’s connections.</p>

<p>See the <a href="{@docRoot}resources/samples/SampleSyncAdapter/index.html">Sample Sync
Adapter</a> app for an example (specifically, see the <a
href="{@docRoot}resources/samples/SampleSyncAdapter/res/xml-v14/contacts.html">contacts.xml</a>
file).</p>


<h4>Large photos</h4>

<p>Android now supports high resolution photos for contacts. Now, when you push a photo into a
contact record, the system processes it into both a 96x96 thumbnail (as it has previously) and a
256x256 "display photo" that's stored in a new file-based photo store (the exact dimensions that the
system chooses may vary in the future). You can add a large photo to a contact by putting a large
photo in the usual {@link android.provider.ContactsContract.CommonDataKinds.Photo#PHOTO} column of a
data row, which the system will then process into the appropriate thumbnail and display photo
records.</p>


<h4>Contact Usage Feedback</h4>

<p>The new {@link android.provider.ContactsContract.DataUsageFeedback} APIs allow you to  help track
how often the user uses particular methods of contacting people, such as how often the user uses
each phone number or e-mail address. This information helps improve the ranking for each contact
method associated with each person and provide better suggestions for contacting each person.</p>





<h3 id="Calendar">Calendar Provider</h3>

<p>The new calendar APIs allow you to read, add, modify and delete calendars, events, attendees,
reminders and alerts, which are stored in the Calendar Provider.</p>

<p>A variety of apps and widgets can use these APIs to read and modify calendar events. However,
some of the most compelling use cases are sync adapters that synchronize the user's calendar from
other calendar services with the Calendar Provider, in order to offer a unified location for all the
user's events. Google Calendar events, for example, are synchronized with the Calendar Provider by
the Google Calendar Sync Adapter, allowing these events to be viewed with Android's built-in
Calendar app.</p>

<p>The data model for calendars and event-related information in the Calendar Provider is
defined by {@link android.provider.CalendarContract}. All the user’s calendar data is stored in a
number of tables defined by various subclasses of {@link android.provider.CalendarContract}:</p>

<ul>
<li>The {@link android.provider.CalendarContract.Calendars} table holds the calendar-specific
information. Each row in this table contains the details for a single calendar, such as the name,
color, sync information, and so on.</li>

<li>The {@link android.provider.CalendarContract.Events} table holds event-specific information.
Each row in this table contains the information for a single event, such as the
event title, location, start time, end time, and so on. The event can occur one time or recur
multiple times. Attendees, reminders, and extended properties are stored in separate tables and
use the event’s {@code _ID} to link them with the event.</li>

<li>The {@link android.provider.CalendarContract.Instances} table holds the start and end time for
occurrences of an event. Each row in this table represents a single occurrence. For one-time events
there is a one-to-one mapping of instances to events. For recurring events, multiple rows are
automatically generated to correspond to the multiple occurrences of that event.</li>

<li>The {@link android.provider.CalendarContract.Attendees} table holds the event attendee or guest
information. Each row represents a single guest of an event. It specifies the type of guest the
person is and the person’s response for the event.</li>

<li>The {@link android.provider.CalendarContract.Reminders} table holds the alert/notification data.
Each row represents a single alert for an event. An event can have multiple reminders. The number of
reminders per event is specified in {@code MAX_REMINDERS}, which is set by the sync adapter that
owns the given calendar. Reminders are specified in number-of-minutes before the event is
scheduled and specify an alarm method such as to use an alert, email, or SMS to remind
the user.</li>

<li>The {@link android.provider.CalendarContract.ExtendedProperties} table hold opaque data fields
used by the sync adapter. The provider takes no action with items in this table except to delete
them when their related events are deleted.</li>
</ul>

<p>To access a user’s calendar data with the Calendar Provider, your application must request 
the {@link android.Manifest.permission#READ_CALENDAR} permission (for read access) and
{@link android.Manifest.permission#WRITE_CALENDAR} (for write access).</p>


<h4>Event intent</h4>

<p>If all you want to do is add an event to the user’s calendar, you can use an {@link
android.content.Intent#ACTION_INSERT} intent with the data defined by {@link
android.provider.CalendarContract.Events#CONTENT_URI Events.CONTENT_URI} in order to start an
activity in the Calendar app that creates new events. Using the intent does not require any
permission and you can specify event details with the following extras:</p>

<ul>
  <li>{@link android.provider.CalendarContract.EventsColumns#TITLE Events.TITLE}: Name for the
event</li>
  <li>{@link
android.provider.CalendarContract#EXTRA_EVENT_BEGIN_TIME CalendarContract.EXTRA_EVENT_BEGIN_TIME}:
Event begin time in milliseconds from the
epoch</li>
  <li>{@link
android.provider.CalendarContract#EXTRA_EVENT_END_TIME CalendarContract.EXTRA_EVENT_END_TIME}: Event
end time in milliseconds from the epoch</li>
  <li>{@link android.provider.CalendarContract.EventsColumns#EVENT_LOCATION Events.EVENT_LOCATION}:
Location of the event</li>
  <li>{@link android.provider.CalendarContract.EventsColumns#DESCRIPTION Events.DESCRIPTION}: Event
description</li>
  <li>{@link android.content.Intent#EXTRA_EMAIL Intent.EXTRA_EMAIL}: Email addresses of those to
invite</li>
  <li>{@link android.provider.CalendarContract.EventsColumns#RRULE Events.RRULE}: The recurrence
rule for the event</li>
  <li>{@link android.provider.CalendarContract.EventsColumns#ACCESS_LEVEL Events.ACCESS_LEVEL}:
Whether the event is private or public</li>
  <li>{@link android.provider.CalendarContract.EventsColumns#AVAILABILITY Events.AVAILABILITY}:
Whether the time period of this event allows for other events to be scheduled at the same time</li>
</ul>




<h3 id="Voicemail">Voicemail Provider</h3>

<p>The new Voicemail Provider allows applications to add voicemails to the
device, in order to present all the user's voicemails in a single visual presentation. For instance,
it’s possible that a user has multiple voicemail sources, such as
one from the phone’s service provider and others from VoIP or other alternative voice
services. These apps can use the Voicemail Provider APIs to add their voicemails to the device. The
built-in Phone application then presents all voicemails to the user in a unified presentation.
Although the system’s Phone application is the only application that can read all the voicemails,
each application that provides voicemails can read those that it has added to the system (but cannot
read voicemails from other services).</p>

<p>Because the APIs currently do not allow third-party apps to read all the voicemails from the
system, the only third-party apps that should use the voicemail APIs are those that have voicemail
to deliver to the user.</p>

<p>The {@link android.provider.VoicemailContract} class defines the content provider for the
Voicemail Provder. The subclasses {@link android.provider.VoicemailContract.Voicemails} and {@link
android.provider.VoicemailContract.Status} provide tables in which apps can
insert voicemail data for storage on the device. For an example of a voicemail provider app, see the
<a href="{@docRoot}resources/samples/VoicemailProviderDemo/index.html">Voicemail Provider
Demo</a>.</p>





<h3 id="Multimedia">Multimedia</h3>

<p>Android 4.0 adds several new APIs for applications that interact with media such as photos,
videos, and music.</p>


<h4>Media Effects</h4>

<p>A new media effects framework allows you to apply a variety of visual effects to images and
videos. For example, image effects allow you to easily fix red-eye, convert an image to grayscale,
adjust brightness, adjust saturation, rotate an image, apply a fisheye effect, and much more. The
system performs all effects processing on the GPU to obtain maximum performance.</p>

<p>For maximum performance, effects are applied directly to OpenGL textures, so your application
must have a valid OpenGL context before it can use the effects APIs. The textures to which you apply
effects may be from bitmaps, videos or even the camera. However, there are certain restrictions that
textures must meet:</p>
<ol>
<li>They must be bound to a {@link android.opengl.GLES20#GL_TEXTURE_2D} texture image</li>
<li>They must contain at least one mipmap level</li>
</ol>

<p>An {@link android.media.effect.Effect} object defines a single media effect that you can apply to
an image frame. The basic workflow to create an {@link android.media.effect.Effect} is:</p>

<ol>
<li>Call {@link android.media.effect.EffectContext#createWithCurrentGlContext
EffectContext.createWithCurrentGlContext()} from your OpenGL ES 2.0 context.</li>
<li>Use the returned {@link android.media.effect.EffectContext} to call {@link
android.media.effect.EffectContext#getFactory EffectContext.getFactory()}, which returns an instance
of {@link android.media.effect.EffectFactory}.</li>
<li>Call {@link android.media.effect.EffectFactory#createEffect createEffect()}, passing it an
effect name from @link android.media.effect.EffectFactory}, such as {@link
android.media.effect.EffectFactory#EFFECT_FISHEYE} or {@link
android.media.effect.EffectFactory#EFFECT_VIGNETTE}.</li>
</ol>

<p>You can adjust an effect’s parameters by calling {@link android.media.effect.Effect#setParameter
setParameter()} and passing a parameter name and parameter value. Each type of effect accepts
different parameters, which are documented with the effect name. For example, {@link
android.media.effect.EffectFactory#EFFECT_FISHEYE} has one parameter for the {@code scale} of the
distortion.</p>

<p>To apply an effect on a texture, call {@link android.media.effect.Effect#apply apply()} on the
{@link
android.media.effect.Effect} and pass in the input texture, it’s width and height, and the output
texture. The input texture  must be bound to a {@link android.opengl.GLES20#GL_TEXTURE_2D} texture
image (usually done by calling the {@link android.opengl.GLES20#glTexImage2D glTexImage2D()}
function). You may provide multiple mipmap levels. If the output texture has not been bound to a
texture image, it will be automatically bound by the effect as a {@link
android.opengl.GLES20#GL_TEXTURE_2D} and with one mipmap level (0), which will have the same
size as the input.</p> 

<p>All effects listed in {@link android.media.effect.EffectFactory} are guaranteed to be supported.
However, some additional effects available from external libraries are not supported by all devices,
so you must first check if the desired effect from the external library is supported by calling
{@link android.media.effect.EffectFactory#isEffectSupported isEffectSupported()}.</p>


<h4>Remote control client</h4>

<p>The new {@link android.media.RemoteControlClient} allows media players to enable playback
controls from remote control clients such as the device lock screen. Media players can also expose
information about the media currently playing for display on the remote control, such as track
information and album art.</p>

<p>To enable remote control clients for your media player, instantiate a {@link
android.media.RemoteControlClient} with its constructor, passing it a {@link
android.app.PendingIntent} that broadcasts {@link
android.content.Intent#ACTION_MEDIA_BUTTON}. The intent must also declare the explicit {@link
android.content.BroadcastReceiver} component in your app that handles the {@link
android.content.Intent#ACTION_MEDIA_BUTTON} event.</p>

<p>To declare which media control inputs your player can handle, you must call {@link
android.media.RemoteControlClient#setTransportControlFlags setTransportControlFlags()} on your
{@link android.media.RemoteControlClient}, passing a set of {@code FLAG_KEY_MEDIA_*} flags, such as
{@link android.media.RemoteControlClient#FLAG_KEY_MEDIA_PREVIOUS} and {@link
android.media.RemoteControlClient#FLAG_KEY_MEDIA_NEXT}.</p>

<p>You must then register your {@link android.media.RemoteControlClient} by passing it to {@link
android.media.AudioManager#registerRemoteControlClient MediaManager.registerRemoteControlClient()}.
Once registered, the broadcast receiver you declared when you instantiated the {@link
android.media.RemoteControlClient} will receive {@link android.content.Intent#ACTION_MEDIA_BUTTON}
events when a button is pressed from a remote control. The intent you receive includes the {@link
android.view.KeyEvent} for the media key pressed, which you can retrieve from the intent with {@link
android.content.Intent#getParcelableExtra getParcelableExtra(Intent.EXTRA_KEY_EVENT)}.</p>

<p>To display information on the remote control about the media playing, call {@link
android.media.RemoteControlClient#editMetadata editMetaData()} and add metadata to the returned
{@link android.media.RemoteControlClient.MetadataEditor}. You can supply a bitmap for media artwork,
numerical information such as elapsed time, and text information such as the track title. For
information on available keys see the {@code METADATA_KEY_*} flags in {@link
android.media.MediaMetadataRetriever}.</p>

<p>For a sample implementation, see the <a
href="{@docRoot}resources/samples/RandomMusicPlayer/index.html">Random Music Player</a>, which
provides compatibility logic such that it enables the remote control client on Android 4.0
devices while continuing to support devices back to Android 2.1.</p>


<h4>Media player</h4>

<ul>
<li>Streaming online media from {@link android.media.MediaPlayer} now requires the {@link
android.Manifest.permission#INTERNET} permission. If you use {@link android.media.MediaPlayer} to
play content from the Internet, be sure to add the {@link android.Manifest.permission#INTERNET}
permission to your manifest or else your media playback will not work beginning with Android
4.0.</li>

<li>{@link android.media.MediaPlayer#setSurface(Surface) setSurface()} allows you define a {@link
android.view.Surface} to behave as the video sink.</li>

<li>{@link android.media.MediaPlayer#setDataSource(Context,Uri,Map) setDataSource()} allows you to
send additional HTTP headers with your request, which can be useful for HTTP(S) live streaming</li>

<li>HTTP(S) live streaming now respects HTTP cookies across requests</li>
</ul>


<h4>Media types</h4>

<p>Android 4.0 adds support for:</p>
<ul>
<li>HTTP/HTTPS live streaming protocol version 3 </li>
<li>ADTS raw AAC audio encoding</li>
<li>WEBP images</li>
<li>Matroska video</li>
</ul>
<p>For more info, see <a href="{@docRoot}guide/appendix/media-formats.html">Supported Media
Formats</a>.</p>





<h3 id="Camera">Camera</h3>

<p>The {@link android.hardware.Camera} class now includes APIs for detecting faces and controlling
focus and metering areas.</p>


<h4>Face detection</h4>

<p>Camera apps can now enhance their abilities with Android’s face detection APIs, which not
only detect the face of a subject, but also specific facial features, such as the eyes and mouth.
</p>

<p>To detect faces in your camera application, you must register a {@link
android.hardware.Camera.FaceDetectionListener} by calling {@link
android.hardware.Camera#setFaceDetectionListener setFaceDetectionListener()}. You can then start
your camera surface and start  detecting faces by calling {@link
android.hardware.Camera#startFaceDetection}.</p>

<p>When the system detects one or more faces in the camera scene, it calls the {@link
android.hardware.Camera.FaceDetectionListener#onFaceDetection onFaceDetection()} callback in your
implementation of {@link android.hardware.Camera.FaceDetectionListener}, including an array of
{@link android.hardware.Camera.Face} objects.</p>

<p>An instance of the {@link android.hardware.Camera.Face} class provides various information about
the face detected, including:</p>
<ul>
<li>A {@link android.graphics.Rect} that specifies the bounds of the face, relative to the camera's
current field of view</li>
<li>An integer betwen 1 and 100 that indicates how confident the system is that the object is a
human face</li>
<li>A unique ID so you can track multiple faces</li>
<li>Several {@link android.graphics.Point} objects that indicate where the eyes and mouth are
located</li>
</ul>

<p class="note"><strong>Note:</strong> Face detection may not be supported on some
devices, so you should check by calling {@link
android.hardware.Camera.Parameters#getMaxNumDetectedFaces()} and ensure the return
value is greater than zero. Also, some devices may not support identification of eyes and mouth,
in which case, those fields in the {@link android.hardware.Camera.Face} object will be null.</p>

  
<h4>Focus and metering areas</h4>

<p>Camera apps can now control the areas that the camera uses for focus and for metering white
balance
and auto-exposure. Both features use the new {@link android.hardware.Camera.Area} class to specify
the region of the camera’s current view that should be focused or metered. An instance of the {@link
android.hardware.Camera.Area} class defines the bounds of the area with a {@link
android.graphics.Rect} and the area's weight&mdash;representing the level of importance of that
area, relative to other areas in consideration&mdash;with an integer.</p>

<p>Before setting either a focus area or metering area, you should first call {@link
android.hardware.Camera.Parameters#getMaxNumFocusAreas} or {@link
android.hardware.Camera.Parameters#getMaxNumMeteringAreas}, respectively. If these return zero, then
the device does not support the corresponding feature.</p>

<p>To specify the focus or metering areas to use, simply call {@link
android.hardware.Camera.Parameters#setFocusAreas setFocusAreas()} or {@link
android.hardware.Camera.Parameters#setMeteringAreas setMeteringAreas()}. Each take a {@link
java.util.List} of {@link android.hardware.Camera.Area} objects that indicate the areas to consider
for focus or metering. For example, you might implement a feature that allows the user to set the
focus area by touching an area of the preview, which you then translate to an {@link
android.hardware.Camera.Area} object and request that the camera focus on that area of the scene.
The focus or exposure in that area will continually update as the scene in the area changes.</p>


<h4>Continuous auto focus for photos</h4>

<p>You can now enable continuous auto focusing (CAF) when taking photos. To enable CAF in your
camera app, pass {@link android.hardware.Camera.Parameters#FOCUS_MODE_CONTINUOUS_PICTURE}
to {@link android.hardware.Camera.Parameters#setFocusMode setFocusMode()}. When ready to capture
a photo, call {@link android.hardware.Camera#autoFocus autoFocus()}. Your {@link
android.hardware.Camera.AutoFocusCallback} immediately receives a callback to indicate whether
focus was achieved. To resume CAF after receiving the callback, you must call {@link
android.hardware.Camera#cancelAutoFocus()}.</p>

<p class="note"><strong>Note:</strong> Continuous auto focus is also supported when capturing
video, using {@link android.hardware.Camera.Parameters#FOCUS_MODE_CONTINUOUS_VIDEO}, which was
added in API level 9.</p>


<h4>Other camera features</h4>

<ul>  
<li>While recording video, you can now call {@link android.hardware.Camera#takePicture
takePicture()} to save a photo without interrupting the video session. Before doing so, you should
call {@link android.hardware.Camera.Parameters#isVideoSnapshotSupported} to be sure the hardware
supports it.</li>

<li>You can now lock auto exposure and white balance with {@link
android.hardware.Camera.Parameters#setAutoExposureLock setAutoExposureLock()} and {@link
android.hardware.Camera.Parameters#setAutoWhiteBalanceLock setAutoWhiteBalanceLock()} to prevent
these properties from changing.</li>

<li>You can now call {@link android.hardware.Camera#setDisplayOrientation
setDisplayOrientation()} while the camera preview is running. Previously, you could call this
only before beginning the preview, but you can now change the orientation at any time.</li>
</ul>


<h4>Camera broadcast intents</h4>

<ul>
<li>{@link android.hardware.Camera#ACTION_NEW_PICTURE Camera.ACTION_NEW_PICTURE}:
This indicates that the user has captured a new photo. The built-in Camera app invokes this
broadcast after a photo is captured and third-party camera apps should also broadcast this intent
after capturing a photo.</li>
<li>{@link android.hardware.Camera#ACTION_NEW_VIDEO Camera.ACTION_NEW_VIDEO}:
This indicates that the user has captured a new video. The built-in Camera app invokes this
broadcast after a video is recorded and third-party camera apps should also broadcast this intent
after capturing a video.</li>
</ul>





<h3 id="AndroidBeam">Android Beam (NDEF Push with NFC)</h3>

<p>Android Beam is a new NFC feature that allows you to send NDEF messages from one device to
another (a process also known as “NDEF Push"). The data transfer is initiated when two
Android-powered devices that support Android Beam are in close proximity (about 4 cm), usually with
their backs touching. The data inside the NDEF message can contain any data that you wish to share
between devices. For example, the People app shares contacts, YouTube shares videos, and Browser
shares URLs using Android Beam.</p>

<p>To transmit data between devices using Android Beam, you need to create an {@link
android.nfc.NdefMessage} that contains the information you want to share while your activity is in
the foreground. You must then pass the {@link android.nfc.NdefMessage} to the system in one of two
ways:</p>

<ul>
<li>Define a single {@link android.nfc.NdefMessage} to push while in the activity:
<p>Call {@link android.nfc.NfcAdapter#setNdefPushMessage setNdefPushMessage()} at any time to set
the message you want to send. For instance, you might call this method and pass it your {@link
android.nfc.NdefMessage} during your activity’s {@link android.app.Activity#onCreate onCreate()}
method. Then, whenever Android Beam is activated with another device while the activity is in the
foreground, the system sends the {@link android.nfc.NdefMessage} to the other device.</p></li>

<li>Define the {@link android.nfc.NdefMessage} to push at the time that Android Beam is initiated:
<p>Implement {@link android.nfc.NfcAdapter.CreateNdefMessageCallback}, in which your
implementation of the {@link
android.nfc.NfcAdapter.CreateNdefMessageCallback#createNdefMessage createNdefMessage()}
method returns the {@link android.nfc.NdefMessage} you want to send. Then pass the {@link
android.nfc.NfcAdapter.CreateNdefMessageCallback} implementation to {@link
android.nfc.NfcAdapter#setNdefPushMessageCallback setNdefPushMessageCallback()}.</p>
<p>In this case, when Android Beam is activated with another device while your activity is in the
foreground, the system calls {@link
android.nfc.NfcAdapter.CreateNdefMessageCallback#createNdefMessage createNdefMessage()} to retrieve
the {@link android.nfc.NdefMessage} you want to send. This allows you to define the {@link
android.nfc.NdefMessage} to deliver only once Android Beam is initiated, in case the contents
of the message might vary throughout the life of the activity.</p></li>
</ul>

<p>In case you want to run some specific code once the system has successfully delivered your NDEF
message to the other device, you can implement {@link
android.nfc.NfcAdapter.OnNdefPushCompleteCallback} and set it with {@link
android.nfc.NfcAdapter#setOnNdefPushCompleteCallback setNdefPushCompleteCallback()}. The system will
then call {@link android.nfc.NfcAdapter.OnNdefPushCompleteCallback#onNdefPushComplete
onNdefPushComplete()} when the message is delivered.</p>

<p>On the receiving device, the system dispatches NDEF Push messages in a similar way to regular NFC
tags. The system invokes an intent with the {@link android.nfc.NfcAdapter#ACTION_NDEF_DISCOVERED}
action to start an activity, with either a URL or a MIME type set according to the first {@link
android.nfc.NdefRecord} in the {@link android.nfc.NdefMessage}. For the activity you want to
respond, you can declare intent filters for the URLs or MIME types your app cares about. For more
information about Tag Dispatch see the <a
href="{@docRoot}guide/topics/nfc/index.html#dispatch">NFC</a> developer guide.</p>

<p>If you want your {@link android.nfc.NdefMessage} to carry a URI, you can now use the convenience
method {@link android.nfc.NdefRecord#createUri createUri} to construct a new {@link
android.nfc.NdefRecord} based on either a string or a {@link android.net.Uri} object. If the URI is
a special format that you want your application to also receive during an Android Beam event, you
should create an intent filter for your activity using the same URI scheme in order to receive the
incoming NDEF message.</p>

<p>You should also pass an “Android application record" with your {@link android.nfc.NdefMessage} in
order to guarantee that your application handles the incoming NDEF message, even if other
applications filter for the same intent action. You can create an Android application record by
calling {@link android.nfc.NdefRecord#createApplicationRecord createApplicationRecord()}, passing it
your application’s package name. When the other device receives the NDEF message with the
application record and multiple applications contain activities that handle the specified intent,
the system always delivers the message to the activity in your application (based on the matching
application record). If the target device does not currently have your application installed, the
system uses the Android application record to launch Google Play and take the user to the
application in order to install it.</p>

<p>If your application doesn’t use NFC APIs to perform NDEF Push messaging, then Android provides a
default behavior: When your application is in the foreground on one device and Android Beam is
invoked with another Android-powered device, then the other device receives an NDEF message with an
Android application record that identifies your application. If the receiving device has the
application installed, the system launches it; if it’s not installed, Google Play opens and takes
the user to your application in order to install it.</p>

<p>You can read more about Android Beam and other NFC features in the <a
href="{@docRoot}guide/topics/nfc/nfc.html">NFC Basics</a> developer guide. For some example code
using Android Beam, see the <a
href="{@docRoot}resources/samples/AndroidBeamDemo/src/com/example/android/beam/Beam.html">Android
Beam Demo</a>.</p>





<h3 id="WiFiDirect">Wi-Fi Direct</h3>

<p>Android now supports Wi-Fi Direct for peer-to-peer (P2P) connections between Android-powered
devices and other device types without a hotspot or Internet connection. The Android framework
provides a set of Wi-Fi P2P APIs that allow you to discover and connect to other devices when each
device supports Wi-Fi Direct, then communicate over a speedy connection across distances much longer
than a Bluetooth connection.</p>

<p>A new package, {@link android.net.wifi.p2p}, contains all the APIs for performing peer-to-peer
connections with Wi-Fi. The primary class you need to work with is {@link
android.net.wifi.p2p.WifiP2pManager}, which you can acquire by calling {@link
android.app.Activity#getSystemService getSystemService(WIFI_P2P_SERVICE)}. The {@link
android.net.wifi.p2p.WifiP2pManager} includes APIs that allow you to:</p>
<ul>
<li>Initialize your application for P2P connections by calling {@link
android.net.wifi.p2p.WifiP2pManager#initialize initialize()}</li>

<li>Discover nearby devices by calling {@link android.net.wifi.p2p.WifiP2pManager#discoverPeers
discoverPeers()}</li>

<li>Start a P2P connection by calling {@link android.net.wifi.p2p.WifiP2pManager#connect
connect()}</li>
<li>And more</li>
</ul>

<p>Several other interfaces and classes are necessary as well, such as:</p>
<ul>
<li>The {@link android.net.wifi.p2p.WifiP2pManager.ActionListener} interface allows you to receive
callbacks when an operation such as discovering peers or connecting to them succeeds or fails.</li>

<li>{@link android.net.wifi.p2p.WifiP2pManager.PeerListListener} interface allows you to receive
information about discovered peers. The callback provides a {@link
android.net.wifi.p2p.WifiP2pDeviceList}, from which you can retrieve a {@link
android.net.wifi.p2p.WifiP2pDevice} object for each device within range and get information such as
the device name, address, device type, the WPS configurations the device supports, and more.</li>

<li>The {@link android.net.wifi.p2p.WifiP2pManager.GroupInfoListener} interface allows you to
receive information about a P2P group. The callback provides a {@link
android.net.wifi.p2p.WifiP2pGroup} object, which provides group information such as the owner, the
network name, and passphrase.</li>

<li>{@link android.net.wifi.p2p.WifiP2pManager.ConnectionInfoListener} interface allows you to
receive information about the current connection. The callback provides a {@link
android.net.wifi.p2p.WifiP2pInfo} object, which has information such as whether a group has been
formed and who is the group owner.</li>
</ul>

<p>In order to use the Wi-Fi P2P APIs, your app must request the following user permissions:</p>
<ul>
<li>{@link android.Manifest.permission#ACCESS_WIFI_STATE}</li>
<li>{@link android.Manifest.permission#CHANGE_WIFI_STATE}</li>
<li>{@link android.Manifest.permission#INTERNET} (although your app doesn’t technically connect
to the Internet, communicating to Wi-Fi Direct peers with standard java sockets requires Internet
permission).</li>
</ul>

<p>The Android system also broadcasts several different actions during certain Wi-Fi P2P events:</p>
<ul>
<li>{@link android.net.wifi.p2p.WifiP2pManager#WIFI_P2P_CONNECTION_CHANGED_ACTION}: The P2P
connection state has changed. This carries {@link
android.net.wifi.p2p.WifiP2pManager#EXTRA_WIFI_P2P_INFO} with a {@link
android.net.wifi.p2p.WifiP2pInfo} object and {@link
android.net.wifi.p2p.WifiP2pManager#EXTRA_NETWORK_INFO} with a {@link android.net.NetworkInfo}
object.</li>

<li>{@link android.net.wifi.p2p.WifiP2pManager#WIFI_P2P_STATE_CHANGED_ACTION}: The P2P state has
changed between enabled and disabled. It carries {@link
android.net.wifi.p2p.WifiP2pManager#EXTRA_WIFI_STATE} with either {@link
android.net.wifi.p2p.WifiP2pManager#WIFI_P2P_STATE_DISABLED} or {@link
android.net.wifi.p2p.WifiP2pManager#WIFI_P2P_STATE_ENABLED}</li>

<li>{@link android.net.wifi.p2p.WifiP2pManager#WIFI_P2P_PEERS_CHANGED_ACTION}: The list of peer
devices has changed.</li>

<li>{@link android.net.wifi.p2p.WifiP2pManager#WIFI_P2P_THIS_DEVICE_CHANGED_ACTION}: The details for
this device have changed.</li>
</ul>

<p>See the  {@link android.net.wifi.p2p.WifiP2pManager} documentation for more information. Also
look at the <a href="{@docRoot}resources/samples/WiFiDirectDemo/index.html">Wi-Fi Direct Demo</a>
sample application.</p>





<h3 id="Bluetooth">Bluetooth Health Devices</h3>

<p>Android now supports Bluetooth Health Profile devices, so you can create applications that use
Bluetooth to communicate with health devices that support Bluetooth, such as heart-rate monitors,
blood meters, thermometers, and scales.</p>

<p>Similar to regular headset and A2DP profile devices, you must call {@link
android.bluetooth.BluetoothAdapter#getProfileProxy getProfileProxy()} with a {@link
android.bluetooth.BluetoothProfile.ServiceListener} and the {@link
android.bluetooth.BluetoothProfile#HEALTH} profile type to establish a connection with the profile
proxy object.</p>

<p>Once you’ve acquired the Health Profile proxy (the {@link android.bluetooth.BluetoothHealth}
object), connecting to and communicating with paired health devices involves the following new
Bluetooth classes:</p>
<ul>
<li>{@link android.bluetooth.BluetoothHealthCallback}: You must extend this class and implement the
callback methods to receive updates about changes in the application’s registration state and
Bluetooth channel state.</li>
<li>{@link android.bluetooth.BluetoothHealthAppConfiguration}: During callbacks to your {@link
android.bluetooth.BluetoothHealthCallback}, you’ll receive an instance of this object, which
provides configuration information about the available Bluetooth health device, which you must use
to perform various operations such as initiate and terminate connections with the {@link
android.bluetooth.BluetoothHealth} APIs.</li>
</ul>

<p>For more information about using the Bluetooth Health Profile, see the documentation for {@link
android.bluetooth.BluetoothHealth}.</p>





<h3 id="A11y">Accessibility</h3>

<p>Android 4.0 improves accessibility for sight-impaired users with new explore-by-touch mode
and extended APIs that allow you to provide more information about view content or
develop advanced accessibility services.</p>


<h4>Explore-by-touch mode</h4>

<p>Users with vision loss can now explore the screen by touching and dragging a finger across the
screen to hear voice descriptions of the content. Because the explore-by-touch mode works like a
virtual cursor, it allows screen readers to identify the descriptive text the same way that screen
readers can when the user navigates with a d-pad or trackball&mdash;by reading information provided
by {@link android.R.attr#contentDescription android:contentDescription} and {@link
android.view.View#setContentDescription setContentDescription()} upon a simulated "hover" event. So,
consider this is a reminder that you should provide descriptive text for the views in your
application, especially for {@link android.widget.ImageButton}, {@link android.widget.EditText},
{@link android.widget.ImageView} and other widgets that might not naturally contain descriptive
text.</p>


<h4>Accessibility for views</h4>

<p>To enhance the information available to accessibility services such as screen readers, you can
implement new callback methods for accessibility events in your custom {@link
android.view.View} components.</p>

<p>It's important to first note that the behavior of the {@link
android.view.View#sendAccessibilityEvent sendAccessibilityEvent()} method has changed in Android
4.0. As with previous version of Android, when the user enables accessibility services on the device
and an input event such as a click or hover occurs, the respective view is notified with a call to
{@link android.view.View#sendAccessibilityEvent sendAccessibilityEvent()}. Previously, the
implementation of {@link android.view.View#sendAccessibilityEvent sendAccessibilityEvent()} would
initialize an {@link android.view.accessibility.AccessibilityEvent} and send it to {@link
android.view.accessibility.AccessibilityManager}. The new behavior involves some additional callback
methods that allow the view and its parents to add more contextual information to the event:
<ol>
  <li>When invoked, the {@link
android.view.View#sendAccessibilityEvent sendAccessibilityEvent()} and {@link
android.view.View#sendAccessibilityEventUnchecked sendAccessibilityEventUnchecked()} methods defer
to {@link android.view.View#onInitializeAccessibilityEvent onInitializeAccessibilityEvent()}. 
  <p>Custom implementations of {@link android.view.View} might want to implement {@link
android.view.View#onInitializeAccessibilityEvent onInitializeAccessibilityEvent()} to
attach additional accessibility information to the {@link
android.view.accessibility.AccessibilityEvent}, but should also call the super implementation to
provide default information such as the standard content description, item index, and more.
However, you should not add additional text content in this callback&mdash;that happens
next.</p></li>
  <li>Once initialized, if the event is one of several types that should be populated with text
information, the view then receives a call to {@link
android.view.View#dispatchPopulateAccessibilityEvent dispatchPopulateAccessibilityEvent()}, which
defers to the {@link android.view.View#onPopulateAccessibilityEvent onPopulateAccessibilityEvent()}
callback.
  <p>Custom implementations of {@link android.view.View} should usually implement {@link
android.view.View#onPopulateAccessibilityEvent onPopulateAccessibilityEvent()} to add additional
text content to the {@link android.view.accessibility.AccessibilityEvent} if the {@link
android.R.attr#contentDescription android:contentDescription} text is missing or
insufficient. To add more text description to the
{@link android.view.accessibility.AccessibilityEvent}, call {@link
android.view.accessibility.AccessibilityEvent#getText()}.{@link java.util.List#add add()}.</p>
</li>
  <li>At this point, the {@link android.view.View} passes the event up the view hierarchy by calling
{@link android.view.ViewGroup#requestSendAccessibilityEvent requestSendAccessibilityEvent()} on the
parent view. Each parent view then has the chance to augment the accessibility information by
adding an {@link android.view.accessibility.AccessibilityRecord}, until it
ultimately reaches the root view, which sends the event to the {@link
android.view.accessibility.AccessibilityManager} with {@link
android.view.accessibility.AccessibilityManager#sendAccessibilityEvent
sendAccessibilityEvent()}.</li>
</ol>

<p>In addition to the new methods above, which are useful when extending the {@link
android.view.View} class, you can also intercept these event callbacks on any {@link
android.view.View} by extending {@link
android.view.View.AccessibilityDelegate AccessibilityDelegate} and setting it on the view with
{@link android.view.View#setAccessibilityDelegate setAccessibilityDelegate()}.
When you do, each accessibility method in the view defers the call to the corresponding method in
the delegate. For example, when the view receives a call to {@link
android.view.View#onPopulateAccessibilityEvent onPopulateAccessibilityEvent()}, it passes it to the
same method in the {@link android.view.View.AccessibilityDelegate}. Any methods not handled by
the delegate are given right back to the view for default behavior. This allows you to override only
the methods necessary for any given view without extending the {@link android.view.View} class.</p>


<p>If you want to maintain compatibility with Android versions prior to 4.0, while also supporting
the new the accessibility APIs, you can do so with the latest version of the <em>v4 support
library</em> (in <a href="{@docRoot}sdk/compatibility-library.html">Compatibility Package, r4</a>)
using a set of utility classes that provide the new accessibility APIs in a backward-compatible
design.</p>




<h4>Accessibility services</h4>

<p>If you're developing an accessibility service, the information about various accessibility events
has been significantly expanded to enable more advanced accessibility feedback for users. In
particular, events are generated based on view composition, providing better context information and
allowing accessibility services to traverse view hierarchies to get additional view information and
deal with special cases.</p>

<p>If you're developing an accessibility service (such as a screen reader), you can access
additional content information and traverse view hierarchies with the following procedure:</p>
<ol>
<li>Upon receiving an {@link android.view.accessibility.AccessibilityEvent} from an application,
call the {@link android.view.accessibility.AccessibilityEvent#getRecord(int)
AccessibilityEvent.getRecord()} to retrieve a specific {@link
android.view.accessibility.AccessibilityRecord} (there may be several records attached to the
event).</li>

<li>From either {@link android.view.accessibility.AccessibilityEvent} or an individual {@link
android.view.accessibility.AccessibilityRecord}, you can call {@link 
android.view.accessibility.AccessibilityRecord#getSource() getSource()} to retrieve a {@link
android.view.accessibility.AccessibilityNodeInfo} object.
  <p>An {@link android.view.accessibility.AccessibilityNodeInfo} represents a single node
of the window content in a format that allows you to query accessibility information about that
node. The {@link android.view.accessibility.AccessibilityNodeInfo} object returned from {@link
android.view.accessibility.AccessibilityEvent} describes the event source, whereas the source from
an {@link android.view.accessibility.AccessibilityRecord} describes the predecessor of the event
source.</p></li>

<li>With the {@link android.view.accessibility.AccessibilityNodeInfo}, you can query information
about it, call {@link
android.view.accessibility.AccessibilityNodeInfo#getParent getParent()} or {@link
android.view.accessibility.AccessibilityNodeInfo#getChild getChild()} to traverse the view
hierarchy, and even add child views to the node.</li>
</ol>

<p>In order for your application to publish itself to the system as an accessibility service, it
must declare an XML configuration file that corresponds to {@link
android.accessibilityservice.AccessibilityServiceInfo}. For more information about creating an
accessibility service, see {@link
android.accessibilityservice.AccessibilityService} and {@link
android.accessibilityservice.AccessibilityService#SERVICE_META_DATA
SERVICE_META_DATA} for information about the XML configuration.</p>


<h4>Other accessibility APIs</h4>

<p>If you're interested in the device's accessibility state, the {@link
android.view.accessibility.AccessibilityManager} has some new APIs such as:</p>
<ul>
  <li>{@link android.view.accessibility.AccessibilityManager.AccessibilityStateChangeListener}
is an interface that allows you to receive a callback whenever accessibility is enabled or
disabled.</li>
  <li>{@link android.view.accessibility.AccessibilityManager#getEnabledAccessibilityServiceList
    getEnabledAccessibilityServiceList()} provides information about which accessibility services
    are currently enabled.</li>
  <li>{@link android.view.accessibility.AccessibilityManager#isTouchExplorationEnabled()} tells
  you whether the explore-by-touch mode is enabled.</li>
</ul>






<h3 id="SpellChecker">Spell Checker Services</h3>

<p>A new spell checker framework allows apps to create spell checkers in a manner similar to the
input method framework (for IMEs). To create a new spell checker, you must implement a service that
extends
{@link android.service.textservice.SpellCheckerService} and extend the {@link
android.service.textservice.SpellCheckerService.Session} class to provide spelling suggestions based
on text provided by the interface's callback methods. In the {@link
android.service.textservice.SpellCheckerService.Session} callback methods, you must return the
spelling suggestions as {@link android.view.textservice.SuggestionsInfo} objects. </p>

<p>Applications with a spell checker service must declare the {@link
android.Manifest.permission#BIND_TEXT_SERVICE} permission as required by the service.
The service must also declare an intent filter with {@code &lt;action
android:name="android.service.textservice.SpellCheckerService" />} as the intent’s action and should
include a {@code &lt;meta-data&gt;} element that declares configuration information for the spell
checker. </p>

<p>See the sample <a href="{@docRoot}resources/samples/SpellChecker/SampleSpellCheckerService/index.html">
Spell Checker Service</a> app and
sample <a href="{@docRoot}resources/samples/SpellChecker/HelloSpellChecker/index.html">
Spell Checker Client</a> app for example code.</p>




<h3 id="TTS">Text-to-speech Engines</h3>

<p>Android’s text-to-speech (TTS) APIs have been significantly extended to allow applications to
more easily implement custom TTS engines, while applications that want to use a TTS engine have a
couple new APIs for selecting an engine.</p>


<h4>Using text-to-speech engines</h4>

<p>In previous versions of Android, you could use the {@link android.speech.tts.TextToSpeech} class
to perform text-to-speech (TTS) operations using the TTS engine provided by the system or set a
custom engine using {@link android.speech.tts.TextToSpeech#setEngineByPackageName
setEngineByPackageName()}. In Android 4.0, the {@link
android.speech.tts.TextToSpeech#setEngineByPackageName setEngineByPackageName()} method has been
deprecated and you can now specify the engine to use with a new {@link
android.speech.tts.TextToSpeech} constructor that accepts the package name of a TTS engine.</p>

<p>You can also query the available TTS engines with {@link
android.speech.tts.TextToSpeech#getEngines()}. This method returns a list of {@link
android.speech.tts.TextToSpeech.EngineInfo} objects, which include meta data such as the engine’s
icon, label, and package name.</p>


<h4>Building text-to-speech engines</h4>

<p>Previously, custom engines required that the engine be built using an undocumented native header
file. In Android 4.0, there is a complete set of framework APIs for building TTS engines. </p>

<p>The basic setup requires an implementation of {@link android.speech.tts.TextToSpeechService} that
responds to the {@link android.speech.tts.TextToSpeech.Engine#INTENT_ACTION_TTS_SERVICE} intent. The
primary work for a TTS engine happens during the {@link
android.speech.tts.TextToSpeechService#onSynthesizeText onSynthesizeText()} callback in a service
that extends {@link android.speech.tts.TextToSpeechService}. The system delivers this method two
objects:</p>
<ul>
<li>{@link android.speech.tts.SynthesisRequest}: This contains various data including the text to
synthesize, the locale, the speech rate, and voice pitch.</li>
<li>{@link android.speech.tts.SynthesisCallback}: This is the interface by which your TTS engine
delivers the resulting speech data as streaming audio. First the engine must call {@link
android.speech.tts.SynthesisCallback#start start()} to indicate that the engine is ready to deliver
the audio, then call {@link android.speech.tts.SynthesisCallback#audioAvailable audioAvailable()},
passing it the audio data in a byte buffer. Once your engine has passed all audio through the
buffer, call {@link android.speech.tts.SynthesisCallback#done()}.</li>
</ul>

<p>Now that the framework supports a true API for creating TTS engines, support for the native code
implementation has been removed. Look for a blog post about a compatibility layer
that you can use to convert your old TTS engines to the new framework.</p>

<p>For an example TTS engine using the new APIs, see the <a
href="{@docRoot}resources/samples/TtsEngine/index.html">Text To Speech Engine</a> sample app.</p>






<h3 id="NetworkUsage">Network Usage</h3>

<p>Android 4.0 gives users precise visibility of how much network data their applications are using.
The Settings app provides controls that allow users to manage set limits for network data usage and
even disable the use of background data for individual apps. In order to avoid users disabling your
app’s access to data from the background, you should develop strategies to use the data
connection efficiently and adjust your usage depending on the type of connection available.</p>

<p>If your application performs a lot of network transactions, you should provide user settings that
allow users to control your app’s data habits, such as how often your app syncs data, whether to
perform uploads/downloads only when on Wi-Fi, whether to use data while roaming, etc. With these
controls available to them, users are much less likely to disable your app’s access to data when
they approach their limits, because they can instead precisely control how much data your app uses.
If you provide a preference activity with these settings, you should include in its manifest
declaration an intent filter for the {@link android.content.Intent#ACTION_MANAGE_NETWORK_USAGE}
action. For example:</p>

<pre>
&lt;activity android:name="DataPreferences" android:label="@string/title_preferences">
    &lt;intent-filter>
       &lt;action android:name="android.intent.action.MANAGE_NETWORK_USAGE" />
       &lt;category android:name="android.intent.category.DEFAULT" />
    &lt;/intent-filter>
&lt;/activity>
</pre>

<p>This intent filter indicates to the system that this is the activity that controls your
application’s data usage. Thus, when the user inspects how much data your app is using from the
Settings app, a “View application settings" button is available that launches your
preference activity so the user can refine how much data your app uses.</p>

<p>Also beware that {@link android.net.ConnectivityManager#getBackgroundDataSetting()} is now
deprecated and always returns true&mdash;use  {@link
android.net.ConnectivityManager#getActiveNetworkInfo()} instead. Before you attempt any network
transactions, you should always call {@link android.net.ConnectivityManager#getActiveNetworkInfo()}
to get the {@link android.net.NetworkInfo} that represents the current network and query {@link
android.net.NetworkInfo#isConnected()} to check whether the device has a
connection. You can then check other connection properties, such as whether the device is
roaming or connected to Wi-Fi.</p>








<h3 id="RenderScript">RenderScript</h3>

<p>Three major features have been added to RenderScript:</p>

<ul>
  <li>Off-screen rendering to a framebuffer object</li>
  <li>Rendering inside a view</li>
  <li>RS for each from the framework APIs</li>
</ul>

<p>The {@link android.renderscript.Allocation} class now supports a {@link
android.renderscript.Allocation#USAGE_GRAPHICS_RENDER_TARGET} memory space, which allows you to
render things directly into the {@link android.renderscript.Allocation} and use it as a framebuffer
object.</p>

<p>{@link android.renderscript.RSTextureView} provides a means to display RenderScript graphics
inside of a {@link android.view.View},  unlike {@link android.renderscript.RSSurfaceView}, which
creates a separate window. This key difference allows you to do things such as move, transform, or
animate an {@link android.renderscript.RSTextureView} as well as draw RenderScript graphics inside
a view that lies within an activity layout.</p>

<p>The {@link android.renderscript.Script#forEach Script.forEach()} method allows you to call
RenderScript compute scripts from the VM level and have them automatically delegated to available
cores on the device. You do not use this method directly, but any compute RenderScript that you
write will have a {@link android.renderscript.Script#forEach forEach()}  method that you can call in
the reflected RenderScript class. You can call the reflected {@link
android.renderscript.Script#forEach forEach()} method by passing in an input {@link
android.renderscript.Allocation} to process, an output {@link android.renderscript.Allocation} to
write the result to, and a {@link android.renderscript.FieldPacker} data structure in case the
RenderScript needs more information. Only one of the {@link android.renderscript.Allocation}s is
necessary and the data structure is optional.</p>









<h3 id="Enterprise">Enterprise</h3>

<p>Android 4.0 expands the capabilities for enterprise application with the following features.</p>

<h4>VPN services</h4>

<p>The new {@link android.net.VpnService} allows applications to build their own VPN (Virtual
Private Network), running as a {@link android.app.Service}. A VPN service creates an interface for a
virtual network with its own address and routing rules and performs all reading and writing with a
file descriptor.</p>

<p>To create a VPN service, use {@link android.net.VpnService.Builder}, which allows you to specify
the network address, DNS server, network route, and more. When complete, you can establish the
interface by calling {@link android.net.VpnService.Builder#establish()}, which returns a {@link
android.os.ParcelFileDescriptor}. </p>

<p>Because  a VPN service can intercept packets, there are security implications.  As such, if you
implement {@link android.net.VpnService}, then your service must require the {@link
android.Manifest.permission#BIND_VPN_SERVICE} to ensure that only the system can bind to it (only
the system is granted this permission&mdash;apps cannot request it). To then use your VPN service,
users must manually enable it in the system settings.</p>


<h4>Device policies</h4>

<p>Applications that manage the device restrictions can now disable the camera using {@link
android.app.admin.DevicePolicyManager#setCameraDisabled setCameraDisabled()} and the {@link
android.app.admin.DeviceAdminInfo#USES_POLICY_DISABLE_CAMERA} property (applied with a {@code
&lt;disable-camera /&gt;} element in the policy configuration file).</p>


<h4>Certificate management</h4>

<p>The new {@link android.security.KeyChain} class provides APIs that allow you to import and access
certificates in the system key store. Certificates streamline the installation of both client
certificates (to validate the identity of the user) and certificate authority certificates (to
verify server identity). Applications such as web browsers or email clients can access the installed
certificates to authenticate users to servers. See the {@link android.security.KeyChain}
documentation for more information.</p>







<h3 id="Sensors">Device Sensors</h3>

<p>Two new sensor types have been added in Android 4.0:</p>

<ul>
  <li>{@link android.hardware.Sensor#TYPE_AMBIENT_TEMPERATURE}: A temperature sensor that provides
the ambient (room) temperature in degrees Celsius.</li>
  <li>{@link android.hardware.Sensor#TYPE_RELATIVE_HUMIDITY}: A humidity sensor that provides the
relative ambient (room) humidity as a percentage.</li>
</ul>

<p>If a device has both {@link android.hardware.Sensor#TYPE_AMBIENT_TEMPERATURE} and  {@link
android.hardware.Sensor#TYPE_RELATIVE_HUMIDITY} sensors, you can use them to calculate the dew point
and the absolute humidity.</p>

<p>The previous temperature sensor, {@link android.hardware.Sensor#TYPE_TEMPERATURE}, has been
deprecated. You should use the {@link android.hardware.Sensor#TYPE_AMBIENT_TEMPERATURE} sensor
instead.</p>

<p>Additionally, Android’s three synthetic sensors have been greatly improved so they now have lower
latency and smoother output. These sensors include the gravity sensor ({@link
android.hardware.Sensor#TYPE_GRAVITY}), rotation vector sensor ({@link
android.hardware.Sensor#TYPE_ROTATION_VECTOR}), and linear acceleration sensor ({@link
android.hardware.Sensor#TYPE_LINEAR_ACCELERATION}). The improved sensors rely on the gyroscope
sensor to improve their output, so the sensors appear only on devices that have a gyroscope.</p>





<h3 id="ActionBar">Action Bar</h3>

<p>The {@link android.app.ActionBar} has been updated to support several new behaviors. Most
importantly, the system gracefully manages the action bar’s size and configuration when running on
smaller screens in order to provide an optimal user experience on all screen sizes. For example,
when the screen is narrow (such as when a handset is in portrait orientation), the action bar’s
navigation tabs appear in a “stacked bar," which appears directly below the main action bar. You can
also opt-in to a “split action bar," which places all action items in a separate bar at the bottom
of the screen when the screen is narrow.</p>


<h4>Split action bar</h4>

<p>If your action bar includes several action items, not all of them will fit into the action bar on
a narrow screen, so the system will place more of them into the overflow menu. However, Android 4.0
allows you to enable “split action bar" so that more action items can appear on the screen in a
separate bar at the bottom of the screen. To enable split action bar, add {@link
android.R.attr#uiOptions android:uiOptions} with {@code "splitActionBarWhenNarrow"} to either your
<a href="{@docRoot}guide/topics/manifest/application-element.html">{@code &lt;application&gt;}</a>
tag or
individual <a href="{@docRoot}guide/topics/manifest/activity-element.html">{@code
&lt;activity&gt;}</a> tags
in your manifest file. When enabled, the system will add an additional bar at the bottom of the
screen for all action items when the screen is narrow (no action items will appear in the primary
action bar).</p>

<p>If you want to use the navigation tabs provided by the {@link android.app.ActionBar.Tab} APIs,
but don’t need the main action bar on top (you want only the tabs to appear at the top), then enable
the split action bar as described above and also call {@link
android.app.ActionBar#setDisplayShowHomeEnabled setDisplayShowHomeEnabled(false)} to disable the
application icon in the action bar. With nothing left in the main action bar, it
disappears&mdash;all that’s left are the navigation tabs at the top and the action items at the
bottom of the screen.</p>


<h4>Action bar styles</h4>

<p>If you want to apply custom styling to the action bar, you can use new style properties {@link
android.R.attr#backgroundStacked} and {@link android.R.attr#backgroundSplit} to apply a background
drawable or color to the stacked bar and split bar, respectively. You can also set these styles at
runtime with {@link android.app.ActionBar#setStackedBackgroundDrawable
setStackedBackgroundDrawable()} and {@link android.app.ActionBar#setSplitBackgroundDrawable
setSplitBackgroundDrawable()}.</p>


<h4>Action provider</h4>

<p>The new {@link android.view.ActionProvider} class allows you to create a specialized handler for
action items. An action provider can define an action view, a default action behavior, and a submenu
for each action item to which it is associated. When you want to create an action item that has
dynamic behaviors (such as a variable action view, default action, or submenu), extending {@link
android.view.ActionProvider} is a good solution in order to create a reusable component, rather than
handling the various action item transformations in your fragment or activity.</p>

<p>For example, the {@link android.widget.ShareActionProvider} is an extension of {@link
android.view.ActionProvider} that facilitates a “share" action from the action bar. Instead of using
traditional action item that invokes the {@link android.content.Intent#ACTION_SEND} intent, you can
use this action provider to present an action view with a drop-down list of applications that handle
the {@link android.content.Intent#ACTION_SEND} intent. When the user selects an application to use
for the action, {@link android.widget.ShareActionProvider} remembers that selection and provides it
in the action view for faster access to sharing with that app.</p>

<p>To declare an action provider for an action item, include the {@code android:actionProviderClass}
attribute in the <a href="{@docRoot}guide/topics/resources/menu-resource.html#item-element">{@code
&lt;item&gt;}</a> element for your activity’s options menu, with the class name of the action
provider as the value. For example:</p>

<pre>
&lt;item android:id="@+id/menu_share"
      android:title="Share"
      android:showAsAction="ifRoom"
      android:actionProviderClass="android.widget.ShareActionProvider" /&gt;
</pre>

<p>In your activity’s {@link android.app.Activity#onCreateOptionsMenu onCreateOptionsMenu()}
callback method, retrieve an instance of the action provider from the menu item and set the
intent:</p>

<pre>
public boolean onCreateOptionsMenu(Menu menu) {
    getMenuInflater().inflate(R.menu.options, menu);
    ShareActionProvider shareActionProvider =
          (ShareActionProvider) menu.findItem(R.id.menu_share).getActionProvider();
    // Set the share intent of the share action provider.
    shareActionProvider.setShareIntent(createShareIntent());
    ...
    return super.onCreateOptionsMenu(menu);
}
</pre>

<p>For an example using the {@link android.widget.ShareActionProvider}, see <a
href="{@docRoot}resources/samples/ApiDemos/src/com/example/android/apis/app/ActionBarShareActionProviderActivity.html"
>ActionBarShareActionProviderActivity</a> in ApiDemos.</p>


<h4>Collapsible action views</h4>

<p>Action items that provide an action view can now toggle between their action view state and
traditional action item state. Previously only the {@link android.widget.SearchView} supported
collapsing when used as an action view, but now you can add an action view for any action item and
switch between the expanded state (action view is visible) and collapsed state (action item is
visible).</p>

<p>To declare that an action item that contains an action view be collapsible, include the {@code
“collapseActionView"} flag in the {@code android:showAsAction} attribute for the <a
href="{@docRoot}guide/topics/resources/menu-resource.html#item-element">{@code
&lt;item&gt;}</a> element in the menu’s XML file.</p>

<p>To receive callbacks when an action view switches between expanded and collapsed, register an
instance of {@link android.view.MenuItem.OnActionExpandListener} with the respective {@link
android.view.MenuItem} by calling {@link android.view.MenuItem#setOnActionExpandListener
setOnActionExpandListener()}. Typically, you should do so during the {@link
android.app.Activity#onCreateOptionsMenu onCreateOptionsMenu()} callback.</p>

<p>To control a collapsible action view, you can call {@link
android.view.MenuItem#collapseActionView()} and {@link android.view.MenuItem#expandActionView()} on
the respective {@link android.view.MenuItem}.</p>

<p>When creating a custom action view, you can also implement the new {@link
android.view.CollapsibleActionView} interface to receive callbacks when the view is expanded and
collapsed.</p>


<h4>Other APIs for action bar</h4>
<ul>
<li>{@link android.app.ActionBar#setHomeButtonEnabled setHomeButtonEnabled()} allows you to specify
whether the icon/logo behaves as a button to navigate home or “up" (pass “true" to make it behave as
a button).</li>

<li>{@link android.app.ActionBar#setIcon setIcon()} and {@link android.app.ActionBar#setLogo
setLogo()} allow you to define the action bar icon or logo at runtime.</li>

<li>{@link android.app.Fragment#setMenuVisibility Fragment.setMenuVisibility()} allows you to enable
or disable the visibility of the options menu items declared by the fragment. This is useful if the
fragment has been added to the activity, but is not visible, so the menu items should be
hidden.</li>

<li>{@link android.app.FragmentManager#invalidateOptionsMenu
FragmentManager.invalidateOptionsMenu()}
allows you to invalidate the activity options menu during various states of the fragment lifecycle
in which using the equivalent method from {@link android.app.Activity} might not be available.</li>
</ul>








<h3 id="UI">User Interface and Views</h3>

<p>Android 4.0 introduces a variety of new views and other UI components.</p>


<h4>GridLayout</h4>

<p>{@link android.widget.GridLayout} is a new view group that places child views in a rectangular
grid. Unlike {@link android.widget.TableLayout}, {@link android.widget.GridLayout} relies on a flat
hierarchy and does not make use of intermediate views such as table rows for providing structure.
Instead, children specify which row(s) and column(s) they should occupy (cells can span multiple
rows and/or columns), and by default are laid out sequentially across the grid’s rows and columns.
The {@link android.widget.GridLayout} orientation determines whether sequential children are by
default laid out horizontally or vertically. Space between children may be specified either by using
instances of the new {@link android.widget.Space} view or by setting the relevant margin parameters
on children.</p>

<p>See <a
href="{@docRoot}resources/samples/ApiDemos/src/com/example/android/apis/view/index.html">ApiDemos</a
>
for samples using {@link android.widget.GridLayout}.</p>



<h4>TextureView</h4>

<p>{@link android.view.TextureView} is a new view that allows you to display a content stream, such
as a video or an OpenGL scene. Although similar to {@link android.view.SurfaceView}, {@link
android.view.TextureView} is unique in that it behaves like a regular view, rather than creating a
separate window, so you can treat it like any other {@link android.view.View} object. For example,
you can apply transforms, animate it using {@link android.view.ViewPropertyAnimator}, or
adjust its opacity with {@link android.view.View#setAlpha setAlpha()}.</p>

<p>Beware that {@link android.view.TextureView} works only within a hardware accelerated window.</p>

<p>For more information, see the {@link android.view.TextureView} documentation.</p>


<h4>Switch widget</h4>

<p>The new {@link android.widget.Switch} widget is a two-state toggle that users can drag to one
side or the other (or simply tap) to toggle an option between two states.</p>

<p>You can use the {@code android:textOn} and {@code android:textOff} attributes to specify the text
to appear on the switch when in the on and off setting. The {@code android:text} attribute also
allows you to place a label alongside the switch.</p>

<p>For a sample using switches, see the <a
href="{@docRoot}resources/samples/ApiDemos/res/layout/switches.html">switches.xml</a> layout file
and respective <a
href="{@docRoot}resources/samples/ApiDemos/src/com/example/android/apis/view/Switches.html">Switches
</a> activity.</p>


<h4>Popup menus</h4>

<p>Android 3.0 introduced {@link android.widget.PopupMenu} to create short contextual menus that pop
up at an anchor point you specify (usually at the point of the item selected). Android 4.0 extends
the {@link android.widget.PopupMenu} with a couple useful features:</p>
<ul>
<li>You can now easily inflate the contents of a popup menu from an XML <a
href="{@docRoot}guide/topics/resources/menu-resource.html">menu resource</a> with {@link
android.widget.PopupMenu#inflate inflate()}, passing it the menu resource ID.</li>
<li>You can also now create a {@link android.widget.PopupMenu.OnDismissListener} that receives a
callback when the menu is dismissed.</li>
</ul>


<h4>Preferences</h4>

<p>A new {@link android.preference.TwoStatePreference} abstract class serves as the basis for
preferences that provide a two-state selection option. The new {@link
android.preference.SwitchPreference} is an extension of {@link
android.preference.TwoStatePreference} that provides a {@link android.widget.Switch} widget in the
preference view to allow users to toggle a setting on or off without the need to open an additional
preference screen or dialog. For example, the Settings application uses a {@link
android.preference.SwitchPreference} for the Wi-Fi and Bluetooth settings.</p>



<h4>System themes</h4>

<p>The default theme for all applications that target Android 4.0 (by setting either <a
href="{@docRoot}guide/topics/manifest/uses-sdk-element.html#target">{@code targetSdkVersion}</a> or
<a href="{@docRoot}guide/topics/manifest/uses-sdk-element.html#min">{@code minSdkVersion}</a> to
{@code “14"} or higher) is now the
"device default" theme: {@link android.R.style#Theme_DeviceDefault Theme.DeviceDefault}. This may be
the dark Holo theme or a different dark theme defined by the specific device.</p>

<p>The {@link android.R.style#Theme_Holo Theme.Holo} family of themes are guaranteed to not change
from one device to another when running the same version of Android. If you explicitly
apply any of the {@link android.R.style#Theme_Holo Theme.Holo} themes to your activities, you can
rest assured that these themes will not change character on different devices within the same
platform version.</p>

<p>If you wish for your app to blend in with the overall device theme (such as when different OEMs
provide different default themes for the system), you should explicitly apply themes from the {@link
android.R.style#Theme_DeviceDefault Theme.DeviceDefault} family.</p>


<h4>Options menu button</h4>

<p>Beginning with Android 4.0, you'll notice that handsets no longer require a Menu hardware button.
However, there's no need for you to worry about this if your existing application provides an <a
href="{@docRoot}guide/topics/ui/menus.html#options-menu">options menu</a> and expects there to be a
Menu button. To ensure that existing apps continue to work as they expect, the system provides an
on-screen Menu button for apps that were designed for older versions of Android.</p>

<p>For the best user experience, new and updated apps should instead use the {@link
android.app.ActionBar} to provide access to menu items and set <a
href="{@docRoot}guide/topics/manifest/uses-sdk-element.html#target">{@code targetSdkVersion}</a> to
{@code "14"} to take advantage of the latest framework default behaviors.</p>



<h4>Controls for system UI visibility</h4>

<p>Since the early days of Android, the system has managed a UI component known as the <em>status
bar</em>, which resides at the top of handset devices to deliver information such as the carrier
signal, time, notifications, and so on. Android 3.0 added the <em>system bar</em> for tablet
devices, which resides at the bottom of the screen to provide system navigation controls (Home,
Back, and so forth) and also an interface for elements traditionally provided by the status bar.  In
Android 4.0, the system provides a new type of system UI called the <em>navigation bar</em>. You
might consider the navigation bar a re-tuned version of the system bar designed for
handsets&mdash;it provides navigation controls
for devices that don’t have hardware counterparts for navigating the system, but it leaves out the
system bar's notification UI and setting controls. As such, a device that provides the navigation
bar also has the status bar at the top.</p>

<p>To this day, you can hide the status bar on handsets using the {@link
android.view.WindowManager.LayoutParams#FLAG_FULLSCREEN} flag. In Android 4.0, the APIs that control
the system bar’s visibility have been updated to better reflect the behavior of both the system bar
and navigation bar:</p>
<ul>
<li>The {@link android.view.View#SYSTEM_UI_FLAG_LOW_PROFILE} flag replaces the {@code
STATUS_BAR_HIDDEN} flag. When set, this flag enables “low profile" mode for the system bar or
navigation bar. Navigation buttons dim and other elements in the system bar also hide. Enabling
this is useful for creating more immersive games without distraction for the system navigation
buttons.</li>

<li>The {@link android.view.View#SYSTEM_UI_FLAG_VISIBLE} flag replaces the {@code
STATUS_BAR_VISIBLE} flag to request the system bar or navigation bar be visible.</li>

<li>The {@link android.view.View#SYSTEM_UI_FLAG_HIDE_NAVIGATION} is a new flag that requests
the navigation bar hide completely. Be aware that this works only for the <em>navigation bar</em>
used by some handsets (it does <strong>not</strong> hide the system bar on tablets). The navigation
bar returns to view as soon as the system receives user input. As such, this mode is useful
primarily for video playback or other cases in which the whole screen is needed but user input is
not required.</li>
</ul>

<p>You can set each of these flags for the system bar and navigation bar by calling {@link
android.view.View#setSystemUiVisibility setSystemUiVisibility()} on any view in your activity. The
window manager combines (OR-together) all flags from all views in your window and
apply them to the system UI as long as your window has input focus. When your window loses input
focus (the user navigates away from your app, or a dialog appears), your flags cease to have effect.
Similarly, if you remove those views from the view hierarchy their flags no longer apply.</p>

<p>To synchronize other events in your activity with visibility changes to the system UI (for
example, hide the action bar or other UI controls when the system UI hides), you should register a
{@link android.view.View.OnSystemUiVisibilityChangeListener} to be notified when the visibility
of the system bar or navigation bar changes.</p>

<p>See the <a
href="{@docRoot}resources/samples/ApiDemos/src/com/example/android/apis/view/OverscanActivity.html">
OverscanActivity</a> class for a demonstration of different system UI options.</p>





<h3 id="Input">Input Framework</h3>

<p>Android 4.0 adds support for cursor hover events and new stylus and mouse button events.</p>

<h4>Hover events</h4>

<p>The {@link android.view.View} class now supports “hover" events to enable richer interactions
through the use of pointer devices (such as a mouse or other devices that drive an on-screen
cursor).</p>

<p>To receive hover events on a view, implement the {@link android.view.View.OnHoverListener} and
register it with {@link android.view.View#setOnHoverListener setOnHoverListener()}. When a hover
event occurs on the view, your listener receives a call to {@link
android.view.View.OnHoverListener#onHover onHover()}, providing the {@link android.view.View} that
received the event and a {@link android.view.MotionEvent} that describes the type of hover event
that occurred. The hover event can be one of the following:</p>
<ul>
<li>{@link android.view.MotionEvent#ACTION_HOVER_ENTER}</li>
<li>{@link android.view.MotionEvent#ACTION_HOVER_EXIT}</li>
<li>{@link android.view.MotionEvent#ACTION_HOVER_MOVE}</li>
</ul>

<p>Your {@link android.view.View.OnHoverListener} should return true from {@link
android.view.View.OnHoverListener#onHover onHover()} if it handles the hover event.  If your
listener returns false, then the hover event will be dispatched to the parent view as usual.</p>

<p>If your application uses buttons or other widgets that change their appearance based on the
current state, you can now use the {@code android:state_hovered} attribute in a <a
href="{@docRoot}guide/topics/resources/drawable-resource.html#StateList">state list drawable</a> to
provide a different background drawable when a cursor hovers over the view.</p>

<p>For a demonstration of the new hover events, see the <a
href="{@docRoot}resources/samples/ApiDemos/src/com/example/android/apis/view/Hover.html">Hover</a> class in
ApiDemos.</p>


<h4>Stylus and mouse button events</h4>

<p>Android now provides APIs for receiving input from a stylus input device such as a digitizer
tablet peripheral or a stylus-enabled touch screen.</p>

<p>Stylus input operates in a similar manner to touch or mouse input.  When the stylus is in contact
with the digitizer, applications receive touch events just like they would when a finger is used to
touch the display.  When the stylus is hovering above the digitizer, applications receive hover
events just like they would when a mouse pointer was being moved across the display when no buttons
are pressed.</p>

<p>Your application can distinguish between finger, mouse, stylus and eraser input by querying the
“tool type" associated with each pointer in a {@link android.view.MotionEvent} using {@link
android.view.MotionEvent#getToolType getToolType()}.  The currently defined tool types are: {@link
android.view.MotionEvent#TOOL_TYPE_UNKNOWN}, {@link android.view.MotionEvent#TOOL_TYPE_FINGER},
{@link android.view.MotionEvent#TOOL_TYPE_MOUSE}, {@link android.view.MotionEvent#TOOL_TYPE_STYLUS},
and {@link android.view.MotionEvent#TOOL_TYPE_ERASER}.  By querying the tool type, your application
can choose to handle stylus input in different ways from finger or mouse input.</p>

<p>Your application can also query which mouse or stylus buttons are pressed by querying the “button
state" of a {@link android.view.MotionEvent} using {@link android.view.MotionEvent#getButtonState
getButtonState()}.  The currently defined button states are: {@link
android.view.MotionEvent#BUTTON_PRIMARY}, {@link android.view.MotionEvent#BUTTON_SECONDARY}, {@link
android.view.MotionEvent#BUTTON_TERTIARY}, {@link android.view.MotionEvent#BUTTON_BACK}, and {@link
android.view.MotionEvent#BUTTON_FORWARD}. For convenience, the back and forward mouse buttons are
automatically mapped to the {@link android.view.KeyEvent#KEYCODE_BACK} and {@link
android.view.KeyEvent#KEYCODE_FORWARD} keys.  Your application can handle these keys to support
mouse button based back and forward navigation.</p>

<p>In addition to precisely measuring the position and pressure of a contact, some stylus input
devices also report the distance between the stylus tip and the digitizer, the stylus tilt angle,
and the stylus orientation angle.  Your application can query this information using {@link
android.view.MotionEvent#getAxisValue getAxisValue()} with the axis codes {@link
android.view.MotionEvent#AXIS_DISTANCE}, {@link android.view.MotionEvent#AXIS_TILT}, and {@link
android.view.MotionEvent#AXIS_ORIENTATION}.</p>

<p>For a demonstration of tool types, button states and the new axis codes, see the <a
href="{@docRoot}resources/samples/ApiDemos/src/com/example/android/apis/graphics/TouchPaint.html">TouchPaint
</a> class in ApiDemos.</p>






<h3 id="Properties">Properties</h3>

<p>The new {@link android.util.Property} class provides a fast, efficient, and easy way to specify a
property on any object that allows callers to generically set/get values on target objects. It also
allows the functionality of passing around field/method references and allows code to set/get values
of the property without knowing the details of what the fields/methods are.</p>

<p>For example, if you want to set the value of field {@code bar} on object {@code foo}, you would
previously do this:</p>
<pre>
foo.bar = value;
</pre>

<p>If you want to call the setter for an underlying private field {@code bar}, you would previously
do this:</p>
<pre>
foo.setBar(value);
</pre>

<p>However, if you want to pass around the {@code foo} instance and have some other code set the
{@code bar} value, there is really no way to do it prior to Android 4.0.</p>

<p>Using the {@link android.util.Property} class, you can declare a {@link android.util.Property}
object {@code BAR} on class {@code Foo} so that you can set the field on instance {@code foo} of
class {@code Foo} like this:</p>
<pre>
BAR.set(foo, value);
</pre>

<p>The {@link android.view.View} class now leverages the {@link android.util.Property} class to
allow you to set various fields, such as transform properties that were added in Android 3.0 ({@link
android.view.View#ROTATION}, {@link android.view.View#ROTATION_X}, {@link
android.view.View#TRANSLATION_X}, etc.).</p>

<p>The {@link android.animation.ObjectAnimator} class also uses the {@link android.util.Property}
class, so you can create an {@link android.animation.ObjectAnimator} with a {@link
android.util.Property}, which is faster, more efficient, and more type-safe than the string-based
approach.</p>






<h3 id="HwAccel">Hardware Acceleration</h3>

<p>Beginning with Android 4.0, hardware acceleration for all windows is enabled by default if your
application has set either <a
href="{@docRoot}guide/topics/manifest/uses-sdk-element.html#target">{@code targetSdkVersion}</a> or
<a href="{@docRoot}guide/topics/manifest/uses-sdk-element.html#min">{@code minSdkVersion}</a> to
{@code “14"} or higher. Hardware acceleration generally results in smoother animations, smoother
scrolling, and overall better performance and response to user interaction.</p>

<p>If necessary, you can manually disable hardware acceleration with the <a
href="{@docRoot}guide/topics/manifest/activity-element.html#hwaccel">{@code hardwareAccelerated}</a>
attribute for individual <a href="{@docRoot}guide/topics/manifest/activity-element.html">{@code
&lt;activity&gt;}</a> elements or the <a
href="{@docRoot}guide/topics/manifest/application-element.html">{@code &lt;application&gt;}</a>
element. You can alternatively disable hardware acceleration for individual views by calling {@link
android.view.View#setLayerType setLayerType(LAYER_TYPE_SOFTWARE)}.</p>

<p>For more information about hardware acceleration, including a list of unsupported drawing
operations, see the <a href="{@docRoot}guide/topics/graphics/hardware-accel.html">Hardware
Acceleration</a> document.</p>



<h3 id="Jni">JNI Changes</h3>

<p>In previous versions of Android, JNI local references weren’t indirect handles; Android used
direct pointers. This wasn't a problem as long as the garbage collector didn't move objects, but it
seemed to work because it made it possible to write buggy code. In Android 4.0, the system now uses
indirect references in order to detect these bugs.</p>

<p>The ins and outs of JNI local references are described in “Local and Global References" in <a
href="{@docRoot}guide/practices/design/jni.html">JNI Tips</a>. In Android 4.0, <a
href="http://android-developers.blogspot.com/2011/07/debugging-android-jni-with-checkjni.html">
CheckJNI</a> has been enhanced to detect these errors. Watch the <a
href="http://android-developers.blogspot.com/">Android Developers Blog</a> for an upcoming post
about common errors with JNI references and how you can fix them.</p>

<p>This change in the JNI implementation only affects apps that target Android 4.0 by setting either
the <a href="{@docRoot}guide/topics/manifest/uses-sdk-element.html#target">{@code
targetSdkVersion}</a> or <a href="{@docRoot}guide/topics/manifest/uses-sdk-element.html#min">{@code
minSdkVersion}</a> to {@code “14"} or higher. If you’ve set these attributes to any lower value,
then JNI local references behave the same as in previous versions.</p>





<h3 id="WebKit">WebKit</h3>
<ul>
<li>WebKit updated to version 534.30</li>
<li>Support for Indic fonts (Devanagari, Bengali, and Tamil, including the complex character support
needed for combining glyphs) in {@link android.webkit.WebView} and the built-in Browser</li>
<li>Support for Ethiopic, Georgian, and Armenian fonts in {@link android.webkit.WebView} and the
built-in Browser</li>
<li>Support for <a
href="http://google-opensource.blogspot.com/2009/05/introducing-webdriver.html">WebDriver</a> makes
it easier for you to test apps that use {@link android.webkit.WebView}</li>
</ul>


<h4>Android Browser</h4>

<p>The Browser application adds the following features to support web applications:</p>
<ul>
<li>Updated V8 JavaScript compiler for faster performance</li>
<li>Plus other notable enhancements carried over from <a
href="{@docRoot}sdk/android-3.0.html">Android
3.0</a> are now available for handsets:
<ul>
<li>Support for fixed position elements on all pages</li>
<li><a href="http://dev.w3.org/2009/dap/camera/">HTML media capture</a></li>
<li><a href="http://dev.w3.org/geo/api/spec-source-orientation.html">Device orientation
events</a></li>
<li><a href="http://www.w3.org/TR/css3-3d-transforms/">CSS 3D transformations</a></li>
</ul>
</li>
</ul>



<h3 id="Permissions">Permissions</h3>

<p>The following are new permissions:</p>
<ul>
<li>{@link android.Manifest.permission#ADD_VOICEMAIL}: Allows a voicemail service to add voicemail
messages to the device.</li>
<li>{@link android.Manifest.permission#BIND_TEXT_SERVICE}: A service that implements {@link
android.service.textservice.SpellCheckerService} must require this permission for itself.</li>
<li>{@link android.Manifest.permission#BIND_VPN_SERVICE}: A service that implements {@link
android.net.VpnService} must require this permission for itself.</li>
<li>{@link android.Manifest.permission#READ_PROFILE}: Provides read access to the {@link
android.provider.ContactsContract.Profile} provider.</li>
<li>{@link android.Manifest.permission#WRITE_PROFILE}: Provides write access to the {@link
android.provider.ContactsContract.Profile} provider.</li>
</ul>



<h3 id="DeviceFeatures">Device Features</h3>

<p>The following are new device features:</p>
<ul>
<li>{@link android.content.pm.PackageManager#FEATURE_WIFI_DIRECT}: Declares that the application
uses
Wi-Fi for peer-to-peer communications.</li>
</ul>


<div class="special" style="margin-top:3em">
<p>For a detailed view of all API changes in Android {@sdkPlatformVersion} (API Level
{@sdkPlatformApiLevel}), see the <a
href="{@docRoot}sdk/api_diff/{@sdkPlatformApiLevel}/changes.html">API Differences Report</a>.</p>
</div>


<h2 id="Honeycomb">Previous APIs</h2>

<p>In addition to everything above, Android 4.0 naturally supports all APIs from previous releases.
Because the Android 3.x platform is available only for large-screen devices, if you've
been developing primarily for handsets, then you might not be aware of all the APIs added to Android
in these recent releases.</p>

<p>Here's a look at some of the most notable APIs you might have missed that are now available
on handsets as well:</p>

<dl>
  <dt><a href="android-3.0.html">Android 3.0</a></dt>
  <dd>
    <ul>
      <li>{@link android.app.Fragment}: A framework component that allows you to separate distinct
elements of an activity into self-contained modules that define their own UI and lifecycle. See the
<a href="{@docRoot}guide/topics/fundamentals/fragments.html">Fragments</a> developer guide.</li>
      <li>{@link android.app.ActionBar}: A replacement for the traditional title bar at the top of
the activity window. It includes the application logo in the left corner and provides a new
interface for menu items. See the
<a href="{@docRoot}guide/topics/ui/actionbar.html">Action Bar</a> developer guide.</li>
      <li>{@link android.content.Loader}: A framework component that facilitates asynchronous
loading of data in combination with UI components to dynamically load data without blocking the
main thread. See the
<a href="{@docRoot}guide/topics/fundamentals/loaders.html">Loaders</a> developer guide.</li>
      <li>System clipboard: Applications can copy and paste data (beyond mere text) to and from
the system-wide clipboard. Clipped data can be plain text, a URI, or an intent. See the
<a href="{@docRoot}guide/topics/clipboard/copy-paste.html">Copy and Paste</a> developer guide.</li>
      <li>Drag and drop: A set of APIs built into the view framework that facilitates drag and drop
operations. See the
<a href="{@docRoot}guide/topics/ui/drag-drop.html">Drag and Drop</a> developer guide.</li>
      <li>An all new flexible animation framework allows you to animate arbitrary properties of any
object (View, Drawable, Fragment, Object, or anything else) and define animation aspects such
as duration, interpolation, repeat and more. The new framework makes Animations in Android
simpler than ever. See the
<a href="{@docRoot}guide/topics/graphics/prop-animation.html">Property Animation</a> developer
guide.</li>
      <li>RenderScript graphics and compute engine: RenderScript offers a high performance 3D
graphics rendering and compute API at the native level, which you write in the C (C99 standard),
providing the type of performance you expect from a native environment while remaining portable
across various CPUs and GPUs. See the
<a href="{@docRoot}guide/topics/renderscript/index.html">RenderScript</a> developer
guide.</li>
      <li>Hardware accelerated 2D graphics: You can now enable the OpenGL renderer for your
application by setting {android:hardwareAccelerated="true"} in your manifest element's <a
href="{@docRoot}guide/topics/manifest/application-element.html"><code>&lt;application&gt;</code></a>
element or for individual <a
href="{@docRoot}guide/topics/manifest/activity-element.html"><code>&lt;activity&gt;</code></a>
elements. This results
in smoother animations, smoother scrolling, and overall better performance and response to user
interaction.
      <p class="note"><strong>Note:</strong> If you set your application's <a
href="{@docRoot}guide/topics/manifest/uses-sdk-element.html#min">{@code minSdkVersion}</a> or <a
href="{@docRoot}guide/topics/manifest/uses-sdk-element.html#target">{@code targetSdkVersion}</a> to
{@code "14"} or higher, hardware acceleration is enabled by default.</p></li>
      <li>And much, much more. See the <a href="android-3.0.html">Android 3.0 Platform</a>
notes for more information.</li>
    </ul>
  </dd>
  
  <dt><a href="android-3.1.html">Android 3.1</a></dt>
  <dd>
    <ul>
      <li>USB APIs: Powerful new APIs for integrating connected peripherals with
Android applications. The APIs are based on a USB stack and services that are
built into the platform, including support for both USB host and device interactions. See the <a
href="{@docRoot}guide/topics/usb/index.html">USB Host and Accessory</a> developer guide.</li>
      <li>MTP/PTP APIs: Applications can interact directly with connected cameras and other PTP
devices to receive notifications when devices are attached and removed, manage files and storage on
those devices, and transfer files and metadata to and from them. The MTP API implements the PTP
(Picture Transfer Protocol) subset of the MTP (Media Transfer Protocol) specification. See the
{@link android.mtp} documentation.</li>
      <li>RTP APIs: Android exposes an API to its built-in RTP (Real-time Transport Protocol) stack,
which applications can use to manage on-demand or interactive data streaming. In particular, apps
that provide VOIP, push-to-talk, conferencing, and audio streaming can use the API to initiate
sessions and transmit or receive data streams over any available network. See the {@link
android.net.rtp} documentation.</li>
      <li>Support for joysticks and other generic motion inputs.</li>
      <li>See the <a href="android-3.1.html">Android 3.1 Platform</a>
notes for many more new APIs.</li>
    </ul>
  </dd>
  
  <dt><a href="android-3.2.html">Android 3.2</a></dt>
  <dd>
    <ul>
      <li>New screens support APIs that give you more control over how your applications are
displayed across different screen sizes. The API extends the existing screen support model with the
ability to precisely target specific screen size ranges by dimensions, measured in
density-independent pixel units (such as 600dp or 720dp wide), rather than by their generalized
screen sizes (such as large or xlarge). For example, this is important in order to help you
distinguish between a 5" device and a 7" device, which would both traditionally be bucketed as
"large" screens. See the blog post, <a
href="http://android-developers.blogspot.com/2011/07/new-tools-for-managing-screen-sizes.html">
New Tools for Managing Screen Sizes</a>.</li>
      <li>New constants for <a
href="{@docRoot}guide/topics/manifest/uses-feature-element.html">{@code &lt;uses-feature&gt;}</a> to
declare landscape or portrait screen orientation requirements.</li>
      <li>The device "screen size" configuration now changes during a screen orientation
change. If your app targets API level 13 or higher, you must handle the {@code "screenSize"}
configuration change if you also want to handle the {@code "orientation"} configuration change. See
<a href="{@docRoot}guide/topics/manifest/activity-element.html#config">{@code
android:configChanges}</a> for more information.</li>
      <li>See the <a href="android-3.2.html">Android 3.2 Platform</a>
notes for other new APIs.</li>
    </ul>
  </dd>

</dl>




<h2 id="api-level">API Level</h2>

<p>The Android {@sdkPlatformVersion} API is assigned an integer
identifier&mdash;<strong>{@sdkPlatformApiLevel}</strong>&mdash;that is stored in the system itself.
This identifier, called the "API level", allows the system to correctly determine whether an
application is compatible with the system, prior to installing the application. </p>

<p>To use APIs introduced in Android {@sdkPlatformVersion} in your application, you need compile the
application against an Android platform that supports API level {@sdkPlatformApiLevel} or
higher. Depending on your needs, you might also need to add an
<code>android:minSdkVersion="{@sdkPlatformApiLevel}"</code> attribute to the
<a href="{@docRoot}guide/topics/manifest/uses-sdk-element.html">{@code &lt;uses-sdk&gt;}</a>
element.</p>

<p>For more information, see the <a href="{@docRoot}guide/appendix/api-levels.html">API Levels</a>
document. </p>


<h2 id="apps">Built-in Applications</h2>

<p>The system image included in the downloadable platform provides these
built-in applications:</p>

<table style="border:0;padding-bottom:0;margin-bottom:0;">
<tr>
<td style="border:0;padding-bottom:0;margin-bottom:0;">
<ul>
<li>API Demos</li>
<li>Browser</li>
<li>Calculator</li>
<li>Calendar</li>
<li>Camera</li>
<li>Clock</li>
<li>Custom Locale</li>
<li>Dev Tools</li>
<li>Downloads</li>
<li>Email</li>
<li>Gallery</li>
</ul>
</td>
<td style="border:0;padding-bottom:0;margin-bottom:0;padding-left:5em;">
<ul>
<li>Gestures Builder</li>
<li>Messaging</li>
<li>Music</li>
<li>People</li>
<li>Phone</li>
<li>Search</li>
<li>Settings</li>
<li>Speech Recorder</li>
<li>Widget Preview</li>
</ul>
</td>
</tr>
</table>


<h2 id="locs" style="margin-top:.75em;">Locales</h2>

<p>The system image included in the downloadable SDK platform provides a variety of built-in
locales. In some cases, region-specific strings are available for the locales. In other cases, a
default version of the language is used. The languages that are available in the Android 3.0 system
image are listed below (with <em>language</em>_<em>country/region</em> locale descriptor).</p>

<table style="border:0;padding-bottom:0;margin-bottom:0;">
<tr>
<td style="border:0;padding-bottom:0;margin-bottom:0;">
<ul>
<li>Arabic, Egypt (ar_EG)</li>
<li>Arabic, Israel (ar_IL)</li>
<li>Bulgarian, Bulgaria (bg_BG)</li>
<li>Catalan, Spain (ca_ES)</li>
<li>Czech, Czech Republic (cs_CZ)</li>
<li>Danish, Denmark(da_DK)</li>
<li>German, Austria (de_AT)</li>
<li>German, Switzerland (de_CH)</li>
<li>German, Germany (de_DE)</li>
<li>German, Liechtenstein (de_LI)</li>
<li>Greek, Greece (el_GR)</li>
<li>English, Australia (en_AU)</li>
<li>English, Canada (en_CA)</li>
<li>English, Britain (en_GB)</li>
<li>English, Ireland (en_IE)</li>
<li>English, India (en_IN)</li>
<li>English, New Zealand (en_NZ)</li>
<li>English, Singapore(en_SG)</li>
<li>English, US (en_US)</li>
<li>English, South Africa (en_ZA)</li>
<li>Spanish (es_ES)</li>
<li>Spanish, US (es_US)</li>
<li>Finnish, Finland (fi_FI)</li>
<li>French, Belgium (fr_BE)</li>
<li>French, Canada (fr_CA)</li>
<li>French, Switzerland (fr_CH)</li>
<li>French, France (fr_FR)</li>
<li>Hebrew, Israel (he_IL)</li>
<li>Hindi, India (hi_IN)</li>
</ul>
</td>
<td style="border:0;padding-bottom:0;margin-bottom:0;padding-left:5em;">
<li>Croatian, Croatia (hr_HR)</li>
<li>Hungarian, Hungary (hu_HU)</li>
<li>Indonesian, Indonesia (id_ID)</li>
<li>Italian, Switzerland (it_CH)</li>
<li>Italian, Italy (it_IT)</li>
<li>Japanese (ja_JP)</li>
<li>Korean (ko_KR)</li>
<li>Lithuanian, Lithuania (lt_LT)</li>
<li>Latvian, Latvia (lv_LV)</li>
<li>Norwegian bokmål, Norway (nb_NO)</li>
<li>Dutch, Belgium (nl_BE)</li>
<li>Dutch, Netherlands (nl_NL)</li>
<li>Polish (pl_PL)</li>
<li>Portuguese, Brazil (pt_BR)</li>
<li>Portuguese, Portugal (pt_PT)</li>
<li>Romanian, Romania (ro_RO)</li>
<li>Russian (ru_RU)</li></li>
<li>Slovak, Slovakia (sk_SK)</li>
<li>Slovenian, Slovenia (sl_SI)</li>
<li>Serbian (sr_RS)</li>
<li>Swedish, Sweden (sv_SE)</li>
<li>Thai, Thailand (th_TH)</li>
<li>Tagalog, Philippines (tl_PH)</li>
<li>Turkish, Turkey (tr_TR)</li>
<li>Ukrainian, Ukraine (uk_UA)</li>
<li>Vietnamese, Vietnam (vi_VN)</li>
<li>Chinese, PRC (zh_CN)</li>
<li>Chinese, Taiwan (zh_TW)</li>
</td>
</tr>
</table>

<p class="note"><strong>Note:</strong> The Android platform may support more
locales than are included in the SDK system image. All of the supported locales
are available in the <a href="http://source.android.com/">Android Open Source
Project</a>.</p>

<h2 id="skins">Emulator Skins</h2>

<p>The downloadable platform includes the following emulator skins:</p>

<ul>
  <li>
    QVGA (240x320, low density, small screen)
  </li>
  <li>
    WQVGA400 (240x400, low density, normal screen)
  </li>
  <li>
    WQVGA432 (240x432, low density, normal screen)
  </li>
  <li>
    HVGA (320x480, medium density, normal screen)
  </li>
  <li>
    WVGA800 (480x800, high density, normal screen)
  </li>
  <li>
    WVGA854 (480x854 high density, normal screen)
  </li>
  <li>
    WXGA720 (1280x720, extra-high density, normal screen) <span class="new">new</span>
  </li>
  <li>
    WSVGA (1024x600, medium density, large screen) <span class="new">new</span>
  </li>
  <li>
    WXGA (1280x800, medium density, xlarge screen)
  </li>
</ul>

<p>To test your application on an emulator that represents the latest Android device, you can create
an AVD with the new WXGA720 skin (it's an xhdpi, normal screen device). Note that the emulator
currently doesn't support the new on-screen navigation bar for devices without hardware navigation
buttons, so when using this skin, you must use keyboard keys <em>Home</em> for the Home button,
<em>ESC</em> for the Back button, and <em>F2</em> or <em>Page-up</em> for the Menu button.</p>

<p>However, due to performance issues in the emulator when running high-resolution screens such as
the one for the WXGA720 skin, we recommend that you primarily use the traditional WVGA800 skin
(hdpi, normal screen) to test your application.</p>