xref: /frameworks/base/docs/html/about/versions/kitkat.jd

page.title=Android KitKat

@jd:body


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<!-- BEGIN ANDROID 4.4 -->
<div id="44-android-44" class="version-section">

  <div style="padding:0px 0px 0px 60px;margin-top:-3px;float:right;">
    <img src="{@docRoot}design/media/index_landing_page.png" alt="Android 4.4 on phone and tablet" width="380">
  </div>

  <div class="landing-docs" style="float:right;clear:both;margin:22px 0 2em 3em;">
  <div class="col-4 normal-links highlights" style="font-size:12px;">
    <h3 id="thisd" >Key Developer Features</h3>
    <ul style="list-style-type:none;">
      <!--<li><a href="#44-ui">UI refresh</a></li>-->
      <li><a href="#44-hce">Host Card Emulation</a></li>
      <li><a href="#44-printing">Printing framework</a></li>
      <li><a href="#44-storage-access">Storage access framework</a></li>
      <li><a href="#44-sensors">Low-power sensors</a></li>
      <li><a href="#44-sms-provider">SMS provider</a></li>
      <li><a href="#44-immersive">Full-screen Immersive mode</a></li>
      <li><a href="#44-transitions">Transitions framework</a></li>
      <li><a href="#44-webview">Chromium WebView</a></li>
      <li><a href="#44-screen-recording">Screen recording</a></li>
      <li><a href="#44-renderscript-ndk">RenderScript NDK</a></li>
      <li><a href="#44-bluetooth">Bluetooth HOGP and MAP</a></li>
      <li><a href="#44-ir-blasters">IR Blasters</a></li>
      <li><a href="#44-closed-captioning">Closed captioning settings</a></li>
      <li><a href="#44-international-users">RTL features</a></li>
      <li><a href="#44-security">Security enhancements</a></li>
      <li><a href="#44-tools">Tools for analyzing memory use</a></li>
    </ul>
  </div>
</div>

<p>Welcome to Android 4.4 KitKat!</p>

<p>
  Android KitKat brings all of Android's most innovative, most beautiful, and
  most useful features to more devices everywhere.
</p>

<p>
  This document provides a glimpse of what's new for developers.
</p>

<p>
  Find out more about KitKat for consumers at <a href=
  "http://www.android.com/versions/kit-kat-4-4/">www.android.com</a>.
</p>


<h2 id="svelte" style="line-height:1.25em;">Making Android for everyone</h2>

<p>
  <span style="white-space:nowrap;">Android 4.4</span> is designed to run fast,
  smooth, and responsively on a much broader range of devices than ever before
  &mdash; including on millions of entry-level devices around the world that
  have as little as <strong>512MB RAM</strong>.
</p>

<p>
  KitKat streamlines every major component to reduce memory use and introduces
  new APIs and tools to help you create innovative, responsive,
  memory-efficient applications.
</p>

<p>
  OEMs building the next generation of Android devices can take advantage of
  <strong>targeted recommendations and options</strong> to run <span style=
  "white-space:nowrap;">Android 4.4</span> efficiently, even on low-memory
  devices. Dalvik JIT code cache tuning, kernel samepage merging (KSM), swap to
  zRAM, and other optimizations help manage memory. New configuration options
  let OEMs tune out-of-memory levels for processes, set graphics cache sizes,
  control memory reclaim, and more.
</p>

<p>
  In Android itself, changes across the system improve memory management and
  reduce memory footprint. Core system processes are trimmed to <strong>use
  less heap</strong>, and they now more <strong>aggressively protect system
  memory</strong> from apps consuming large amounts of RAM. When multiple
  services start at once &mdash; such as when network connectivity changes
  &mdash; Android now <strong>launches the services serially</strong>, in small
  groups, to avoid peak memory demands.
</p>

<p>
  For developers, <span style="white-space:nowrap;">Android 4.4</span> helps
  you deliver <strong>apps that are efficient and responsive</strong> on all
  devices. A new API, <span style=
  "font-size:11.5px;font-family:monospace;">ActivityManager.isLowRamDevice()</span>,
  lets you tune your app's behavior to match the device's memory configuration.
  You can modify or disable large-memory features as needed, depending on the
  use-cases you want to support on entry-level devices. Learn more about
  optimizing your apps for low-memory devices <a
  href="{@docRoot}training/articles/memory.html">here</a>.
</p>

<p>
  New tools give also give you powerful insight into your app's memory use. The
  <strong>procstats tool</strong> details memory use over time, with run times
  and memory footprint for foreground apps and background services. An
  on-device view is also available as a new developer option. The
  <strong>meminfo tool</strong> is enhanced to make it easier to spot memory
  trends and issues, and it reveals additional memory overhead that hasn't
  previously been visible.
</p>


<h2 id="44-hce">New NFC capabilities through Host Card Emulation</h2>

<p>
  <span style="white-space:nowrap;">Android 4.4</span> introduces new platform
  support for secure NFC-based transactions through <strong>Host Card
  Emulation</strong> (HCE), for payments, loyalty programs, card access,
  transit passes, and other custom services. With HCE, any app on an Android
  device can emulate an NFC smart card, letting users tap to initiate
  transactions with an app of their choice &mdash; no provisioned secure
  element (SE) in the device is needed. Apps can also use a new <strong>Reader
  Mode</strong> to act as readers for HCE cards and other NFC-based
  transactions.
</p>

<div style="float:right;margin:32px;width:200px;">
  <img src="{@docRoot}images/kk-contactless-card.png" alt="" width="200" style=
  "margin-bottom:0;">
</div>

<p>
  Android HCE emulates ISO/IEC 7816 based smart cards that use the contactless
  ISO/IEC 14443-4 (ISO-DEP) protocol for transmission. These cards are used by
  many systems today, including the existing EMVCO NFC payment infrastructure.
  Android uses Application Identifiers (AIDs) as defined in ISO/IEC 7816-4 as
  the basis for routing transactions to the correct Android applications.
</p>

<p>
  Apps declare the AIDs they support in their manifest files, along with a
  category identifier that indicates the type of support available (for
  example, "payments"). In cases where multiple apps support the same AID in
  the same category, Android displays a dialog that lets the user choose which
  app to use.
</p>

<p>
  When the user taps to pay at a point-of-sale terminal, the system extracts
  the preferred AID and routes the transaction to the correct application. The
  app reads the transaction data and can use any local or network-based
  services to verify and then complete the transaction.
</p>

<p>
  Android HCE requires an NFC controller to be present in the device. Support
  for HCE is already widely available on most NFC controllers, which offer
  dynamic support for both HCE and SE transactions. <span style=
  "white-space:nowrap;">Android 4.4</span> devices that support NFC will
  include Tap &amp; Pay for easy payments using HCE.
</p>


<h2 id="44-printing">Printing framework</h2>

<p>
  Android apps can now print any type of content over Wi-Fi or
  cloud-hosted services such as Google Cloud Print. In print-enabled apps,
  users can discover available printers, change paper sizes, choose specific
  pages to print, and print almost any kind of document, image, or file.
</p>

<p>
  <span style="white-space:nowrap;">Android 4.4</span> introduces native
  platform support for printing, along with APIs for managing printing and
  adding new types of printer support. The platform provides a print manager
  that mediates between apps requesting printing and installed print services
  that handle print requests. The print manager provides shared services and a
  system UI for printing, giving users consistent control over printing from
  any app. The print manager also ensures the security of content as it's
  passed across processes, from an app to a print service.
</p>

<div style="float:right;margin:22px 0px 0px 24px;width:490px;">
  <img src="{@docRoot}images/kk-print-land-n5.jpg" alt="" width="471" style=
  "margin-bottom:0;">
  <p class="img-caption" style=
  "padding-top:1.5em;margin-left:6px;line-height:1.25em;width:480px;">
    You can add printing support to your apps or develop print services to
    support specific types of printers.
  </p>
</div>

<p>
  Printer manufacturers can use new APIs to develop their own <strong>print
  services</strong> &mdash; pluggable components that add vendor-specific logic
  and services for communicating with specific types of printers. They can
  build print services and distribute them through Google Play, making it easy
  for users to find and install them on their devices. Just as with other apps,
  you can update print services over-the-air at any time.
</p>

<p>
  <strong>Client apps</strong> can use new APIs to add printing capabilities to
  their apps with minimal code changes. In most cases, you would add a print
  action to your Action Bar and a UI for choosing items to print. You would
  also implement APIs to create print jobs, query the print manager for status,
  and cancel jobs. This lets you print nearly any type of content, from local
  images and documents to network data or a view rendered to a canvas.
</p>

<p>
  For broadest compatibility, Android uses PDF as its primary file format for
  printing. Before printing, your app needs to generate a properly paginated
  PDF version of your content. For convenience, the printing API provides
  native and WebView helper classes to let you create PDFs using standard
  Android drawing APIs. If your app knows how to draw the content, it can
  quickly create a PDF for printing.
</p>

<p>
  Most devices running <span style="white-space:nowrap;">Android 4.4</span>
  will include Google Cloud Print pre-installed as a print service, as well as
  several Google apps that support printing, including Chrome, Drive, Gallery,
  and QuickOffice.
</p>

<h2 id="44-storage-access">Storage access framework</h2>

<p>
  A new <strong>storage access framework</strong> makes it simple for users to
  browse and open documents, images, and other files across all of their their
  preferred document storage providers. A standard, easy-to-use UI lets users
  browse files and access recents in a consistent way across apps and
  providers.
</p>

<div style="float:right;margin:22px 0px 0px 24px;width:490px;">
  <img src="{@docRoot}images/kk-saf2-n5.jpg" alt="" width="240" style=
  "margin-bottom:0;"> <img src="{@docRoot}images/kk-saf1-n5.jpg" alt="" width="240"
  style="margin-bottom:0;padding-left:6px;">
  <p class="img-caption" style=
  "padding-top:1.5em;margin-left:6px;line-height:1.25em;width:480px;">
    Box and others have integrated their services into the storage access
    framework, giving users easy access to their documents from apps across the
    system.
  </p>
</div>

<p>
  Cloud or local storage services can participate in this ecosystem by
  implementing a new document provider class that encapsulates their services.
  The provider class includes all of the APIs needed to register the provider
  with the system and manage browsing, reading, and writing documents in the
  provider. The document provider can give users access to any remote or local
  data that can be represented as files &mdash; from text, photos, and
  wallpapers to video, audio, and more.
</p>

<p>
  If you build a <strong>document provider</strong> for a cloud or local
  service, you can deliver it to users as part of your existing Android app.
  After downloading and installing the app, users will have instant access to
  your service from any app that participates in the framework. This can help
  you gain exposure and user engagement, since users will find your services
  more easily.
</p>

<p>
  If you develop a <strong>client app</strong> that manages files or documents,
  you can integrate with the storage access framework just by using new
  <span style="font-size:11.5px;">CREATE_DOCUMENT</span> or <span style=
  "font-size:11.5px;">OPEN_DOCUMENT</span> intents to open or create files
  &mdash; the system automatically displays the standard UI for browsing
  documents, including all available document providers.
</p>

<p>
  You can integrate your client app one time, for all providers, without any
  vendor-specific code. As users add or remove providers, they’ll continue to
  have access to their preferred services from your app, without changes or
  updates needed in your code.
</p>

<p>
  The storage access framework is integrated with the existing <span style=
  "font-size:11.5px;">GET_CONTENT</span> intent, so users also have access to
  all of their previous content and data sources from the new system UI for
  browsing. Apps can continue using <span style=
  "font-size:11.5px;">GET_CONTENT</span> as a way to let users import data. The
  storage access framework and system UI for browsing make it easier for users
  to find and import their data from a wider range of sources.
</p>
<p>
  Most devices running <span style="white-space:nowrap;">Android 4.4</span>
  will include Google Drive and local storage pre-integrated as document
  providers, and Google apps that work with files also use the new framework.
</p>


<h2 id="44-sensors">Low-power sensors</h2>

<h4 id="44-sensor-batching">Sensor batching</h4>

<p>
  <span style="white-space:nowrap;">Android 4.4</span> introduces platform
  support for <strong>hardware sensor batching</strong>, a new optimization
  that can dramatically reduce power consumed by ongoing sensor activities.
</p>

<p>
  With sensor batching, Android works with the device hardware to collect and
  deliver sensor events efficiently in batches, rather than individually as
  they are detected. This lets the device's application processor remain in a
  low-power idle state until batches are delivered. You can request batched
  events from any sensor using a standard event listener, and you can control
  the interval at which you receive batches. You can also request immediate
  delivery of events between batch cycles.
</p>

<p>
  Sensor batching is ideal for low-power, long-running use-cases such as
  fitness, location tracking, monitoring, and more. It can makes your app more
  efficient and it lets you track sensor events continuously &mdash; even while
  the screen is off and the system is asleep.
</p>

<p>
  Sensor batching is currently available on Nexus 5, and we're working with our
  chipset partners to bring it to more devices as soon as possible.
</p>

<div style="float:right;margin:1em 0em 0em 3em;width:490px;clear:both">
  <img src="{@docRoot}images/kk-sensors-moves-n5.jpg" alt="" width="240" style=
  "margin-bottom:0;"> <img src="{@docRoot}images/kk-sensors-runtastic-n5.jpg" alt=""
  width="240" style="margin-bottom:0;padding-left:4px;">
  <p class="img-caption" style=
  "padding-top:1.5em;margin-left:6px;line-height:1.25em;">
    <strong>Moves</strong> and <strong>Runtastic Pedometer</strong> are using
    the hardware step-detector to offer long-running, low-power services.
  </p>
</div>

<h4 id="44-step-detector">Step Detector and Step Counter</h4>

<p>
  <span style="white-space:nowrap;">Android 4.4</span> also adds platform
  support for two new composite sensors &mdash; step detector
  and step counter &mdash; that let your app track steps when
  the user is walking, running, or climbing stairs. These new sensors are
  implemented in hardware for low power consumption.
</p>

<p>
  The step detector analyzes accelerometer input to recognize when the user has
  taken a step, then triggers an event with each step. The step counter tracks
  the total number of steps since the last device reboot and triggers an event
  with each change in the step count. Because the logic and sensor management
  is built into the platform and underlying hardware, you don't need to
  maintain your own detection algorithms in your app.
</p>

<p>
  Step detector and counter sensors are available on Nexus 5, and we're working
  with our chipset partners to bring them to new devices as soon as possible.
</p>


<h2 id="44-sms-provider">SMS provider</h2>

<p>
  If you develop a messaging app that uses SMS or MMS, you can now use a
  <strong>shared SMS provider and new APIs</strong> to manage your app's
  message storage and retrieval. The new SMS provider and APIs define a
  standardized interaction model for all apps that handle SMS or MMS messages.
</p>

<p>
  Along with the new provider and APIs, <span style=
  "white-space:nowrap;">Android 4.4</span> introduces <strong>new
  semantics</strong> for receiving messages and writing to the provider. When a
  message is received, the system routes it directly to the user's default
  messaging app using the new <span style=
  "font-size:11.5px;">SMS_DELIVER</span> intent. Other apps can still listen
  for incoming messages using the <span style=
  "font-size:11.5px;">SMS_RECEIVED</span> intent. Also, the system now allows
  only the default app to write message data to the provider, although other
  apps can read at any time. Apps that are not the user's default can still
  send messages &mdash; the system handles writing those messages to the
  provider on behalf of the app, so that users can see them in the default app.
</p>

<p>
  The new provider and semantics help to improve the user's experience when
  multiple messaging apps are installed, and they help you to build new
  messaging features with fully-supported, forward-compatible APIs.
</p>


<h2 id="44-beautiful-apps">New ways to build beautiful apps</h2>

<div style="float:right;margin:14px 0px 0px 24px;width:246px;">
  <img src="{@docRoot}images/kk-immersive-n5.jpg" alt="" width="240" style=
  "margin-bottom:0;">
  <p class="img-caption" style=
  "padding-top:1.5em;margin-left:6px;line-height:1.25em;">
    A new <strong>immersive mode</strong> lets apps use every pixel on the
    screen to show content and capture touch events.
  </p>
</div>

<h4 id="44-immersive">Full-screen Immersive mode</h4>
<p>
  Now your apps can use <strong>every pixel on the device screen</strong> to
  showcase your content and capture touch events. <span style=
  "white-space:nowrap;">Android 4.4</span> adds a new full-screen immersive
  mode that lets you create full-bleed UIs reaching from edge to edge on phones
  and tablets, <strong>hiding all system UI</strong> such as the status bar and
  navigation bar. It's ideal for rich visual content such as photos, videos,
  maps, books, and games.
</p>

<p>
  In the new mode, the system UI stays hidden, even while users are interacting
  with your app or game &mdash; you can capture touch events from anywhere
  across the screen, even areas that would otherwise be occupied by the system
  bars. This gives you a great way to create a larger, richer, more immersive
  UI in your app or game and also reduce visual distraction.
</p>

<p>
  To make sure that users always have easy, consistent access to system UI from
  full-screen immersive mode, <span style="white-space:nowrap;">Android
  4.4</span> supports a new gesture &mdash; in immersive mode, an edge swipe
  from the top or bottom of the screen now reveals the system UI.
</p>

<p>
  To return to immersive mode, users can touch the screen outside of the bar
  bounds or wait for a short period for the bars to auto-hide. For a consistent
  user experience, the new gesture also works with previous methods of hiding
  the status bar.
</p>

<h4 id="44-transitions">Transitions framework for animating scenes</h4>

<p>
  Most apps structure their flows around several key UI states that expose
  different actions. Many apps also use animation to help users understand
  their progress through those states and the actions available in each. To
  make it easier to create <strong>high-quality animations</strong> in your
  app, <span style="white-space:nowrap;">Android 4.4</span> introduces a new
  transitions framework.
</p>

<p>
  The transitions framework lets you define <strong>scenes</strong>, typically
  view hierarchies, and transitions, which describe how to animate or transform
  the scenes when the user enters or exits them. You can use several predefined
  transition types to animate your scenes based on specific properties, such as
  layout bounds, or visibility. There's also an auto-transition type that
  automatically fades, moves, and resizes views during a scene change. In
  addition, you can define custom transitions that animate the properties that
  matter most to your app, and you can plug in your own animation styles if
  needed.
</p>

<p>
  With the transitions framework you can also <strong>animate changes to your
  UI on the fly</strong>, without needing to define scenes. For example, you
  can make a series of changes to a view hierarchy and then have the
  TransitionManager automatically run a delayed transition on those changes.
</p>

<p>
  Once you've set up transitions, it's straightforward to invoke them from your
  app. For example, you can call a single method to begin a transition, make
  various changes in your view hierarchy, and on the next frame animations will
  automatically begin that animate the changes you specified.
</p>

<div style="float:right;margin:0px 0px 22px 32px;width:340px;">
  <img src="{@docRoot}images/kk-home.jpg" alt="translucent system UI" widtdh="340"
  style="margin-bottom:0">
  <p class="img-caption" style=
  "padding-top:1.5em;line-height:1.25em;margin-bottom:0;">
    Apps can use new window styles to request translucent system bars.
  </p>
</div>

<p>
  For custom control over the transitions that run between specific scenes in
  your application flow, you can use the TransitionManager. The
  TransitionManager lets you define the relationship between scenes and the
  transitions that run for specific scene changes.
</p>

<h4 id="44-translucent-system-ui">Translucent system UI styling</h4>

<p>
  To get the most impact out of your content, you can now use new window styles
  and themes to request <strong>translucent system UI</strong>, including both
  the status bar and navigation bar. To ensure the legibility of navigation bar
  buttons or status bar information, subtle gradients is shown behind the
  system bars. A typical use-case would be an app that needs to show through to
  a wallpaper.
</p>

<h4 id="44-notification-access">Enhanced notification access</h4>

<p>
  Notification listener services can now see <strong>more information about
  incoming notifications</strong> that were constructed using the notification
  builder APIs. Listener services can access a notification's actions as well
  as new extras fields &mdash; text, icon, picture, progress, chronometer, and
  many others &mdash; to extract cleaner information about the notification and
  present the information in a different way.
</p>

<div style="float:left;margin:1em 2em 1em 2em;">
  <a href=""><img src="{@docRoot}images/kk-chromium-icon.png" alt="" height="160" style=
  "margin-bottom:0em;"></a>
</div>

<h4 id="44-webview">Chromium WebView</h4>

<p>
  <span style="white-space:nowrap;">Android 4.4</span> includes a completely
  new implementation of WebView that's based on <a href=
  "http://www.chromium.org/Home" class="external-link">Chromium</a>. The new
  Chromium WebView gives you the latest in standards support, performance, and
  compatibility to build and display your web-based content.
</p>

<p>
  Chromium WebView provides broad support for HTML5, CSS3, and JavaScript. It
  supports most of the HTML5 features available in Chrome for Android 30. It
  also brings an updated version of the JavaScript Engine (V8) that delivers
  dramatically improved JavaScript performance.
</p>

<p stydle="clear:both;">
  In addition, the new Chromium WebView supports remote debugging using
  <a class="external-link" href=
  "https://developers.google.com/chrome-developer-tools/docs/remote-debugging#debugging-webviews">
  Chrome DevTools</a>. For example, you can use Chrome DevTools on your
  development machine to inspect, debug, and analyze your WebView content live
  on a mobile device.
</p>

<p>
  The new Chromium WebView is included on all compatible devices running
  <span style="white-space:nowrap;">Android 4.4</span> and higher. You can take
  advantage of the new WebView right away, and with minimum modifications to
  existing apps and content. In most cases, your content will migrate to the
  new implementation seamlessly.
</p>


<h2 id="44-media">New media capabilities</h2>

<h4 id="44-screen-recording">Screen recording</h4>

<p>
  Now it's easy to create high-quality video of your app, directly from your
  Android device. <span style="white-space:nowrap;">Android 4.4</span> adds
  support for screen recording and provides a <strong>screen recording
  utility</strong> that lets you start and stop recording on a device that's
  connected to your Android SDK environment over USB. It's a great new way to
  create walkthroughs and tutorials for your app, testing materials, marketing
  videos, and more.
</p>

<p>
  With the screen recording utility, you can capture video of your device screen
  contents and store the video as an MP4 file on the device. You can record at any
  device-supported resolution and bitrate you want, and the output retains the
  aspect ratio of the display. By default, the utility selects a resolution
  equal or close to the device's display resolution in the current orientation.
  When you are done recording, you can share the video directly from your
  device or pull the MP4 file to your host computer for post-production.
</p>

<p>
  If your app plays video or other protected content that you don’t want to be
  captured by the screen recorder, you can use <span style=
  "font-size:11.5px;font-family:monospace;white-space:nowrap;">SurfaceView.setSecure()</span>
  to mark the content as secure.
</p>

<p>
  You can access screen recording through the adb tool included in the Android
  SDK, using the command <span style=
  "font-size:11.5px;font-family:monospace;white-space:nowrap;">adb shell
  screenrecord</span>. You can also launch it through the DDMS panel in Android
  Studio.
</p>

<h4 id="44-adaptive-playback">Resolution switching through adaptive playback</h4>

<p>
  <span style="white-space:nowrap;">Android 4.4</span> brings formal support
  for adaptive playback into the Android media framework. Adaptive playback is
  an optional feature of video decoders for MPEG-DASH and other formats that
  enables <strong>seamless change in resolution during playback</strong>. The
  client can start to feed the decoder input video frames of a new resolution
  and the resolution of the output buffers change automatically, and without a
  significant gap.
</p>

<p>
  Resolution switching in <span style="white-space:nowrap;">Android 4.4</span>
  lets media apps offer a significantly better streaming video experience. Apps
  can check for adaptive playback support at runtime using existing APIs and
  implement resolution-switching using new APIs introduced in <span style=
  "white-space:nowrap;">Android 4.4</span>.
</p>

<h4 id="44-cenc">Common Encryption for DASH</h4>

<p>
  Android now supports the <strong>Common Encryption (CENC)</strong> for
  MPEG-DASH, providing a standard, multiplatform DRM scheme for managing
  protecting content. Apps can take advantage of CENC through Android's modular
  DRM framework and platform APIs for supporting DASH.
</p>

<h4 id="44-hls">HTTP Live Streaming</h4>

<p>
  <span style="white-space:nowrap;">Android 4.4</span> updates the platform's
  HTTP Live Streaming (HLS) support to a superset of version 7 of the HLS
  specification (version 4 of the protocol). See the <a href=
  "http://tools.ietf.org/html/draft-pantos-http-live-streaming-07" class=
  "external-link">IETF draft</a> for details.
</p>
<h4 id="44-audio-tunneling">Audio Tunneling to DSP</h4>

<p>
  For high-performance, lower-power audio playback, <span style=
  "white-space:nowrap;">Android 4.4</span> adds platform support for
  audio tunneling to a digital signal processor (DSP) in the
  device chipset. With tunneling, audio decoding and output effects are
  off-loaded to the DSP, waking the application processor less often and using
  less battery.
</p>

<p>
  Audio tunneling can <strong>dramatically improve battery life</strong> for
  use-cases such as listening to music over a headset with the screen off. For
  example, with audio tunneling, Nexus 5 offers a total off-network audio
  playback time of up to 60 hours, an increase of over 50% over non-tunneled
  audio.
</p>

<p>
  Media applications can take advantage of audio tunneling on supported devices
  without needing to modify code. The system applies tunneling to optimize
  audio playback whenever it's available on the device.
</p>

<div style="float:right;padding-top:1em;width:372px;margin-left:2em;">
  <img src="{@docRoot}images/kk-loudnessEnhancerAnnotated.png" alt=
  "Visualizer showing loudness enhancer audio effect" width="360" height="252"
  style="border:1px solid #ddd;border-radius: 6px;">
  <p class="img-caption" style="margin-left:6px;line-height:1.25em;">
    Visualization of how the LoudnessEnhancer effect can make speech content
    more audible.
  </p>
</div>

<p>
  Audio tunneling requires support in the device hardware. Currently audio
  tunneling is available on Nexus 5 and we're working with our chipset partners
  to make it available on more devices as soon as possible.
</p>

<h4 id="44-audio-monitoring">Audio monitoring</h4>

<p>
  Apps can use new monitoring tools in the Visualizer effect to get updates on
  the <strong>peak and RMS levels</strong> of any currently playing audio on
  the device. For example, you could use this creatively in music visualizers
  or to implement playback metering in a media player.
</p>

<h4 id="44-loudness">Loudness enhancer</h4>

<p>
  Media playback applications can <strong>increase the loudness of spoken
  content</strong> by using the new LoudnessEnhancer effect, which acts as
  compressor with time constants that are specifically tuned for speech.
</p>

<h4 id="44-audio-timestamps">Audio timestamps for improved AV sync</h4>

<p>
  The audio framework can now report <strong>presentation timestamps</strong>
  from the audio output HAL to applications, for better audio-video
  synchronization. Audio timestamps let your app determine when a specific
  audio frame will be (or was) presented off-device to the user; you can use
  the timestamp information to more accurately synchronize audio with video
  frames.
</p>

<h4 id="44-miracast">Wi-Fi CERTIFIED Miracast™</h4>

<p>
  <span style="white-space:nowrap;">Android 4.4</span> devices can now be
  certified to the Wi-Fi Alliance Wi-Fi Display Specification as Miracast
  compatible. To help with testing, a new Wireless Display developer option
  exposes advanced configuration controls and settings for Wireless Display
  certification. You can access the option at <strong>Settings &gt; Developer
  options &gt; Wireless display certification</strong>. Nexus 5 is a Miracast
  certified wireless display device.
</p>

<h2 id="44-renderscript">RenderScript Compute</h2>

<div style="float:right;padding-top:1em;width:372px;margin-left:2em;">
  <img src="{@docRoot}images/kk-rs-chart-versions.png" alt=
  "Renderscipt optimizations chart" width="360" height="252" style=
  "border:1px solid #ddd;border-radius: 6px;">
  <p class="img-caption" style="margin-left:6px;line-height:1.25em;">
    Performance benchmarks for Android&nbsp;4.4 relative to Android&nbsp;4.3,
    run on the same devices (Nexus 7, Nexus 10).
  </p>
</div>

<h4>Ongoing performance improvements</strong></h4>

<p>
  When your apps use RenderScript, they'll benefit from <strong>ongoing
  performance tuning</strong> in the RenderScript runtime itself, without the
  need for recompilation. The chart at right shows performance gains in Android
  4.4 on two popular chipsets.
</p>

<h4>GPU acceleration</h4>

<p>
  Any app using RenderScript on a supported device benefits from GPU
  acceleration, without code changes or recompiling. Since the Nexus 10 first
  debuted RenderScript GPU acceleration, various other hardware partners have
  added support.
</p>

<p>
  Now with <span style="white-space:nowrap;">Android 4.4</span>, GPU
  acceleration is available on the Nexus 5, as well as the Nexus 4, Nexus 7
  (2013), and Nexus 10, and we're working with our partners to bring it to more
  devices as soon as possible.
</p>

<h4 id="44-renderscript-ndk">RenderScript in the Android NDK</h4>

<p>
  Now you can take advantage of RenderScript <strong>directly from your native
  code</strong>. A new C++ API in the Android Native Development Kit (NDK) lets
  you access the same RenderScript functionality available through the
  framework APIs, including script intrinsics, custom kernels, and more.
</p>

<p>
  If you have large, performance-intensive tasks to handle in native code, you
  can perform those tasks using RenderScript and integrate them with your
  native code. RenderScript offers great performance across a wide range of
  devices, with automatic support for multi-core CPUs, GPUs, and other
  processors.
</p>

<p>
  When you build an app that uses the RenderScript through the NDK, you can
  distribute it to any device running Android 2.2 or or higher, just like with
  the RenderScript support library available for framework APIs.
</p>


<h2 id="44-graphics">Graphics</h2>

<h4 id="44-surfaceflinger">GLES2.0 SurfaceFlinger</h4>

<p>
  <span style="white-space:nowrap;">Android 4.4</span> upgrades its
  SurfaceFlinger from OpenGL ES 1.0 to OpenGL ES 2.0.
</p>

<h4 id="44-composer">New Hardware Composer support for virtual displays</h4>

<p>
  The latest version of Android Hardware Composer, HWComposer 1.3, supports
  hardware composition of one virtual display in addition to the primary,
  external (e.g. HDMI) display, and has improved OpenGL ES interoperability.
</p>


<h2 id="44-connectivity">New Types of Connectivity</h2>

<h4 id="44-bluetooth">New Bluetooth profiles</h4>

<p>
  <span style="white-space:nowrap;">Android 4.4</span> support for two new
  Bluetooth profiles to let apps support a broader range of low-power and media
  interactions. <strong>Bluetooth HID over GATT</strong> (HOGP) gives apps a
  low-latency link with low-power peripheral devices such as mice, joysticks,
  and keyboards. <strong>Bluetooth MAP</strong> lets your apps exchange
  messages with a nearby device, for example an automotive terminal for
  handsfree use or another mobile device. As an <strong>extension to Bluetooth
  AVRCP 1.3</strong>, users can now set absolute volume on the system from
  their Bluetooth devices.
</p>

<p>
  Platform support for HOGP, MAP, and AVRCP is built on the Bluedroid Bluetooth
  stack introduced by Google and Broadcom in Android 4.2. Support is available
  right away on Nexus devices and other Android-compatible devices that offer
  compatible Bluetooth capabilities.
</p>

<h4 id="44-ir-blasters">IR Blasters</h4>

<p>
  <span style="white-space:nowrap;">Android 4.4</span> introduces platform
  support for built-in <strong>IR blasters</strong>, along with a new API and
  system service that let you create apps to take advantage them.
</p>

<p>
  Using the new API, you can build apps that let users remotely control nearby
  TVs, tuners, switches, and other electronic devices. The API lets your app
  check whether the phone or tablet has an infrared emitter, query it's carrier
  frequencies, and then send infrared signals.
</p>

<p>
  Because the API is standard across Android devices running <span style=
  "white-space:nowrap;">Android 4.4</span> or higher, your app can support the
  broadest possible range of vendors without writing custom integration code.
</p>

<h4 id="44-wifi-tdls">Wi-Fi TDLS support</h4>

<p>
  <span style="white-space:nowrap;">Android 4.4</span> introduces a seamless
  way to stream media and other data faster between devices already on the same
  Wi-Fi network by supporting Wi-Fi Tunneled Direct Link Setup (TDLS).
</p>


<h2 id="44-accessibility">Accessibility</h2>

<h4 id="44-closed-captioning">System-wide settings for closed captioning</h4>

<p>
  <span style="white-space:nowrap;">Android 4.4</span> now supports a better
  accessibility experience across apps by adding system-wide preferences for
  Closed Captioning. Users can go to <strong>Settings</strong> &gt;
  <strong>Accessibility</strong> &gt; <strong>Captions</strong> to set global
  captioning preferences, such as whether to show captions and what language,
  text size, and text style to use.
</p>

<p>
  Apps that use video can now access the user's captioning settings and
  <strong>adjust presentation to meet the user's preferences</strong>. A new
  captioning manager API lets you check and monitor the user's captioning
  preferences. The captioning manager provides you with the user's preferred
  captioning state as well as preferred locale, scaling factor, and text style.
  The text style includes foreground and background colors, edge properties,
  and typeface.
</p>

<div style="float:right;margin:22px 0px 0px 24px;width:490px;">
  <img src="{@docRoot}images/kk-captions-n5.jpg" alt="" width="471" style=
  "margin-bottom:0;">
  <p class="img-caption" style=
  "padding-top:1.5em;margin-left:6px;line-height:1.25em;width:480px;">
    Apps can now refer to the user's <strong>system-wide captions
    preferences</strong>. An example of the expected display style is shown
    right in the settings.
  </p>
</div>

<p>
  In addition, apps that use <strong>VideoView</strong> can use a new API to
  pass a captioning stream along with a video stream for rendering. The system
  automatically handles the display of the captions on video frames according
  to the user's systemwide settings. Currently, VideoView supports auto-display
  of captions in WebVTT format only.
</p>

<p>
  <strong>All apps that show captions</strong> should make sure to check the
  user's systemwide captioning preferences and render captions as closely as
  possible to those preferences. For more insight into how specific
  combinations of settings should look, you can look at a preview of captions
  in different languages, sizes, and styles right in the Settings app.
</p>

<h4 id="44-enhanced-apis">Enhanced Accessibility APIs</h4>

<p>
  <span style="white-space:nowrap;">Android 4.4</span> extends the
  accessibility APIs to support <strong>more precise structural and semantic
  description</strong> and observation of onscreen elements. With the new APIs,
  developers can improve the quality of accessible feedback by providing
  accessibility services with more information about on-screen elements.
</p>

<p>
  In accessibility nodes, developers can now determine whether a node is a
  popup, get its input type, and more. You can also use new APIs to work with
  nodes that contain grid-like information, such as lists and tables. For
  example, you can now specify new supported actions, collection information,
  live region modes, and more.
</p>

<p>
  New accessibility events let developers more closely follow the changes that
  are taking place in window content, and they can now listen for changes in
  the touch exploration mode on the device.
</p>


<h2 id="44-international-users">Support for international Users</h2>

<h4 id="44-drawable-mirroring">Drawable mirroring for RTL locales</h4>

<p>
  If your app is targeting users who use RTL scripts, you can use a new API to
  declare that a <strong>drawable should be auto-mirrored</strong> when the
  user's locale setting includes an RTL language.
</p>

<p>
  Declaring a drawable as auto-mirrored helps you <strong>prevent duplication
  of assets</strong> in your app and reduces the the size of your APK. When you
  have drawables that are the reusable for both LTR and RTL presentations, you
  can declare the default versions as auto-mirrored and then omit those
  Drawables from your RTL resources.
</p>

<div style="float:right;margin:16px 12px 0px 32px;width:260px;clear:both;">
  <img src="{@docRoot}images/kk-pseudolocale-rtl.png" alt="" width="260" style=
  "margin-bottom:0;">
  <p class="img-caption" style="padding-top:1.5em;line-height:1.25em;">
    The <strong>Force RTL layout</strong> option makes it easier to test your app's localization.
  </p>
</div>

<p>
  You can declare various types of drawables as auto-mirrored in your
  application code, such as bitmap, nine-patch, layer, state list, and other
  drawables. You can also declare a drawable as auto-mirrored in your resource
  files by using a new attribute.
</p>

<h4 id="44-pseudolocale-rtl">Force RTL Layout</h4>

<p>
  To make it easier to test and debug your layouts, Android includes a new
  developer option to force RTL layout direction in all apps.
</p>

<p>
  The Force RTL layout option switches the device to RTL layout for all locales and
  displays text in your current language. This can help you find layout issues
  across your app, without having to display the app in an RTL language. You
  can access the RTL pseudo-localed as in <strong>Settings &gt; Developer
  options &gt; Force RTL layout direction</strong>.
</p>


<h2 id="44-security">Security enhancements</h2>

<h4 id="44-selinux">SELinux (enforcing mode)</h4>

<p>
  <span style="white-space:nowrap;">Android 4.4</span> updates its SELinux
  configuration from "permissive" to "enforcing." This means potential policy
  violations within a SELinux domain that has an enforcing policy will be
  blocked.
</p>

<h4 id="44-crytpo">Improved cryptographic algorithms</h4>

<p>
  Android has improved its security further by adding support for two more
  cryptographic algorithms. Elliptic Curve Digital Signature Algorithm (ECDSA)
  support has been added to the keystore provider improving security of digital
  signing, applicable to scenarios such as signing of an application or a data
  connection. The Scrypt key derivation function is implemented to protect the
  cryptographic keys used for full-disk encryption.
</p>

<h4 id="44-other">Other enhancements</h4>

<p>
  On multiuser devices, VPNs are now applied per user. This can allow a user to
  route all network traffic through a VPN without affecting other users on the
  device. Also, Android now supports FORTIFY_SOURCE level 2, and all code is
  compiled with those protections. FORTIFY_SOURCE has been enhanced to work
  with clang.
</p>


<h2 id="44-tools">Tools for analyzing memory use</h2>

<h4 id="44-procstats">Procstats</h4>

<p>
  A new tool called <strong>procstats</strong> helps you analyze the memory
  resources your app uses, as well as the resources used by other apps and
  services running on the system.
</p>

<p>
  Procstats keeps track of <strong>how apps are running over time</strong>,
  providing data about their execution durations and memory use to help
  determine how efficiently they are performing. This is most important for
  apps that start services that run in the background, since it lets you
  monitor how long they are running and how much RAM they are using while doing
  so. Procstats will also collect data for foreground applications about memory
  use over time to determine the overall memory profile of the app.
</p>

<p>
  Procstats can help you identify background services started by your app. You
  can keep track of how long those services continue running and how much RAM
  they use while doing so. Procstats also lets you profile your app while it's
  in the foreground, using its memory use over time to determine its overall
  memory profile.
</p>

<div style="margin:2em 0em;width:780px;">
  <div style="float:left;width:390px;">
    <img src="{@docRoot}images/kk-procstats.png" alt="" width="360" style=
    "margin-bottom:0;box-shadow: 3px 10px 18px 1px #eee;border:1px solid #ddd;border-radius: 6px;">
    <p class="img-caption" style=
    "padding-top:1.5em;line-height:1.25em;width:360px;">
      The new <strong>procstats</strong> tool lets you check the memory use of
      apps and services over time.
    </p>
  </div>

  <div style="float:right;width:390px;">
    <img src="{@docRoot}images/kk-meminfo.png" alt="" width="360" style=
    "margin-bottom:0;box-shadow: 3px 10px 12px 1px #eee;border:1px solid #ddd;border-radius: 6px;">
    <p class="img-caption" style=
    "padding-top:1.5em;line-height:1.25em;width:360px;">
      The enhanced <strong>meminfo</strong> tool lets you see details of memory
      use for an app.
    </p>
  </div>
</div>

<p style="clear:both;">
  You can access procstats from the adb tool included in the Android SDK,
  <span style="font-size:11.5px;font-family:monospace;white-space:nowrap;">adb
  shell dumpsys procstats</span>. Also, for on-device profiling, see the
  Process Stats developer option, below.
</p>


<h4 id="44-procstats-ondevice" style="clear:both">On-device memory status and profiling</h4>

<p>
  <span style="white-space:nowrap;">Android 4.4</span> includes a new developer
  option to make it easier to analyze your app's memory profile while it's
  running on any device or emulator. It's especially useful to get a view of
  how your app uses memory and performs on devices with low RAM. You can access
  the option at <strong>Settings &gt; Developer options &gt; Process
  stats</strong>
</p>

<div style="float:right;margin:22px 0px 0px 24px;width:490px;">
  <img src="{@docRoot}images/kk-proc-device-overview-n5.jpg" alt="" width="240" style=
  "margin-bottom:0;"> <img src="{@docRoot}images/kk-proc-device-detail-n5.jpg" alt=""
  width="240" style="margin-bottom:0;padding-left:6px;">
  <p class="img-caption" style=
  "padding-top:1.5em;margin-left:6px;line-height:1.25em;width:480px;">
    <strong>Process stats</strong> is a convenient way to check your app's
    memory use. You can see how your app compares to other apps and zoom in on
    specific data about your app or it's background services.
  </p>
</div>

<p>
  The <strong>Process Stats</strong> option shows you a variety of high-level
  metrics on your app's memory use, based on data collected using the new
  procstats service. On the main screen you can see a summary of system memory
  status. Green indicates relative amount of time spent with low RAM usage,
  yellow indicates moderate RAM usage, and red indicates high (critical) RAM
  usage
</p>

<p>
  Below the summary is a list summarizing each app's <strong>memory load on the
  system</strong>. For each app, a blue bar indicates the relative computed
  memory load (runtime x avg_pss) of its process, and a percentage number
  indicates the relative amount of time spent in the background. You can filter
  the list to show only foreground, background, or cached processes, and you
  can include or exclude system processes. You can also change the duration of
  the data collected to 3, 6, 12, or 24 hours, and you can include or exclude
  uss memory.
</p>

<p>
  To take a closer look at a specific app's memory usage in isolation, tap the
  app. For each app, you can now see a summary of the memory consumed and the
  percentage of the collection interval that the app has been running. You can
  also see the average and maximum usage over the collection period, and below
  the app's services and the percentage of time they've been running.
</p>

<p>
  Analyzing your app using the data in Process Stats can reveal issues and
  suggest possible optimizations for your app. For example, if your app is
  running longer than it should or using too much memory over a period of time,
  there could be bugs in your code that you can resolve to improve your app's
  performance, especially when running on a device with low RAM.
</p>

</div><!-- END ANDROID 4.4 -->