android_frameworks_base/docs/html/preview/api-overview.jd

page.title=API Overview
excludeFromSuggestions=true
sdk.platform.apiLevel=20
@jd:body


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

<h2>In this document
    <a href="#" onclick="hideNestedItems('#toc44',this);return false;" class="header-toggle">
        <span class="more">show more</span>
        <span class="less" style="display:none">show less</span></a></h2>

<ol id="toc44" class="hide-nested">
  <li><a href="#Behaviors">Important Behavior Changes</a>
    <ol>
      <li><a href="#ART">New Android Runtime (ART)</a></li>
      <li><a href="#BehaviorNotifications">If your app implements notifications...</a></li>
      <li><a href="#BehaviorMediaControl">If your app uses RemoteControlClient...</a></li>
<li><a href="#BehaviorGetRecentTasks">If your app uses ActivityManager.getRecentTasks()...</a></li>
    </ol>
  </li>
  <li><a href="#UI">User Interface</a>
    <ol>
      <li><a href="#MaterialDesign">Material design support</a></li>
      <li><a href="#LockscreenNotifications">Lockscreen notifications</a></li>
      <li><a href="#NotificationsMetadata">Notifications metadata</a></li>
      <li><a href="#Recents">Concurrent documents and activities in the Recents screen</a></li>
      <li><a href="#WebView">WebView updates</a></li>
    </ol>
  </li>
  <li><a href="#Graphics">Graphics</a>
    <ol>
      <li><a href="#OpenGLES-3-1">Support for OpenGL ES 3.1</a></li>
      <li><a href="#AndroidExtensionPack">Android Extension Pack</a></li>
    </ol>
  </li>
  <li><a href="#Multimedia">Multimedia</a>
    <ol>
      <li><a href="#Camera-v2">Camera API for advanced camera capabilities</a></li>
      <li><a href="#AudioPlayback">Audio playback</a></li>
      <li><a href="#MediaPlaybackControl">Media playback control</a></li>
    </ol>
  </li>
  <li><a href="#Storage">Storage</a>
    <ol>
      <li><a href="#DirectorySelection">Directory selection</a></li>
    </ol>
  </li>
  <li><a href="#Wireless">Wireless and Connectivity</a>
    <ol>
      <li><a href="#Multinetwork">Multiple network connections</a></li>
      <li><a href="#BluetoothBroadcasting">Bluetooth broadcasting</a></li>
      <li><a href="#NFCEnhancements">NFC enhancements</a></li>
    </ol>
  </li>
  <li><a href="#Power">Power Efficiency</a>
    <ol>
      <li><a href="#JobScheduler">Scheduling Jobs</a></li>
      <li><a href="#PowerMeasurementTools">Developer tools for power measurement</a>
    </ol>
  </li>
  <li><a href="#Enterprise">Enterprise</a>
    <ol>
      <li><a href="#ManagedProvisioning">Managed provisioning</a></li>
      <li><a href="#TaskLocking">Task locking</a></li>
    </ol>
  </li>
  <li><a href="#Printing">Printing Framework</a>
    <ol>
      <li><a href="#PDFRender">Render PDF as bitmap</a></li>
    </ol>
  </li>
  <li><a href="#TestingA11y">Testing &amp; Accessibility</a>
    <ol>
      <li><a href="#TestingA11yImprovements">Testing and accessibility improvements</a></li>
    </ol>
  </li>
  <li><a href="#IME">IME</a>
    <ol>
      <li><a href="#Switching">Easier switching between input languages</a></li>
    </ol>
  </li>
  <li><a href="#Manifest">Manifest Declarations</a>
    <ol>
      <li><a href="#ManifestFeatures">Declarable required features</a></li>
    </ol>
  </li>
</ol>

</div>
</div>

<p>The L Developer Preview gives you an advance look at the upcoming release
for the Android platform, which offers new features for users and app
developers. This document provides an introduction to the most notable APIs.</p>

<p>The L Developer Preview is intended for <strong>developer early
adopters</strong> and <strong>testers</strong>. If you are interested in
influencing the direction of the Android framework,
<a href="{@docRoot}preview/setup-sdk.html">give the L Developer Preview a
try</a> and send us your feedback!</p>

<p class="caution"><strong>Caution:</strong> Do not not publish apps
that use the L Developer Preview to the Google Play store.</p>

<p class="note"><strong>Note:</strong> This document often refers to classes and
methods that do not yet have reference material available on <a
href="{@docRoot}">developer.android.com</a>. These API elements are
formatted in {@code code style} in this document (without hyperlinks). For the
preliminary API documentation for these elements, download the <a
href="http://storage.googleapis.com/androiddevelopers/preview/l-developer-preview-reference.zip">preview
reference</a>.</p>

<h2 id="Behaviors">Important Behavior Changes</h2>

<p>If you have previously published an app for Android, be aware that your app
  might be affected by changes in the upcoming release.</p>

<h3 id="ART">New Android Runtime (ART)</h3>

<p>The 4.4 release introduced a new, experimental Android runtime, ART. Under
4.4, ART was optional, and the default runtime remained Dalvik. With the L
Developer Preview, ART is now the default runtime.</p>

<p>For an overview of ART's new features, see
<a href="https://source.android.com/devices/tech/dalvik/art.html">Introducing
ART</a>. Some of the major new features are:</p>

<ul>
  <li>Ahead-of-Time (AOT) compilation</li>
  <li>Improved garbage collection (GC)</li>
  <li>Improved debugging support</li>
</ul>

<p>Most Android apps should just work without change under ART. However, some
techniques that work on Dalvik do not work on ART. For information about the
most important issues, see
<a href="{@docRoot}guide/practices/verifying-apps-art.html">Verifying App
Behavior on the Android Runtime (ART)</a>. Pay particular attention if:</p>

<ul>
  <li>Your app uses Java Native Interface (JNI) to run C/C++ code.</li>
  <li>You use development tools that generate non-standard code (such as some
      obfuscators).</li>
  <li>You use techniques that are incompatible with compacting garbage
      collection. (ART does not currently implement compacting GC, but
      compacting GC is under development in the Android Open-Source
      Project.)</li>
</ul>

<h3 id="BehaviorNotifications">If your app implements notifications...</h3>

<p>Notifications are drawn with dark text atop white (or very light)
backgrounds to match the new material design widgets. Make sure that all your
notifications look right with the new color scheme:</p>

<div class="figure" style="width:320px">
  <img src="images/hun-example.png"
    srcset="images/hun-example@2x.png 2x"
    alt="" width="320" height="541" id="figure1" />
  <p class="img-caption">
    <strong>Figure 1.</strong> Fullscreen activity showing a heads-up notification
  </p>
</div>

<ul>

  <li>Update or remove assets that involve color.</li>

  <li>The system automatically inverts action icons in notifications. Use
  {@code android.app.Notification. Builder.setColor()} to set an accent color
  in a circle behind your {@link android.app.Notification#icon} image.</li>

  <li>The system ignores all non-alpha channels in action icons and the main
  notification icon. You should assume that these icons are alpha-only.</li>

</ul>

<p>If you are currently adding sounds and vibrations to your notifications by
using the {@link android.media.Ringtone}, {@link android.media.MediaPlayer},
or {@link android.os.Vibrator} classes, remove this code so that
the system can present notifications correctly in Do
not Disturb mode. Instead, use the {@link android.app.Notification.Builder}
methods instead to add sounds and vibration.</p>

<p>Notifications now appear in a small floating window
(also called a <em>heads-up notification</em>) when the device is active
(that is, the device is unlocked and its screen is on). These notifications
appear similar to the compact form of your notification, except that the
heads-up notification also shows action buttons. Users can act on, or dismiss,
a heads-up notification without leaving the current app.</p>

<p>Examples of conditions that may trigger heads-up notifications include:</p>

<ul>
  <li>The user's activity is in fullscreen mode (the app uses
{@link android.app.Notification#fullScreenIntent}), or</li>
  <li>The notification has high priority and uses ringtones or
    vibrations</li>
</ul>

<p>If your app implements notifications under those scenarios, make sure that
heads-up notifications are presented correctly.</p>

<h3 id="BehaviorMediaControl">If your app uses RemoteControlClient...</h3>

<p>Lockscreens in the L Developer Preview do not show transport controls for
your {@link android.media.RemoteControlClient}. Instead, your app can provide
media playback control from the lockscreen through a notification. This
gives your app more control over the presentation of media buttons, while
providing a consistent experience for users across the lockscreen and
unlocked device.</p>

<p>The L Developer Preview introduces a new
{@code android.app.Notification.MediaStyle} template which is recommended for
this purpose. {@code MediaStyle} converts notification actions that you added
with
{@link android.app.Notification.Builder#addAction(int, java.lang.CharSequence,
  android.app.PendingIntent)
Notification.Builder.addAction()} into compact buttons embedded in your app's
media playback notifications.</p>

<p>If you are using the new
{@code android.media.session.MediaSession} class
(see <a href="#MediaPlaybackControl">Media Playback Control</a> below), attach
your session token with {@code Notification.MediaStyle.setMediaToken()} to
inform the system that this notification controls an ongoing media session.</p>

<p>Call {@code
Notification.Builder.setVisibility(Notification.VISIBILITY_PUBLIC)} to mark a
notification as safe to show atop any lockscreen (secure or otherwise). For more
information, see <a href="#LockscreenNotifications">Lockscreen Notifications</a>.</p>

<h3 id="BehaviorGetRecentTasks">If your app uses ActivityManager.getRecentTasks()...</h3>

<p>With the introduction of the new <em>concurrent documents and activities
tasks</em> feature in the upcoming release (see <a href="#Recents">Concurrent
documents and activities in Recents screen</a> below),
the {@link android.app.ActivityManager#getRecentTasks
ActivityManager.getRecentTasks()} method is now deprecated to improve user
privacy. For backward compatibility, this method still returns a small subset of
its data, including the calling application’s own tasks and possibly some other
non-sensitive tasks (such as Home). If your app is using this method to retrieve
its own tasks, use {@code android.app.ActivityManager.getAppTasks()} instead to
retrieve that information.</p>

<h2 id="UI">User Interface</h2>

<h3 id="MaterialDesign">Material design support</h3>

<p>The upcoming release adds support for Android's new <em>material</em> design
style. You can create apps with material design that are visually dynamic and
have UI element transitions that feel natural to users. This support includes:</p>

<ul>

  <li>The material theme</li>
  <li>View shadows</li>
  <li>The {@code RecyclerView} widget</li>
  <li>Drawable animation and styling effects</li>
  <li>Material design animation and activity transition effects</li>
  <li>Animators for view properties based on the state of a view</li>
  <li>Customizable UI widgets and app bars with color palettes that you control</li>
</ul>

<p>To learn more about adding material design functionality to your app, see
<a href="{@docRoot}preview/material/index.html">Material Design</a>.</p>

<h3 id="LockscreenNotifications">Lockscreen notifications</h3>
<p>Lockscreens in the L Developer Preview have the ability to present
notifications. Users can choose via <em>Settings</em> whether to allow
sensitive notification content to be shown over a secure lockscreen.</p>

<p>Your app can control the level of detail visible when its notifications are
displayed over the secure lockscreen. To control the visibility level, call
{@code android.app.Notification.Builder.setVisibility()} and specify one of these
values:</p>

<ul>
<li>{@code VISIBILITY_PRIVATE}. Shows basic information, such as the
notification’s icon, but hides the notification’s full content.</li>
<li>{@code VISIBILITY_PUBLIC}. Shows the notification’s full content.</li>
<li>{@code VISIBILITY_SECRET}. Shows nothing, excluding even the
notification’s icon.</li>
</ul>

<p>When {@code VISIBILITY_PRIVATE} is set, you can also provide a redacted
version of the notification content that hides personal details. For example,
an SMS app might display a notification that shows "You have 3 new text messages."
but hides the message content and senders. To provide this alternative
notification, first create the replacement notification using
{@link android.app.Notification.Builder}. When you create the private
notification object, attach the replacement notification to it through the
{@code Notification.Builder.setPublicVersion()} method.</p>

<h3 id="NotificationsMetadata">Notifications metadata</h3>
<p>The L Developer Preview uses metadata associated with your app notifications
to sort the notifications more intelligently. To set the metadata, call the
following methods in {@code android.app.Notification.Builder} when you
construct the notification:</p>

<ul>
<li>{@code setCategory()}. Depending on the message category, this tells
the system how to handle your app notifications when the device is
in <em>Do not Disturb</em> mode (for example, if your notification represents an
incoming call, instant message, or alarm).
<li>{@code setPriority()}. Notifications with the priority field set to
{@code PRIORITY_MAX} or {@code PRIORITY_HIGH} will appear in a small floating
window if the notification also has sound or vibration.</li>
<li>{@code addPerson()}. Allows you to add a list of people to a notification.
Your app can use this to signal to the system that it should group together
notifications from the specified people, or rank notifications from these
people as being more important.</li>
</ul>

<h3 id="Recents">Concurrent documents and activities in the Recents screen</h3>

<p>In previous releases, the
<a href="{@docRoot}design/get-started/ui-overview.html">Recents screen</a>
could only display a single task for each app that the user interacted with
most recently. Now your app can open more tasks as
needed for additional concurrent activities for documents.
This feature facilitates multitasking by letting users quickly switch between
individual activities and documents from the Recents screen, with a consistent
switching experience across all apps.
Examples of such concurrent tasks might include open tabs in a web
browser app, documents in a productivity app, concurrent matches in
a game, or chats in a messaging app. Your app can manage its tasks
through the {@code android.app.ActivityManager.AppTask} class.</p>

<p>To insert a logical break so that the system treats your activity as a new
task, use {@code android.content.Intent.FLAG_ACTIVITY_NEW_DOCUMENT} when
launching the activity with {@link android.app.Activity#startActivity(android.content.Intent)
startActivity()}. You can also get this behavior by declaring the
<a href="{@docRoot}guide/topics/manifest/activity-element.html">&lt;activity&gt;</a>
attribute {@code documentLaunchMode="intoExisting"} or {@code ="always"} in your
manifest.</p>

<p>You can also mark that a task should be removed from the Recents screen
when all its activities are closed. To do this, use {@code
android.content.Intent.FLAG_ACTIVITY_AUTO_REMOVE_FROM_RECENTS} when starting the
root activity for
the task. You can also set this behavior for an activity by declaring the
<a href="{@docRoot}guide/topics/manifest/activity-element.html">&lt;activity&gt;</a>
attribute {@code autoRemoveFromRecents=“true”} in your manifest.</p>

<p>To avoid cluttering the Recents screen, you can set the maximum number of
tasks from your app that can appear in that screen. To do this, set the
<a href="{@docRoot}guide/topics/manifest/application-element.html">&lt;application&gt;</a>
attribute {@code android:maxRecent}. The current maximum that can be specified
is 100 tasks per user.</a></p>

<h3 id="WebView">WebView updates</h3>
<p>The L Developer Preview updates the {@link android.webkit.WebView}
implementation to Chromium M36, bringing security and stability enhancements,
as well as bug fixes. The default user-agent string for a
{@link android.webkit.WebView}  running on the L Developer Preview has
been updated to incorporate 36.0.0.0 as the version number.</p>

<p>Additionally, this release brings support for the
<a href="http://webaudio.github.io/web-audio-api/" class="external-link">WebAudio</a>,
<a href="https://www.khronos.org/webgl/" class="external-link">WebGL</a>, and
<a href="http://www.webrtc.org/" class="external-link">WebRTC</a> open standards. To learn more about
the new features included in this release, see <a href="https://developer.chrome.com/multidevice/webview/overview" class="external-link">WebView for Android</a>.</p>

<h2 id="Graphics">Graphics</h2>

<h3 id="OpenGLES-3-1">Support for OpenGL ES 3.1</h3>
<p>The L Developer Preview adds Java interfaces and native support for OpenGL
ES 3.1. Key new functionality provided in OpenGL ES 3.1 includes:</p>

<ul>
<li>Compute shaders
<li>Separate shader objects
<li>Indirect draw commands
<li>Multisample and stencil textures
<li>Shading language improvements
<li>Extensions for advanced blend modes and debugging
<li>Backward compatibility with OpenGL ES 2.0 and 3.0
</ul>

<p>The Java interface for OpenGL ES 3.1 on Android is provided with {@code GLES31}. When
using OpenGL ES 3.1, be sure that you declare it in your manifest file with the
<a href="{@docRoot}guide/topics/manifest/uses-feature-element.html">{@code &lt;uses-feature&gt;}</a>
tag and the {@code android:glEsVversion} attribute. For example:</p>

<pre>
&lt;manifest&gt;
    &lt;uses-feature android:glEsVersion="0x00030001" /&gt;
    ...
&lt;/manifest&gt;
</pre>

<p>For more information about using OpenGL ES, including how to check the
device’s supported OpenGL ES version at runtime, see the
<a href="{@docRoot}guide/topics/graphics/opengl.html">OpenGL ES API guide</a>.</p>

<h3 id="AndroidExtensionPack">Android Extension Pack</h3>

<p>In addition to OpenGL ES 3.1, this release provides an extension pack with Java interfaces and
native support for advanced graphics functionality. These extensions are treated as a single
package by Android. (If the {@code ANDROID_extension_pack_es31} extension is present, your app can
assume all extensions in the package are present and enable the shading language features with
a single {@code #extension} statement.</p>
<p>The extension pack supports:</p>
<ul>
<li>Guaranteed fragment shader support for shader storage buffers, images, and
  atomics (fragment shader support is optional in OpenGL ES 3.1.)</li>
<li>Tessellation and geometry shaders</li>
<li>ASTC (LDR) texture compression format</li>
<li>Per-sample interpolation and shading</li>
<li>Different blend modes for each color attachment in a frame buffer</li>
</ul>

<p>The Java interface for the extension pack is provided with {@code GLES31Ext}.
In your app manifest, you can declare that support for the extension pack is
required, with the
<a href="{@docRoot}guide/topics/manifest/uses-feature-element.html">{@code &lt;uses-feature&gt;}</a>
tag, but the precise syntax is not finalized in the L Developer Preview.</p>

<h2 id="Multimedia">Multimedia</h2>

<h3 id="Camera-v2">Camera API for advanced camera capabilities</h3>

<p>The L Developer Preview introduces the new {@code android.hardware.camera2}
API to facilitate fine-grain photo capture and image processing. You can now
programmatically access the camera devices available to the system with {@code
CameraManager.getCameraIdList()} and connect to a specific device with {@code
CameraManager.openCamera()}. To start capturing images, create a {@code
CameraCaptureSession} and specify the {@link android.view.Surface} objects for
the captured images. The {@code CameraCaptureSession} can be configured to take
single shots or multiple images in a burst.</p>

<p>To be notified when new images are captured, implement the
{@code CameraCaptureSession.CaptureListener()} interface and set it in your
capture request. Now when the system completes the image capture request, your
{@code CameraCaptureSession.CaptureListener()} receives a call to
{@code onCaptureCompleted()}, providing you with the image capture metadata in a
{@code CaptureResult}.</p>

<p>To see an example of how to use the updated Camera API, refer to the {@code Camera2Basic}
and {@code Camera2Video} implementation samples in this release.</p>

<h3 id="AudioPlayback">Audio playback</h3>
<p>This release includes the following changes to
  {@link android.media.AudioTrack}:</p>
<ul>
  <li>Your app can now supply audio data in floating-point format
({@code android.media.AudioFormat.ENCODING_PCM_FLOAT}). This permits greater
dynamic range, more consistent precision, and greater headroom. Floating-point
arithmetic is especially useful during intermediate calculations. Playback
end-points use integer format for audio data, and with lower bit-depth. (In the
L Developer Preview, portions of the internal pipeline are not yet
floating-point.)
  <li>Your app can now supply audio data as a {@link java.nio.ByteBuffer}, in
the same format as provided by {@link android.media.MediaCodec}.
  <li>The {@code WRITE_NON_BLOCKING} option can simplify buffering and
    multithreading for some apps.
</ul>

<h3 id="MediaPlaybackControl">Media playback control</h3>
<p>You can now build your own media controller app with the new
{@code android.media.session.MediaController} class, which provides
simplified transport controls APIs that replace those in
{@link android.media.RemoteControlClient}. The {@code MediaController} class
allows thread-safe control of playback from a non-UI process, making it easier
to control your media playback service from your app’s user interface.

<p>You can also create multiple controllers to send playback commands,
media keys, and other events to the same ongoing
{@code android.media.session.MediaSession}. When you add a controller, you must
call {@code MediaSession.getSessionToken()} to request an access
token in order for your app to interact with the session.</p>

<p>You can now send transport commands such as "play", "stop", "skip", and
"set rating" by using {@code MediaController.TransportControls}. To handle
in-bound media transport commands from controllers attached to the session,
override the callback methods in
{@code MediaSession.TransportControlsCallback}.</p>

<p>You can also create rich notifications that allow playback control tied to a
media session with the new {@code android.app.Notification.MediaStyle} class. By
using the new notification and media APIs, you will ensure that the System UI
knows about your playback and can extract and show album art.</p>

<h2 id="Storage">Storage</h2>

<h3 id="DirectorySelection">Directory selection</h3>

<p>The L Developer Preview extends the <a href="{@docRoot}guide/topics/providers/document-provider.html">Storage Access Framework</a> to let users select an entire directory subtree,
giving apps read/write access to all contained documents without requiring user
confirmation for each item.</p>

<p>To select a directory subtree, build and send an
{@code android.intent.action.OPEN_DOCUMENT_TREE} {@link android.content.Intent}.
The system displays all
{@link android.provider.DocumentsProvider} instances that support subtree selection,
letting the user browse and select a directory. The returned URI represents access to the selected
subtree. You can then use {@code DocumentsContract.buildChildDocumentsUriUsingTree()}
and {@code DocumentsContract.buildDocumentUriUsingTree()} along with
{@code ContentResolver.query()} to explore the subtree.</p>

<p>The new {@code DocumentsContract.createDocument()} method lets you create
new documents or directories anywhere under the subtree. To manage
existing documents, use {@code DocumentsContract.renameDocument()} and
{@code DocumentsContract.deleteDocument()}. Check {@code DocumentsContract.Document.COLUMN_FLAGS}
to verify provider support for these calls before issuing them.</p>

<p>If you're implementing a {@link android.provider.DocumentsProvider} and want
to support subtree selection, implement {@code DocumentsProvider.isChildDocument()}
and include {@code Documents.Contract.FLAG_SUPPORTS_IS_CHILD} in your
{@code Root.COLUMN_FLAGS}.</p>

<p>The L Developer Preview also introduces new package-specific directories on
shared storage where your app can place media files for inclusion in
{@link android.provider.MediaStore}. The new
{@code android.content.Context.getExternalMediaDirs()} returns paths to these
directories on all shared storage devices. Similarly to
{@link android.content.Context#getExternalFilesDir(java.lang.String) Context.getExternalFilesDir()},
no additional permissions are needed by your app to access the returned paths. The
platform periodically scans for new media in these directories, but you can also
use {@link android.media.MediaScannerConnection} to explicitly scan for new
content.</p>

<h2 id="Wireless">Wireless &amp; Connectivity</h2>

<h3 id="Multinetwork">Multiple network connections</h3>
<p>The L Developer Preview provides new multi-networking APIs. These let your app
dynamically scan for available networks with specific capabilities, and
establish a connection to them. This is useful when your app requires a
specialized network, such as an SUPL, MMS, or carrier-billing network, or if
you want to send data using a particular type of transport protocol.</p>

<p>To select and connect to a network dynamically from your app follow these
steps:</p>

<ol>
 <li>Create a {@link android.net.ConnectivityManager}.</li>
 <li>Create a
  {@code android.net.NetworkRequest} to specify the network features and transport
  type your app is interested in.</li>
  <li>To scan for suitable networks, call
  {@code ConnectivityManager.requestNetwork()} or
  {@code ConnectivityManager.registerNetworkCallback()}, and pass in the
  {@code NetworkRequest} object and an implementation of
  {@code ConnectivityManager.NetworkCallbackListener}.</li>

</ol>

<p>When the system detects a suitable network, it connects to the network and
invokes the {@code NetworkCallbackListener.onAvailable()} callback. You can use
the {@code android.net.Network} object from the callback to get additional
information about the network, or to direct traffic to use the selected
network.</p>

<h3 id="BluetoothBroadcasting">Bluetooth broadcasting</h3>
<p>Android 4.3 introduced platform support for
  <a href="{@docRoot}guide/topics/connectivity/bluetooth-le.html">Bluetooth Low Energy</a>
(BLE) in the central role. In the L Developer Preview, an Android device can now
act as a Bluetooth LE <em>peripheral device</em>. Apps can use this capability
to make their presence known to
nearby devices. For instance, you can build apps that allow a device to
function as a pedometer or health monitor and communicate its data with another
BLE device.</p>

<p>The new {@code android.bluetooth.le} APIs enable your apps to broadcast
advertisements, scan for responses, and form connections with nearby BLE devices.
You must add the {@code android.permission.BLUETOOTH_ADMIN} permission in your
manifest in order for your app to use the new advertising and scanning features.</a>

<p>To begin Bluetooth LE advertising so that other devices can discover
your app, call {@code android.bluetooth.le.BluetoothAdvertiser.startAdvertising()}
and pass in an implementation of the
{@code android.bluetooth.le.AdvertiseCallback} class. The callback object
receives a report of the success or failure of the advertising operation.</p>

<p> The L Developer Preview introduces the {@code
android.bluetooth.le.ScanFilter} class so that your app can scan for only the
specific types of devices it is interested in. To begin scanning for Bluetooth
LE devices, call {@code android.bluetooth.le.BluetoothLeScanner.startScan()} and
pass in a list of filters. In the method call, you must also provide an
implementation of {@code android.bluetooth.le.ScanCallback} to report if a
Bluetooth LE advertisement is found. </p>

<h3 id="NFCEnhancements">NFC enhancements</h3>
<p>The L Developer Preview adds these enhancements to enable wider and more
flexible use of NFC:</p>

<ul>
<li>Android Beam is now available in the share menu.
<li>Your app can invoke the Android Beam on the user’s device to share data by
calling {@code android.nfc.NfcAdapter.invokeBeam()}. This avoids the need for
the user to manually tap the device against another NFC-capable device to
complete the data transfer.
<li>You can use the new {@code android.nfc.NdefRecord.createTextRecord()} method
to create an NDEF record containing UTF-8 text data.
<li>If you are developing a payment app, you now have the ability to
register an NFC application ID (AID) dynamically by calling
{@code android.nfc.cardemulation.CardEmulation.registerAidsForService()}.
You can also use {@code android.nfc.cardemulation.CardEmulation.setPreferredService()}
to set the preferred card emulation service that should be used when a specific
activity is in the foreground.
</ul>

<h2 id="Power">Power Efficiency</h2>

<h3 id="JobScheduler">Scheduling jobs</h3>
<p>The L Developer Preview provides a new {@code android.app.job.JobScheduler}
API that lets you optimize battery life by defining jobs for the system to run
asynchronously at a later time or under specified conditions (such as when the
device is charging). This is useful in such situations as:</p>
<ul>
  <li>The app has non-user-facing work that you can defer.</li>
  <li>The app has work you'd prefer to do when the unit is plugged in.</li>
  <li>The app has a task that requires network access (or requires a Wi-Fi
    connection).</li>
  <li>The app has a number of tasks that you want to run as a batch on a regular
   schedule.</li>

</ul>

<p>A unit of work is encapsulated by a {@code android.app.job.JobInfo} object.
This object provides an exact description of the criteria to be used for
scheduling.</p>

<p>Use the {@code android.app.job.JobInfo.Builder} to configure how the
scheduled task should run. You can schedule the task to run under specific
conditions, such as:</p>

<ul>
  <li>The device is charging</li>
  <li>The device is connected to an unmetered network</li>
  <li>The system deems the device to be idle</li>
  <li>Completion with a minimum delay or within a specific deadline.</li>
</ul>

<p>For example, you can add code like this to run your task on an
unmetered network:</p>

<pre>
JobInfo uploadTask = new JobInfo.Builder(mJobId, mServiceComponent)
        .setRequiredNetworkCapabilities(JobInfo.NetworkType.UNMETERED)
        .build();

JobScheduler jobScheduler =
        (JobScheduler) context.getSystemService(Context.JOB_SCHEDULER_SERVICE)
jobScheduler.schedule(uploadTask);
</pre>

<p>To see an example of how to use the {@code JobScheduler} API, refer to the
{@code JobSchedulerSample} implementation sample in this release.</p>

<h3 id="PowerMeasurementTools">Developer tools for power measurement</h3>
<p>The L Developer Preview provides several new developer tools and APIs to help
you better measure and understand your app's power usage.</p>

<dl>
<dt><strong>batterystats</strong></dt>
<dd>
<p>The {@code dumpsys batterystats} command allows you to generate interesting
statistical data about battery usage on a device, organized by unique user ID
(UID). The statistics generated by the tool include:</p>

<ul>
<li>History of battery related events
<li>Global statistics for the device
<li>Approximated power use per UID and system component
<li>Per-app mobile ms per packet
<li>System UID aggregated statistics
<li>App UID aggregated statistics
</ul>

<p>Use the {@code --help} option to learn about the various options for
tailoring the output. For example, to print battery usage
statistics for a given app package since the device was last charged, run this
command:
<pre>
$ adb shell dumpsys batterystats --charged &lt;package-name&gt;
</pre>
</dd>

<dt><strong>Battery Historian</strong></dt>
<dd>
<p>The Battery Historian tool ({@code historian.par}) analyzes Android
bug reports from the L Developer Preview and creates an HTML visualization of
power-related events. It can
also visualize power consumption data from a power monitor, and attempts to
map power usage to the wake locks seen. You can find the Battery Historian tool
in {@code &lt;sdk&gt;/tools}.</p>

<img src="images/battery_historian.png"
     srcset="images/battery_historian@2x.png 2x"
    alt="" width="760" height="462"
    id="figure2" />
<p class="img-caption">
  <strong>Figure 2.</strong>HTML visualization generated by the Battery
      Historian tool.
</p>

<p>For best results, you should first enable full wake lock reporting, to allow
the Battery Historian tool to monitor uninterrupted over an extended period of
time:</p>
<pre>
$ adb shell dumpsys batterystats --enable full-wake-history
</pre>

<p>You should also reset battery statistics at the beginning of a
measurement:</p>
<pre>
$ adb shell dumpsys batterystats --reset
</pre>

<p>To generate an HTML visualization:</p>
<pre>
$ historian.par [-p powerfile] bugreport.txt > out.html
</pre>
</dd>

</dl>

<h2 id="Enterprise">Enterprise</h2>
<h3 id="ManagedProvisioning">Managed provisioning</h3>

<div class="figure" style="width:360px">
  <img src="images/managed_apps_launcher.png"
    srcset="images/managed_apps_launcher@2x.png 2x"
    alt="" width="360" height="609" id="figure3" />
  <p class="img-caption">
    <strong>Figure 3.</strong> Launcher screen showing managed apps (marked with
    a lock badge)
  </p>
</div>

<p>The L Developer Preview provides new functionality for running apps within
an enterprise environment. A
<a href="{@docRoot}guide/topics/admin/device-admin.html">device administrator</a> can
initiate a managed provisioning process to add a co-present but separate <em>managed profile</em> to a device, if the user has an existing personal account.
Apps that are associated with managed profiles will appear alongside
non-managed apps in the user’s Launcher, Recent apps screen, and notifications.</p>

<p>To start the managed provisioning process, send {@code
ACTION_PROVISION_MANAGED_PROFILE} in an {@link android.content.Intent}. If the
call is successful, the system triggers the {@code
android.app.admin.DeviceAdminReceiver. onProfileProvisioningComplete()} callback.
You can then call {@code app.admin.DevicePolicyManager. setProfileEnabled()} to
enable this managed profile.</p>

<p>If you are developing a Launcher app, you can use the new {@code
android.content.pm.LauncherApps} class to get a list of launchable activities
for the current user and any associated managed profiles. Your Launcher can make
the managed apps visually prominent by appending a “work” badge to the icon
drawable with {@code android.os.UserManager. getBadgeDrawableForUser()}.</p>

<p>To see an example of how to use the new functionality, refer to the
{@code BasicManagedProfile} implementation sample in this release.</p>

<h3 id="TaskLocking">Task locking</h3>
<p>The L Developer Preview introduces a new task locking API that
lets you temporarily restrict users from leaving your app or being interrupted
by notifications. This could be used, for example, if you are developing an
education app to support high stakes assessment requirements on Android.
Once your app activates this mode, users will not be able to see
notifications, access other apps, or return to the Home screen, until your
app exits the mode.</p>

<p>To prevent unauthorized usage, only authorized apps can activate task locking.
Furthermore, task locking authorization must be granted by a
specially-configured <em>device owner</em> app, through the {@code android.app.admin.DevicePolicyManager.setLockTaskComponents()} method.</p>

<p>To set up a device owner, follow these steps:</p>
<ol>
<li>Attach a device running an Android <a href="https://source.android.com/source/building-running.html" class="external-link">{@code userdebug}</a> build to your development machine.</li>
<li>Install your device owner app.</li>
<li>Create a {@code device_owner.xml} file and save it to the {@code /data/system}
directory on the device.
<pre>
$ adb root
$ adb shell stop
$ rm /tmp/device_owner.xml
$ echo "&lt;?xml version='1.0' encoding='utf-8' standalone='yes' ?&gt;"
&gt;&gt; /tmp/device_owner.xml
$ echo "&lt;device-owner package=\"&lt;your_device_owner_package&gt;\"
name=\"*&lt;your_organization_name&gt;\" /&gt;" &gt;&gt; /tmp/device_owner.xml
$ adb push /tmp/device_owner.xml /data/system/device_owner.xml
$ adb reboot
</pre>
</li>
</ol>

<p>Before using the task locking API in your app, verify that your activity is
authorized by calling {@code DevicePolicyManager.isLockTaskPermitted()}.</p>

<p>To activate task locking, call
{@code android.app.Activity.startLockTask()} from your authorized activity.</p>

<p>When task locking is active, the following behavior takes effect:</p>

<ul>
<li>The status bar is blank, and user notifications and status information is
hidden.</li>
<li>The Home and Recent Apps buttons are hidden.</li>
<li>Other apps may not launch new activities.</li>
<li>The current app may start new activities, as long as doing so does not
create new tasks.</li>
<li>The user remains locked on your app until an authorized activity calls
{@code Activity.stopLockTask()}.</li>
</ul>

<h2 id="Printing">Printing Framework</h2>

<h3 id="PDFRender">Render PDF as bitmap</h3>
<p>You can now render PDF document pages into bitmap images for printing by
using the new {@code android.graphics.pdf.PdfRenderer} class. You must specify a
{@link android.os.ParcelFileDescriptor} that is seekable (that is, the content
can be randomly accessed) on which the system writes the the printable content.
Your app can obtain a page for rendering with {@code openPage()}, then call
{@code render()} to turn the opened {@code PdfRenderer.Page} into a bitmap. You
can also set additional parameters if you only want to convert a portion of the
document into a bitmap image (for example, to implement
<a href="http://en.wikipedia.org/wiki/Tiled_rendering" class="external-link">tiled rendering</a> in
order to zoom in on the document).</p>

<h2 id="TestingA11y">Testing &amp; Accessibility </h2>

<h3 id="TestingA11yImprovements">Testing and accessibility improvements</h3>
<p>The L Developer Preview adds the following support for testing and
accessibility:</p>

<ul>
<li>You can use the new {@code android.app.UiAutomation.getWindowAnimationFrameStats()}
and {@code android.app.UiAutomation.getWindowContentFrameStats()} methods to
capture frame statistics for window animations and content. This lets you
write instrumentation tests to evaluate if the app under test is rendering
frames at a sufficient refresh frequency to provide a smooth user experience.

<li>You can execute shell commands from your instrumentation test with the new
{@code android.app.UiAutomation.executeShellCommand()}. The command execution
is similar to running {@code adb shell} from a host connected to the device. This
allows you to use shell based tools such as {@code dumpsys}, {@code am},
{@code content}, and {@code pm}.

<li>Accessibility services and test tools that use the accessibility APIs
(such as <a href="{@docRoot}tools/help/uiautomator/index.html">uiautomator</a>)
can now retrieve detailed information about the properties of windows on the
screen that sighted users can interact with. To retrieve a list of
{@code android.view.accessibility.AccessibilityWindowInfo} objects
representing the windows information, call the new
{@code android.accessibilityservice.AccessibilityService.getWindows()} method.
<li>You can use the new {@code android.view.accessibility.AccessibilityNodeInfo.AccessibilityAction} to define standard or customized
actions to perform on an {@link android.view.accessibility.AccessibilityNodeInfo}.
The new {@code AccessibilityAction} class replaces the actions-related APIs
previously found in {@code AccessibilityNodeInfo}.
</ul>

<h2 id="IME">IME</h2>

<h3 id="Switching">Easier switching between input languages</h3>

<p>Beginning in the L Developer Preview, users can more easily switch between
all <a href="{@docRoot}guide/topics/text/creating-input-method.html">input
method editors (IME)</a> supported by the platform. Performing the designated
switching action (usually touching a Globe icon on the soft keyboard) will cycle
among all such IMEs. This change takes place in
{@link android.view.inputmethod.InputMethodManager#shouldOfferSwitchingToNextInputMethod
InputMethodManager.shouldOfferSwitchingToNextInputMethod()}.</p>

<p>In addition, the framework now checks whether the next IME includes a
switching mechanism at all (and, thus, whether that IME supports switching to
the IME after it). An
IME with a switching mechanism will not cycle to an IME without one. This
change takes place in
{@link android.view.inputmethod.InputMethodManager#switchToNextInputMethod
InputMethodManager.switchToNextInputMethod}.

<p>To see an example of how to use the updated IME-switching APIs, refer to the
updated soft-keyboard implementation sample in this release.</p>

<h2 id="Manifest">Manifest Declarations</h2>

<h3 id="ManifestFeatures">Declarable required features</h3>
<p>The following values are now supported in the
<a href="{@docRoot}guide/topics/manifest/uses-feature-element.html">{@code &lt;uses-feature&gt;}</a>
element, so you can ensure that your app is installed only on devices that provide the features
your app needs.</p>

<ul>
<li>{@code FEATURE_LEANBACK}. Declares that your app must be installed only on
devices that support the
<a href="{@docRoot}training/tv/index.html">Android TV</a> user interface.
Example:
<pre>
&lt;uses-feature android:name="android.software.leanback"
              android:required="true" /&gt;
</pre>

<li>{@code FEATURE_WEBVIEW}. Declares that your app must only be installed on
devices that fully implement the {@code android.webkit.*} APIs. Example:
<pre>
&lt;uses-feature android:name="android.software.webview"
              android:required="true" /&gt;
</pre>
</ul>

<p class="note">For a detailed view of all API changes in the L Developer Preview, see the
<a href="{@docRoot}preview/reference.html">API Differences Report</a>.</p>