docs: N Preview 1 - Behavior Changes

<h2>In this document</h2>

<ol id="toc44" class="hide-nested">

  <li><a href="#behavior-power">Battery Performance</a>

<ol>

  <li><a href="#perf">Performance Improvements</a>

    <ol>

      <li><a href="#doze">Doze</a></li>

      <li><a href="#bg-opt">Background Optimizations</a></li>

    </ol>

  </li>

  <li><a href="#">Permissions Changes</a></li>

  <li><a href="#behavior-power">Accessibility Improvements</a>

  <li><a href="#perm">Permissions Changes</a></li>

  <li><a href="#accessibility">Accessibility Improvements</a>

    <ol>

      <li><a href="#doze">Screen Zoom</a></li>

      <li><a href="#bg-opt">Vision Settings in Setup Wizard</a></li>

      <li><a href="#screen-zoom">Screen Zoom</a></li>

      <li><a href="#vision-settings">Vision Settings in Setup Wizard</a></li>

    </ol>

  </li>

  <li><a href="#">Platform Migration toward OpenJDK 8</a></li>

  <li><a href="#">NDK Apps Linking to Platform Libraries</a></li>

  <li><a href="#open-jdk">Platform Migration toward OpenJDK 8</a></li>

  <li><a href="#ndk">NDK Apps Linking to Platform Libraries</a></li>

  <li><a href="#afw">Android for Work</a></li>

</ol>

<h2>See Also</h2>

<ol>

  <li><a href="{@docRoot}preview/api-overview.html">

    M Developer Preview API Overview</a></li>

    N Developer Preview API Overview</a></li>

</ol>

</div>

</p>

<h2 id="batt-perf">Battery Performance</h2>

<h2 id="perf">Performance Improvements</h2>

<p>

  The Preview contains system behavior changes aimed at improving the battery

  life of devices. These changes can impact the availability of system

  resources and system notifications to your app. You should review these

  changes and evaluate how your app may need to adjust to them.

  life of devices, RAM usage, and app performance. These changes can impact the

  availability of system resources and system notifications to your app. You

  should review these changes and evaluate how your app may need to adjust to

  them.

</p>

<h3 id="doze">Doze</h3>

  stationary, for example, when a handset is traveling in a user’s pocket.

</p>

<img src="" alt="" height="XXX" id="figure1" />

<img src="{@docRoot}preview/images/doze-diagram-1.png"

  alt="" height="251px" id="figure1" />

<p class="img-caption">

  <strong>Figure 1.</strong> Illustration of how Doze applies a first level of

  system activity restrictions to improve battery life.

<p>

  When a device is on battery power, and the screen has been off for a certain

  time, the device enters Doze and applies the first subset of restrictions: It

  shuts off app network access, and defers jobs and syncs. After some more time

  elapses, the system applies the rest of the Doze restrictions to {@link

  android.os.PowerManager.WakeLock}, {@link android.app.AlarmManager} alarms,

  GPS, and Wi-Fi scans.. Regardless of whether some or all Doze restrictions

  are being applied, the system wakes the device for brief maintenance windows,

  during which applications are allowed network access and can execute any

  deferred jobs/syncs.

  shuts off app network access, and defers jobs and syncs. If the device is

  stationary for a certain time after entering Doze, the system applies the

  rest of the Doze restrictions to {@link android.os.PowerManager.WakeLock},

  {@link android.app.AlarmManager} alarms, GPS, and Wi-Fi scans.. Regardless of

  whether some or all Doze restrictions are being applied, the system wakes the

  device for brief maintenance windows, during which applications are allowed

  network access and can execute any deferred jobs/syncs.

</p>

<img src="" alt="" height="XXX" id="figure1" />

<img src="{@docRoot}preview/images/doze-diagram-2.png"

  alt="" id="figure2" />

<p class="img-caption">

  <strong>Figure 1.</strong> Illustration of how Doze applies a second level of

  system activity restrictions to further improve battery life.

  <strong>Figure 2.</strong> Illustration of how Doze applies a second level of

  system activity restrictions after the device is stationary for a certain time.

</p>

<p>

  Note that activating the screen on or plugging in the device exits Doze and

  removes these processing restrictions. The additional behavior does not

  affect recommendations and best practices in adapting your app to the prior

  version of Doze introduced in Android 6.0 (API level 23). You should still

  version of Doze introduced in Android 6.0 (API level 23), as discussed in

  <a href=”{@docRoot}/training/monitoring-device-state/doze-standby.html”>

  Optimizing for Doze and App Standby</a>. You should still

  follow those recommendations, such as using Google Cloud Messaging (GCM) to

  send and receive messages, and start planning updates for the additional Doze

  behavior.

  send and receive messages, and start planning updates to accomodate the

  additional Doze behavior.

</p>

<h3 id="bg-opt">Background Optimizations</h3>

<h3 id="bg-opt">Project Svelte: Background Optimizations</h3>

<p>

  The Preview removes three implicit broadcasts in order to help optimize both

  </li>

  <li>Apps cannot send or receive {@code NEW_PICTURE} or {@code NEW_VIDEO}

  broadcasts.

  broadcasts. This optimization affects all apps, not only those

  targeting the Preview.

  </li>

</ul>

</p>

<h2 id="">Permissions Changes</h2>

<h2 id="perm">Permissions Changes</h2>

<p>

  The Preview includes changes to permissions that may affect your app,

<h2 id="">Accessibility Improvements</h2>

<h2 id="accessibility">Accessibility Improvements</h2>

<p>

  This Preview includes changes intended to improve the usability of the

</p>

<h3 id="">Screen Zoom</h3>

<h3 id="screen-zoom">Screen Zoom</h3>

<p>

  The Preview enables users to set <strong>Display size</strong>which magnifies

  sw320dp</a>, which is the width of a Nexus 4, a common medium-sized phone.

</p>

<div class="cols">

<img src="{@docRoot}images/image-0.png" alt="" height="XXX" id="figure1" />

<div class="col-6">

  <img src="{@docRoot}preview/images/screen-zoom-1.png" alt="" height="XXX" id="figure1" />

</div>

<div class="col-6">

  <img src="{@docRoot}preview/images/screen-zoom-2.png" alt="" height="XXX" id="figure1" />

</div>

</div> <!-- end cols -->

<p class="img-caption">

  <strong>Figure 1.</strong> The screen on the right shows the effect of

  <strong>Figure 3.</strong> The screen on the right shows the effect of

  increasing the Display size of a device running an N Preview system image.

</p>

<p>

  When the device density changes, the system notifies running apps in the

  following ways:

</p>

<h3 id="">Vision Settings in Setup Wizard</h3>

<h3 id="vision-settings">Vision Settings in Setup Wizard</h3>

<p>

  The Preview includes Vision Settings on the Welcome screen, where users can

</ul>

<h2 id="">Android for Work</h2>

<h2 id="ndk">NDK Apps Linking to Platform Libraries</h2>

<p>

  The Preview contains changes for apps that target Android for Work, including

  changes to certificate installation, password resetting, secondary user

  management, and access to device identifiers. If you are building apps for

  Android for Work environments, you should review these changes and modify

  your app accordingly.

  The Preview includes namespace changes to prevent loading of non-public APIs.

  If you use the NDK, you should only be using public APIs from the Android

  platform. Using non-public APIs in the next official release of Android

  can cause your app to crash.

</p>

<ul>

  <li>You must install a delegated certificate installer before the DPC can set

  it. For both profile and device-owner apps targeting the N SDK, you should

  install the delegated certificate installer before the device policy

  controller (DPC) calls

  <code>DevicePolicyManager.setCertInstallerPackage()</code>. If the installer

  is not already installed, the system throws an

  <code>IllegalArgumentException</code>.

  </li>

  <li>Reset password restrictions for device admins now apply to profile

  owners.Device admins can no longer use

  <code>DevicePolicyManager.resetPassword()</code>to clear passwords or change

  ones that are already set. Device admins can still set a password, but only

  when the device has no password, PIN, or pattern.

  </li>

  <li>Device and profile owners can manage accounts even if restrictions are

  set.Device owners and profile owners can call the Account Management APIs

  even if <code>DISALLOW_MODIFY_ACCOUNTS</code> user restrictions are in place.

  </li>

  <li>Device owners can manage secondary users more easily.When a device is

  running in device owner mode, the <code>DISALLOW_ADD_USER</code> restriction

  is automatically set. This prevents users from creating unmanaged secondary

  users. In addition, the <code>CreateUser()</code> and

  <code>createAndInitial()</code> methods are deprecated; the new

  <code>DevicePolicyManager.createAndManageUser()</code> method replaces them.

  </li>

  <li>Device owners can access device identifiers.A Device owner can access the

  Wi-Fi MAC address of a device, using

  <code>DevicePolicyManagewr.getWifiMacAddress()</code> . If Wi-Fi has never

  been enabled on the device, this method returns a value of {@code null}.

  </li>

</ul>

<h2 id="">NDK Apps Linking to Platform Libraries</h2>

<p>

  In the Preview, an application built with the NDK and targeting the N Preview

  API cannot link against the platform libraries shipped with the NDK. This

  change affects both the dlopen(3) and DT_NEEDED entries in your {@code .so}

  files.

  In order to alert you to use of non-public APIs, apps running on a Preview

  device generate an error in logcat output when an app calls a non-public API.

  This error is also displayed on the device screen as a message to help

  raise awareness of this situation. You should review your app code to

  remove use of non-public platform APIs and thoroughly test your apps using

  a preview device or emulator.

</p>

<p>

  your APK contains all the .so files you intended to link against.

</p>

<p class="caution">

  <strong>Caution:</strong> Some third-party libraries may link to non-public

  APIs. If your app uses these libraries, your app may crash when running

  on the next official release of Android.

</p>

<p>

  Apps should not depend on or use native libraries that are not included in

  the NDK, because they may change, or be removed from one Android release to

  {@code libcrypto.so} from BoringSSL or OpenSSL in your app.

  </li>

</ul>

<h2 id="afw">Android for Work</h2>

<p>

  The Preview contains changes for apps that target Android for Work, including

  changes to certificate installation, password resetting, secondary user

  management, and access to device identifiers. If you are building apps for

  Android for Work environments, you should review these changes and modify

  your app accordingly.

</p>

<ul>

  <li>You must install a delegated certificate installer before the DPC can set

  it. For both profile and device-owner apps targeting the N SDK, you should

  install the delegated certificate installer before the device policy

  controller (DPC) calls

  <code>DevicePolicyManager.setCertInstallerPackage()</code>. If the installer

  is not already installed, the system throws an

  <code>IllegalArgumentException</code>.

  </li>

  <li>Reset password restrictions for device admins now apply to profile

  owners.Device admins can no longer use

  <code>DevicePolicyManager.resetPassword()</code>to clear passwords or change

  ones that are already set. Device admins can still set a password, but only

  when the device has no password, PIN, or pattern.

  </li>

  <li>Device and profile owners can manage accounts even if restrictions are

  set.Device owners and profile owners can call the Account Management APIs

  even if <code>DISALLOW_MODIFY_ACCOUNTS</code> user restrictions are in place.

  </li>

  <li>Device owners can manage secondary users more easily.When a device is

  running in device owner mode, the <code>DISALLOW_ADD_USER</code> restriction

  is automatically set. This prevents users from creating unmanaged secondary

  users. In addition, the <code>CreateUser()</code> and

  <code>createAndInitial()</code> methods are deprecated; the new

  <code>DevicePolicyManager.createAndManageUser()</code> method replaces them.

  </li>

  <li>Device owners can access device identifiers.A Device owner can access the

  Wi-Fi MAC address of a device, using

  <code>DevicePolicyManagewr.getWifiMacAddress()</code> . If Wi-Fi has never

  been enabled on the device, this method returns a value of {@code null}.

  </li>

</ul>