docs/html/topic/arc/index.jd

page.title=Optimizing Apps for Chromebooks
@jd:body

<div id="qv-wrapper">
    <div id="qv">
      <h2>On this page</h2>

      <ol>
        <li><a href="#update-manifest">Update Your App's Manifest File</a></li>
        <li><a href="#leverage">Leverage Support for Multi-Window Mode</li>
        <li><a href="#keyboard">Support the Keyboard, Trackpad, and Mouse</a></li>
        <li><a href="#backup">Use Backup and Restore Effectively</a></li>
        <li><a href="#update-ndk">Update the NDK Libraries</a></li>
        <li><a href="#support-new-features">Plan Support for New Android Features</a></li>
        <li><a href="#testing">Test Your App</a></li>
        <li><a href="#setup">Set Up ADB</a></li>
        <li><a href="#learning-materials">Additional Learning Materials</a></li>
      </ol>
    </div>
  </div>

<p>
Google Chromebooks now support the Google Play Store and Android apps. This
document describes some ways that you can optimize your Android apps for
Chromebooks.
</p>

<h2 id="update-manifest">Update Your App's Manifest File</h2>

<p>
To begin optimizing your Android app for Chromebooks, update your manifest file
(<code>AndroidManifest.xml</code>) to account for some key hardware and software
differences between Chromebooks and other devices running Android.
</p>

<p>
As of Chrome OS version M53, all Android apps that don't explicitly require the
<a
href="{@docRoot}guide/topics/manifest/uses-feature-element.html#touchscreen-hw-features"><code>android.hardware.touchscreen</code></a>
feature will also work on Chrome OS devices that support the
<code>android.hardware.faketouch</code> feature. However, if you want your app
to work on all Chromebooks in the best possible way, go to your manifest file
and adjust the settings so that the <code>android.hardware.touchscreen</code>
feature is not required, as shown in the following example. You should also
review your mouse and keyboard interactions.
</p>

<pre>
&lt;manifest xmlns:android="http://schemas.android.com/apk/res/android"
          ... &gt;
    &lt;!-- Some Chromebooks don't support touch. Although not essential,
         it's a good idea to explicitly include this declaration. --&gt;
    &lt;uses-feature android:name="android.hardware.touchscreen"
                  android:required="false" /&gt;
&lt;/manifest&gt;
</pre>

<p>
Different devices often have different sensors available in them. See the <a
href="https://developer.android.com/guide/topics/sensors/sensors_overview.html">Sensors
Overview</a> document for an overview of all sensors that the Android platform
supports. Although Android handheld devices may have GPS and accelerometers,
sensors are not guaranteed to be available in every Chromebook. However, there
are cases where the functionality of a sensor is provided in another way. For
example, Chromebooks may not have GPS sensors, but they still provide location
data based on Wi-Fi connections. If you want your app to run on Chromebooks,
regardless of sensor support, you should update your manifest file so that none
of the sensors are required.
</p>

<p class="note"><strong>Note</strong>: If you don't require a particular sensor
for your app but still use measurements from the sensor when it's available,
make sure you dynamically check for the sensor's availability before trying to
gather information from it in your app.
</p>

<p>
Some software features are unsupported on Chromebooks. For example, apps that
provide custom IMEs, app widgets, live wallpapers, and app launchers aren't
supported and won't be available for installation on Chromebooks. For a complete
list of software features that aren't currently supported on Chromebooks, see <a
href="{@docRoot}topic/arc/manifest.html#incompat-software-features">incompatible
software features</a>.
</p>

<h2 id="leverage">Leverage Support for Multi-Window Mode</h2>

<p>
The implementation of Android apps on Chrome OS includes basic multi-window
support. Instead of automatically drawing over the full screen, Android renders
apps on Chrome OS into layouts that are appropriate for this form factor. Google
provides support for the most common window layouts:

<ul>
  <li>
    <strong>Portrait</strong> &ndash; Similar to Nexus 5.
  </li>
  <li>
    <strong>Landscape</strong> &ndash; Similar to Nexus 7.
  </li>
  <li>
    <strong>Maximized</strong> &ndash; Uses all available screen pixels.
  </li>
</ul>

<p>
In addition, end users are presented with window controls to toggle among all
available layouts. By choosing the correct orientation option, you can ensure
that the user has the correct layout upon launching the app. If an app is
available in portrait and landscape, it defaults to landscape if possible. After
this option is set, it is remembered on a per-app basis. Google recommends that
you test your app to ensure that it handles changes in window size
appropriately.
</p>

<h2 id="keyboard">Support the Keyboard, Trackpad, and Mouse</h2>

<p>
All Chromebooks have a physical keyboard and a trackpad, and some Chromebooks
have a touchscreen as well. Some devices can even convert from a laptop to a
tablet.
</p>

<p>
Many existing apps already support mouse and trackpad interactions with no extra
work required. However, it's always best to adjust your app's behavior
appropriately when users interact with it using a trackpad instead of a
touchscreen, and you should support and distinguish between both interfaces
properly. Given the support for physical keyboards, you can now provide hotkeys
to enable your app's users to be more productive. For example, if your app
supports printing, you can use <strong>Ctrl+P</strong> to open a print dialog.
</p>

<h2 id="backup">Use Backup and Restore Effectively</h2>

<p>
One of the strongest features of Chromebooks is that users can easily migrate
from one device to another. That is, if someone stops using one Chromebook and
starts using another, they simply have to sign in, and all of their apps appear.
</p>

<p class="note"><strong>Tip: </strong> Although it's not mandatory, backing up
your app's data to the cloud is a good idea.
</p>

<p>
Chromebooks can also be shared among a large number of people, such as in
schools. Since local storage is not infinite, entire accounts&mdash;together
with their storage&mdash;can be removed from the device at any point. For
educational settings, it's a good idea to keep this scenario in mind.
</p>

<h2 id="update-ndk">Update the NDK Libraries</h2>

<p>
If your app uses the Android NDK libraries, and its target SDK version is 23 or
higher, ensure that text relocations are removed from both the ARM and x86
versions of your NDK libraries, as they're not compatible in Android 6.0 (API
level 23) and higher. By leaving text relocations in your NDK libraries, you may
also cause incompatibility errors with Chromebooks, especially when running on
a device that uses an x86 architecture.
</p>

<p class="note"><strong>Note: </strong>To view more details on updating NDK
libraries properly, see the <a
href="https://developer.android.com/about/versions/marshmallow/android-6.0-changes.html#behavior-runtime">
Runtime</a> section of the Android 6.0 Changes document.
</p>

<h2 id="support-new-features">Plan Support for New Android Features</h2>

<p>
Android apps on Chromebooks initially ship with APIs for Android 6.0 (API level
23). By following the best practices outlined above, your app is likely to be
compatible with the multi-window improvements introduced in Android 7.0 (API
level 24). It's good to plan support for the APIs and behaviors available as of
Android 7.0, which feature several improvements. For example, multi-window
support is better integrated, and you're able to resize activities arbitrarily,
making them feel more natural. You can also access APIs for drag-and-drop
operations across apps and mouse cursor control.
</p>

<h2 id="testing">Test Your App</h2>

<p>
To <a href="{@docRoot}topic/arc/sideload.html">load</a> your app onto your
Chromebook for testing, you must enter <em>Developer</em> mode on your Chrome OS
device and enable <em>unknown sources</em>. See the <a class="external-link"
href="https://www.chromium.org/chromium-os/poking-around-your-chrome-os-device#TOC-Putting-your-Chrome-OS-Device-into-Developer-Mode">
Putting your Chrome OS Device into Developer Mode</a> document for detailed
instructions about moving your device into Developer mode. After your device is
in Developer mode, you can go to your Chrome settings and select <strong>Enable
Unknown Sources</strong> under the <em>security in app</em> settings.
</p>

<p>
After enabling Developer mode, you can load an Android app onto your Chrome OS
device using one of several methods. For more details, see the <a
href="{@docRoot}topic/arc/sideload.html#load-app">Load Your App</a> section of
the Loading Apps on Chromebooks page.
</p>

<p class="note"><strong>Note: </strong>To ensure that your Android app works
well on a variety of Chromebook devices and available form factors, Google
recommends that you test your app on an ARM-based Chromebook, an x86-based
Chromebook, a device with a touchscreen and one without one, and on a
convertible device (one that can change between a laptop and a tablet). To view
the full list of supported devices, see the <a
href="{@docRoot}topic/arc/device-support.html">Chrome OS Device Support for
Apps</a> page.</p>

<h2 id="setup">Set Up ADB</h2>

<p>
Before attempting to set up an ADB connection, you must start your Chrome OS in
<a class="external-link"
href="https://www.chromium.org/chromium-os/poking-around-your-chrome-os-device">
Developer Mode</a> so that you have the ability to install Android apps on the
Chromebook.
</p>

<p class="caution"><strong>Caution: </strong>After switching your Chrome OS
device to Developer mode, it restarts and clears all existing data on the
device.
</p>

<p>
To set up ADB, complete the following steps:
</p>

<ol>
  <li>
    Press <strong>Ctrl+D</strong> to start your device.
  </li>
  <li>
    Finish the setup process.
  </li>
  <li>
    Log into your test account.
  </li>
  <li>
    Accept the Google Play Store terms and service conditions.
  </li>
</ol>

<h3>Configure the firewall</h3>

<p>
To configure the Chrome OS firewall to allow incoming ADB connections, complete
the following steps:
</p>

<ol>
  <li>
    Press <strong>Ctrl+Alt+T</strong> to start the Chrome OS terminal.
  </li>
  <li>
    Type <strong>shell</strong> to get to the bash command shell:
<pre class="no-pretty-print">
crosh> shell
chronos@localhost / $
</pre>
  </li>
  <li>
    Type the following commands to set up developer features and enable
    disk-write access for the firewall settings changes:
<pre class="no-pretty-print">
chronos@localhost / $ sudo /usr/libexec/debugd/helpers/dev_features_rootfs_verification
chronos@localhost / $ sudo reboot
</pre>
    The <em>sudo reboot</em> command restarts your Chromebook.
<p class="note"><strong>Note</strong>: You can press the <strong>Tab</strong>
key to enable autocompletion of file names.</p>
  </li>
  <li>
    After your device restarts, log in to your test account and type the
    following command to enable the <em>secure shell</em> and configure the
    firewall properly:
<pre class="no-pretty-print">
chronos@localhost / $ sudo /usr/libexec/debugd/helpers/dev_features_ssh
</pre>
    You can now exit out of the shell.
  </li>
</ol>

<p class="note"><strong>Note</strong>: You must complete this procedure only
once on your Chromebook.</p>

<h3>Check the IP address of your Chromebook</h3>

<p>
To verify the IP address of your Chromebook, complete the following steps:
</p>

<ol>
  <li>
    Click the clock icon in the bottom-right area of the screen.
  </li>
  <li>
    Click <strong>Settings</strong>.
  </li>
  <li>
    The <em>Internet Connection</em> section in the Settings area lists all of
    the available networks. Select the one that you want to use for ADB.
  </li>
  <li>
    Take note of the IP address that appears.
  </li>
</ol>

<h3>Enable ADB debugging</h3>

<p>
To enable ADB debugging, complete the following steps:
</p>

<ol>
  <li>
    Click the clock icon in the bottom-right area of the screen.
  </li>
  <li>
    Click <strong>Settings</strong>.
  </li>
  <li>
    In the <em>Android Apps</em> section, click the <strong>Settings</strong>
    link in the line that reads <em>Manage your Android apps in Settings</em>.
    This brings up the Android apps settings.
  </li>
  <li>
    Click <strong>About device</strong>.
  </li>
  <li>
    Click <strong>Build number</strong> seven times to move into Developer mode.
  </li>
  <li>
    Click the arrow in the top-left area of the window to go back to the main
    Settings screen.
  </li>
  <li>
    Click the new <strong>Developer options</strong> item, activate <strong>ADB
    debugging</strong>, and then click <strong>OK</strong> to allow ADB
    debugging.
  </li>
  <li>
    Return to your development machine and use ADB to connect to your
    Chromebook's using its IP address and port 22.
  </li>
  <li>
    On your Chromebook, click <strong>Allow</strong> when prompted whether you
    want to allow the debugger. Your ADB session is established.
  </li>
</ol>

<h4>Troubleshooting ADB debugging</h4>

<p>
Sometimes the ADB device shows that it's offline when everything is connected
properly. In this case, complete the following steps to troubleshoot the issue:
</p>

<ol>
  <li>
    Deactivate <strong>ADB debugging</strong> in <em>Developer options</em>.
  </li>
  <li>
    In a terminal window, run <code>adb kill-server</code>.
  </li>
  <li>
    Re-activate the <strong>ADB debugging</strong> option.
  </li>
  <li>
    In a terminal window, attempt to run <code>adb connect</code>.
  </li>
  <li>
    Click <strong>Allow</strong> when prompted whether you want to allow
    debugging. Your ADB session is established.
  </li>
</ol>

<h2 id="learning-materials">Additional Learning Materials</h2>

<p>
To learn more about optimizing your Android apps for Chromebooks, consult the
following resources:
</p>

<ul>
  <li>
    Review the
    <a class="external-link" href="http://android-developers.blogspot.com/2016/05/bring-your-android-app-to-chromebooks.html">
    Bring your Android App to Chromebooks</a> I/O session.
  </li>
  <li>
    Post a question on the <a class="external-link"
    href="https://plus.sandbox.google.com/+AndroidDevelopers">Android developer
    community</a> with hashtag <em>#AndroidAppsOnChromeOS</em>.
  </li>
</ul>