android_frameworks_base/docs/html/guide/practices/compatibility.jd

page.title=Device Compatibility
excludeFromSuggestions=true
@jd:body

<div id="qv-wrapper">
<div id="qv">
<h2>In this document</h2>
<ol>
  <li><a href="#defined">What Does "Compatibility" Mean?</a></li>
  <li><a href="#how">Controlling Your App's Availability to Devices</a>
    <ol>
      <li><a href="#Features">Device features</a></li>
      <li><a href="#Versions">Platform version</a></li>
      <li><a href="#Screens">Screen configuration</a></li>
    </ol>
  </li>
  <li><a href="#filtering">Controlling Your App's Availability for Business Reasons</a></li>
</ol>

<h2>See also</h2>
 <ol>
<li><a
href="{@docRoot}google/play/filters.html">Filtering on Google Play</a></li>
<li><a
href="{@docRoot}guide/topics/resources/providing-resources.html">Providing Resources</a></li>
<li><a href="http://source.android.com/compatibility/index.html" class="external-link">
Android Compatibility</a></li>
</ol>


</div> </div>

<p>Android is designed to run on many different types of devices, from phones
to tablets and televisions. As a developer,
the range of devices provides a huge potential audience for your app. In order for your app
to be successful on all these devices, it should tolerate some feature variability
and provide a flexible user interface that adapts to different screen
configurations.</p>

<p>To facilitate your effort toward that goal, Android provides a dynamic app framework in which
you can provide configuration-specific <a href="{@docRoot}guide/topics/resources/overview.html"
>app resources</a> in static files (such as different XML layouts
for different screen sizes). Android then loads the appropriate resources based on
the current device configuration. So with some forethought to your app design and some additional
app resources, you can publish a single application package (APK) that provides an optimized user
experience on a variety of devices.

<p>If necessary, however, you can specify your app's feature requirements and control
which types of devices can install your app from Google Play Store. This page explains how you can
control which devices have access to your apps, and how to prepare your apps to make sure they
reach the right audience. For more information about how you can make your app adapt
to different devices, read <a href="{@docRoot}training/basics/supporting-devices/index.html"
>Supporting Different Devices</a>.</p>



<h2 id="defined">What Does "Compatibility" Mean?</h2>

<p>As you read more about Android development, you'll probably encounter the term "compatibility"
in various situations. There are two types of compatibility: <em>device compatibility</em>
and <em>app compatibility</em>.

<p>Because Android is an open source project, any hardware manufacturer can build a device
that runs the Android operating system. Yet, a <b>device is "Android compatible"</b> only if
it can correctly run apps written for the
<em>Android execution environment</em>. The exact details of the Android execution
environment are defined by the <a href="http://source.android.com/compatibility/overview.html"
class="external-link">Android compatibility program</a> and each device must pass the Compatibility
Test Suite (CTS) in order to be considered compatible.</p>

<p>As an app developer, you don't need to worry about whether a device is Android compatible, because
only devices that are Android compatible include Google Play Store. So you can rest assured that
users who install your app from Google Play Store are using an Android compatible device.</p>


<p>However, you do need to consider whether your <b>app is compatible</b> with each potential
device configuration. Because Android runs on a wide range of device configurations, some features are not
available on all devices. For example, some devices may not include a
compass sensor. If your app's core functionality requires the use
of a compass sensor, then your app is compatible only with devices that
include a compass sensor.</p>




<h2 id="how">Controlling Your App's Availability to Devices</h2>

<p>Android supports a variety of features your app can leverage through platform APIs. Some
features are hardware-based (such as a compass sensor), some are software-based (such as app
widgets), and some are dependent on the platform version. Not every device supports every feature,
so you may need to control your app's availability to devices based on your app's required
features.</p>


<p>To achieve the largest user-base possible for your app, you should strive to support as many
device configurations as possible using a single APK. In most situations, you can do so by
disabling optional features at runtime and <a
href="{@docRoot}guide/topics/resources/providing-resources.html">providing app resources</a>
with alternatives for different configurations (such as different layouts for different
screen sizes).
If necessary, however, you can restrict your app's availability to devices through Google Play
Store based on the following device characteristics:</p>

<ul>
  <li><a href="#Features">Device features</a>
  <li><a href="#Version">Platform version</a>
  <li><a href="#Screens">Screen configuration</a>
</ul>


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

<p>In order for you to manage your app’s availability based on device features,
Android defines <em>feature IDs</em> for any hardware or software feature
that may not be available on all devices. For instance, the
feature ID for the compass sensor is {@link
android.content.pm.PackageManager#FEATURE_SENSOR_COMPASS} and the feature ID for app widgets
is {@link android.content.pm.PackageManager#FEATURE_APP_WIDGETS}.</p>

<p>If necessary, you can prevent users from installing your app when their devices don't provide a
given feature by declaring it with a <a href=
"{@docRoot}guide/topics/manifest/uses-feature-element.html">{@code &lt;uses-feature&gt;}</a>
element in your app's <a href="{@docRoot}guide/topics/manifest/manifest-intro.html">manifest
file</a>.</p>

<p>For example, if your app does not make sense on a device that lacks a compass sensor,
you can declare the compass sensor as required with the following manifest tag:</p>

<pre>
&lt;manifest ... >
    &lt;uses-feature android:name="android.hardware.sensor.compass"
                  android:required="true" />
    ...
&lt;/manifest>
</pre>

<p>Google Play Store compares the features your app requires to the features available on
each user's device to determine whether your app is compatible with each device.
If the device does not provide all the features your app requires, the user cannot install
your app.</p>

<p>However, if your app's primary functionality does not <em>require</em>
a device feature, you should set the <a href=
"{@docRoot}guide/topics/manifest/uses-feature-element.html#required">{@code required}</a>
attribute to {@code "false"} and check
for the device feature at runtime. If the app feature is not available on the current device,
gracefully degrade the corresponding app feature. For example, you can query whether
a feature is available by calling
{@link android.content.pm.PackageManager#hasSystemFeature hasSystemFeature()} like this:</p>

<pre>
PackageManager pm = getPackageManager();
if (!pm.hasSystemFeature(PackageManager.FEATURE_SENSOR_COMPASS)) {
    // This device does not have a compass, turn off the compass feature
    disableCompassFeature();
}
</pre>

<p>For information about all the filters you can
use to control the availability of your app to users through Google Play Store, see the 
<a href="{@docRoot}google/play/filters.html">Filters on Google Play</a>
document.</p>

<p class="note"><strong>Note:</strong> Some <a href=
"{@docRoot}guide/topics/security/permissions.html">system permissions</a> implicitly require the
availability of a device feature. For example, if your app requests permission to access to {@link
android.Manifest.permission#BLUETOOTH}, this implicitly requires the {@link
android.content.pm.PackageManager#FEATURE_BLUETOOTH} device feature. You can disable filtering based
on this feature and make your app available to devices without Bluetooth by setting the <a href=
"{@docRoot}guide/topics/manifest/uses-feature-element.html#required">{@code required}</a> attribute
to {@code "false"} in the <a href=
"{@docRoot}guide/topics/manifest/uses-feature-element.html">{@code &lt;uses-feature&gt;}</a> tag.
For more information about implicitly required device features, read <a href=
"{@docRoot}guide/topics/manifest/uses-feature-element.html#permissions">Permissions that Imply
Feature Requirements</a>.</p>







<h3 id="Versions">Platform version</h3>

<p>Different devices may run different versions of the Android platform,
such as Android 4.0 or Android 4.4. Each successive platform version often adds new APIs not
available in the previous version. To indicate which set of APIs are available, each
platform version specifies an <a
href="{@docRoot}guide/topics/manifest/uses-sdk-element.html#ApiLevels">API level</a>. For instance,
Android 1.0 is API level 1 and Android 4.4 is API level 19.</p>

<p>The API level allows you to declare the minimum version with which your app is
compatible, using the <a href="{@docRoot}guide/topics/manifest/uses-sdk-element.html">{@code
&lt;uses-sdk>}</a> manifest tag and its <a href="{@docRoot}guide/topics/manifest/uses-sdk-element.html#min">{@code minSdkVersion}</a> attribute.</p>

<p>For example, the <a href="{@docRoot}guide/topics/providers/calendar-provider.html">Calendar
Provider</a> APIs were added in Android 4.0 (API level 14). If your app cannot function without
these APIs, you should declare API level 14 as your app's minimum supported
version like this:</p>

<pre>
&lt;manifest ... >
    &lt;uses-sdk android:minSdkVersion="14" android:targetSdkVersion="19" />
    ...
&lt;/manifest>
</pre>

<p>The <a href="{@docRoot}guide/topics/manifest/uses-sdk-element.html#min">{@code
minSdkVersion}</a> attribute declares the minimum version with which your app is compatible
and the <a href="{@docRoot}guide/topics/manifest/uses-sdk-element.html#target">{@code
targetSdkVersion}</a> attribute declares the highest version on which you've optimized
your app.</p>

<p>Each successive version of Android provides compatibility for apps that were built using
the APIs from previous platform versions, so your app should always be compitible with future
versions of Android while using the documented Android APIs.</p>

<p class="note"><strong>Note:</strong>
The <a href="{@docRoot}guide/topics/manifest/uses-sdk-element.html#target">{@code
targetSdkVersion}</a> attribute does not prevent your app from being installed on platform
versions that are higher than the specified value,
but it is important because it indicates to the system whether your
app should inherit behavior changes in newer versions. If you don't update the
<a href="{@docRoot}guide/topics/manifest/uses-sdk-element.html#target">{@code
targetSdkVersion}</a> to the latest version, the system assumes that your
app requires some backward-compatibility behaviors when running on the latest version.
For example, among the <a href="{@docRoot}about/versions/android-4.4.html#Behaviors"
>behavior changes in Android 4.4</a>, alarms created with the {@link android.app.AlarmManager} APIs
are now inexact by default so the system can batch app alarms and preserve system power,
but the system will retain the previous API behavior for your app if your target API level
is lower than "19".</p>

<p>However, if your app uses APIs added in a more recent
platform version, but does not require them for its primary functionality,
you should check the API level at runtime and gracefully degrade
the corresponding features when the API level is too low. In this case,
set the <a href="{@docRoot}guide/topics/manifest/uses-sdk-element.html#min">{@code
minSdkVersion}</a> to the lowest value possible for your app's primary functionality,
then compare the current system's version, {@link android.os.Build.VERSION#SDK_INT}, to one the
codename constants in {@link android.os.Build.VERSION_CODES} that corresponds to the
API level you want to check. For example:</p>

<pre>
if (Build.VERSION.SDK_INT < Build.VERSION_CODES.HONEYCOMB) {
    // Running on something older than API level 11, so disable
    // the drag/drop features that use {@link android.content.ClipboardManager} APIs
    disableDragAndDrop();
}
</pre>






<h3 id="Screens">Screen configuration</h3>

<p>Android runs on devices of various sizes, from phones to tablets and TVs.
In order to categorize devices by their screen type, Android defines two characteristics for
each device: screen size (the physical size of the screen) and screen density (the physical
density of the pixels on the screen, known as <acronym title="dots per inch">DPI</acronym>).
To simplify the different configurations, Android generalizes these variants into groups that make
them easier to target:</p>

<ul>
  <li>Four generalized sizes: small, normal, large, and xlarge.</li>
  <li>And several generalized densities: mdpi (medium), hdpi (hdpi), xhdpi (extra high),
  xxhdpi (extra-extra high), and others.</li>
</ul>

<p>By default, your app is compatible with all screen sizes and densities,
because the system makes the appropriate adjustments to your UI layout and image
resources as necessary for each screen. However, you should optimize the user experience for each
screen configuration by adding specialized layouts for different screen sizes and
optimized bitmap images for common screen densities.</p>

<p>For information about how to create alternative resources for different screens
and how to restrict your app to certain screen sizes when necessary, read <a
href="{@docRoot}training/basics/supporting-devices/screens.html">Supporting Different Screens</a>.
</p>








<h2 id="filtering">Controlling Your App's Availability for Business Reasons</h2>

<p>In addition to restricting your app's availability based on device characteristics,
it’s possible you may need to restrict your app’s availability for
business or legal reasons. For instance, an app that displays train schedules
for the London Underground is unlikely to be useful to users outside the United
Kingdom. For this type of situation, Google Play Store provides
filtering options in the developer console that allow you to control your app’s
availability for non-technical reasons such as the user's locale or wireless carrier.</p>

<p>Filtering for technical compatibility (such as required hardware components)
is always based on information contained within your APK file. But
filtering for non-technical reasons (such as geographic locale) is always
handled in the Google Play developer console.</p>






<div class="next-docs">
<div class="col-6">
  <h2 class="norule">Continue reading about:</h2>
  <dl>
    <dt><a
href="{@docRoot}guide/topics/resources/providing-resources.html">Providing Resources</a></dt>
    <dd>Information about how Android apps are structured to separate app resources from the
   app code, including how you can provide alternative resources for specific device
   configurations.
    </dd>
    <dt><a href="{@docRoot}google/play/filters.html">Filters on Google Play</a></dt>
    <dd>Information about the different ways that Google Play Store can prevent your app
   from being installed on different devices.</dd>
  </dl>
</div>
<div class="col-6">
  <h2 class="norule">You might also be interested in:</h2>
  <dl>
    <dt><a href="{@docRoot}guide/topics/security/permissions.html"
        >System Permissions</a></dt>
    <dd>How Android restricts app access to certain APIs with a permission system that requires
  the user's consent for your app to use those APIs.</dd>
  </dl>
</div>
</div>