docs/html/guide/practices/screens-distribution.jd

page.title=Distributing to Specific Screens
parent.title=Supporting Multiple Screens
parent.link=screens_support.html

@jd:body

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

  <h2>Quickview</h2>
  <ul>
    <li>If necessary, you can control distribution of your application based on the device
screen configuration</li>
  </ul>

  <h2>In this document</h2>
  <ol>
    <li><a href="#FilteringHansetApps">Declaring an App is Only for Handsets</a></li>
    <li><a href="#FilteringTabletApps">Declaring an App is Only for Tablets</a></li>
    <li><a href="#MultiApks">Publishing Multiple APKs for Different Screens</a></li>
  </ol>

  <h2>See also</h2>
  <ol>
    <li><a
href="{@docRoot}guide/practices/screens_support.html">Supporting Multiple Screens</a></li>
    <li><a
href="{@docRoot}guide/practices/optimizing-for-3.0.html">Optimizing Apps for Android 3.0</a></li>
  </ol>

</div>
</div>



<p>Although we recommend that you design your application to function properly on multiple
configurations of screen size and density, you can instead choose to limit the distribution of your
application to certain types of screens, such as only tablets and other large devices or only
handsets and similar-sized devices. To do so, you can enable filtering by external services such as
Android Market by adding elements to your manifest file that specify the screen configurations your
application supports.</p>

<p>However, before you decide to restrict your application to certain screen configurations, you
should understand the techniques for <a
href="{@docRoot}guide/practices/screens_support.html">supporting multiple screens</a> and implement
them to the best of your ability. By supporting multiple screens, your application can be made
available to the greatest number of users with different devices, using a single APK.</p>



<h2 id="FilteringHandsetApps">Declaring an App is Only for Handsets</h2>

<p>Because the system generally scales applications to fit larger screens well, you shouldn't
need to filter your application from larger screens. As long as you follow the <a
href="{@docRoot}guide/practices/screens_support.html#screen-independence">Best Practices for Screen
Independence</a>, your application should work well on larger screens such as tablets. However, you
might discover that your application can't scale up well or perhaps you've decided to publish two
versions of your application for different screen configurations. In such a case, you can use the <a
href="{@docRoot}guide/topics/manifest/compatible-screens-element.html">{@code
&lt;compatible-screens>}</a> element to manage the distribution of your application based on
combinations of screen size and density. External services such as Android Market use this
information to apply filtering to your application, so that only devices that have a screen
configuration with which you declare compatibility can download your application.</p>

<p>The <a href="{@docRoot}guide/topics/manifest/compatible-screens-element.html">{@code
&lt;compatible-screens>}</a> element must contain one or more {@code &lt;screen&gt;} elements. Each
{@code &lt;screen&gt;} element specifies a screen configuration with which your application is
compatible, using both the {@code android:screenSize} and {@code android:screenDensity} attributes.
Each {@code &lt;screen&gt;} element <strong>must include both attributes</strong> to specify an
individual screen configuration&mdash;if either attribute is missing, then the element is invalid
(external services such as Android Market will ignore it).</p>

<p>For example, if your application is compatible with only small and normal size screens,
regardless of screen density, you must specify eight different {@code &lt;screen&gt;} elements,
because each screen size has four density configurations. You must declare each one of
these; any combination of size and density that you do <em>not</em> specify is considered a screen
configuration with which your application is <em>not</em> compatible. Here's what the manifest
entry looks like if your application is compatible with only small and normal screen sizes:</p>

<pre>
&lt;manifest ... >
    &lt;compatible-screens>
        &lt;!-- all small size screens -->
        &lt;screen android:screenSize="small" android:screenDensity="ldpi" />
        &lt;screen android:screenSize="small" android:screenDensity="mdpi" />
        &lt;screen android:screenSize="small" android:screenDensity="hdpi" />
        &lt;screen android:screenSize="small" android:screenDensity="xhdpi" />
        &lt;!-- all normal size screens -->
        &lt;screen android:screenSize="normal" android:screenDensity="ldpi" />
        &lt;screen android:screenSize="normal" android:screenDensity="mdpi" />
        &lt;screen android:screenSize="normal" android:screenDensity="hdpi" />
        &lt;screen android:screenSize="normal" android:screenDensity="xhdpi" />
    &lt;/compatible-screens>
    ...
    &lt;application ... >
        ...
    &lt;application>
&lt;/manifest>
</pre>

<p class="note"><strong>Note:</strong> Although you can also use the <a
href="{@docRoot}guide/topics/manifest/compatible-screens-element.html">{@code
&lt;compatible-screens>}</a> element for the reverse scenario (when your application is not
compatible with smaller screens), it's easier if you instead use the <a
href="{@docRoot}guide/topics/manifest/supports-screens-element.html">{@code
&lt;supports-screens>}</a> as discussed in the next section, because it doesn't require you
to specify each screen density your application supports.</p>




<h2 id="FilteringTabletApps">Declaring an App is Only for Tablets</h2>

<p>If you don't want your app to be used on handsets (perhaps your app truly makes sense only on a
large screen) or you need time to optimize it for smaller screens, you can prevent small-screen
devices from downloading your app by using the <a
href="{@docRoot}guide/topics/manifest/supports-screens-element.html">{@code
&lt;supports-screens>}</a> manifest element.</p>

<p>For example, if you want your application to be available only to tablet devices, you can declare
the element in your manifest like this:</p>

<pre>
&lt;manifest ... >
    &lt;supports-screens android:smallScreens="false"
                      android:normalScreens="false"
                      android:largeScreens="true"
                      android:xlargeScreens="true"
                      android:requiresSmallestWidthDp="600" />
    ...
    &lt;application ... >
        ...
    &lt;/application>
&lt;/manifest>
</pre>

<p>This describes your app's screen-size support in two different ways:</p>

<ul>
  <li>It declares that the app does <em>not</em> support the screen sizes "small" and
"normal", which are traditionally not tablets.</li>
  <li>It declares that the app requires a screen size with a minimum usable area that is at least
600dp wide.</li>
</ul>

<p>The first technique is for devices that are running Android 3.1 or older, because those devices
declare their size based on generalized screen sizes. The <a
href="{@docRoot}guide/topics/manifest/supports-screens-element.html#requiresSmallest">{@code
requiresSmallestWidthDp}</a> attribute is for devices running Android 3.2 and newer, which includes
the capability for apps to specify size requirements based on a minimum number of
density-independent pixels available.  In this example, the app declares a minimum width requirement
of 600dp, which generally implies a 7"-or-greater screen. </p>

<p>Your size choice might be different, of course, based on how well your design works on different
screen sizes; for example, if your design works well only on screens that are 9" or larger, you
might require a minimum width of 720dp.</p>

<p>The catch is that you must compile your application against Android 3.2 or higher in order to use
the <code>requiresSmallestWidthDp</code> attribute. Older versions don't understand this attribute
and will raise a compile-time error. The safest thing to do is develop your app against the platform
that matches the API level you've set for <a
href="{@docRoot}guide/topics/manifest/uses-sdk-element.html#min">minSdkVersion</a
>. When you're making final preparations to build your release candidate, change the build target to
Android 3.2 and add the <code>requiresSmallestWidthDp</code> attribute. Android versions older than
3.2 simply ignore that XML attribute, so there's no risk of a runtime failure.</p>

<p>For more information about why the "smallest width" screen size is
important for supporting different screen sizes, read <a
href="http://android-developers.blogspot.com/2011/07/new-tools-for-managing-screen-sizes.html">New
Tools for Managing Screen Sizes</a>.</p>

<p class="caution"><strong>Caution:</strong> If you use the <a
href="{@docRoot}guide/topics/manifest/supports-screens-element.html">{@code
&lt;supports-screens>}</a> element for the reverse scenario (when your application is not compatible
with <em>larger</em> screens) and set the larger screen size attributes to {@code "false"}, then
external services such as Android Market <strong>do not</strong> apply filtering. Your application
will still be available to larger screens, but when it runs, it will not resize to fit the screen.
Instead, the system will emulate a handset screen size (about 320dp x 480dp; see <a
href="{@docRoot}guide/practices/screen-compat-mode.html">Screen Compatibility Mode</a> for more
information). If you want
to prevent your application from being downloaded on larger screens, use <a
href="{@docRoot}guide/topics/manifest/compatible-screens-element.html">{@code
&lt;compatible-screens>}</a>, as discussed in the previous section about <a
href="#FilteringHandsetApps">Declaring an App is Only for Handsets</a>.</p>

<p>Remember, you should strive to make your application available to as many devices as possible by
applying all necessary techniques for <a
href="{@docRoot}guide/practices/screens_support.html">supporting multiple screens</a>. You should
use <a href="{@docRoot}guide/topics/manifest/compatible-screens-element.html">{@code
&lt;compatible-screens>}</a> or <a
href="{@docRoot}guide/topics/manifest/supports-screens-element.html">{@code
&lt;supports-screens>}</a> only when you cannot provide compatibility on all screen configurations
or you have decided to provide different versions of your application for different sets of screen
configurations.</p>



<h2 id="MultiApks">Publishing Multiple APKs for Different Screens</h2>

<p>Although we recommend that you publish one APK for your application, Android Market allows
you to publish multiple APKs for the same
application when each APK supports a different set of screen configurations (as declared in
the manifest file). For example, if you want to publish both a handset version and a tablet
version of your application, but you're unable to make the same APK work for both screen sizes,
you can actually publish two APKs for the same application listing. Depending on each device's
screen configuration, Android Market will deliver it the APK that you've declared to support that
device's screen.</p>

<p>Beware, however, that publishing multiple APKs for the same application is
considered an advanced feature and <strong>most applications should publish only one
APK that can support a wide range of device configurations</strong>. Supporting multiple screen
sizes, especially, is within reason using a single APK, as long as you follow the guide to
<a href="{@docRoot}guide/practices/screens_support.html">Supporting Multiple Screens</a>.</p>

<p>If you need more information about how to publish multiple APKs on Android Market, read <a
href="{@docRoot}guide/market/publishing/multiple-apks.html">Multiple APK Support</a>.</p>