android_frameworks_base/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">Filtering a Handset Application from Tablets</a></li>
    <li><a href="#FilteringTabletApps">Filtering a Tablet Application from Handsets</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 {@code .apk}.</p>



<h2 id="FilteringHandsetApps">Filtering a Handset Application from Tablets</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">Filtering a Tablet Application from Handsets</h2>

<p>If your application's UI is adversely affected when the system scales your application down to
smaller screens, you should add <a
href="{@docRoot}guide/topics/resources/providing-resources.html#AlternativeResources">alternative
layouts</a> for smaller screens to adjust the layout for those screens. However, sometimes your
layout still might not fit a smaller screen or you've explicitly designed your application only for
tablets and other large devices. In this case, you can manage the availability of your application
to smaller screens 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 large and extra large
screens, 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" /&gt;
    &lt;application ... >
        ...
    &lt;application>
&lt;/manifest>
</pre>

<p>External services such as Android Market read this manifest element and use it to ensure that
your application is available only to devices with either a large or an extra large screen.</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 draw it in a "postage stamp" window that's the same relative size as the
screen size that your application does support (see <a
href="screens-support-1.5.html#CompatMode">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">Filtering a Handset Application from Tablets</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>