xref: /frameworks/base/docs/html/guide/topics/resources/localization.jd

page.title=Localizing with Resources
parent.title=Application Resources
page.tags="localizing","localization","resources", "formats", "l10n"
parent.link=index.html
@jd:body

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

<h2>Quickview</h2>

<ul>
  <li>Use resource sets to create a localized app.</li>
  <li>Android loads the correct resource set for the user's language and locale.</li>
  <li>If localized resources are not available, Android loads your default resources.</li>
</ul>

<h2>In this document</h2>
<ol>
  <li><a href="#resource-switching">Overview: Resource-Switching in Android</a></li>
<li><a href="#using-framework">Using Resources for Localization</a></li>
<li><a href="#strategies">Localization Strategies</a></li>
<li><a href="#testing">Testing Localized Applications</a></li>
</ol>

<h2>See also</h2>
  <ol>
    <li><a href="{@docRoot}distribute/googleplay/publish/localizing.html">Localization Checklist</a></li>
    <li><a href="{@docRoot}guide/topics/resources/providing-resources.html">Providing Resources</a></li>
    <li><a href="{@docRoot}guide/topics/ui/declaring-layout.html">Layouts</a></li>
    <li><a href="{@docRoot}reference/android/app/Activity.html#ActivityLifecycle">Activity Lifecycle</a></li>
</ol>
</div>
</div>

<p>Android will run on many  devices in many  regions. To reach the most users,
your application should handle text, audio files, numbers, currency, and
graphics in ways appropriate to the locales where your application will be used.
</p>

<p>This document describes best practices for localizing Android
applications. The principles apply whether you are developing your application  
using ADT with Eclipse, Ant-based tools, or any other IDE. </p>

<p>You should already have a working knowledge of Java and be  familiar with
Android resource loading, the declaration of user interface elements in XML,
development considerations such as Activity lifecycle, and general principles of
internationalization and localization. </p>

<p>It is good practice to use the Android resource framework to separate the
localized aspects of your application as much as possible from the core Java
functionality:</p>

<ul>
  <li>You can put most or all of the <em>contents</em> of your application's
user interface into resource files, as described in this document and in <a
href="{@docRoot}guide/topics/resources/providing-resources.html">Providing Resources</a>.</li>
  <li>The <em>behavior</em> of the user interface, on the other hand, is driven
by your Java code. 
    For example, if users input data that needs to be formatted or sorted
differently depending on locale, then you would use Java to handle the data
programmatically. This document does not cover how to  localize your Java code.
</li>
</ul>

<p>For a short guide to localizing strings in your app, see the training lesson, <a
href="{@docRoot}training/basics/supporting-devices/languages.html">Supporting Different Languages</a>. </p>


<h2 id="resource-switching">Overview: Resource-Switching in Android</h2>

<p>Resources are text strings, layouts, sounds, graphics, and any other static
data that your  Android application  needs. An application can include multiple
sets of resources, each customized for a different device configuration. When a
user runs the application,  Android    automatically selects and loads the 
resources that best match the device.</p>

<p>(This document focuses on localization and locale. For a complete description
of resource-switching and all the types of configurations that you can
specify &#8212; screen orientation, touchscreen type, and so on &#8212; see <a
href="{@docRoot}guide/topics/resources/providing-resources.html#AlternativeResources">Providing
Alternative Resources</a>.)</p>

<table border="0" cellspacing="0" cellpadding="0">
  <tr border="0">
    <td width="180" style="border: 0pt none ;"><p class="special-note">
    <strong>When you write your application:</strong>
    <br><br>
    You create a set of default resources, plus alternatives to be used in
    different locales.</p></td>
    <td style="border: 0pt none; padding:0">
    <p style="border:0; padding:0"><img src="../../../images/resources/right-arrow.png" alt="right-arrow" 
    width="51" height="17"></p></td>
    <td width="180" style="border: 0pt none ;"><p class="special-note">
    <strong>When a user runs your application:</strong>
    <br><br>The Android system selects which resources to load, based on the
    device's locale.</p></td>
  </tr>
</table>

<p>When you write your application, you create default and alternative resources
for your application to use. To create  resources, you place files within
specially named subdirectories of the project's <code>res/</code> directory.
</p>



<h3 id="defaults-r-important">Why Default Resources Are Important</h3>

<p>Whenever the application runs in a locale for which you have not provided
locale-specific text,  Android will load the default strings from
<code>res/values/strings.xml</code>. If this default  file is absent, or if it 
is missing a string that your application needs, then your application will not run 
and will show an error. 
The example below illustrates what can happen when the default text file is incomplete. </p>

<p><em>Example:</em>
<p>An application's Java code refers to just two strings, <code>text_a</code> and 
	<code>text_b</code>. This application includes a localized resource file 
	(<code>res/values-en/strings.xml</code>) that defines <code>text_a</code> and 
	<code>text_b</code> in English. This application also includes a default 
	resource file (<code>res/values/strings.xml</code>) that includes a
definition for <code>text_a</code>, but not for <code>text_b</code>:
<ul>
  <li>This application might compile without a problem. An IDE such as Eclipse 
  	will not highlight any errors if a resource is missing.</li>
  <li>When this application is launched on a device with locale set to English, 
  	the application  might run without a problem, because 
  	<code>res/values-en/strings.xml</code> contains both of the needed text 
  	strings.</li>
  <li>However, <strong>the user  will see an error message and a Force Close 
  	button</strong> when this application is launched on a device set to a 
  	language other than English. The application will not load.</li>
</ul>


<p>To prevent this situation, make sure that a <code>res/values/strings.xml</code> 
	file exists and that it defines every needed string. The situation applies to 
	all types of resources, not just strings: You 
	need to create a  set of default resource files containing all 
	the resources that your application calls upon &#8212; layouts, drawables, 
	animations, etc. For information about testing, see <a href="#test-for-default">
	Testing for Default Resources</a>.</p>

<h2 id="using-framework">Using Resources for Localization</h2>

<h3 id="creating-defaults">How to Create Default Resources</h3>

<p>Put the application's default text in
a file with the following location and name:</p>
<p><code>&nbsp;&nbsp;&nbsp;&nbsp;res/values/strings.xml</code> (required directory)</p>

<p>The text strings in <code>res/values/strings.xml</code> should  use the
default language, which is the language that you expect most of your application's users to
speak.  </p>

<p>The default resource set must also include any default drawables and layouts, 
	and can include other types of resources such as animations. 
<br>
  <code>&nbsp;&nbsp;&nbsp;&nbsp;res/drawable/</code>(required directory holding at least
  one graphic file, for the application's icon on Google Play)<br>
  <code>&nbsp;&nbsp;&nbsp;&nbsp;res/layout/</code> (required directory holding an XML
  file that defines the default layout)<br>
  <code>&nbsp;&nbsp;&nbsp;&nbsp;res/anim/</code> (required if you have any 
  <code>res/anim-<em>&lt;qualifiers&gt;</em></code> folders)<br>
  <code>&nbsp;&nbsp;&nbsp;&nbsp;res/xml/</code> (required if you have any 
  <code>res/xml-<em>&lt;qualifiers&gt;</em></code> folders)<br>
  <code>&nbsp;&nbsp;&nbsp;&nbsp;res/raw/</code> (required if you have any 
  <code>res/raw-<em>&lt;qualifiers&gt;</em></code> folders)
</p>

<p class="note"><strong>Tip:</strong> In your code, examine each reference to 
	an Android resource. Make sure that a default resource is defined for each
	one. Also make sure that the default string file is complete: A <em>
	localized</em> string file can contain a subset of the strings, but the 
	<em>default</em> string file must contain them all. 
</p>

<h3 id="creating-alternatives">How to Create Alternative Resources</h3>

<p>A large part of localizing an application is providing alternative text for
different languages. In some cases you will also provide alternative graphics,
sounds, layouts, and other locale-specific resources. </p>

<p>An application can specify many <code>res/<em>&lt;qualifiers&gt;</em>/</code>
directories, each with different qualifiers. To create an alternative resource for
a different locale, you use a qualifier that specifies a language or a 
language-region combination. (The name of a resource directory must conform 
to the naming scheme described in 
<a href="{@docRoot}guide/topics/resources/providing-resources.html#AlternativeResources">Providing
Alternative Resources</a>,
or else it will not compile.)</p>

<p><em>Example:</em></p>

<p>Suppose that your application's default language is English. Suppose also
that you want to localize all the text in your application to French, and most
of the text in your application (everything except the application's title) to
Japanese. In this case, you could create three alternative <code>strings.xml</code>
files, each stored in a locale-specific resource directory:</p>

<ol>
  <li><code>res/values/strings.xml</code><br>
    Contains  English text for all  the strings that the application uses,
including text for a string named <code>title</code>.</li>
  <li><code>res/values-fr/strings.xml</code><br>
    Contain French text for all  the strings, including <code>title</code>.</li>
  <li><code>res/values-ja/strings.xml</code><br>
    Contain Japanese text for all  the strings <em>except</em>
<code>title</code>.<br>
  <code></code></li>
</ol>

<p>If your Java code refers to <code>R.string.title</code>,  here is what will
happen at runtime:</p>

<ul>
  <li>If the device is set to any language other than French, Android will load
<code>title</code> from the <code>res/values/strings.xml</code> file.</li>
  <li>If the device is set to French, Android will load <code>title</code> from
the <code>res/values-fr/strings.xml</code> file.</li>
</ul>

<p>Notice that if the device is set to Japanese, Android will look for
<code>title</code> in the <code>res/values-ja/strings.xml</code> file. But
because no such string is included in that file, Android will fall back to the
default, and will load  <code>title</code> in English from the
<code>res/values/strings.xml</code> file.  </p>

<h3 id="resource-precedence">Which Resources Take Precedence?</h3>

<p> If multiple resource files match a device's configuration, Android follows a
set of rules in deciding which file to use. Among the qualifiers that can be
specified in a resource directory name, <strong>locale almost always takes
precedence</strong>. </p>
<p><em>Example:</em></p>

<p>Assume that an application  includes a default set of graphics and two other
sets of graphics, each optimized for a different device setup:</p>

<ul>
  <li><code>res/drawable/</code><br>
    Contains
  default graphics.</li>
  <li><code>res/drawable-small-land-stylus/</code><br>
  Contains  graphics optimized for use with a device that expects input from a 
  stylus and has a QVGA low-density screen in landscape orientation.</li>
  <li><code>res/drawable-ja/</code> <br>
  Contains  graphics optimized for use with Japanese.</li>
</ul>

<p>If the application runs on a device that is configured to use Japanese,
Android will load graphics from  <code>res/drawable-ja/</code>, even if the
device happens to be one that expects input from a stylus and has a QVGA 
low-density screen in landscape orientation.</p>

<p class="note"><strong>Exception:</strong> The only qualifiers that take
precedence over locale in the selection process are MCC and MNC (mobile country
code and mobile network code). </p>

<p><em>Example:</em></p>

<p>Assume that you have the following situation:</p>

<ul>
  <li>The application code calls for <code>R.string.text_a</code></li>
  <li>Two relevant resource files are available:
    <ul>
      <li><code>res/values-mcc404/strings.xml</code>, which includes
<code>text_a</code> in the application's default language, in this case
English.</li>
      <li><code>res/values-hi/strings.xml</code>, which includes
<code>text_a</code> in Hindi.</li>
    </ul>
  </li>
  <li>The application is running on a device that has the following
configuration:
    <ul>
      <li>The SIM card is connected to a mobile network in India (MCC 404).</li>
      <li>The language is set to Hindi (<code>hi</code>).</li>
    </ul>
  </li>
</ul>

<p>Android will load <code>text_a</code> from
<code>res/values-mcc404/strings.xml</code> (in English), even if the device is
configured for Hindi. That is because in the resource-selection process, Android
will prefer an MCC match over a language match. </p>

<p>The selection process is not always as straightforward as these examples
suggest. Please read  <a
href="{@docRoot}guide/topics/resources/providing-resources.html#BestMatch">How Android Finds
the Best-matching Resource</a> for a more nuanced description of the
process. All the qualifiers are described and listed in order of
precedence in <a
href="{@docRoot}guide/topics/resources/providing-resources.html#table2">Table 2 of Providing
Alternative Resources</a>.</p>

<h3 id="referring-to-resources">Referring to Resources in Java</h3>

<p>In your application's Java code, you refer to  resources using the syntax
<code>R.<em>resource_type</em>.<em>resource_name</em></code> or
<code>android.R.<em>resource_type</em>.<em>resource_name</em></code><em>.</em>
For more about this, see <a
href="{@docRoot}guide/topics/resources/accessing-resources.html">Accessing Resources</a>.</p>

<h2 id="strategies">Localization Strategies</h2>

<h4 id="failing2">Design your application  to work in any locale</h4>

<p>You cannot assume anything about the device on which a user will
run your application. The device might have hardware that you were not
anticipating, or it might be set to a locale that you did not plan for or that 
you cannot test. Design your application so that it will function normally or fail gracefully no 
matter what device it runs on.</p>

<p class="note"><strong>Important:</strong> Make sure that your application
includes a full set of default resources.</p> <p>Make sure to include
<code>res/drawable/</code> and a <code>res/values/</code> folders (without any
additional modifiers in the folder names) that contain all the images and text
that your application will need. </p>

<p>If an application is missing even one default resource, it will not run on a 
	device that is set to an unsupported locale. For example, the 
	<code>res/values/strings.xml</code> default file might lack one string that 
	the application needs: When the application runs in an unsupported locale and 
	attempts to load <code>res/values/strings.xml</code>, the user will see an 
	error message and a Force Close button. An IDE such as Eclipse will not 
	highlight this kind of error, and you will not see the problem when you 
	test the application on a device or emulator that is set to a supported locale.</p>

<p>For more information, see <a href="#test-for-default">Testing for Default Resources</a>.</p>

<h4>Design a flexible layout</h4>

<p> If you need to rearrange your layout to fit a certain language (for example
German with its long words), you can create an alternative layout for that
language (for example <code>res/layout-de/main.xml</code>). However, doing this
can make your application harder to maintain.  It is better to create a single
layout that is more flexible.</p>

<p>Another typical situation is a language that requires something different in
its layout. For example, you might have a contact form that should include  two
name fields when the application runs in Japanese, but three name fields when
the application  runs in some other language. You could handle this in either of
two ways:</p>

<ul>
  <li>Create  one  layout with a field that you can programmatically enable or
disable, based on the language, or</li>
  <li>Have the main layout include another layout that  includes the changeable
field. The second layout can have different configurations for different
languages.</li>
</ul>

<h4>Avoid creating more resource files and text strings than you need</h4>

<p>You probably do not need to create a locale-specific
alternative for every resource in your application. For example, the layout
defined in the <code>res/layout/main.xml</code> file might work in any locale,
in which case there would be no need to create any alternative layout files.
</p>

<p>Also, you might not need to create alternative text for every
string. For example, assume the following:</p>

<ul>
  <li>Your application's default language is American
English. Every string that the application uses is defined, using American
English spellings, in <code>res/values/strings.xml</code>. </li>

  <li>For  a few important phrases, you want to provide
British English spelling. You want these alternative strings to be used when your
application runs on a device in the United Kingdom. </li>
</ul>

<p>To do this, you could create a small file called
<code>res/values-en-rGB/strings.xml</code> that includes only the strings that
should be different when the application  runs in the U.K. For all the rest of
the strings, the application will fall back to the defaults and use what is
defined in <code>res/values/strings.xml</code>.</p>

<h4>Use the Android Context object for manual locale lookup</h4>

<p>You can look up the locale using the {@link android.content.Context} object
that Android makes available:</p>

<pre>String locale = context.getResources().getConfiguration().locale.getDisplayName();</pre>

<h2 id="testing">Testing Localized Applications</h2>

<h3 id="device">Testing on a Device</h3>
<p>Keep in mind that the device you are testing may be significantly different from 
	the devices available to consumers in other geographies. The locales available 
	on your device may differ from those available on other devices. Also, the 
	resolution and density of the device screen may differ, which could affect 
	the display of strings and drawables in your UI.</p>

<p>To change the locale on a device, use  the Settings application  (Home &gt;
Menu &gt; Settings &gt; Locale &amp; text &gt; Select locale). </p>

<h3 id="emulator">Testing on an Emulator</h3>

<p>For details about using the emulator, see See <a
href="{@docRoot}tools/help/emulator.html">Android Emulator</a>.</p>
<h4>Creating and using a custom locale</h4>

<p>A &quot;custom&quot; locale is a language/region combination that the Android
system image does not explicitly support. (For a list of supported locales in
Android platforms see the Version Notes in the <a
href="{@docRoot}sdk/index.html">SDK</a> tab). You can test
how your application will run in a custom locale by creating a custom locale in
the emulator. There are two ways to do this:</p>

<ul>
  <li>Use the Custom Locale application, which is accessible from the
Application tab. (After you create a custom locale, switch to it by 
pressing and holding the locale name.)</li>
  <li>Change to a custom locale from the adb shell, as described below.</li>
</ul>

<p>When you set the emulator to a locale that is not available in the Android
system image, the system itself will display in its default language. Your
application, however, should localize properly.</p>

<h4>Changing the emulator locale from the adb shell</h4>

<p>To change the locale in the emulator by using the adb shell. </p>

<ol>
  <li>Pick the locale you want to test and determine its language and region codes, for
example <code>fr</code> for French and <code>CA</code> for Canada.<br>
  </li>
  <li>Launch an emulator.</li>
  <li>From a command-line shell on the host computer, run the following
command:<br>
    <code>adb shell</code><br>
  or if you have a device attached, specify that you want the emulator by adding
the <code>-e</code> option:<br>
  <code>adb -e shell</code></li>
  <li>At  the  adb shell prompt (<code>#</code>), run this command: <br>
    <code>setprop persist.sys.language  [<em>language code</em>];setprop
persist.sys.country [<em>country  code</em>];stop;sleep 5;start <br>
    </code>Replace bracketed sections with the  appropriate codes from Step
1.</li>
</ol>

<p>For instance, to test in Canadian French:</p>

<p><code>setprop persist.sys.language  fr;setprop persist.sys.country
CA;stop;sleep 5;start </code></p>

<p>This will cause the emulator  to restart. (It will look like a full reboot,
but it is not.) Once the Home screen appears again, re-launch your application (for
example, click the Run icon in Eclipse), and the application will launch with
the new locale. </p>

<h3 id="test-for-default">Testing for Default Resources</h3>
<p>Here's how to test whether an application includes every string resource that it needs:  </p>
<ol><li>Set the emulator or device to a language that your application does not 
	support. For example, if the application has French strings in 
	<code>res/values-fr/</code> but does not have any Spanish strings in 
	<code>res/values-es/</code>, then set the emulator's locale to Spanish. 
	(You can use the Custom Locale application to set the emulator to an 
	unsupported locale.)</li>
	<li>Run the application.</li>  
<li>If the application shows an error message and a Force Close button, it might 
	be looking for a string that is not available. Make sure that your 
	<code>res/values/strings.xml</code> file includes a definition for 
	every string that the application uses.</li>
</ol> 
</p> 

<p>If the test is successful, repeat it for other types of 
	configurations. For example, if the application has a layout file called 
	<code>res/layout-land/main.xml</code> but does not contain a file called 
	<code>res/layout-port/main.xml</code>, then set the emulator or device to 
	portrait orientation and see if the application will run. 


<h2 id="checklist">Localization Checklist</h2>

<p>For an overview of the process of localizing an Android application, see the <a href="{@docRoot}distribute/googleplay/publish/localizing.html">Localization Checklist</a>.</p>