<h2>In this document</h2>
<ol>
- <li><a href="#ResourcesInCode">Accessing Resources in Code</a></li>
- <li><a href="#ReferencesToResources">Accessing Resources in Other XML Resources</a>
+ <li><a href="#ResourcesFromCode">Accessing Resources from Code</a></li>
+ <li><a href="#ResourcesFromXml">Accessing Resources from XML</a>
<ol>
<li><a href="#ReferencesToThemeAttributes">Referencing style attributes</a></li>
</ol>
</li>
+ <li><a href="#PlatformResources">Accessing Platform Resources</a></li>
</ol>
<h2>See also</h2>
</div>
-<p>There are two ways you can reference your resources for use in your application:</p>
+
+
+<p>Once you provide a resource in your application (discussed in <a
+href="providing-resources.html">Providing Resources</a>), you can apply it by
+referencing its resource ID. All resource IDs are defined in your project's {@code R} class, which
+the {@code aapt} tool automatically generates.</p>
+
+<p>When your application is compiled, {@code aapt} generates the {@code R} class, which contains
+resource IDs for all the resources in your {@code
+res/} directory. For each type of resource, there is an {@code R} subclass (for example,
+{@code R.drawable} for all drawable resources) and for each resource of that type, there is a static
+integer (for example, {@code R.drawable.icon}). This integer is the resource ID that you can use
+to retrieve your resource.</p>
+
+<p>Although the {@code R} class is where resource IDs are specified, you should never need to
+look there to discover a resource ID. A resource ID is always composed of:</p>
+<ul>
+ <li>The <em>resource type</em>: Each resource is grouped into a "type," such as {@code
+string}, {@code drawable}, and {@code layout}. For more about the different types, see <a
+href="available-resources.html">Resource Types</a>.
+ </li>
+ <li>The <em>resource name</em>, which is either: the filename,
+excluding the extension; or the value in the XML {@code android:name} attribute, if the
+resource is a simple value (such as a string).</li>
+</ul>
+
+<p>There are two ways you can access a resource:</p>
<ul>
- <li><strong>From your code:</strong> Using an integer from a sub-class in your {@code R} class,
-such as:
- <p>{@code R.string.hello}</p>
- <p>You will see Android APIs that accept this kind of resource identifier as a method parameter
-(usually defined as the {@code id} parameter).</p>
+ <li><strong>In code:</strong> Using an static integer from a sub-class of your {@code R}
+class, such as:
+ <pre class="classic no-pretty-print">R.string.hello</pre>
+ <p>{@code string} is the resource type and {@code hello} is the resource name. There are many
+Android APIs that can access your resources when you provide a resource ID in this format. See
+<a href="#ResourcesFromCode">Accessing Resources in Code</a>.</p>
</li>
- <li><strong>From another resource:</strong> Using a special XML syntax that corresponds to the
-{@code R} sub-class, such as:
- <p>{@code @string/hello}</p>
- <p>You can use this syntax in an XML resource any place where a value is expected that is
-matched by the existing resource. For example, if you need to provide a string in either an XML
-attribute or element value, you can reference a resource instead of providing a hard-coded
-string.</p>
+ <li><strong>In XML:</strong> Using a special XML syntax that also corresponds to
+the resource ID defined in your {@code R} class, such as:
+ <pre class="classic no-pretty-print">@string/hello</pre>
+ <p>{@code string} is the resource type and {@code hello} is the resource name. You can use this
+syntax in an XML resource any place where a value is expected that you provide in a resource. See <a
+href="#ResourcesFromXml">Accessing Resources from XML</a>.</p>
</li>
</ul>
-<h2 id="ResourcesInCode">Accessing Resources in Code </h2>
+<h2 id="ResourcesFromCode">Accessing Resources in Code </h2>
-<p>When your application is compiled, Android generates the {@code R.java} file (inside
-the {@code gen/} directory), which contains resource
-identifiers to all the resources in your {@code res/} directory. For each type of resource, a
-specific subclass is added to the {@code R} class (for example,
-{@code R.drawable}) and for each resource of that type, a static
-integer is added to the subclass (for example,
-{@code R.drawable.icon}). This integer is the resource ID and you can use it to retrieve
-your resource from your application code.</p>
+<p>You can use a resource in code by passing the resource ID as a method parameter. For
+example, you can set an {@link android.widget.ImageView} to use the {@code res/drawable/myimage.png}
+resource using {@link android.widget.ImageView#setImageResource(int) setImageResource()}:</p>
+<pre>
+ImageView imageView = (ImageView) findViewById(R.id.myimageview);
+imageView.setImageResource(<strong>R.drawable.myimage</strong>);
+</pre>
+<p>You can also retrieve individual resources using methods in {@link
+android.content.res.Resources}, which you can get an instance of
+with {@link android.content.Context#getResources()}.</p>
<div class="sidebox-wrapper">
<div class="sidebox">
<h2>Access to Original Files</h2>
<p>While uncommon, you might need access your original files and directories. If you do, then
-saving your files in {@code res/} won't work for you. Instead, you can save your resources in the
+saving your files in {@code res/} won't work for you, because the only way to read a resource from
+{@code res/} is with the resource ID. Instead, you can save your resources in the
{@code assets/} directory.</p>
-<p>Files saved in the {@code assets/} directory will <em>not</em> be given a resource
+<p>Files saved in the {@code assets/} directory are <em>not</em> given a resource
ID, so you can't reference them through the {@code R} class or from XML resources. Instead, you can
query files in the {@code assets/} directory like a normal file system and read raw data using
{@link android.content.res.AssetManager}.</p>
<p>However, if all you require is the ability to read raw data (such as a video or audio file),
then save the file in the {@code res/raw/} directory and read a stream of bytes using {@link
-android.content.res.Resources#openRawResource(int)}.</p>
+android.content.res.Resources#openRawResource(int) openRawResource()}.</p>
</div>
</div>
-<p class="caution"><strong>Caution:</strong> You should never modify the {@code
-R.java} file by hand—it is generated by the {@code aapt} tool when your project is
-compiled. Any changes will be overridden next time you compile.</p>
+<h3>Syntax</h3>
-<p>Here is the syntax to reference a resource in code:</p>
-<p>
-<code>[<em><package_name></em>.]R.<em><resource_type></em>.<em><resource_name></em></code>
-</p>
+<p>Here's the syntax to reference a resource in code:</p>
+
+<pre class="classic no-pretty-print">
+[<em><package_name></em>.]R.<em><resource_type></em>.<em><resource_name></em>
+</pre>
<ul>
<li><em>{@code <package_name>}</em> is the name of the package in which the resource is located (not
required when referencing resources from your own package).</li>
<li><em>{@code <resource_type>}</em> is the {@code R} subclass for the resource type.</li>
- <li><em>{@code <resource_name>}</em> is either the {@code
-android:name} attribute value (for some resources defined in XML files) or the resource filename
-without the extension.</li>
+ <li><em>{@code <resource_name>}</em> is either the resource filename
+without the extension or the {@code android:name} attribute value in the XML element (for simple
+values).</li>
</ul>
<p>See <a href="resource-types.html">Resource Types</a> for
more information about each resource type and how to reference them.</p>
-<p>In many cases, you can supply an API method with the resource ID. For example, to set the image
-for an {@link android.widget.ImageView}:</p>
-<pre>
-ImageView iv = (ImageView) findViewById(R.id.myimageview);
-iv.setImageResource(R.drawable.myimage);
-</pre>
-<p>You can also retrieve your
-resource objects using methods in {@link android.content.res.Resources}, which you can create an
-instance of with {@link android.content.Context#getResources Context.getResources()}. For example,
-to get a string:</p>
-<pre>
-Resources res = this.getResources();
-String string = res.getString(R.string.mystring);
-</pre>
+<h3>Use cases</h3>
-<p>You can also access resources from the platform by prefixing the {@code android}
-namespace. Android contains a number of standard resources, such as styles and themes for your
-layout, button backgrounds, and layouts. To refer to these in code, qualify your reference with the
-<code>android</code> package name. For example,
-<code>android.R.layout.simple_gallery_item</code>.</p>
+<p>There are many methods that accept a resource ID parameter and you can retrieve resources using
+methods in {@link android.content.res.Resources}. You can get an instance of {@link
+android.content.res.Resources} with {@link android.content.Context#getResources
+Context.getResources()}.</p>
-<p>Here are some examples of using resources in code:</p>
+
+<p>Here are some examples of accessing resources in code:</p>
<pre>
// Load a background for the current screen from a drawable resource
{@link android.app.Activity#getWindow()}.{@link
android.view.Window#setBackgroundDrawableResource(int)
-setBackgroundDrawableResource}(R.drawable.my_background_image) ;
+setBackgroundDrawableResource}(<strong>R.drawable.my_background_image</strong>) ;
// Set the Activity title by getting a string from the Resources object, because
// this method requires a CharSequence rather than a resource ID
{@link android.app.Activity#getWindow()}.{@link android.view.Window#setTitle(CharSequence)
setTitle}(getResources().{@link android.content.res.Resources#getText(int)
-getText}(R.string.main_title));
+getText}(<strong>R.string.main_title</strong>));
// Load a custom layout for the current screen
{@link android.app.Activity#setContentView(int)
-setContentView}(R.layout.main_screen);
+setContentView}(<strong>R.layout.main_screen</strong>);
// Set a slide in animation by getting an Animation from the Resources object
mFlipper.{@link android.widget.ViewAnimator#setInAnimation(Animation)
setInAnimation}(AnimationUtils.loadAnimation(this,
- R.anim.hyperspace_in));
+ <strong>R.anim.hyperspace_in</strong>));
// Set the text on a TextView object using a resource ID
-TextView msgTextView = (TextView) findViewById(R.id.msg);
-msgTextView.{@link android.widget.TextView#setText(int) setText}(R.string.hello_message);
+TextView msgTextView = (TextView) findViewById(<strong>R.id.msg</strong>);
+msgTextView.{@link android.widget.TextView#setText(int)
+setText}(<strong>R.string.hello_message</strong>);
</pre>
+<p class="caution"><strong>Caution:</strong> You should never modify the {@code
+R.java} file by hand—it is generated by the {@code aapt} tool when your project is
+compiled. Any changes are overridden next time you compile.</p>
+
+
+<h2 id="ResourcesFromXml">Accessing Resources from XML</h2>
+<p>You can define values for some XML attributes and elements using a
+reference to an existing resource. You will often do this when creating layout files, to
+supply strings and images for your widgets.</p>
+<p>For example, if you add a {@link android.widget.Button} to your layout, you should use
+a <a href="string-resource.html">string resource</a> for the button text:</p>
+
+<pre>
+<Button
+ android:layout_width="fill_parent"
+ android:layout_height="wrap_content"
+ android:text="<strong>@string/submit</strong>" />
+</pre>
-<h2 id="ReferencesToResources">Accessing Resources in other XML Resources</h2>
-<p>When creating an XML resource, some values for attributes and elements can be a reference to
-an existing resource. This is often used in layout files to supply strings and images.</p>
+<h3>Syntax</h3>
<p>Here is the syntax to reference a resource in an XML resource:</p>
-<p><code>@[<em><package_name></em>:]<em><resource_type></em>/<em><resource_name></em></code></p>
+
+<pre class="classic no-pretty-print">
+@[<em><package_name></em>:]<em><resource_type></em>/<em><resource_name></em>
+</pre>
<ul>
<li>{@code <package_name>} is the name of the package in which the resource is located (not
required when referencing resources from the same package)</li>
<li>{@code <resource_type>} is the
{@code R} subclass for the resource type</li>
- <li>{@code <resource_name>} is either the {@code
-android:name} attribute value (for some resources defined in XML files) or the resource filename
-without the extension</li>
+ <li>{@code <resource_name>} is either the resource filename
+without the extension or the {@code android:name} attribute value in the XML element (for simple
+values).</li>
</ul>
<p>See <a href="resource-types.html">Resource Types</a> for
more information about each resource type and how to reference them.</p>
-<p>For example, if you have the following resource file that includes a <a
+
+<h3>Use cases</h3>
+
+<p>In some cases you must use a resource for a value in XML (for example, to apply a drawable image
+to a widget), but you can also use a resource in XML any place that accepts a simple value. For
+example, if you have the following resource file that includes a <a
href="more-resources.html#Color">color resource</a> and a <a
href="string-resource.html">string resource</a>:</p>
<EditText xmlns:android="http://schemas.android.com/apk/res/android"
android:layout_width="fill_parent"
android:layout_height="fill_parent"
- <strong>android:textColor="@color/opaque_red"
- android:text="@string/hello"</strong> />
+ android:textColor="<strong>@color/opaque_red</strong>"
+ android:text="<strong>@string/hello</strong>" />
</pre>
<p>In this case you don't need to specify the package name in the resource reference because the
<EditText xmlns:android="http://schemas.android.com/apk/res/android"
android:layout_width="fill_parent"
android:layout_height="fill_parent"
- <strong>android:textColor="@android:color/secondary_text_dark"</strong>
+ android:textColor="<strong>@android:color/secondary_text_dark</strong>"
android:text="@string/hello" />
</pre>
-<p class="note"><strong>Note:</strong> You should always use a string resource when supplying
-strings in a layout file, as demonstrated above, so that the strings can be localized. For
-
information about creating alternative resources (such as localized strings), see <a
+<p class="note"><strong>Note:</strong> You should use string resources at all times, so that your
+application can be localized for other languages. For information about creating alternative
+resources (such as localized strings), see <a
href="providing-resources.html#AlternativeResources">Providing Alternative
Resources</a>.</p>
-<p>This facility for referencing resources between resources can also be used to create
-alias resources. For example, you can create new drawable resources that is an alias for an existing
-image:</p>
+<p>You can even use resources in XML to create aliases. For example, you can create a
+drawable resource that is an alias for another drawable resource:</p>
<pre>
<?xml version="1.0" encoding="utf-8"?>
android:src="@drawable/other_drawable" />
</pre>
-<p>This is discussed further in <a href="providing-resources.html#AliasResources">Creating
-alias resources</a>.</p>
-
+<p>This sounds redundant, but can be very useful when using alternative resource. Read more about
+<a href="providing-resources.html#AliasResources">Creating alias resources</a>.</p>
<h3 id="ReferencesToThemeAttributes">Referencing style attributes</h3>
-<p>A style attribute resource is another type of resource that allows you to reference the value
+<p>A style attribute resource allows you to reference the value
of an attribute in the currently-applied theme. Referencing a style attribute allows you to
customize the look of UI elements by styling them to match standard variations supplied by the
current theme, instead of supplying a hard-coded value. Referencing a style attribute
format, but instead of the at-symbol ({@code @}), use a question-mark ({@code ?}), and the
resource type portion is optional. For instance:</p>
-<p>
-<code>
+<pre class="classic">
?[<em><package_name></em>:][<em><resource_type></em>/]<em><resource_name></em>
-</code>
-</p>
+</pre>
-<p>For example, here's how you might reference an attribute in a layout,
-to set the text color to match the "primary" text color of the system theme:</p>
+<p>For example, here's how you can reference an attribute to set the text color to match the
+"primary" text color of the system theme:</p>
<pre>
<EditText id="text"
android:layout_width="fill_parent"
android:layout_height="wrap_content"
- <strong>android:textColor="?android:textColorSecondary"</strong>
+ android:textColor="<strong>?android:textColorSecondary</strong>"
android:text="@string/hello_world" />
</pre>
-<p>Using this markup, you are
-supplying the name of an attribute resource that will be looked up in the theme.
-Because the system resource tool knows that an attribute resource is expected,
+<p>Here, the {@code android:textColor} attribute specifies the name of a style attribute
+in the current theme. Android now uses the value applied to the {@code android:textColorSecondary}
+style attribute as the value for {@code android:textColor} in this widget. Because the system
+resource tool knows that an attribute resource is expected in this context,
you do not need to explicitly state the type (which would be
-<code>?android:attr/textColorSecondary</code>), so you can exclude the {@code attr} type.</p>
+<code>?android:attr/textColorSecondary</code>)—you can exclude the {@code attr} type.</p>
+
+
+
+<h2 id="PlatformResources">Accessing Platform Resources</h2>
+
+<p>Android contains a number of standard resources, such as styles, themes, and layouts. To
+access these resource, qualify your resource reference with the
+<code>android</code> package name. For example, Android provides a layout resource you can use for
+list items in a {@link android.widget.ListAdapter}:</p>
+
+<pre>
+{@link android.app.ListActivity#setListAdapter(ListAdapter)
+setListAdapter}(new {@link
+android.widget.ArrayAdapter}<String>(this, <strong>android.R.layout.simple_list_item_1</strong>, myarray));
+</pre>
+<p>In this example, {@link android.R.layout#simple_list_item_1} is a layout resource defined by the
+platform for items in a {@link android.widget.ListView}. You can use this instead of creating
+your own layout for list items. (For more about using {@link android.widget.ListView}, see the
+<a href="{@docRoot}resources/tutorials/views/hello-listview.html">List View Tutorial</a>.)</p>
android:toXScale="<em>float</em>"
android:fromYScale="<em>float</em>"
android:toYScale="<em>float</em>"
- android:pivotX="<em>string</em>"
- android:pivotY="<em>string</em>" />
+ android:pivotX="<em>float</em>"
+ android:pivotY="<em>float</em>" />
<<a href="#translate-element">translate</a>
- android:fromX="<em>string</em>"
- android:toX="<em>string</em>"
- android:fromY="<em>string</em>"
- android:toY="<em>string</em>" />
+ android:fromX="<em>float</em>"
+ android:toX="<em>float</em>"
+ android:fromY="<em>float</em>"
+ android:toY="<em>float</em>" />
<<a href="#rotate-element">rotate</a>
android:fromDegrees="<em>float</em>"
android:toDegrees="<em>float</em>"
- android:pivotX="<em>string</em>"
- android:pivotY="<em>string</em>" />
+ android:pivotX="<em>float</em>"
+ android:pivotY="<em>float</em>" />
<<a href="#set-element">set</a>>
...
</set>
<p class="caps">attributes:</p>
<dl class="atn-list">
<dt><code>android:fromXDelta</code></dt>
- <dd><em>Float or percentage</em>. Starting X offset. Either in: pixels relative to the
-normal position, in percentage relative to the element width (%), or relative to the parent width
-(%p).</dd>
+ <dd><em>Float or percentage</em>. Starting X offset. Expressed either: in pixels relative
+to the normal position (such as {@code "5"}), in percentage relative to the element width (such as
+{@code "5%"}), or in percentage relative to the parent width (such as {@code "5%p"}).</dd>
<dt><code>android:toXDelta</code></dt>
- <dd><em>Float or percentage</em>. Ending X offset. Either in: pixels relative to the
-normal position, in percentage relative to the element width (%), or relative to the parent width
-(%p).</dd>
+ <dd><em>Float or percentage</em>. Ending X offset. Expressed either: in pixels relative
+to the normal position (such as {@code "5"}), in percentage relative to the element width (such as
+{@code "5%"}), or in percentage relative to the parent width (such as {@code "5%p"}).</dd>
<dt><code>android:fromYDelta</code></dt>
- <dd><em>Float or percentage</em>. Starting Y offset. Either in: pixels relative to the
-normal position, in percentage relative to the element height (%), or relative to the parent height
-(%p).</dd>
+ <dd><em>Float or percentage</em>. Starting Y offset. Expressed either: in pixels relative
+to the normal position (such as {@code "5"}), in percentage relative to the element height (such as
+{@code "5%"}), or in percentage relative to the parent height (such as {@code "5%p"}).</dd>
<dt><code>android:toYDelta</code></dt>
- <dd><em>Float or percentage</em>. Ending Y offset. Either in: pixels relative to the
-normal position, in percentage relative to the element height (%), or relative to the parent height
-(%p).</dd>
+ <dd><em>Float or percentage</em>. Ending Y offset. Expressed either: in pixels relative
+to the normal position (such as {@code "5"}), in percentage relative to the element height (such as
+{@code "5%"}), or in percentage relative to the parent height (such as {@code "5%p"}).</dd>
</dl>
<p>For more attributes supported by <code><translate></code>, see the
{@link android.view.animation.Animation} class reference (of which, all XML attributes are
<p class="caps">attributes:</p>
<dl class="atn-list">
<dt><code>android:fromDegrees</code></dt>
- <dd><em>Integer</em>. Starting angular position, in degrees.</dd>
+ <dd><em>Float</em>. Starting angular position, in degrees.</dd>
<dt><code>android:toDegrees</code></dt>
- <dd><em>Integer</em>. Ending angular position, in degrees.</dd>
+ <dd><em>Float</em>. Ending angular position, in degrees.</dd>
<dt><code>android:pivotX</code></dt>
- <dd><em>Integer or percentage</em>. The X coordinate of the center of rotation, in total
-pixels (where 0 is the left edge) or percentage of the screen width.</dd>
+ <dd><em>Float or percentage</em>. The X coordinate of the center of rotation. Expressed
+either: in pixels relative to the object's left edge (such as {@code "5"}), in percentage relative
+to the object's left edge (such as {@code "5%"}), or in percentage relative to the parent
+container's left edge (such as {@code "5%p"}).</dd>
<dt><code>android:pivotY</code></dt>
- <dd><em>Integer or percentage</em>. The Y coordinate of the center of rotation, in total
-pixels (where 0 is the top edge) or percentage of the screen height.</dd>
+ <dd><em>Float or percentage</em>. The Y coordinate of the center of rotation. Expressed
+either: in pixels relative to the object's top edge (such as {@code "5"}), in percentage relative
+to the object's top edge (such as {@code "5%"}), or in percentage relative to the parent
+container's top edge (such as {@code "5%p"}).</dd>
</dl>
<p>For more attributes supported by <code><rotate></code>, see the
{@link android.view.animation.Animation} class reference (of which, all XML attributes are
<p>Here's a brief summary of each resource type:</p>
+<div class="sidebox-wrapper">
+<div class="sidebox">
+<h2>{@code R.id} Is Not a Resource</h2>
+
+<p>You will often use an {@code R.id} integer to handle {@link android.view.View} objects in
+your UI. Although the {@code id} is a subclass of the {@code R} class, it is not considered a
+"resource" because it is not a reference to an externalized application resource. The {@code id}
+is simply a unique identifier that allows you to handle elements in your UI by instantiating
+objects with {@link android.app.Activity#findViewById(int) findViewById()}.</p>
+
+<p>For information about using {@code R.id} with your UI, see <a
+href="{@docRoot}guide/topics/ui/declaring-layout.html#attributes">Declaring Layout</a>.</p>
+
+</div>
+</div>
+
+
<dl>
<dt><a href="{@docRoot}guide/topics/resources/animation-resource.html">Animation Resources</a></dt>
<dd>Define pre-determined animations.<br/>
android:centerX="<em>integer</em>"
android:centerY="<em>integer</em>"
android:centerColor="<em>integer</em>"
+ android:endColor="<em>color</em>"
android:gradientRadius="<em>integer</em>"
- android:type=""
- android:usesLevel=""
android:startColor="<em>color</em>"
- android:endColor="<em>color</em>" />
+ android:type=["linear" | "radial" | "sweep"]
+ android:usesLevel=["true" | "false"] />
<<a href="#solid-element">solid</a>
android:color="<em>color</em>" />
<<a href="#stroke-element">stroke</a>
<dd>Specifies a gradient color for the shape.
<p class="caps">attributes:</p>
<dl class="atn-list">
- <dt><code>android:type</code></dt>
- <dd><em>Keyword</em>. The type of gradient pattern to apply. Valid values are:
- <table>
- <tr><th>Value</th><th>Description</th></tr>
- <tr><td>{@code "linear"}</td>
- <td>A linear gradient. This is the default.</td></tr>
- <tr><td>{@code "radial"}</td>
- <td>A radial gradient. The start color is the center color.</td></tr>
- <tr><td>{@code "sweep"}</td>
- <td>A sweeping line gradient. </td></tr>
- </table>
- </dd>
<dt><code>android:angle</code></dt>
<dd><em>Integer</em>. The angle for the gradient, in degrees. 0 is left to right, 90 is
bottom to top. It must be a multiple of 45. Default is 0.</dd>
<dt><code>android:centerColor</code></dt>
<dd><em>Color</em>. Optional color that comes between the start and end colors, as a
hexadecimal value or <a href="more-resources.html#Color">color resource</a>.</dd>
+ <dt><code>android:endColor</code></dt>
+ <dd><em>Color</em>. The ending color, as a hexadecimal
+value or <a href="more-resources.html#Color">color resource</a>.</dd>
<dt><code>android:gradientRadius</code></dt>
<dd><em>Float</em>. The radius for the gradient. Only applied when {@code
android:type="radial"}.</dd>
- <dt><code>android:useLevel</code></dt>
- <dd><em>Boolean</em>. "true" if this is used as a {@link
-android.graphics.drawable.LevelListDrawable}.</dd>
<dt><code>android:startColor</code></dt>
<dd><em>Color</em>. The starting color, as a hexadecimal
value or <a href="more-resources.html#Color">color resource</a>.</dd>
- <dt><code>android:endColor</code></dt>
- <dd><em>Color</em>. The ending color, as a hexadecimal
-value or <a href="more-resources.html#Color">color resource</a>.</dd>
+ <dt><code>android:type</code></dt>
+ <dd><em>Keyword</em>. The type of gradient pattern to apply. Valid values are:
+ <table>
+ <tr><th>Value</th><th>Description</th></tr>
+ <tr><td>{@code "linear"}</td>
+ <td>A linear gradient. This is the default.</td></tr>
+ <tr><td>{@code "radial"}</td>
+ <td>A radial gradient. The start color is the center color.</td></tr>
+ <tr><td>{@code "sweep"}</td>
+ <td>A sweeping line gradient. </td></tr>
+ </table>
+ </dd>
+ <dt><code>android:useLevel</code></dt>
+ <dd><em>Boolean</em>. "true" if this is used as a {@link
+android.graphics.drawable.LevelListDrawable}.</dd>
</dl>
</dd>
<dt id="solid-element"><code><solid></code></dt>
to provide this functionality, you must organize resources in your project's {@code res/}
directory, using various sub-directories that group resources by type and configuration.</p>
-<div class="figure" style="width:441px">
+<div class="figure" style="width:421px">
<img src="{@docRoot}images/resources/resource_devices_diagram1.png" height="137" alt="" />
<p class="img-caption">
<strong>Figure 1.</strong> Two device configurations, both using default
resources.</p>
</div>
-<div class="figure" style="width:441px">
+<div class="figure" style="width:421px">
<img src="{@docRoot}images/resources/resource_devices_diagram2.png" height="137" alt="" />
<p class="img-caption">
<strong>Figure 2.</strong> Two device configurations, one using alternative
<?xml version="1.0" encoding="utf-8"?>
<<a href="#viewgroup-element"><em>ViewGroup</em></a> xmlns:android="http://schemas.android.com/apk/res/android"
android:id="@+id/<em>name</em>"
- android:layout_height="@+id/<em>string_name</em>"
- android:layout_width="@+id/<em>string_name</em>"
- [<em>other attributes</em>] >
+ android:layout_height=["<em>dimension</em>" | "fill_parent" | "wrap_content"]
+ android:layout_width=["<em>dimension</em>" | "fill_parent" | "wrap_content"]
+ [<em>ViewGroup-specific attributes</em>] >
<<a href="#view-element"><em>View</em></a>
android:id="@+id/<em>name</em>"
- android:layout_height="@+id/<em>string_name</em>"
- android:layout_width="@+id/<em>string_name</em>"
- [<em>other attributes</em>] >
+ android:layout_height=["<em>dimension</em>" | "fill_parent" | "wrap_content"]
+ android:layout_width=["<em>dimension</em>" | "fill_parent" | "wrap_content"]
+ [<em>View-specific attributes</em>] >
<<a href="#requestfocus-element">requestFocus</a>/>
</<em>View</em>>
<<a href="#viewgroup-element"><em>ViewGroup</em></a> >
<pre>
<?xml version="1.0" encoding="utf-8"?>
<<a href="#menu-element">menu</a> xmlns:android="http://schemas.android.com/apk/res/android">
- <<a href="#item-element">item</a> android:id="<em>resource ID</em>"
+ <<a href="#item-element">item</a> android:id="@+id/<em>id_name</em>"
android:menuCategory=["container" | "system" | "secondary" | "alternative"]
android:orderInCategory="<em>integer</em>"
android:title="<em>string</em>"
android:titleCondensed="<em>string</em>"
- android:icon="<em>drawable resource</em>"
+ android:icon="@[package:]drawable/<em>drawable_resource_name</em>"
android:alphabeticShortcut="<em>string</em>"
android:numericShortcut="<em>string</em>"
android:checkable=["true" | "false"]
<dd>XML file saved at <code>res/menu/example_menu.xml</code>:
<pre>
<menu xmlns:android="http://schemas.android.com/apk/res/android">
- <item android:id="@+id/example_item"
- android:title="Example Item"
- android:icon="@drawable/example_item_icon" />
- <group android:id="@+id/example_group">
+ <item android:id="@+id/item1"
+ android:title="@string/item1"
+ android:icon="@drawable/group_item1_icon" />
+ <group android:id="@+id/group">
<item android:id="@+id/group_item1"
- android:title="Group Item 1"
- android:icon="@drawable/example_item1_icon" />
+ android:title="@string/group_item1"
+ android:icon="@drawable/group_item1_icon" />
<item android:id="@+id/group_item2"
- android:title="Group Item 2"
- android:icon="@drawable/example_item2_icon" />
+ android:title="G@string/group_item2"
+ android:icon="@drawable/group_item2_icon" />
</group>
<item android:id="@+id/submenu"
- android:title="Sub Menu" >
+ android:title="@string/submenu_title" >
<menu>
- <item android:id="@+id/submenu_item"
- android:title="Sub Menu Item" />
+ <item android:id="@+id/submenu_item1"
+ android:title="@string/submenu_item1" />
</menu>
</item>
</menu>
<div id="qv">
<h2>Quickview</h2>
<ul>
- <li>Different types of resources belong in different sub-directories of {@code res/}</li>
+ <li>Different types of resources belong in different subdirectories of {@code res/}</li>
<li>Alternative resources provide configuration-specific resource files</li>
</ul>
<h2>In this document</h2>
<ol>
+ <li><a href="#ResourceTypes">Grouping Resource Types</a></li>
<li><a href="#AlternativeResources">Providing Alternative Resources</a>
<ol>
+ <li><a href="#QualifierRules">Qualifier name rules</a></li>
<li><a href="#AliasResources">Creating alias resources</a></li>
</ol>
</li>
<ol>
<li><a href="accessing-resources.html">Accessing Resources</a></li>
<li><a href="available-resources.html">Resource Types</a></li>
+ <li><a href="{@docRoot}guide/practices/screens_support.html">Supporting Multiple
+Screens</a></li>
</ol>
</div>
</div>
-<p>There are several types of resource files you can
-include in your application and each type belongs in a specific sub-directory of your project's
-{@code res/} directory. Absolutely no files should be saved directly inside {@code res/}.</p>
+<p>You should always externalize application resources such as images and strings from your
+code, so that you can maintain them independently. You can also provide alternative resources for
+specific device configurations, by grouping them in specially-named resource directories. Android
+will then automatically apply the appropriate resource based on the current configuration. For
+instance, you might want to provide a different UI layout depending on the screen size.</p>
-<p>For example, here's the file hierarchy for a simple project:</p>
+<p>Once you save your resources external to your application code, you can access them
+using resource IDs that are generated in your project's {@code R} class. How to use
+resources in your application is discussed in <a href="accessing-resources.html">Accessing
+Resources</a>.</p>
-<pre class="no-pretty-print">
+
+<h2 id="ResourceTypes">Grouping Resource Types</h2>
+
+<p>You should place each type of resource in a specific subdirectory of your project's
+{@code res/} directory. For example, here's the file hierarchy for a simple project:</p>
+
+<pre class="classic no-pretty-print">
MyProject/
src/ <span style="color:black">
MyActivity.java </span>
drawable/ <span style="color:black">
icon.png </span>
layout/ <span style="color:black">
- main_layout.xml </span>
+ main.xml
+ info.xml</span>
values/ <span style="color:black">
strings.xml </span>
</pre>
-<p>This project includes an image resource, a layout resource, and string resource file.</p>
+<p>The {@code res/} directory contains all the resources (in subdirectories): an image resource, two
+layout resources, and a string resource file. The resource directory names are important and are
+described in table 1.</p>
-<p>Table 1 lists the different {@code res/} sub-directories supported
-and describes the types of resource files that belong in each one.</p>
-
-<p class="table-caption" id="table1"><strong>Table 1.</strong> Resource directories. Each directory
-belongs inside the project {@code res/} directory.</p>
+<p class="table-caption" id="table1"><strong>Table 1.</strong> Resource directories
+supported inside project {@code res/} directory.</p>
<table>
<tr>
<th scope="col">Directory</th>
- <th scope="col">Resource Types</th>
+ <th scope="col">Resource Type</th>
</tr>
<tr>
<tr>
<td><code>color/</code></td>
<td>XML files that define a state list of colors. See <a href="color-list-resource.html">Color
-State List Resources</a></td>
+State List Resource</a></td>
</tr>
<tr>
<td><code>drawable/</code></td>
<td><p>Bitmap files ({@code .png}, {@code .9.png}, {@code .jpg}, {@code .gif}) or XML files that
-are compiled into the following Drawable resource subtypes:</p>
+are compiled into the following drawable resource subtypes:</p>
<ul>
<li>Bitmap files</li>
<li>Nine-Patches (re-sizable bitmaps)</li>
system. To open these resources with a raw {@link java.io.InputStream}, call {@link
android.content.res.Resources#openRawResource(int)
Resources.openRawResource()} with the resource ID, which is {@code R.raw.<em>filename</em>}.</p>
- <p>However, if you require direct access to original file names and file hierarchy, instead of
-using a resource ID to access your files, you might consider saving some resources in the {@code
-assets/} directory, instead of {@code res/raw/}. You can query data in the {@code assets/} directory
-like an ordinary file system, search through the directory and read raw data using {@link
-android.content.res.AssetManager}.</p></td>
+ <p>However, if you need access to original file names and file hierarchy, you might consider
+saving some resources in the {@code
+assets/} directory (instead of {@code res/raw/}). Files in {@code assets/} are not given a
+resource ID, so you can read them only using {@link android.content.res.AssetManager}.</p></td>
</tr>
<tr>
<td><code>values/</code></td>
<td><p>XML files that contain simple values, such as strings, integers, and colors.</p>
- <p>Unlike the other {@code res/} subdirectories, this one
- can hold files that contain descriptions of more than one resource, rather than
-just one resource for the file. The XML element types of an XML file in {@code values/} control
-how these resources are defined in the {@code R} class. For example, a {@code <string>}
-element will create an
-{@code R.string} resource, and a {@code <color>} element will create an {@code R.color}
+ <p>Whereas XML resource files in other {@code res/} subdirectories define a single resource
+based on the XML filename, files in the {@code values/} directory describe multiple resources.
+For a file in this directory, each child of the {@code <resources>} element defines a single
+resource. For example, a {@code <string>} element creates an
+{@code R.string} resource and a {@code <color>} element creates an {@code R.color}
resource.</p>
- <p>While the name of a file in this directory is arbitrary and not related to the name given
-to a resource produced, you might want to separate different types of resources into different
-files for easier maintenance. Here are some filename conventions for some of the different types
-of resources you can save here:</p>
+ <p>Because each resource is defined with its own XML element, you can name the file
+whatever you want and place different resource types in one file. However, for clarity, you might
+want to place unique resource types in different files. For example, here are some filename
+conventions for resources you can create in this directory:</p>
<ul>
- <li>arrays.xml
to define resource arrays (<a
+ <li>arrays.xml
for resource arrays (<a
href="more-resources.html#TypedArray">typed arrays</a>).</li>
- <li>colors.xml
to define <a
href="more-resources.html#Color">color values</a></li>
- <li>dimens.xml
to define <a
href="more-resources.html#Dimension">dimension values</a>.</li>
- <li>strings.xml
to define <a href="string-resource.html">string
+ <li>strings.xml
for <a href="string-resource.html">string
values</a>.</li>
- <li>styles.xml
to define <a href="style-resource.html">styles</a>.</li>
+ <li>styles.xml
for <a href="style-resource.html">styles</a>.</li>
</ul>
<p>See <a href="string-resource.html">String Resources</a>,
<a href="style-resource.html">Style Resource</a>, and
<tr>
<td><code>xml/</code></td>
- <td>Arbitrary XML files that are compiled and can be read at runtime by calling {@link
+ <td>Arbitrary XML files that can be read at runtime by calling {@link
android.content.res.Resources#getXml(int) Resources.getXML()}. Various XML configuration files
-must
also be saved here, such as a <a
+must be saved here, such as a <a
href="{@docRoot}guide/topics/search/searchable-config.html">searchable configuration</a>.
<!-- or preferences configuration. --></td>
</tr>
</table>
+<p class="note"><strong>Note:</strong> You should never save resource files directly inside the
+{@code res/} directory.</p>
+
<p>For more information about certain types of resources, see the <a
href="available-resources.html">Resource Types</a> documentation.</p>
-
-
+<p>How to access resources in the {@code res/} subdirectories is discussed in <a
+href="accessing-resources.html">Accessing Resources</a>.
+</p>
<h2 id="AlternativeResources">Providing Alternative Resources</h2>
-<div class="figure" style="width:441px">
+<div class="figure" style="width:421px">
<img src="{@docRoot}images/resources/resource_devices_diagram2.png" height="137" alt="" />
<p class="img-caption">
<strong>Figure 1.</strong> Two device configurations, one using alternative resources.</p>
</div>
<p>Almost every application should provide alternative resources to support specific device
-configurations. For instance, you should include different drawable resources for different
-screen densities and different string resources for different languages. At runtime, Android
-will automatically detect the current device configuration and then load the appropriate
+configurations. For instance, you should include alternative drawable resources for different
+screen densities and alternative string resources for different languages. At runtime, Android
+automatically detects the current device configuration and loads the appropriate
resources.</p>
-<p>For each set of resources for which you want to provide configuration-specific alternatives:</p>
+<p>To specify configuration-specific alternatives for a set of resources:</p>
<ol>
<li>Create a new directory in {@code res/} named in the form {@code
<em><resources_name></em>-<em><config_qualifier></em>}.
<p>You can append more than one <em>{@code <config_qualifier>}</em>. Separate each
one with a dash.</p>
</li>
- <li>Save your alternative resources in this directory, named exactly the same as the default
-resource files.</li>
+ <li>Save your alternative resources in this new directory. The resource files must be named
+exactly the same as the default resource files.</li>
</ol>
<p>For example, here are some default and alternative resources:</p>
-<pre class="no-pretty-print">
+<pre class="classic no-pretty-print">
res/
drawable/ <span style="color:black">
icon.png
background.png </span>
</pre>
-<p>The {@code hdpi} qualifier indicates that the resources are for devices with a high-density
-screen. While the images in each directory are different, the filenames are
-identical. This way, the resource ID that you use to reference the {@code icon.png} image is
-always the same. When you request the {@code icon} drawable, Android will select the
+<p>The {@code hdpi} qualifier indicates that the resources in that directory are for devices with a
+high-density screen. While the images in each drawable directory are sized for a specific screen
+density, the filenames are
+the same. This way, the resource ID that you use to reference the {@code icon.png} or {@code
+background.png} image is always the same, but Android selects the
version of that drawable that best matches the current device configuration.</p>
<p>Android supports several configuration qualifiers and you can
-add multiple qualifiers to one directory name in order to further specify the configuration, by
-separating the qualifiers with dashes. Table 2 lists the valid configuration qualifiers, in order
-of precedence—they must be specified in the directory name in the order that they are listed
-in the table.</p>
+add multiple qualifiers to one directory name, by separating each qualifier with a dash. Table 2
+lists the valid configuration qualifiers, in order of precedence—if you use multiple
+qualifiers, they must be added to the directory name in the order they are listed in the
+table.</p>
<p class="table-caption" id="table2"><strong>Table 2.</strong> Alternative resource qualifier
names.</p>
-<table border="1">
+<table>
<tr>
<th>Qualifier</th>
<th>Values</th>
etc.
</td>
<td>
- <p>Specifies resources based on the mobile country code (MCC), optionally followed by mobile
-network code (MNC)
- from the SIM in the device. For example, <code>mcc310</code> is U.S. on any carrier,
+ <p>The mobile country code (MCC), optionally followed by mobile network code (MNC)
+ from the SIM card in the device. For example, <code>mcc310</code> is U.S. on any carrier,
<code>mcc310-mnc004</code> is U.S. on Verizon, and <code>mcc208-mnc00</code> is France on
Orange.</p>
- <p>If the device uses a radio connection (GSM phone), the MCC will come
- from the SIM, and the MNC will come from the network to which the
- device is attached.</p>
- <p>You might sometimes use the MCC alone, for example to include country-specific legal
-resources in your application, but if you only need to specify based on language, then use the
-language and region qualifier below. If you decide to use the MCC and MNC qualifier, you
-should do so with great care and completely test that it works as expected.</p></td>
+ <p>If the device uses a radio connection (GSM phone), the MCC comes
+ from the SIM, and the MNC comes from the network to which the
+ device is connected.</p>
+ <p>You can also use the MCC alone (for example, to include country-specific legal
+resources in your application). If you need to specify based on the language only, then use the
+<em>language and region</em> qualifier instead (discussed next). If you decide to use the MCC and
+MNC qualifier, you should do so with care and test that it works as expected.</p>
+ <p>Also see the configuration fields {@link
+android.content.res.Configuration#mcc}, and {@link
+android.content.res.Configuration#mnc}, which indicate the current mobile country code
+and mobile network code, respectively.</p>
+ </td>
</tr>
<tr>
<td>Language and region</td>
<code>fr-rCA</code><br/>
etc.
</td>
- <td><p>Th
is is defined by a two-letter <a
+ <td><p>Th
e language is defined by a two-letter <a
href="http://www.loc.gov/standards/iso639-2/php/code_list.php">ISO
639-1</a> language code, optionally followed by a two letter
<a
href="http://www.iso.org/iso/en/prods-services/iso3166ma/02iso-3166-code-lists/list-en1.html">ISO
- 3166-1-alpha-2</a> region code (preceded by lowercase "r").
+ 3166-1-alpha-2</a> region code (preceded by lowercase "{@code r}").
</p><p>
The codes are <em>not</em> case-sensitive; the {@code r} prefix is used to
distinguish the region portion.
You cannot specify a region alone.</p>
<p>This can change during the life
-of your application if the user changes
their language in the system settings. See <a
+of your application if the user changes
his or her language in the system settings. See <a
href="runtime-changes.html">Handling Runtime Changes</a> for information about
how this can affect your application during runtime.</p>
<p>See <a href="localization.html">Localization</a> for a complete guide to localizing
your application for other langauges.</p>
+ <p>Also see the {@link android.content.res.Configuration#locale} configuration field, which
+indicates the current locale.</p>
</td>
</tr>
<tr>
<code>large</code>
</td>
<td>
- <ul>
- <li> <b>Small screens</b> are based on the space available on a
- QVGA low density screen. Considering a portrait HVGA display, this has
- the same available width but less height -- it is 3:4 vs. HVGA's
+ <ul class="nolist">
+ <li>{@code small}: Screens based on the space available on a
+ low-density QVGA screen. Considering a portrait HVGA display, this has
+ the same available width but less height—it is 3:4 vs. HVGA's
2:3 aspect ratio. Examples are QVGA low density and VGA high
density.</li>
- <li> <b>Normal screens</b> are based on the traditional Android HVGA
- medium density screen. A screen is considered to be normal if it is
+ <li>{@code normal}: Screens based on the traditional
+ medium-density HVGA screen. A screen is considered to be normal if it is
at least this size (independent of density) and not larger. Examples
of such screens a WQVGA low density, HVGA medium density, WVGA
high density.</li>
- <li> <b>Large screens</b> are based on the space available on a
- VGA medium density screen. Such a screen has significantly more
+ <li>{@code large}: Screens based on the space available on a
+ medium-density VGA screen. Such a screen has significantly more
available space in both width and height than an HVGA display.
Examples are VGA and WVGA medium density screens.</li>
</ul>
<p>See <a href="{@docRoot}guide/practices/screens_support.html">Supporting Multiple
Screens</a> for more information.</p>
+ <p>Also see the {@link android.content.res.Configuration#screenLayout} configuration field,
+which indicates whether the screen is small, normal,
+or large.</p>
</td>
</tr>
<tr>
<code>notlong</code>
</td>
<td>
- <p>This is based purely on the aspect ratio of the screen (a "long" screen is wider):
- <ul>
- <li><strong>Long</strong>: WQVGA, WVGA, FWVGA</li>
- <li><strong>Not long</strong>: QVGA, HVGA, and VGA</li>
+ <ul class="nolist">
+ <li>{@code long}: Long screens, such as WQVGA, WVGA, FWVGA</li>
+ <li>{@code notlong}: Not long screens, such as QVGA, HVGA, and VGA</li>
</ul>
- <p>This is not related to the screen orientation.</p>
+ <p>This is based purely on the aspect ratio of the screen (a "long" screen is wider). This
+is not related to the screen orientation.</p>
+ <p>Also see the {@link android.content.res.Configuration#screenLayout} configuration field,
+which indicates whether the screen is long.</p>
</td>
</tr>
<tr>
<code>square</code> -->
</td>
<td>
- <p>Portrait orientation ({@code port}) is vertical and landscape orientation
-({@code land}) is horizontal. <!-- Square mode is currently not used. --> </p>
+ <ul class="nolist">
+ <li>{@code port}: Device is in portrait orientation (vertical)</li>
+ <li>{@code land}: Device is in landscape orientation (horizontal)</li>
+ <!-- Square mode is currently not used. -->
+ </ul>
<p>This can change during the life of your application if the user rotates the
screen. See <a href="runtime-changes.html">Handling Runtime Changes</a> for information about
how this affects your application during runtime.</p>
+ <p>Also see the {@link android.content.res.Configuration#orientation} configuration field,
+which indicates the current device orientation.</p>
</td>
</tr>
<tr>
<code>desk</code>
</td>
<td>
- <p>These configurations can be initiated when the device is placed in a dock.</p>
+ <ul class="nolist">
+ <li>{@code car}: Device is in a car dock</li>
+ <li>{@code desk}: Device is in a desk dock</li>
+ </ul>
<p><em>Added in API Level 8.</em></p>
<p>This can change during the life of your application if the user places the device in a
-dock. See <a href="runtime-changes.html">Handling Runtime Changes</a> for
-information about how this affects your application during runtime. Also see {@link
-android.app.UiModeManager}.</p>
+dock. You can eneable or disable this mode using {@link
+android.app.UiModeManager}. See <a href="runtime-changes.html">Handling Runtime Changes</a> for
+information about how this affects your application during runtime.</p>
</td>
</tr>
<tr>
<code>notnight</code>
</td>
<td>
- <p>
- These configurations can be initiated by the device light sensor (if available).</p>
+ <ul class="nolist">
+ <li>{@code night}: Night time</li>
+ <li>{@code notnight}: Day time</li>
+ </ul>
<p><em>Added in API Level 8.</em></p>
- <p>This can change during the life of your application if the device determines that the
-user environment is a "night" (dark) setting. See <a href="runtime-changes.html">Handling Runtime
-Changes</a> for information about how this affects your application during runtime. You can
-also explicitly set this mode using {@link android.app.UiModeManager}.</p>
+ <p>This can change during the life of your application if night mode is left in
+auto mode (default), in which case the mode changes based on the time of day. You can eneable
+or disable this mode using {@link android.app.UiModeManager}. See <a
+href="runtime-changes.html">Handling Runtime Changes</a> for information about how this affects your
+application during runtime.</p>
</td>
</tr>
<tr>
<code>nodpi</code>
</td>
<td>
- <p>The medium
- density of traditional HVGA screens (mdpi) is defined to be approximately
- 160dpi; low density (ldpi) is 120, and high density (hdpi) is 240. There
- is thus a 4:3 scaling factor between each density, so a 9x9 bitmap
- in ldpi would be 12x12 in mdpi and 16x16 in hdpi. The special
- <code>nodpi</code> density can be used with bitmap resources to prevent
- them from being scaled at load time to match the device density.
- </p><p>
- When Android selects which resource files to use,
- it handles screen density differently than the other qualifiers.
+ <ul class="nolist">
+ <li>{@code ldpi}: Low-density screens; approximately 120dpi.</li>
+ <li>{@code mdpi}: Medium-density (on traditional HVGA) screens; approximately
+160dpi.</li>
+ <li>{@code hdpi}: High-density screens; approximately 240dpi.</li>
+ <li>{@code nodpi}: This can be used for bitmap resources that you do not want to be scaled
+to match the device density.</li>
+ </ul>
+ <p>There is thus a 4:3 scaling factor between each density, so a 9x9 bitmap
+ in ldpi is 12x12 in mdpi and 16x16 in hdpi.</p>
+ <p>When Android selects which resource files to use,
+ it handles screen density differently than the other qualifiers.
In step 1 of <a href="#BestMatch">How Android finds the best
matching directory</a> (below), screen density is always considered to
be a match. In step 4, if the qualifier being considered is screen
- density, Android will select the best final match at that point,
+ density, Android selects the best final match at that point,
without any need to move on to step 5.
</p>
<p>See <a href="{@docRoot}guide/practices/screens_support.html">Supporting Multiple
-Screens</a> for more information.</p>
+Screens</a> for more information about how to handle screen sizes and how Android might scale
+your bitmaps.</p>
</td>
</tr>
<tr>
<code>stylus</code><br/>
<code>finger</code>
</td>
- <td><p>If the device has a resistive touch screen that's suited for use with a stylus,
-then it may use the {@code stylus} resources.</p>
+ <td>
+ <ul class="nolist">
+ <li>{@code notouch}: Device does not have a touchscreen.</li>
+ <li>{@code stylus}: Device has a resistive touchscreen that's suited for use with a
+stylus.</li>
+ <li>{@code finger}: Device has a touchscreen.</li>
+ </ul>
+ <p>Also see the {@link android.content.res.Configuration#touchscreen} configuration field,
+which indicates the type of touchscreen on the device.</p>
</td>
</tr>
<tr>
<td>Keyboard availability</td>
<td>
<code>keysexposed</code><br/>
- <code>keyshidden</code><br/>
<code>keyssoft</code>
</td>
<td>
- <p>If your application has specific resources that should only be used with a soft keyboard,
-use the <code>keyssoft</code> value. If you do not provide <code>keyssoft</code> resources, but do
-provide <code>keysexposed</code> and <code>keyshidden</code>, and the device shows a soft keyboard,
-the system will use <code>keysexposed</code> resources.</p>
- <p>This can change during the life of your application if the user opens a keyboard. See <a
-href="runtime-changes.html">Handling Runtime Changes</a> for information about how this affects your
-application during runtime.</p>
+ <ul class="nolist">
+ <li>{@code keysexposed}: Device has a keyboard available. If the device has a
+software keyboard enabled (which is likely), this may be used even when the hardware keyboard is
+<em>not</em> exposed to the user, even if the device has no hardware keyboard. If no software
+keyboard is provided or it's disabled, then this is only used when a hardware keyboard is
+exposed.</li>
+ <li>{@code keyshidden}: Device has a hardware keyboard available but it is
+hidden <em>and</em> the device does <em>not</em> have a software keyboard enabled.</li>
+ <li>{@code keyssoft}: Device has a software keyboard enabled, whether it's
+visible or not.</li>
+ </ul>
+ <p>If you provide <code>keysexposed</code> resources, but not <code>keyssoft</code>
+resources, the system uses the <code>keysexposed</code> resources regardless of whether a
+keyboard is visible, as long as the system has a software keyboard enabled.</p>
+ <p>This can change during the life of your application if the user opens a hardware
+keyboard. See <a href="runtime-changes.html">Handling Runtime Changes</a> for information about how
+this affects your application during runtime.</p>
+ <p>Also see the configuration fields {@link
+android.content.res.Configuration#hardKeyboardHidden} and {@link
+android.content.res.Configuration#keyboardHidden}, which indicate the visibility of a hardware
+keyboard and and the visibility of any kind of keyboard (including software), respectively.</p>
</td>
</tr>
<tr>
<code>qwerty</code><br/>
<code>12key</code>
</td>
- <td><p>If the device has no hardware keys for text input, then it may use the {@code
-nokeys} resources. Even if the device has a QWERTY keyboard but it is currently hidden, it may use
-the {@code qwerty} resources.</td>
+ <td>
+ <ul class="nolist">
+ <li>{@code nokeys}: Device has no hardware keys for text input.</li>
+ <li>{@code qwert}: Device has a hardware qwerty keyboard, whether it's visible to the user
+or not.</li>
+ <li>{@code 12key}: Device has a hardware 12-key keyboard, whether it's visible to the user
+or not.</li>
+ </ul>
+ <p>Also see the {@link android.content.res.Configuration#keyboard} configuration field,
+which indicates the primary text input method available.</p>
+ </td>
</tr>
<tr>
<td>Navigation key availability</td>
<code>navhidden</code>
</td>
<td>
- <p>
- If the device's navigation keys are currently available to
- the user, it may use the {@code navexposed} resources; if they are not
- available (such as behind a closed lid), it may use the {@code navhidden} resources.</p>
+ <ul class="nolist">
+ <li>{@code navexposed}: Navigation keys are available to the user.</li>
+ <li>{@code navhidden}: Navigation keys are not available (such as behind a closed
+lid).</li>
+ </ul>
<p>This can change during the life of your application if the user reveals the navigation
keys. See <a href="runtime-changes.html">Handling Runtime Changes</a> for
information about how this affects your application during runtime.</p>
+ <p>Also see the {@link android.content.res.Configuration#navigationHidden} configuration
+field, which indicates whether navigation keys are hidden.</p>
</td>
</tr>
<tr>
<code>trackball</code><br/>
<code>wheel</code>
</td>
- <td><p>If the device has no navigation facility other than using the touchscreen, then it
-may use the {@code nonav} resources.</p>
+ <td>
+ <ul class="nolist">
+ <li>{@code nonav}: Device has no navigation facility other than using the
+touchscreen.</li>
+ <li>{@code dpad}: Device has a directional-pad (d-pad) for navigation.</li>
+ <li>{@code trackball}: Device has a trackball for navigation.</li>
+ <li>{@code wheel}: Device has a directional wheel(s) for navigation (uncommon).</li>
+ </ul>
+ <p>Also see the {@link android.content.res.Configuration#navigation} configuration field,
+which indicates the type of navigation method available.</p>
</td>
</tr>
<!-- DEPRECATED
</tr>
</table>
-<p>Here are some important rules about using resource qualifier names:</p>
+
+<h3 id="QualifierRules">Qualifier name rules</h3>
+
+<p>Here are some rules about using resource qualifier names:</p>
<ul>
<li>You can specify multiple qualifiers for a single set of resources, separated by dashes. For
example, <code>drawable-en-rUS-land</code> applies to US-English devices in landscape
orientation.</li>
- <li>The qualifiers must be in the order listed in <a href="#table2">Table 2</a> above. For
+ <li>The qualifiers must be in the order listed in <a href="#table2">table 2</a>. For
example:
<ul>
<li>Wrong: <code>drawable-hdpi-port/</code></li>
<li>Correct: <code>drawable-port-hdpi/</code></li>
</ul>
</li>
- <li>Qualified directories cannot be nested. For example, you cannot have
+ <li>Alternative resource directories cannot be nested. For example, you cannot have
<code>res/drawable/drawable-en/</code>.</li>
<li>Values are case-insensitive. The resource compiler converts directory names
to lower case before processing to avoid problems on case-insensitive
the same drawable files for Spain and France, you <em>cannot</em> have a directory named
<code>drawable-rES-rFR/</code>. Instead you need two resource directories, such as
<code>drawable-rES/</code> and <code>drawable-rFR/</code>, which contain the appropriate files.
-However, you are not required to actually duplicate the same files in both locations (which
-could multiply the size of your package if the files are large). Instead, you can create a
-reference to one instance of the resources. See <a href="#AliasResources">Creating
-alias resources</a>, below.</li>
+However, you are not required to actually duplicate the same files in both locations. Instead, you
+can create an alias to a resource. See <a href="#AliasResources">Creating
+alias resources</a> below.</li>
</ul>
+<p>After you save alternative resources into directories named with
+these qualifiers, Android automatically applies the resources in your application based on the
+current device configuration. Each time a resource is requested, Android checks for alternative
+resource directories that contain the requested resource file, then <a href="#BestMatch">finds the
+best-matching resource</a> (discussed below).</p>
+
<h3 id="AliasResources">Creating alias resources</h3>
<p>When you have a resource that you'd like to use for more than one device
-configuration (but not for all configurations), you <em>don't</em> have to put the same resource in
-each of the alternative resource directories. Instead, you can (in some cases) create an alternative
+configuration (but not for all configurations), you do not need to put the same resource in
+each alternative resource directory. Instead, you can (in some cases) create an alternative
resource that acts as an alias for a resource saved in your default resource directory.</p>
-<p>For example, imagine you have an image, {@code icon.png}, and you have different versions of it
-for different locales, but two locales, English-Canadian and French-Canadian, need to
-use the same version. You might assume that you need to copy the Canadian version of the
-icon into the alternative resource directory for both English-Canadian and French-Canadian, but it's
-not true. What you can do instead is save the Canadian version as {@code icon_ca.png} (any name
-other than {@code icon.png}) and put
+<p class="note"><strong>Note:</strong> Not all resources offer a mechanism by which you can
+create an alias to another resource. In particular, animation, menu, raw, and other unspecified
+resources in the {@code xml/} directory do not offer this feature.</p>
+
+<p>For example, imagine you have an application icon, {@code icon.png}, and need unique version of
+it for different locales. However, two locales, English-Canadian and French-Canadian, need to
+use the same version. You might assume that you need to copy the same image
+into the resource directory for both English-Canadian and French-Canadian, but it's
+not true. Instead, you can save the image that's used for both as {@code icon_ca.png} (any
+name other than {@code icon.png}) and put
it in the default {@code res/drawable/} directory. Then create an {@code icon.xml} file in {@code
res/drawable-en-rCA/} and {@code res/drawable-fr-rCA/} that refers to the {@code icon_ca.png}
resource using the {@code <bitmap>} element. This allows you to store just one version of the
PNG file and two small XML files that point to it. (An example XML file is shown below.)</p>
-<p class="note"><strong>Note:</strong> Not all resources offer a mechanism by which you can
-create an alias to another resource. In particular, animation, menu, raw, and other unspecified
-resources in the {@code xml/} directory don't provide this kind of feature.</p>
-
<h4>Drawable</h4>
android:src="@drawable/icon_ca" />
</pre>
-<p>If you save this file as {@code icon.xml}, it will be compiled into a resource that you
+<p>If you save this file as {@code icon.xml} (in an alternative resource directory, such as
+{@code res/drawable-en-rCA/}), it is compiled into a resource that you
can reference as {@code R.drawable.icon}, but is actually an alias for the {@code
-R.drawable.icon_ca} resource.</p>
+R.drawable.icon_ca} resource (which is saved in {@code res/drawable/}).</p>
<h4>Layout</h4>
</merge>
</pre>
-<p>If you save this file as {@code main.xml}, it will be compiled into a resource you can reference
+<p>If you save this file as {@code main.xml}, it is compiled into a resource you can reference
as {@code R.layout.main}, but is actually an alias for the {@code R.layout.main_ltr}
resource.</p>
<h2 id="BestMatch">How Android Finds the Best-matching Resource</h2>
-<p>Once you have saved alternative resources for your application, Android will pick which of the
-various underlying resource files should be used at runtime for each resource
-requested, depending on the current device configuration. To demonstrate how Android will select the
-resource to use, assume the following drawables are available:</p>
-
-<pre class="no-pretty-print">
-res/drawable/
-res/drawable-en/
-res/drawable-fr-rCA/
-res/drawable-en-port/
-res/drawable-en-notouch-12key/
-res/drawable-port-ldpi/
-res/drawable-port-notouch-12key
+<p>When you request a resource for which you provide alternatives, Android selects which
+alternative resource to use at runtime, depending on the current device configuration. To
+demonstrate how Android selects an alternative resource, assume the following drawable directories
+each contain different versions of the same images:</p>
+
+<pre class="classic no-pretty-print">
+drawable/
+drawable-en/
+drawable-fr-rCA/
+drawable-en-port/
+drawable-en-notouch-12key/
+drawable-port-ldpi/
+drawable-port-notouch-12key/
</pre>
<p>And assume the following is the device configuration:</p>
-<p style="margin-left:2em;">
+<p style="margin-left:1em;">
Locale = <code>en-GB</code> <br/>
Screen orientation = <code>port</code> <br/>
Screen pixel density = <code>hdpi</code> <br/>
Primary text input method = <code>12key</code>
</p>
+<p>By comparing the device configuration to the available alternative resources, Android selects
+drawables from {@code drawable-en-port}. It arrives at this decision using the following logic:</p>
+
+
+<div class="figure" style="width:280px">
+<img src="{@docRoot}images/resources/res-selection-flowchart.png" alt="" height="590" />
+<p class="img-caption"><strong>Figure 2.</strong> Flowchart of how Android finds the
+best-matching resource.</p>
+</div>
-<p>Here is how Android makes the drawable selection and how a drawable will be selected from the
-configuration above: </p>
<ol>
<li>Eliminate resource files that contradict the device configuration.
- <p>The <code>drawable-fr-rCA/</code> directory will be eliminated, because it
-contradicts the locale of the device.</p>
-<pre class="no-pretty-print">
+ <p>The <code>drawable-fr-rCA/</code> directory is eliminated, because it
+contradicts the <code>en-GB</code> locale.</p>
+<pre class="classic no-pretty-print">
drawable/
drawable-en/
<strike>drawable-fr-rCA/</strike>
drawable-en-port/
drawable-en-notouch-12key/
drawable-port-ldpi/
-drawable-port-notouch-12key
+drawable-port-notouch-12key/
</pre>
-<p class="note"><strong>Exception: </strong>Screen pixel density is the one qualifier that is not
-used to eliminate files. Even though the screen density of the device is mdpi,
+<p class="note"><strong>Exception:</strong> Screen pixel density is the one qualifier that is not
+eliminated due to a contradiction. Even though the screen density of the device is mdpi,
<code>drawable-port-ldpi/</code> is not eliminated because every screen density is
-considered to be a match at this point.</p></li>
+considered to be a match at this point. More information is available in the <a
+href="{@docRoot}guide/practices/screens_support.html">Supporting Multiple
+Screens</a> document.</p></li>
- <li>From <a href="#table2">Table 2</a>, pick the (next) highest-precedence qualifier in
-the list. (Start with MCC, then move down through the list.) </li>
- <li>Do any of the available resource directories include this qualifier? </li>
+ <li>Pick the (next) highest-precedence qualifier in the list (<a href="#table2">table 2</a>).
+(Start with MCC, then move down.) </li>
+ <li>Do any of the resource directories include this qualifier? </li>
<ul>
- <li>If No, return to step 2 and look at the next qualifier. In the example,
- the answer is "no" until the language qualifier is reached.</li>
- <li>If Yes, move on to step 4.</li>
+ <li>If No, return to step 2 and look at the next qualifier. (In the example,
+ the answer is "no" until the language qualifier is reached.)</li>
+ <li>If Yes, continue to step 4.</li>
</ul>
</li>
<li>Eliminate resource directories that do not include this qualifier. In the example, the system
eliminates all the directories that do not include a language qualifier:</li>
-<pre class="no-pretty-print">
+<pre class="classic no-pretty-print">
<strike>drawable/</strike>
drawable-en/
drawable-en-port/
drawable-en-notouch-12key/
<strike>drawable-port-ldpi/</strike>
-<strike>drawable-port-notouch-12key</strike>
+<strike>drawable-port-notouch-12key/</strike>
</pre>
<p class="note"><strong>Exception:</strong> If the qualifier in question is screen pixel density,
-Android will
-select the option that most closely matches the device, and the selection process will be complete.
-In general, Android will prefer scaling down a larger original image to scaling up a smaller
-original image.</p>
+Android
+selects the option that most closely matches the device, and the selection process is complete.
+In general, Android prefers scaling down a larger original image to scaling up a smaller
+original image. See <a href="{@docRoot}guide/practices/screens_support.html">Supporting Multiple
+Screens</a>.</p>
</li>
- <li>Go back and repeat steps 2, 3, and 4 until only one choice remains. In the example, screen
+ <li>Go back and repeat steps 2, 3, and 4 until only one directory remains. In the example, screen
orientation is the next qualifier for which there are any matches.
So, resources that do not specify a screen orientation are eliminated:
-<pre class="no-pretty-print">
+<pre class="classic no-pretty-print">
<strike>drawable-en/</strike>
drawable-en-port/
<strike>drawable-en-notouch-12key/</strike>
</pre>
-<p>Only one choice remains, so the drawable will be taken from the {@code drawable-en-port}
-directory.</p>
+<p>The remaining directory is {@code drawable-en-port}.</p>
</li>
</ol>
-<p>Though this procedure is executed for each resource requested, the system will further optimize
+<p>Though this procedure is executed for each resource requested, the system further optimizes
some aspects. One such optimization is that once the device configuration is known, it might
-completely eliminate alternative resources that can never match. For example, if the configuration
+eliminate alternative resources that can never match. For example, if the configuration
language is English ("en"), then any resource directory that has a language qualifier set to
-something other than English will never be included in the pool of resources checked (though a
+something other than English is never included in the pool of resources checked (though a
resource directory <em>without</em> the language qualifier is still included).</p>
<p class="note"><strong>Note:</strong> The <em>precedence</em> of the qualifier (in <a
-href="#table2">Table 2</a>) is more important
+href="#table2">table 2</a>) is more important
than the number of qualifiers that exactly match the device. For example, in step 4 above, the last
choice on the list includes three qualifiers that exactly match the device (orientation, touchscreen
type, and input method), while <code>drawable-en</code> has only one parameter that matches
(language). However, language has a higher precedence than these other qualifiers, so
-<code>drawable-port-notouch-12key</code>
-is out.</p>
+<code>drawable-port-notouch-12key</code> is out.</p>
+
+<p>To learn more about how to use resources in your application, continue to <a
+href="accessing-resources.html">Accessing Resources</a>.</p>
-<p>The following flowchart summarizes how Android selects the resource directory to use.</p>
-<p><img src="{@docRoot}images/resources/res-selection-flowchart.png" alt=""
-height="471" /></p>
<h2>In this document</h2>
<ol>
- <li><a href="#CarryingAnObject">Carrying an Object During a Configuration Change</a></li>
+ <li><a href="#RetainingAnObject">Retaining an Object During a Configuration Change</a></li>
<li><a href="#HandlingTheChange">Handling the Configuration Change Yourself</a>
</ol>
<p>Some device configurations can change during runtime
(such as screen orientation, keyboard availability, and language). When such a change occurs,
-Android's default behavior is to restart the running
+Android restarts the running
Activity ({@link android.app.Activity#onDestroy()} is called, followed by {@link
-android.app.Activity#onCreate(Bundle) onCreate()}). In doing so, the system re-queries your
-application resources for alternatives that might apply to the new configuration.</p>
+android.app.Activity#onCreate(Bundle) onCreate()}). The restart behavior is designed to help your
+application adapt to new configurations by automatically reloading your application with
+alternative resources.</p>
-<p>It is important that your Activity safely handles restarts and restores its previous
+<p>To properly handle a restart, it is important that your Activity restores its previous
state through the normal <a href="{@docRoot}guide/topics/fundamentals.html#lcycles">Activity
-lifecycle</a>. In fact, it's a useful field test to invoke configuration changes (such as changing
-the screen orientation) during various states of your application to be sure that it properly
-restarts itself with the application state intact. So it's in the best interest of your application
-to allow the system to restart your application during any configuration change—this behavior
-is in place to help you by automatically handling configuration changes and adapting your
-application as necessary.</p>
+lifecycle</a>, in which Android calls
+{@link android.app.Activity#onSaveInstanceState(Bundle) onSaveInstanceState()} before it destroys
+your Activity so that you can save data about the application state. You can then restore the state
+during {@link android.app.Activity#onCreate(Bundle) onCreate()} or {@link
+android.app.Activity#onRestoreInstanceState(Bundle) onRestoreInstanceState()}. To test
+that your application restarts itself with the application state intact, you should
+invoke configuration changes (such as changing the screen orientation) while performing various
+tasks in your application.</p>
+
+<p>Your application should be able to restart at any time without loss of user data or
+state in order to handle events such as when the user receives an incoming phone call and then
+returns to your application (read about the
+<a href="{@docRoot}guide/topics/fundamentals.html#lcycles">Activity lifecycle</a>).</p>
<p>However, you might encounter a situation in which restarting your application and
-restoring significant amounts of data can be costly, create a slow user experience, and
-using {@link android.app.Activity#onSaveInstanceState(Bundle) onSaveInstanceState()} does not
-suffice. In such a situation, you have two options:</p>
+restoring significant amounts of data can be costly and create a poor user experience. In such a
+situation, you have two options:</p>
<ol type="a">
- <li><a href="#CarryingAnObject">Carrying an Object During a Configuration Change</a>
- <p>Allow your
-application to restart so that the appropriate configuration changes can take effect, but also
-implement {@link android.app.Activity#onRetainNonConfigurationInstance()} paired with {@link
-android.app.Activity#getLastNonConfigurationInstance()} to carry an {@link java.lang.Object} over
-to the new instance of your Activity.</p>
- <p>This is the recommended technique if you're facing performance issues during the
-configuration restart. It allows your Activity to properly restart and reload resources for
-the new configuration and also allows you to carry your arbitrary data that may be expensive to
-collect again.</p>
+ <li><a href="#RetainAnObject">Retain an object during a configuration change</a>
+ <p>Allow your Activity to restart when a configuration changes, but carry a stateful
+{@link java.lang.Object} to the new instance of your Activity.</p>
+
</li>
- <li><a href="#HandlingTheChange">Handling the Configuration Change Yourself</a>
- <p>Declare that your
-application will handle certain configuration changes and prevent the system from restarting your
-application when such a change occurs. For example, you can declare in your manifest that your
-Activity will handle configuration changes to the screen orientation. When the orientation
-changes, your Activity will not be restarted and your Activity will receive a call to {@link
-android.app.Activity#onConfigurationChanged(Configuration) onConfigurationChanged()} so that you can
-perform necessary changes based on the new configuration.</p>
- <p>This technique should be considered a last resort and temporary solution, because not all
-runtime configuration changes can be handled this way—your application will eventually
-encounter a runtime configuration in which you cannot prevent the Activity from being restarted,
-whereas the first option will handle all configuration changes.</p>
+ <li><a href="#HandlingTheChange">Handle the configuration change yourself</a>
+ <p>Prevent the system from restarting your Activity during certain configuration
+changes and receive a callback when the configurations do change, so that you can manually update
+your Activity as necessary.</p>
</li>
</ol>
-<p class="note"><strong>Note:</strong> Your application should always be able to successfully
-restart at any time without any loss of user data or state in order to handle other events such as
-when the user receives an incoming phone call and then returns to your application (read about the
-<a href="{@docRoot}guide/topics/fundamentals.html#lcycles">Activity lifecycle</a>). The following
-techniques for handling runtime configuration changes should only be necessary to optimize
-performance during specific configuration changes.</p>
-
-
-<h2 id="CarryingAnObject">Carrying an Object During a Configuration Change</h2>
-
-<p>If your application has acquired significant amounts of data during its life, which would be
-costly to recover due to a restart of the Activity, you can use {@link
-android.app.Activity#onRetainNonConfigurationInstance()} paired with {@link
-android.app.Activity#getLastNonConfigurationInstance()} to pass an {@link java.lang.Object}
-to the new Activity instance. The {@link android.app.Activity#onRetainNonConfigurationInstance()}
-method is called between {@link android.app.Activity#onStop()} and {@link
-android.app.Activity#onDestroy()} when your Activity is being shut down due to a configuration
-change. In your implementation of this method, you can return any {@link java.lang.Object} that you
-need to efficiently restore your state after the configuration change. When your Activity is
-created again, you can call {@link
-android.app.Activity#getLastNonConfigurationInstance()} to retrieve the {@link
-java.lang.Object}.</p>
+
+<h2 id="RetainingAnObject">Retaining an Object During a Configuration Change</h2>
+
+<p>If restarting your Activity requires that you recover large sets of data, re-establish a
+network connection, or perform other intensive operations, then a full restart due to a
+configuration change might
+be an unpleasant user experience. Also, it may not be possible for you to completely
+maintain your Activity state with the {@link android.os.Bundle} that the system saves for you during
+the Activity lifecycle—it is not designed to carry large objects (such as bitmaps) and the
+data within it must be serialized then deserialized, which can consume a lot of memory and make the
+configuration change slow. In such a situation, you can alleviate the burden of reinitializing
+your Activity by retaining a stateful Object when your Activity is restarted due to a configuration
+change.</p>
+
+<p>To retain an Object during a runtime configuration change:</p>
+<ol>
+ <li>Override the {@link android.app.Activity#onRetainNonConfigurationInstance()} method to return
+the Object you would like to retain.</li>
+ <li>When your Activity is created again, call {@link
+android.app.Activity#getLastNonConfigurationInstance()} to recover your Object.</li>
+</ol>
+
+<p>Android calls {@link android.app.Activity#onRetainNonConfigurationInstance()} between {@link
+android.app.Activity#onStop()} and {@link
+android.app.Activity#onDestroy()} when it shuts down your Activity due to a configuration
+change. In your implementation of {@link
+android.app.Activity#onRetainNonConfigurationInstance()}, you can return any {@link
+java.lang.Object} that you need in order to efficiently restore your state after the configuration
+change.</p>
<p>A scenario in which this can be valuable is if your application loads a lot of data from the
web. If the user changes the orientation of the device and the Activity restarts, your application
-will need to re-fetch the data, which could be slow. What you can do is implement
+must re-fetch the data, which could be slow. What you can do instead is implement
{@link android.app.Activity#onRetainNonConfigurationInstance()} to return an object carrying your
-data and then retrieve the data when your Activity restarts with {@link
+data and then retrieve the data when your Activity starts again with {@link
android.app.Activity#getLastNonConfigurationInstance()}. For example:</p>
<pre>
means that your application maintains a hold on them and they cannot be garbage-collected, so
lots of memory can be lost.)</p>
-<p>Then get the {@code data} after the restart:</p>
+<p>Then retrieve the {@code data} when your Activity starts again:</p>
<pre>
@Override
}
</pre>
-<p>In this case, {@link android.app.Activity#getLastNonConfigurationInstance()} is called to get
-the data saved during the configuration change, and if it is null (which will happen if the
-Activity is started in any case other than a configuration change) then the data is loaded
+<p>In this case, {@link android.app.Activity#getLastNonConfigurationInstance()} retrieves
+the data saved by {@link android.app.Activity#onRetainNonConfigurationInstance()}. If {@code data}
+is null (which happens when the
+Activity starts due to any reason other than a configuration change) then the data object is loaded
from the original source.</p>
<p>If your application doesn't need to update resources during a specific configuration
change <em>and</em> you have a performance limitation that requires you to
avoid the Activity restart, then you can declare that your Activity handles the configuration change
-itself, which will prevent the system from restarting your Activity.</p>
+itself, which prevents the system from restarting your Activity.</p>
<p class="note"><strong>Note:</strong> Handling the configuration change yourself can make it much
-more difficult to use alternative resources, because the system will not automatically apply them
-for you.</p>
+more difficult to use alternative resources, because the system does not automatically apply them
+for you. This technique should be considered a last resort and is not recommended for most
+applications.</p>
<p>To declare that your Activity handles a configuration change, edit the appropriate <a
href="{@docRoot}guide/topics/manifest/activity-element.html">{@code <activity>}</a> element
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