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author | Scott Main <smain@google.com> | 2010-05-10 09:56:19 -0700 |
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committer | Android Git Automerger <android-git-automerger@android.com> | 2010-05-10 09:56:19 -0700 |
commit | d98da9cfbb238ee83a8612710a2a71309d1e44f5 (patch) | |
tree | b69addc91ee21812ed2b8763321a58be8f38a6ee /docs | |
parent | 6aa19bb7d28395dede5943d6f67fea614c5b407d (diff) | |
parent | 2e9ec96d9eb24bcc3893b449fcecf803628f1aa8 (diff) | |
download | frameworks_base-d98da9cfbb238ee83a8612710a2a71309d1e44f5.zip frameworks_base-d98da9cfbb238ee83a8612710a2a71309d1e44f5.tar.gz frameworks_base-d98da9cfbb238ee83a8612710a2a71309d1e44f5.tar.bz2 |
am 2e9ec96d: am 3d3853a6: am d2f2a80e: am c6cb8a78: docs: revisions to the new resources doc based on editorial feedback plus some fixes to resource references and other misc revisions
Diffstat (limited to 'docs')
-rw-r--r-- | docs/html/guide/topics/resources/accessing-resources.jd | 247 | ||||
-rw-r--r-- | docs/html/guide/topics/resources/animation-resource.jd | 56 | ||||
-rw-r--r-- | docs/html/guide/topics/resources/available-resources.jd | 17 | ||||
-rw-r--r-- | docs/html/guide/topics/resources/drawable-resource.jd | 42 | ||||
-rw-r--r-- | docs/html/guide/topics/resources/index.jd | 4 | ||||
-rw-r--r-- | docs/html/guide/topics/resources/layout-resource.jd | 12 | ||||
-rw-r--r-- | docs/html/guide/topics/resources/menu-resource.jd | 26 | ||||
-rw-r--r-- | docs/html/guide/topics/resources/providing-resources.jd | 491 | ||||
-rw-r--r-- | docs/html/guide/topics/resources/runtime-changes.jd | 136 | ||||
-rw-r--r--[-rwxr-xr-x] | docs/html/images/resources/res-selection-flowchart.png | bin | 23228 -> 32754 bytes |
10 files changed, 605 insertions, 426 deletions
diff --git a/docs/html/guide/topics/resources/accessing-resources.jd b/docs/html/guide/topics/resources/accessing-resources.jd index e3e4055..cf8970c 100644 --- a/docs/html/guide/topics/resources/accessing-resources.jd +++ b/docs/html/guide/topics/resources/accessing-resources.jd @@ -22,12 +22,13 @@ parent.link=index.html <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> @@ -39,154 +40,194 @@ parent.link=index.html </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> @@ -206,8 +247,8 @@ text string:</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 @@ -219,19 +260,18 @@ reference a system resource, you would need to include the package name. For exa <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"?> @@ -239,15 +279,14 @@ image:</p> 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 @@ -257,28 +296,46 @@ essentially says, "use the style that is defined by this attribute, in the curre 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> diff --git a/docs/html/guide/topics/resources/animation-resource.jd b/docs/html/guide/topics/resources/animation-resource.jd index b2fab04..e0ce051 100644 --- a/docs/html/guide/topics/resources/animation-resource.jd +++ b/docs/html/guide/topics/resources/animation-resource.jd @@ -62,18 +62,18 @@ In XML: <code>@[<em>package</em>:]anim/<em>filename</em></code> 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> @@ -158,21 +158,21 @@ android.view.animation.TranslateAnimation}. <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 @@ -183,15 +183,19 @@ inherrited by this element).</p> <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 diff --git a/docs/html/guide/topics/resources/available-resources.jd b/docs/html/guide/topics/resources/available-resources.jd index 19babee..09c55a5 100644 --- a/docs/html/guide/topics/resources/available-resources.jd +++ b/docs/html/guide/topics/resources/available-resources.jd @@ -18,6 +18,23 @@ of application resource that you can provide in your resources directory ({@code <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/> diff --git a/docs/html/guide/topics/resources/drawable-resource.jd b/docs/html/guide/topics/resources/drawable-resource.jd index ec964ed..d8de16a 100644 --- a/docs/html/guide/topics/resources/drawable-resource.jd +++ b/docs/html/guide/topics/resources/drawable-resource.jd @@ -463,11 +463,11 @@ In XML: <code>@[<em>package</em>:]drawable/<em>filename</em></code> 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> @@ -544,18 +544,6 @@ a {@link android.graphics.drawable.LevelListDrawable}. This should normally be " <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> @@ -568,18 +556,30 @@ Does not apply when {@code android:type="linear"}.</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> diff --git a/docs/html/guide/topics/resources/index.jd b/docs/html/guide/topics/resources/index.jd index f602a04..2aa697e 100644 --- a/docs/html/guide/topics/resources/index.jd +++ b/docs/html/guide/topics/resources/index.jd @@ -27,14 +27,14 @@ important as more Android-powered devices become available with different config 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 diff --git a/docs/html/guide/topics/resources/layout-resource.jd b/docs/html/guide/topics/resources/layout-resource.jd index a6b177f..2c51d54 100644 --- a/docs/html/guide/topics/resources/layout-resource.jd +++ b/docs/html/guide/topics/resources/layout-resource.jd @@ -36,14 +36,14 @@ In XML: <code>@[<em>package</em>:]layout/<em>filename</em></code> <?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> > diff --git a/docs/html/guide/topics/resources/menu-resource.jd b/docs/html/guide/topics/resources/menu-resource.jd index c9f27fa..badc403 100644 --- a/docs/html/guide/topics/resources/menu-resource.jd +++ b/docs/html/guide/topics/resources/menu-resource.jd @@ -35,12 +35,12 @@ In XML: <code>@[<em>package</em>:]menu.<em>filename</em></code> <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"] @@ -172,22 +172,22 @@ too long.</dd> <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> diff --git a/docs/html/guide/topics/resources/providing-resources.jd b/docs/html/guide/topics/resources/providing-resources.jd index b495eb8..0f3d389 100644 --- a/docs/html/guide/topics/resources/providing-resources.jd +++ b/docs/html/guide/topics/resources/providing-resources.jd @@ -7,13 +7,15 @@ parent.link=index.html <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> @@ -24,17 +26,30 @@ parent.link=index.html <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> @@ -42,23 +57,23 @@ MyProject/ 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> @@ -70,13 +85,13 @@ href="animation-resource.html">Animation Resources</a>.</td> <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> @@ -107,37 +122,35 @@ Menu. See <a href="menu-resource.html">Menu Resource</a>.</td> 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 + <li>colors.xml for <a href="more-resources.html#Color">color values</a></li> - <li>dimens.xml to define <a + <li>dimens.xml for <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 @@ -147,38 +160,42 @@ values</a>.</li> <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>}. @@ -191,13 +208,13 @@ for which these resources are to be used.</li> <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 @@ -207,22 +224,23 @@ res/ 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> @@ -237,18 +255,22 @@ names.</p> 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> @@ -260,22 +282,24 @@ should do so with great care and completely test that it works as expected.</p>< <code>fr-rCA</code><br/> etc. </td> - <td><p>This is defined by a two-letter <a + <td><p>The 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> @@ -286,24 +310,27 @@ your application for other langauges.</p> <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> @@ -313,12 +340,14 @@ Screens</a> for more information.</p> <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> @@ -329,11 +358,16 @@ Screens</a> for more information.</p> <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> @@ -343,12 +377,15 @@ how this affects your application during runtime.</p> <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> @@ -358,13 +395,16 @@ android.app.UiModeManager}.</p> <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> @@ -376,24 +416,27 @@ also explicitly set this mode using {@link android.app.UiModeManager}.</p> <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> @@ -403,25 +446,45 @@ Screens</a> for more information.</p> <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> @@ -431,9 +494,17 @@ application during runtime.</p> <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> @@ -442,13 +513,16 @@ the {@code qwerty} resources.</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> @@ -459,8 +533,16 @@ information about how this affects your application during runtime.</p> <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 @@ -495,20 +577,23 @@ about these values.</p> </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 @@ -517,36 +602,41 @@ example: 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> @@ -559,9 +649,10 @@ For example:</p> 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> @@ -576,7 +667,7 @@ element, wrapped in a {@code <merge>}. For example:</p> </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> @@ -614,24 +705,24 @@ same way. For example, a color:</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/> @@ -639,85 +730,93 @@ Touchscreen type = <code>notouch</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> diff --git a/docs/html/guide/topics/resources/runtime-changes.jd b/docs/html/guide/topics/resources/runtime-changes.jd index dff664c..d75ff4d 100644 --- a/docs/html/guide/topics/resources/runtime-changes.jd +++ b/docs/html/guide/topics/resources/runtime-changes.jd @@ -8,7 +8,7 @@ parent.link=index.html <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> @@ -24,80 +24,80 @@ Orientation Change</a></li> <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> @@ -116,7 +116,7 @@ leak all the Views and resources of the original Activity instance. (To leak the 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 @@ -132,9 +132,10 @@ public void onCreate(Bundle savedInstanceState) { } </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> @@ -146,11 +147,12 @@ 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 diff --git a/docs/html/images/resources/res-selection-flowchart.png b/docs/html/images/resources/res-selection-flowchart.png Binary files differindex d738b3f..eb70074 100755..100644 --- a/docs/html/images/resources/res-selection-flowchart.png +++ b/docs/html/images/resources/res-selection-flowchart.png |