xref: /frameworks/base/docs/html/guide/components/intents-filters.jd

page.title=Intents and Intent Filters
page.tags="IntentFilter"
@jd:body

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

<h2>In this document</h2>
<ol>
  <li><a href="#Types">Intent Types</a></li>
  <li><a href="#Building">Building an Intent</a>
    <ol>
      <li><a href="#ExampleExplicit">Example explicit intent</a></li>
      <li><a href="#ExampleSend">Example implicit intent</a></li>
      <li><a href="#ForceChooser">Forcing an app chooser</a></li>
    </ol>
  </li>
  <li><a href="#Receiving">Receiving an Implicit Intent</a>
    <ol>
      <li><a href="#ExampleFilters">Example filters</a></li>
    </ol>
  </li>
  <li><a href="#PendingIntent">Using a Pending Intent</a></li>
  <li><a href="#Resolution">Intent Resolution</a>
    <ol>
      <li><a href="#ActionTest">Action test</a></li>
      <li><a href="#CategoryTest">Category test</a></li>
      <li><a href="#DataTest">Data test</a></li>
      <li><a href="#imatch">Intent matching</a></li>
    </ol>
  </li>
</ol>

<h2>See also</h2>
<ol>
<li><a href="{@docRoot}training/basics/intents/index.html">Interacting with Other Apps</a></li>
<li><a href="{@docRoot}training/sharing/index.html">Sharing Content</a></li>
</ol>

</div>
</div>




<p>An {@link android.content.Intent} is a messaging object you can use to request an action
from another <a href="{@docRoot}guide/components/fundamentals.html#Components">app component</a>.
Although intents facilitate communication between components in several ways, there are three
fundamental use-cases:</p>

<ul>
<li><b>To start an activity:</b>
<p>An {@link android.app.Activity} represents a single screen in an app. You can start a new
instance of an {@link android.app.Activity} by passing an {@link android.content.Intent}
to {@link android.content.Context#startActivity startActivity()}. The {@link android.content.Intent}
describes the activity to start and carries any necessary data.</p>

<p>If you want to receive a result from the activity when it finishes,
call {@link android.app.Activity#startActivityForResult
startActivityForResult()}. Your activity receives the result
as a separate {@link android.content.Intent} object in your activity's {@link
android.app.Activity#onActivityResult onActivityResult()} callback.
For more information, see the <a
href="{@docRoot}guide/components/activities.html">Activities</a> guide.</p></li>

<li><b>To start a service:</b>
<p>A {@link android.app.Service} is a component that performs operations in the background
without a user interface. You can start a service to perform a one-time operation
(such as download a file) by passing an {@link android.content.Intent}
to {@link android.content.Context#startService startService()}. The {@link android.content.Intent}
describes the service to start and carries any necessary data.</p>

<p>If the service is designed with a client-server interface, you can bind to the service
from another component by passing an {@link android.content.Intent} to {@link
android.content.Context#bindService bindService()}</code>. For more information, see the <a
href="{@docRoot}guide/components/services.html">Services</a> guide.</p></li>

<li><b>To deliver a broadcast:</b>
<p>A broadcast is a message that any app can receive. The system delivers various
broadcasts for system events, such as when the system boots up or the device starts charging.
You can deliver a broadcast to other apps by passing an {@link android.content.Intent}
to {@link android.content.Context#sendBroadcast(Intent) sendBroadcast()},
{@link android.content.Context#sendOrderedBroadcast(Intent, String)
sendOrderedBroadcast()}, or {@link
android.content.Context#sendStickyBroadcast sendStickyBroadcast()}.</p>
</li>
</ul>




<h2 id="Types">Intent Types</h2>

<p>There are two types of intents:</p>

<ul>
<li><b>Explicit intents</b> specify the component to start by name (the
fully-qualified class name). You'll typically use an explicit intent to start a component in
your own app, because you know the class name of the activity or service you want to start. For
example, start a new activity in response to a user action or start a service to download
a file in the background.</li>

<li><b>Implicit intents</b> do not name a specific component, but instead declare a general action
to perform, which allows a component from another app to handle it. For example, if you want to
show the user a location on a map, you can use an implicit intent to request that another capable
app show a specified location on a map.</li>
</ul>

<p>When you create an explicit intent to start an activity or service, the system immediately
starts the app component specified in the {@link android.content.Intent} object.</p>

<div class="figure" style="width:446px">
<img src="{@docRoot}images/components/intent-filters@2x.png" width="446" alt=""/>
<p class="img-caption"><strong>Figure 1.</strong> Illustration of how an implicit intent is
delivered through the system to start another activity: <b>[1]</b> <em>Activity A</em> creates an
{@link android.content.Intent} with an action description and passes it to {@link
android.content.Context#startActivity startActivity()}. <b>[2]</b> The Android System searches all
apps for an intent filter that matches the intent. When a match is found, <b>[3]</b> the system
starts the matching activity (<em>Activity B</em>) by invoking its {@link
android.app.Activity#onCreate onCreate()} method and passing it the {@link android.content.Intent}.
</p>
</div>

<p>When you create an implicit intent, the Android system finds the appropriate component to start
by comparing the contents of the intent to the <em>intent filters</em> declared in the <a href=
"{@docRoot}guide/topics/manifest/manifest-intro.html">manifest file</a> of other apps on the
device. If the intent matches an intent filter, the system starts that component and delivers it
the {@link android.content.Intent} object. If multiple intent filters are compatible, the system
displays a dialog so the user can pick which app to use.</p>

<p>An intent filter is an expression in an app's manifest file that
specifies the type of intents that the component
would like to receive. For instance, by declaring an intent filter for an activity,
you make it possible for other apps to directly start your activity with a certain kind of intent.
Likewise, if you do <em>not</em> declare any intent filters for an activity, then it can be started
only with an explicit intent.</p>

<p class="caution"><strong>Caution:</strong> To ensure your app is secure, always use an explicit
intent when starting a {@link android.app.Service} and do not
declare intent filters for your services. Using an implicit intent to start a service is a
security hazard because you cannot be certain what service will respond to the intent,
and the user cannot see which service starts.</p>





<h2 id="Building">Building an Intent</h2>

<p>An {@link android.content.Intent} object carries information that the Android system uses
to determine which component to start (such as the exact component name or component
category that should receive the intent), plus information that the recipient component uses in
order to properly perform the action (such as the action to take and the data to act upon).</p>


<p>The primary information contained in an {@link android.content.Intent} is the following:</p>

<dl>

<dt><b>Component name</b></dt>
<dd>The name of the component to start.

<p>This is optional, but it's the critical piece of information that makes an intent
<b>explicit</b>, meaning that the intent should be delivered only to the app component
defined by the component name. Without a component name, the intent is <b>implicit</b> and the
system decides which component should receive the intent based on the other intent information
(such as the action, data, and category&mdash;described below). So if you need to start a specific
component in your app, you should specify the component name.</p>

<p class="note"><strong>Note:</strong> When starting a {@link android.app.Service}, you should
<strong>always specify the component name</strong>. Otherwise, you cannot be certain what service
will respond to the intent, and the user cannot see which service starts.</p>

<p>This field of the {@link android.content.Intent} is a
{@link android.content.ComponentName} object, which you can specify using a fully
qualified class name of the target component, including the package name of the app. For example,
{@code com.example.ExampleActivity}. You can set the component name with {@link
android.content.Intent#setComponent setComponent()}, {@link android.content.Intent#setClass
setClass()}, {@link android.content.Intent#setClassName(String, String) setClassName()}, or with the
{@link android.content.Intent} constructor.</p>

</dd>

<p><dt><b>Action</b></dt>
<dd>A string that specifies the generic action to perform (such as <em>view</em> or <em>pick</em>).

<p>In the case of a broadcast intent, this is the action that took place and is being reported.
The action largely determines how the rest of the intent is structured&mdash;particularly
what is contained in the data and extras.

<p>You can specify your own actions for use by intents within your app (or for use by other
apps to invoke components in your app), but you should usually use action constants
defined by the {@link android.content.Intent} class or other framework classes. Here are some
common actions for starting an activity:</p>

<dl>
<dt>{@link android.content.Intent#ACTION_VIEW}</dt>
   <dd>Use this action in an intent with {@link
   android.content.Context#startActivity startActivity()} when you have some information that
   an activity can show to the user, such as a photo to view in a gallery app, or an address to
   view in a map app.</dd>

<dt>{@link android.content.Intent#ACTION_SEND}</dt>
   <dd>Also known as the "share" intent, you should use this in an intent with {@link
   android.content.Context#startActivity startActivity()} when you have some data that the user can
   share through another app, such as an email app or social sharing app.</dd>
</dl>

<p>See the {@link android.content.Intent} class reference for more
constants that define generic actions.  Other actions are defined
elsewhere in the Android framework, such as in {@link android.provider.Settings} for actions
that open specific screens in the system's Settings app.</p>

<p>You can specify the action for an intent with {@link android.content.Intent#setAction
setAction()} or with an {@link android.content.Intent} constructor.</p>

<p>If you define your own actions, be sure to include your app's package name
as a prefix. For example:</p>
<pre>static final String ACTION_TIMETRAVEL = "com.example.action.TIMETRAVEL";</pre>
</dd>

<dt><b>Data</b></dt>
<dd>The URI (a {@link android.net.Uri} object) that references the data to be acted on and/or the
MIME type of that data. The type of data supplied is generally dictated by the intent's action. For
example, if the action is {@link android.content.Intent#ACTION_EDIT}, the data should contain the
URI of the document to edit.

<p>When creating an intent,
it's often important to specify the type of data (its MIME type) in addition to its URI.
For example, an activity that's able to display images probably won't be able
to play an audio file, even though the URI formats could be similar.
So specifying the MIME type of your data helps the Android
system find the best component to receive your intent.
However, the MIME type can sometimes be inferred from the URI&mdash;particularly when the data is a
{@code content:} URI, which indicates the data is located on the device and controlled by a
{@link android.content.ContentProvider}, which makes the data MIME type visible to the system.</p>

<p>To set only the data URI, call {@link android.content.Intent#setData setData()}.
To set only the MIME type, call {@link android.content.Intent#setType setType()}. If necessary, you
can set both explicitly with {@link
android.content.Intent#setDataAndType setDataAndType()}.</p>

<p class="caution"><strong>Caution:</strong> If you want to set both the URI and MIME type,
<strong>do not</strong> call {@link android.content.Intent#setData setData()} and
{@link android.content.Intent#setType setType()} because they each nullify the value of the other.
Always use {@link android.content.Intent#setDataAndType setDataAndType()} to set both
URI and MIME type.</p>
</dd>

<p><dt><b>Category</b></dt>
<dd>A string containing additional information about the kind of component
that should handle the intent.  Any number of category descriptions can be
placed in an intent, but most intents do not require a category.
Here are some common categories:

<dl>
<dt>{@link android.content.Intent#CATEGORY_BROWSABLE}</dt>
  <dd>The target activity allows itself to be started by a web browser to display data
       referenced by a link&mdash;such as an image or an e-mail message.
  </dd>
<dt>{@link android.content.Intent#CATEGORY_LAUNCHER}</dt>
  <dd>The activity is the initial activity of a task and is listed in
       the system's application launcher.
  </dd>
</dl>

<p>See the {@link android.content.Intent} class description for the full list of
categories.</p>

<p>You can specify a category with {@link android.content.Intent#addCategory addCategory()}.</p>
</dd>
</dl>


<p>These properties listed above (component name, action, data, and category) represent the
defining characteristics of an intent. By reading these properties, the Android system
is able to resolve which app component it should start.</p>

<p>However, an intent can carry additional information that does not affect
how it is resolved to an app component. An intent can also supply:</p>

<dl>
<dt><b>Extras</b></dt>
<dd>Key-value pairs that carry additional information required to accomplish the requested action.
Just as some actions use particular kinds of data URIs, some actions also use particular extras.

<p>You can add extra data with various {@link android.content.Intent#putExtra putExtra()} methods,
each accepting two parameters: the key name and the value.
You can also create a {@link android.os.Bundle} object with all the extra data, then insert
the {@link android.os.Bundle} in the {@link android.content.Intent} with {@link
android.content.Intent#putExtras putExtras()}.</p>

<p>For example, when creating an intent to send an email with
{@link android.content.Intent#ACTION_SEND}, you can specify the "to" recipient with the
{@link android.content.Intent#EXTRA_EMAIL} key, and specify the "subject" with the
{@link android.content.Intent#EXTRA_SUBJECT} key.</p>

<p>The {@link android.content.Intent} class specifies many {@code EXTRA_*} constants
for standardized data types. If you need to declare your own extra keys (for intents that
your app receives), be sure to include your app's package name
as a prefix. For example:</p>
<pre>static final String EXTRA_GIGAWATTS = "com.example.EXTRA_GIGAWATTS";</pre>
</dd>

<dt><b>Flags</b></dt>
<dd>Flags defined in the {@link android.content.Intent} class that function as metadata for the
intent. The flags may instruct the Android system how to launch an activity (for example, which
<a href="{@docRoot}guide/components/tasks-and-back-stack.html">task</a> the activity should belong
to) and how to treat it after it's launched (for example, whether it belongs in the list of recent
activities).

<p>For more information, see the {@link android.content.Intent#setFlags setFlags()} method.</p>
</dd>

</dl>




<h3 id="ExampleExplicit">Example explicit intent</h3>

<p>An explicit intent is one that you use to launch a specific app component, such as
a particular activity or service in your app. To create an explicit intent, define
the component name for the {@link android.content.Intent} object&mdash;all
other intent properties are optional.</p>

<p>For example, if you built a service in your app, named {@code DownloadService},
designed to download a file from the web, you can start it with the following code:</p>

<pre>
// Executed in an Activity, so 'this' is the {@link android.content.Context}
// The fileUrl is a string URL, such as "http://www.example.com/image.png"
Intent downloadIntent = new Intent(this, DownloadService.class);
downloadIntent.setData({@link android.net.Uri#parse Uri.parse}(fileUrl));
startService(downloadIntent);
</pre>

<p>The {@link android.content.Intent#Intent(Context,Class)}
constructor supplies the app {@link android.content.Context} and the
component a {@link java.lang.Class} object. As such,
this intent explicitly starts the {@code DownloadService} class in the app.</p>

<p>For more information about building and starting a service, see the
<a href="{@docRoot}guide/components/services.html">Services</a> guide.</p>




<h3 id="ExampleSend">Example implicit intent</h3>

<p>An implicit intent specifies an action that can invoke any app on the device able
to perform the action. Using an implicit intent is useful when your app cannot perform the
action, but other apps probably can and you'd like the user to pick which app to use.</p>

<p>For example, if you have content you want the user to share with other people, create an intent
with the {@link android.content.Intent#ACTION_SEND} action
and add extras that specify the content to share. When you call
{@link android.content.Context#startActivity startActivity()} with that intent, the user can
pick an app through which to share the content.</p>

<p class="caution"><strong>Caution:</strong> It's possible that a user won't have <em>any</em>
apps that handle the implicit intent you send to {@link android.content.Context#startActivity
startActivity()}. If that happens, the call will fail and your app will crash. To verify
that an activity will receive the intent, call {@link android.content.Intent#resolveActivity
resolveActivity()} on your {@link android.content.Intent} object. If the result is non-null,
then there is at least one app that can handle the intent and it's safe to call
{@link android.content.Context#startActivity startActivity()}. If the result is null,
you should not use the intent and, if possible, you should disable the feature that issues
the intent.</p>


<pre>
// Create the text message with a string
Intent sendIntent = new Intent();
sendIntent.setAction(Intent.ACTION_SEND);
sendIntent.putExtra(Intent.EXTRA_TEXT, textMessage);
sendIntent.setType({@link
        org.apache.http.protocol.HTTP#PLAIN_TEXT_TYPE
        HTTP.PLAIN_TEXT_TYPE}); // "text/plain" MIME type

// Verify that the intent will resolve to an activity
if (sendIntent.resolveActivity(getPackageManager()) != null) {
    startActivity(sendIntent);
}
</pre>

<p class="note"><strong>Note:</strong> In this case, a URI is not used, but the intent's data type
is declared to specify the content carried by the extras.</p>


<p>When {@link android.content.Context#startActivity startActivity()} is called, the system
examines all of the installed apps to determine which ones can handle this kind of intent (an
intent with the {@link android.content.Intent#ACTION_SEND} action and that carries "text/plain"
data). If there's only one app that can handle it, that app opens immediately and is given the
intent. If multiple activities accept the intent, the system
displays a dialog so the user can pick which app to use..</p>


<div class="figure" style="width:200px">
  <img src="{@docRoot}images/training/basics/intent-chooser.png" alt="">
  <p class="img-caption"><strong>Figure 2.</strong> A chooser dialog.</p>
</div>

<h3 id="ForceChooser">Forcing an app chooser</h3>

<p>When there is more than one app that responds to your implicit intent,
the user can select which app to use and make that app the default choice for the
action. This is nice when performing an action for which the user
probably wants to use the same app from now on, such as when opening a web page (users
often prefer just one web browser) .</p>

<p>However, if multiple apps can respond to the intent and the user might want to use a different
app each time, you should explicitly show a chooser dialog. The chooser dialog asks the
user to select which app to use for the action every time (the user cannot select a default app for
the action). For example, when your app performs "share" with the {@link
android.content.Intent#ACTION_SEND} action, users may want to share using a different app depending
on their current situation, so you should always use the chooser dialog, as shown in figure 2.</p>




<p>To show the chooser, create an {@link android.content.Intent} using {@link
android.content.Intent#createChooser createChooser()} and pass it to {@link
android.app.Activity#startActivity startActivity()}. For example:</p>

<pre>
Intent intent = new Intent(Intent.ACTION_SEND);
...

// Always use string resources for UI text.
// This says something like "Share this photo with"
String title = getResources().getString(R.string.chooser_title);
// Create intent to show chooser
Intent chooser = Intent.createChooser(intent, title);

// Verify the intent will resolve to at least one activity
if (sendIntent.resolveActivity(getPackageManager()) != null) {
    startActivity(sendIntent);
}
</pre>

<p>This displays a dialog with a list of apps that respond to the intent passed to the {@link
android.content.Intent#createChooser createChooser()} method and uses the supplied text as the
dialog title.</p>









<h2 id="Receiving">Receiving an Implicit Intent</h2>

<p>To advertise which implicit intents your app can receive, declare one or more intent filters for
each of your app components with an <a href=
"{@docRoot}guide/topics/manifest/intent-filter-element.html">{@code &lt;intent-filter&gt;}</a>
element in your <a href="{@docRoot}guide/topics/manifest/manifest-intro.html">manifest file</a>.
Each intent filter specifies the type of intents it accepts based on the intent's action,
data, and category. The system will deliver an implicit intent to your app component only if the
intent can pass through one of your intent filters.</p>

<p class="note"><strong>Note:</strong> An explicit intent is always delivered to its target,
regardless of any intent filters the component declares.</p>

<p>An app component should declare separate filters for each unique job it can do.
For example, one activity in an image gallery app may have two filters: one filter
to view an image, and another filter to edit an image. When the activity starts,
it inspects the {@link android.content.Intent} and decides how to behave based on the information
in the {@link android.content.Intent} (such as to show the editor controls or not).</p>

<p>Each intent filter is defined by an <a
href="{@docRoot}guide/topics/manifest/intent-filter-element.html">{@code &lt;intent-filter>}</a>
element in the app's manifest file, nested in the corresponding app component (such
as an <a href="{@docRoot}guide/topics/manifest/activity-element.html">{@code &lt;activity>}</a>
element). Inside the <a
href="{@docRoot}guide/topics/manifest/intent-filter-element.html">{@code &lt;intent-filter>}</a>,
you can specify the type of intents to accept using one or more
of these three elements:</p>

<dl>
<dt><a href="{@docRoot}guide/topics/manifest/action-element.html">{@code &lt;action>}</a></dt>
  <dd>Declares the intent action accepted, in the {@code name} attribute. The value
  must be the literal string value of an action, not the class constant.</dd>
<dt><a href="{@docRoot}guide/topics/manifest/data-element.html">{@code &lt;data>}</a></dt>
  <dd>Declares the type of data accepted, using one or more attributes that specify various
  aspects of the data URI (<code>scheme</code>, <code>host</code>, <code>port</code>,
  <code>path</code>, etc.) and MIME type.</dd>
<dt><a href="{@docRoot}guide/topics/manifest/category-element.html">{@code &lt;category>}</a></dt>
  <dd>Declares the intent category accepted, in the {@code name} attribute. The value
  must be the literal string value of an action, not the class constant.

  <p class="note"><strong>Note:</strong> In order to receive implicit intents, you
  <strong>must include</strong> the
  {@link android.content.Intent#CATEGORY_DEFAULT} category in the intent filter. The methods
  {@link android.app.Activity#startActivity startActivity()} and
  {@link android.app.Activity#startActivityForResult startActivityForResult()} treat all intents
  as if they declared the {@link android.content.Intent#CATEGORY_DEFAULT} category.
  If you do not declare this category in your intent filter, no implicit intents will resolve to
  your activity.</p>
  </dd>
</dl>

<p>For example, here's an activity declaration with an intent filter to receive an
{@link android.content.Intent#ACTION_SEND} intent when the data type is text:</p>

<pre>
&lt;activity android:name="ShareActivity">
    &lt;intent-filter>
        &lt;action android:name="android.intent.action.SEND"/>
        &lt;category android:name="android.intent.category.DEFAULT"/>
        &lt;data android:mimeType="text/plain"/>
    &lt;/intent-filter>
&lt;/activity>
</pre>

<p>It's okay to create a filter that includes more than one instance of
<a href="{@docRoot}guide/topics/manifest/action-element.html">{@code &lt;action>}</a>,
<a href="{@docRoot}guide/topics/manifest/data-element.html">{@code &lt;data>}</a>, or
<a href="{@docRoot}guide/topics/manifest/category-element.html">{@code &lt;category>}</a>.
If you do, you simply need to be certain that the component can handle any and all combinations
of those filter elements.</p>

<p>When you want to handle multiple kinds of intents, but only in specific combinations of
action, data, and category type, then you need to create multiple intent filters.</p>


<div class="sidebox-wrapper">
<div class="sidebox">
<h2>Restricting access to components</h2>
<p>Using an intent filter is not a secure way to prevent other apps from starting
your components. Although intent filters restrict a component to respond to only
certain kinds of implicit intents, another app can potentially start your app component
by using an explicit intent if the developer determines your component names.
If it's important that <em>only your own app</em> is able to start one of your components,
set the <a href="{@docRoot}guide/topics/manifest/activity-element.html#exported">{@code
exported}</a> attribute to {@code "false"} for that component.
</p>
</div>
</div>

<p>An implicit intent is tested against a filter by comparing the intent to each of the
three elements. To be delivered to the component, the intent must pass all three tests.
If it fails to match even one of them, the Android system won't deliver the intent to the
component.  However, because a component may have multiple intent filters, an intent that does
not pass through one of a component's filters might make it through on another filter.
More information about how the system resolves intents is provided in the section below
about <a href="#Resolution">Intent Resolution</a>.</p>

<p class="caution"><strong>Caution:</strong> To avoid inadvertently running a different app's
{@link android.app.Service}, always use an explicit intent to start your own service and do not
declare intent filters for your service.</p>

<p class="note"><strong>Note:</strong>
For all activities, you must declare your intent filters in the manifest file.
However, filters for broadcast receivers can be registered dynamically by calling
{@link android.content.Context#registerReceiver(BroadcastReceiver, IntentFilter, String,
Handler) registerReceiver()}. You can then unregister the receiver with {@link
android.content.Context#unregisterReceiver unregisterReceiver()}. Doing so allows your app
to listen for specific broadcasts during only a specified period of time while your app
is running.</p>







<h3 id="ExampleFilters">Example filters</h3>

<p>To better understand some of the intent filter behaviors, look at the following snippet
from the manifest file of a social-sharing app.</p>

<pre>
&lt;activity android:name="MainActivity">
    &lt;!-- This activity is the main entry, should appear in app launcher -->
    &lt;intent-filter>
        &lt;action android:name="android.intent.action.MAIN" />
        &lt;category android:name="android.intent.category.LAUNCHER" />
    &lt;/intent-filter>
&lt;/activity>

&lt;activity android:name="ShareActivity">
    &lt;!-- This activity handles "SEND" actions with text data -->
    &lt;intent-filter&gt;
        &lt;action android:name="android.intent.action.SEND"/>
        &lt;category android:name="android.intent.category.DEFAULT"/>
        &lt;data android:mimeType="text/plain"/>
    &lt;/intent-filter&gt;
    &lt;!-- This activity also handles "SEND" and "SEND_MULTIPLE" with media data -->
    &lt;intent-filter&gt;
        &lt;action android:name="android.intent.action.SEND"/>
        &lt;action android:name="android.intent.action.SEND_MULTIPLE"/>
        &lt;category android:name="android.intent.category.DEFAULT"/>
        &lt;data android:mimeType="application/vnd.google.panorama360+jpg"/>
        &lt;data android:mimeType="image/*"/>
        &lt;data android:mimeType="video/*"/>
    &lt;/intent-filter&gt;
&lt;/activity&gt;
</pre>

<p>The first activity, {@code MainActivity}, is the app's main entry point&mdash;the activity that
opens when the user initially launches the app with the launcher icon:</p>
<ul>
  <li>The {@link android.content.Intent#ACTION_MAIN} action
  indicates this is the main entry point and does not expect any intent data.</li>
  <li>The {@link android.content.Intent#CATEGORY_LAUNCHER} category indicates that this activity's
  icon should be placed in the system's app launcher. If the <a
  href="{@docRoot}guide/topics/manifest/activity-element.html">{@code &lt;activity>}</a> element
  does not specify an icon with {@code icon}, then the system uses the icon from the <a
  href="{@docRoot}guide/topics/manifest/application-element.html">{@code &lt;application>}</a>
  element.</li>
</ul>
<p>These two must be paired together in order for the activity to appear in the app launcher.</p>

<p>The second activity, {@code ShareActivity}, is intended to facilitate sharing text and media
content. Although users might enter this activity by navigating to it from {@code MainActivity},
they can also enter {@code ShareActivity} directly from another app that issues an implicit
intent matching one of the two intent filters.</p>

<p class="note"><strong>Note:</strong> The MIME type,
<a href="https://developers.google.com/panorama/android/">{@code
application/vnd.google.panorama360+jpg}</a>, is a special data type that specifies
panoramic photos, which you can handle with the <a
href="{@docRoot}reference/com/google/android/gms/panorama/package-summary.html">Google
panorama</a> APIs.</p>













<h2 id="PendingIntent">Using a Pending Intent</h2>

<p>A {@link android.app.PendingIntent} object is a wrapper around an {@link
android.content.Intent} object. The primary purpose of a {@link android.app.PendingIntent}
is to grant permission to a foreign application
to use the contained {@link android.content.Intent} as if it were executed from your
app's own process.</p>

<p>Major use cases for a pending intent include:</p>
<ul>
  <li>Declare an intent to be executed when the user performs an action with your <a
  href="{@docRoot}guide/topics/ui/notifiers/notifications.html">Notification</a>
  (the Android system's {@link android.app.NotificationManager}
  executes the {@link android.content.Intent}).
  <li>Declare an intent to be executed when the user performs an action with your
  <a href="{@docRoot}guide/topics/appwidgets/index.html">App Widget</a>
  (the Home screen app executes the {@link android.content.Intent}).
  <li>Declare an intent to be executed at a specified time in the future (the Android
  system's {@link android.app.AlarmManager} executes the {@link android.content.Intent}).
</ul>

<p>Because each {@link android.content.Intent} object is designed to be handled by a specific
type of app component (either an {@link android.app.Activity}, a {@link android.app.Service}, or
a {@link android.content.BroadcastReceiver}), so too must a {@link android.app.PendingIntent} be
created with the same consideration. When using a pending intent, your app will not
execute the intent with a call such as {@link android.content.Context#startActivity
startActivity()}. You must instead declare the intended component type when you create the
{@link android.app.PendingIntent} by calling the respective creator method:</p>

<ul>
  <li>{@link android.app.PendingIntent#getActivity PendingIntent.getActivity()} for an
  {@link android.content.Intent} that starts an {@link android.app.Activity}.</li>
  <li>{@link android.app.PendingIntent#getService PendingIntent.getService()} for an
  {@link android.content.Intent} that starts a {@link android.app.Service}.</li>
  <li>{@link android.app.PendingIntent#getBroadcast PendingIntent.getBroadcast()} for a
  {@link android.content.Intent} that starts an {@link android.content.BroadcastReceiver}.</li>
</ul>

<p>Unless your app is <em>receiving</em> pending intents from other apps,
the above methods to create a {@link android.app.PendingIntent} are the only
{@link android.app.PendingIntent} methods you'll probably ever need.</p>

<p>Each method takes the current app {@link android.content.Context}, the
{@link android.content.Intent} you want to wrap, and one or more flags that specify
how the intent should be used (such as whether the intent can be used more than once).</p>

<p>More information about using pending intents is provided with the documentation for each
of the respective use cases, such as in the <a
href="{@docRoot}guide/topics/ui/notifiers/notifications.html">Notifications</a>
and <a href="{@docRoot}guide/topics/appwidgets/index.html">App Widgets</a> API guides.</p>







<h2 id="Resolution">Intent Resolution</h2>


<p>When the system receives an implicit intent to start an activity, it searches for the
best activity for the intent by comparing the intent to intent filters based on three aspects:</p>

<ul>
  <li>The intent action
  <li>The intent data (both URI and data type)
  <li>The intent category
</ul>

<p>The following sections describe how an intents are matched to the appropriate component(s)
in terms of how the intent filter is declared in an app's manifest file.</p>


<h3 id="ActionTest">Action test</h3>

<p>To specify accepted intent actions, an intent filter can declare zero or more
<a href="{@docRoot}guide/topics/manifest/action-element.html">{@code
&lt;action&gt;}</a> elements.  For example:</p>

<pre>
&lt;intent-filter&gt;
    &lt;action android:name="android.intent.action.EDIT" /&gt;
    &lt;action android:name="android.intent.action.VIEW" /&gt;
    ...
&lt;/intent-filter&gt;
</pre>

<p>To get through this filter, the action specified in the {@link android.content.Intent}
  must match one of the actions listed in the filter.</p>

<p>If the filter does not list any actions, there is nothing for an
intent to match, so all intents fail the test. However, if an {@link android.content.Intent}
does not specify an action, it will pass the test (as long as the filter
contains at least one action).</p>



<h3 id="CategoryTest">Category test</h3>

<p>To specify accepted intent categories, an intent filter can declare zero or more
<a href="{@docRoot}guide/topics/manifest/category-element.html">{@code
&lt;category&gt;}</a> elements.  For example:</p>

<pre>
&lt;intent-filter&gt;
    &lt;category android:name="android.intent.category.DEFAULT" /&gt;
    &lt;category android:name="android.intent.category.BROWSABLE" /&gt;
    ...
&lt;/intent-filter&gt;
</pre>

<p>For an intent to pass the category test, every category in the {@link android.content.Intent}
must match a category in the filter. The reverse is not necessary&mdash;the intent filter may
declare more categories than are specified in the {@link android.content.Intent} and the
{@link android.content.Intent} will still pass. Therefore, an intent with no categories should
always pass this test, regardless of what categories are declared in the filter.</p>

<p class="note"><strong>Note:</strong>
Android automatically applies the the {@link android.content.Intent#CATEGORY_DEFAULT} category
to all implicit intents passed to {@link
android.content.Context#startActivity startActivity()} and {@link
android.app.Activity#startActivityForResult startActivityForResult()}.
So if you want your activity to receive implicit intents, it must
include a category for {@code "android.intent.category.DEFAULT"} in its intent filters (as
shown in the previous {@code &lt;intent-filter>} example.</p>



<h3 id="DataTest">Data test</h3>

<p>To specify accepted intent data, an intent filter can declare zero or more
<a href="{@docRoot}guide/topics/manifest/data-element.html">{@code
&lt;data&gt;}</a> elements.  For example:</p>

<pre>
&lt;intent-filter&gt;
    &lt;data android:mimeType="video/mpeg" android:scheme="http" ... /&gt;
    &lt;data android:mimeType="audio/mpeg" android:scheme="http" ... /&gt;
    ...
&lt;/intent-filter&gt;
</pre>

<p>Each <code><a href="{@docRoot}guide/topics/manifest/data-element.html">&lt;data&gt;</a></code>
element can specify a URI structure and a data type (MIME media type).  There are separate
attributes &mdash; {@code scheme}, {@code host}, {@code port},
and {@code path} &mdash; for each part of the URI:
</p>

<p style="margin-left: 2em">{@code &lt;scheme>://&lt;host>:&lt;port>/&lt;path>}</p>

<p>
For example:
</p>

<p style="margin-left: 2em">{@code content://com.example.project:200/folder/subfolder/etc}</p>

<p>In this URI, the scheme is {@code content}, the host is {@code com.example.project},
the port is {@code 200}, and the path is {@code folder/subfolder/etc}.
</p>

<p>Each of these attributes is optional in a <a
href="{@docRoot}guide/topics/manifest/data-element.html">{@code &lt;data>}</a> element,
but there are linear dependencies:</p>
<ul>
  <li>If a scheme is not specified, the host is ignored.</li>
  <li>If a host is not specified, the port is ignored.</li>
  <li>If both the scheme and host are not specified, the path is ignored.</li>
</ul>

<p>When the URI in an intent is compared to a URI specification in a filter,
it's compared only to the parts of the URI included in the filter. For example:</p>
<ul>
  <li>If a filter specifies only a scheme, all URIs with that scheme match
the filter.</li>
  <li>If a filter specifies a scheme and an authority but no path, all URIs
with the same scheme and authority pass the filter, regardless of their paths.</li>
  <li>If a filter specifies a scheme, an authority, and a path, only URIs with the same scheme,
authority, and path pass the filter.</li>
</ul>

<p class="note"><strong>Note:</strong> A path specification can
contain a wildcard asterisk (*) to require only a partial match of the path name.</p>

<p>The data test compares both the URI and the MIME type in the intent to a URI
and MIME type specified in the filter.  The rules are as follows:
</p>

<ol type="a">
<li>An intent that contains neither a URI nor a MIME type passes the
test only if the filter does not specify any URIs or MIME types.</li>

<li>An intent that contains a URI but no MIME type (neither explicit nor inferable from the
URI) passes the test only if its URI matches the filter's URI format
and the filter likewise does not specify a MIME type.</li>

<li>An intent that contains a MIME type but not a URI passes the test
only if the filter lists the same MIME type and does not specify a URI format.</li>

<li>An intent that contains both a URI and a MIME type (either explicit or inferable from the
URI) passes the MIME type part of the test only if that
type matches a type listed in the filter.  It passes the URI part of the test
either if its URI matches a URI in the filter or if it has a {@code content:}
or {@code file:} URI and the filter does not specify a URI.  In other words,
a component is presumed to support {@code content:} and {@code file:} data if
its filter lists <em>only</em> a MIME type.</p></li>
</ol>

<p>
This last rule, rule (d), reflects the expectation
that components are able to get local data from a file or content provider.
Therefore, their filters can list just a data type and do not need to explicitly
name the {@code content:} and {@code file:} schemes.
This is a typical case.  A <a
href="{@docRoot}guide/topics/manifest/data-element.html">{@code &lt;data>}</a> element
like the following, for example, tells Android that the component can get image data from a content
provider and display it:
</p>

<pre>
&lt;intent-filter&gt;
    &lt;data android:mimeType="image/*" /&gt;
    ...
&lt;/intent-filter&gt;</pre>

<p>
Because most available data is dispensed by content providers, filters that
specify a data type but not a URI are perhaps the most common.
</p>

<p>
Another common configuration is filters with a scheme and a data type.  For
example, a <a
href="{@docRoot}guide/topics/manifest/data-element.html">{@code &lt;data>}</a>
element like the following tells Android that
the component can retrieve video data from the network in order to perform the action:
</p>

<pre>
&lt;intent-filter&gt;
    &lt;data android:scheme="http" android:type="video/*" /&gt;
    ...
&lt;/intent-filter&gt;</pre>



<h3 id="imatch">Intent matching</h3>

<p>Intents are matched against intent filters not only to discover a target
component to activate, but also to discover something about the set of
components on the device.  For example, the Home app populates the app launcher
by finding all the  activities with intent filters that specify the
{@link android.content.Intent#ACTION_MAIN} action and
{@link android.content.Intent#CATEGORY_LAUNCHER} category.</p>

<p>Your application can use intent matching in a similar way.
The {@link android.content.pm.PackageManager} has a set of {@code query...()}
methods that return all components that can accept a particular intent, and
a similar series of {@code resolve...()} methods that determine the best
component to respond to an intent.  For example,
{@link android.content.pm.PackageManager#queryIntentActivities
queryIntentActivities()} returns a list of all activities that can perform
the intent passed as an argument, and {@link
android.content.pm.PackageManager#queryIntentServices
queryIntentServices()} returns a similar list of services.
Neither method activates the components; they just list the ones that
can respond.  There's a similar method,
{@link android.content.pm.PackageManager#queryBroadcastReceivers
queryBroadcastReceivers()}, for broadcast receivers.
</p>