docs/html/training/app-links/index.jd

page.title=Handling App Links
page.image=images/cards/card-app-linking_2x.png
page.keywords=applinking, deeplinks, intents
page.tags=androidm,marshmallow
@jd:body

<div id="tb-wrapper">
  <div id="tb">
    <h2>This lesson teaches you to</h2>
    <ol>
        <li><a href="#url-handling">Understand URI Request Handling</a> </li>
        <li><a href="#intent-handler">Create an Intent Handler for URIs</a></li>
        <li><a href="#request-verify">Request App Links Verification</a></li>
        <li><a href="#web-assoc">Declare Website Associations</a></li>
        <li><a href="#testing">Test App Links</a></li>
    </ol>
  <h2>See also</h2>
  <ol>
    <li><a href="{@docRoot}tools/help/app-link-indexing.html">Supporting URLs and App Indexing in Android Studio</a></li>
  </ol>
  </div>
</div>



<p>
  Users following web links on devices are frequently presented with confusing choices. Tapping a
  link often results in the system asking the user which app should handle that link. For example,
  clicking a URI in an email from a bank might result in a dialog asking the user whether to use
  the browser, or the bank's own app, to open the link. Android 6.0 (API level 23) and higher allow
  an app to designate itself as the default handler of a given type of link. If the user doesn't
  want the app to be the default handler, they can override this behavior from
  <strong>Settings</strong>.
</p>

<p>
  Automatic handling of links requires the cooperation of app developers and website owners.
  A developer must configure their app to declare associations with one or more websites, and to
  request that the system verify those associations. A website owner must, in turn, provide
  that verification by publishing a <a href="http://developers.google.com/digital-asset-links/"><i>Digital
  Asset Links</i></a> file. The general steps for creating verified app links are as follows:
</p>

<ol>
  <li>In your app manifest, create intent filters for your website URIs.</li>
  <li>Configure your app to request verification of app links.</li>
  <li>Publish a Digital Asset Links JSON file on your websites to provide verification.</li>
</ol>

<h2 id="url-handling">Understand URI Request Handling</h2>

<p>
  The app links feature allows your app to become the default handler for the website URIs you
  specify, as long as the user has not already chosen a default app to handle that URI pattern.
  When a clicked link or programmatic request invokes a web URI intent, the Android system
  uses the following criteria, in descending order, to determine how to handle the request:
</p>

<ol>
  <li>
    <strong>The user has set app link associations</strong>: If the user has designated an app to
    handle app links, the system passes the web URI request to that app. A user can set this
    association in one of two ways: clicking <strong>Always</strong> when selecting an app
    from an app-selection dialog; or, opening <em>Settings &gt; Apps &gt; (gear icon)
    &gt; App links</em>, selecting an app to use, and setting the app's
    <strong>App links</strong> property to the <strong>Open in this app</strong> option.
  </li>

  <li>
    <strong>The user has set no association, and there is one supporting app</strong>: If the user
    has not set a preference that matches the web URI request, and there is only one app declaring
    support for the intent’s URI pattern, the system automatically passes the request to that app.
  </li>

  <li>
    <strong>The user has set no association, and there are multiple supporting apps</strong>: If
    there are multiple apps declaring support for the web URI pattern, the system displays an
    app-selection dialog, prompting the user to select the most appropriate app.
  </li>
</ol>

<p>
  In case 2, if the user has newly installed the app, and the system has
  verified it as a handler for this type of link, the system sets the app as the default handler. In
  the other two cases, the presence of a verified app link handler has no effect on system behavior.
</p>


<h2 id="intent-handler">Create an Intent Handler for URIs</h2>

<p>
  App links are based on the <a href="{@docRoot}guide/components/intents-filters.html">Intent</a>
  framework, which enables apps to handle requests from the system or other apps. Multiple apps may
  declare the same web link URI patterns in their intent filters. When a user clicks on a web link
  that does not have a default launch handler, the platform selects an app to handle the request,
  using the criteria described in <a href="#url-handling">Understanding URI Request Handling</a>.
</p>

<p>
  To enable your app to handle links, use intent filters in your app manifest to declare the URI
  patterns that your app handles. The following example shows an intent filter that can
  handle links to {@code http://www.android.com} and {@code https://www.android.com}:
</p>

<pre>
&lt;activity ...&gt;
    &lt;intent-filter&gt;
        &lt;action android:name="android.intent.action.VIEW" /&gt;
        &lt;category android:name="android.intent.category.DEFAULT" /&gt;
        &lt;category android:name="android.intent.category.BROWSABLE" /&gt;
        &lt;data android:scheme="http" /&gt;
        &lt;data android:scheme="https" /&gt;
        &lt;data android:host="www.android.com" /&gt;
    &lt;/intent-filter&gt;
&lt;/activity&gt;
</pre>

<p>
  As this example shows, intent filters for app links must declare an {@code android:scheme}
  value of {@code http}, {@code https}, or both. The filter must not declare
  any other schemes. The filter must also include the {@code android.intent.action.VIEW} and
  {@code android.intent.category.BROWSABLE} category names.
</p>

<p>
  This manifest declaration defines the connection between your app and a website. However, in
  order to have the system treat your app as the default handler for a set of URIs, you must
  also request that the system verify this connection.
  The next section explains how to implement this verification.
</p>


<h2 id="request-verify">Request App Links Verification</h2>

<p>
  In addition to using intent filters to declare an association between your app and a website,
  your manifest must also include an additional declaration for requesting automatic verification.
  When this declaration is present, the Android system attempts to verify your app after
  installation. If the verification succeeds, and the user has not set an alternate
  preference for handling your website URIs, the system automatically routes those URI requests to
  your app.
</p>

<p>
  The system performs app-link verifications by comparing the host names in the data elements of
  the app’s intent filters against the Digital Asset Links files ({@code assetlinks.json}) hosted
  on the respective web domains. To enable the system to verify a host, make sure that your intent
  filter declarations include the {@code android.intent.action.VIEW} intent action and {@code
  android.intent.category.BROWSABLE} intent category.
</p>


<h3 id="config-verify">Enabling automatic verification</h3>

<p>
  To enable link handling verification for your app, set the {@code android:autoVerify} attribute to
  {@code true} on at least one of the web URI intent filters in your app manifest, as shown in the
  following manifest code snippet:
</p>

<pre>
&lt;activity ...&gt;

    &lt;intent-filter <strong>android:autoVerify="true"</strong>&gt;
        &lt;action android:name="android.intent.action.VIEW" /&gt;
        &lt;category android:name="android.intent.category.DEFAULT" /&gt;
        &lt;category android:name="android.intent.category.BROWSABLE" /&gt;
        &lt;data android:scheme="http" android:host="www.android.com" /&gt;
        &lt;data android:scheme="https" android:host="www.android.com" /&gt;
    &lt;/intent-filter&gt;

&lt;/activity&gt;
</pre>

<p>
  When the {@code android:autoVerify} attribute is present, installing your app causes the system
  to attempt to verify all hosts associated with the web URIs in all of your app's intent filters.
  The system treats your app as the default handler for the specified URI pattern only if it
  successfully verifies <em>all</em> app link patterns declared in your manifest.
</p>


<h3 id="multi-host">Supporting app linking for multiple hosts</h3>

<p>
  The system must be able to verify every host specified in the app’s web URI intent filters’ data
  elements against the Digital Asset Links files hosted on the respective web domains. If any
  verification fails, the app is not verified to be a default handler for any of the web URI
  patterns defined in the app's intent filters. For example, an app with the following intent
  filters would fail verification if an {@code assetlinks.json} file were not found at both
  {@code https://www.domain1.com/.well-known/assetlinks.json} and
  {@code https://www.domain2.com/.well-known/assetlinks.json}:
</p>

<pre>
&lt;application&gt;

  &lt;activity android:name=”MainActivity”&gt;
    &lt;intent-filter <strong>android:autoVerify="true"</strong>&gt;
      &lt;action android:name="android.intent.action.VIEW" /&gt;
      &lt;category android:name="android.intent.category.DEFAULT" /&gt;
      &lt;category android:name="android.intent.category.BROWSABLE" /&gt;
      &lt;data android:scheme="http" android:host="www.domain1.com" /&gt;
      &lt;data android:scheme="https" android:host="www.domain1.com" /&gt;
    &lt;/intent-filter&gt;
  &lt;/activity&gt;
  &lt;activity android:name=”SecondActivity”&gt;
    &lt;intent-filter&gt;
      &lt;action android:name="android.intent.action.VIEW" /&gt;
      &lt;category android:name="android.intent.category.DEFAULT" /&gt;
      &lt;category android:name="android.intent.category.BROWSABLE" /&gt;
      &lt;data android:scheme="https" android:host="www.domain2.com" /&gt;
    &lt;/intent-filter&gt;
  &lt;/activity&gt;

&lt;/application
</pre>


<h3 id="multi-subdomain">Supporting app linking for multiple subdomains</h3>

<p>
  The Digital Asset Links protocol treats subdomains as unique, separate hosts. If your intent
  filter lists both the {@code www.example.com} and {@code mobile.example.com} subdomains as
  hosts, you must host a separate {@code assetlink.json} file on each subdomain. For example, an
  app with the following intent filter declaration would pass verification only if the website
  owner published valid {@code assetlinks.json} files at both
  {@code https://www.example.com/.well-known/assetlinks.json} and
  {@code https://mobile.example.com/.well-known/assetlinks.json}:
</p>

<pre>
&lt;application&gt;
  &lt;activity android:name=”MainActivity”&gt;
    &lt;intent-filter <strong>android:autoVerify="true"</strong>&gt;
      &lt;action android:name="android.intent.action.VIEW" /&gt;
      &lt;category android:name="android.intent.category.DEFAULT" /&gt;
      &lt;category android:name="android.intent.category.BROWSABLE" /&gt;
      &lt;data android:scheme="http" android:host="www.example.com" /&gt;
      &lt;data android:scheme="https" android:host="mobile.example.com" /&gt;
    &lt;/intent-filter&gt;
  &lt;/activity&gt;
&lt;/application&gt;
</pre>


<h2 id="web-assoc">Declare Website Associations</h2>

<p>
  For app link verification to be successful, website owners must declare associations
  with apps. A site owner declares the relationship to an app by hosting a Digital Asset Links JSON
  file, with the name {@code assetlinks.json}, at the following well-known location on the domain:
</p>

<pre>
https://<em>domain</em>[:<em>optional_port</em>]/.well-known/assetlinks.json
</pre>

<p class="note">
  <strong>Important:</strong> The system verifies the JSON file via the encrypted HTTPS protocol.
  Make sure that your hosted file is accessible over an HTTPS connection, regardless of whether
  your app's intent filter includes {@code https}.
</p>

<p>
  A Digital Asset Links JSON file indicates the Android apps that are associated with the website.
  The JSON file uses the following fields to identify associated apps:
</p>

<ul>
  <li>{@code package_name}: The package name declared in the app's manifest.</li>

  <li>{@code sha256_cert_fingerprints}: The SHA256 fingerprints of your app’s signing certificate.
    You can use the following command to generate the fingerprint via the Java keytool:

    <pre class="no-pretty-print">
$ keytool -list -v -keystore my-release-key.keystore
    </pre>

    This field supports multiple fingerprints, which can be used to support different versions
    of your app, such as debug and production builds.
  </li>
</ul>

<p>
  The following example {@code assetlinks.json} file grants link-opening rights to a
  {@code com.example} Android app:
</p>

<pre>
[{
  "relation": ["delegate_permission/common.handle_all_urls"],
  "target": {
    "namespace": "android_app",
    "package_name": "com.example",
    "sha256_cert_fingerprints":
    ["14:6D:E9:83:C5:73:06:50:D8:EE:B9:95:2F:34:FC:64:16:A0:83:42:E6:1D:BE:A8:8A:04:96:B2:3F:CF:44:E5"]
  }
}]
</pre>


<h3 id="multiple-apps">Associating a website with multiple apps</h3>

<p>
  A website can declare associations with multiple apps within the same {@code assetlinks.json}
  file. The following file listing shows an example of a statement file that declares association
  with two apps, separately, and resides at
  <code>https://www.example.com/.well-known/assetlinks.json</code>:
</p>

<pre>
[{
  "relation": ["delegate_permission/common.handle_all_urls"],
  "target": {
    "namespace": "android_app",
    "package_name": <strong>"example.com.puppies.app"</strong>,
    "sha256_cert_fingerprints":
    ["<strong>14:6D:E9:83:C5:73:06:50:D8:EE:B9:95:2F:34:FC:64:16:A0:83:42:E6:1D:BE:A8:8A:04:96:B2:3F:CF:44:E5</strong>"]
  }
  },
  {
  "relation": ["delegate_permission/common.handle_all_urls"],
  "target": {
    "namespace": "android_app",
    "package_name": "<strong>example.com.monkeys.app</strong>",
    "sha256_cert_fingerprints":
    ["<strong>14:6D:E9:83:C5:73:06:50:D8:EE:B9:95:2F:34:FC:64:16:A0:83:42:E6:1D:BE:A8:8A:04:96:B2:3F:CF:44:E5</strong>"]
  }
}]
</pre>

<p>
  Different apps may handle links for different resources under the same web host. For example,
  app1 may declare an intent filter for {@code https://example.com/articles}, and app2 may declare
  an intent filter for {@code https://example.com/videos}.
</p>

<p class="note">
  <strong>Note:</strong> Multiple apps associated with a domain may be signed with the same or
  different certificates.
</p>


<h3 id="multi-site">Associating multiple websites with a single app</h3>

<p>
  Multiple websites can declare associations with the same app in their respective {@code
  assetlinks.json} files. The following file listings show an example of how to declare the
  association of domain1 and domain2 with app1. The first listing shows the association of
  domain1 with app1:
</p>

<pre>
https://www.domain1.com/.well-known/assetlinks.json

[{
  "relation": ["delegate_permission/common.handle_all_urls"],
  "target": {
    "namespace": "android_app",
    "package_name": "<strong>com.mycompany.app1</strong>",
    "sha256_cert_fingerprints":
    ["<strong>14:6D:E9:83:C5:73:06:50:D8:EE:B9:95:2F:34:FC:64:16:A0:83:42:E6:1D:BE:A8:8A:04:96:B2:3F:CF:44:E5</strong>"]
  }
}]
</pre>

<p>The next listing shows the association of domain2 with app1. Only the very last line, which
specifies the URL, is different:</p>

<pre>
https://www.domain2.com/.well-known/assetlinks.json

[{
  "relation": ["delegate_permission/common.handle_all_urls"],
  "target": {
    "namespace": "android_app",
    "package_name": "<strong>com.mycompany.app1</strong>",
    "sha256_cert_fingerprints":
    ["<strong>14:6D:E9:83:C5:73:06:50:D8:EE:B9:95:2F:34:FC:64:16:A0:83:42:E6:1D:BE:A8:8A:04:96:B2:3F:CF:44:E5</strong>"]
  }
}]
</pre>

<h2 id="testing">Test App Links</h2>

<p>
  When implementing the app linking feature, you should test the linking functionality to
  make sure the system can associate your app with your websites, and handle URI requests,
  as you expect.
</p>


<h3 id="test-hosts">Confirm the list of hosts to verify</h3>

<p>
  When testing, you should confirm the list of associated hosts that the system should verify
  for your app. Make a list of all web URIs whose corresponding intent filters include the following
  attributes and elements:
</p>

<ul>
  <li>{@code android:scheme} attribute with a value of {@code http} or {@code https}
  </li>
  <li>{@code android:host} attribute with a domain URI pattern
  </li>
  <li>{@code android.intent.action.VIEW} category element
  </li>
  <li>{@code android.intent.category.BROWSABLE} category element
  </li>
</ul>

<p>
  Use this list to check that a Digital Asset Links JSON file is provided on each named host
  and subdomain.
</p>


<h3 id="test-dal-files">Confirm the Digital Asset Links files</h3>

<p>
  For each website, use the Digital Asset Links API to confirm that the Digital Asset Links JSON
  file is properly hosted and defined:
</p>

<pre>
https://digitalassetlinks.googleapis.com/v1/statements:list?
   source.web.site=https://<strong>&lt;domain1&gt;:&lt;port&gt;</strong>&amp;
   relation=delegate_permission/common.handle_all_urls
</pre>


<h3 id="test-intent">Testing a web URI intent</h3>

<p>
  Once you have confirmed the list of websites to associate with your app, and you have confirmed
  that the hosted JSON file is valid, install the app on your device. Wait at least 20 seconds for
  the asynchronous verification process to complete. Use the following command to check
  whether the system verified your app and set the correct link handling policies:
</p>

<pre>
adb shell am start -a android.intent.action.VIEW \
    -c android.intent.category.BROWSABLE \
    -d "http://&lt;domain1&gt;:&lt;port&gt;"
</pre>


<h3 id="check-link-policies">Check link policies</h3>

<p>
  As part of your testing process, you can check the current system settings for link handling.
  Use the following command to get a listing of existing link-handling policies for all
  applications:
</p>

<pre>
adb shell dumpsys package domain-preferred-apps
 --or--
adb shell dumpsys package d
</pre>

<p class="note">
  <strong>Note:</strong> Make sure you wait at least 20 seconds after installation of your app to
  allow for the system to complete the verification process.
</p>

<p>
  The command returns a listing of each user or profile defined on the device,
  preceded by a header in the following format:
</p>

<pre>
App linkages for user 0:
</pre>

<p>
  Following this header, the output uses the following format to list the link-handling settings
  for that user:
</p>

<pre>
Package: com.android.vending
Domains: play.google.com market.android.com
Status: always : 200000002
</pre>

<p>This listing indicates which apps are associated with which domains for that user:</p>

<ul>
  <li>{@code Package} - Identifies an app by its package name, as declared in its manifest.
  </li>
  <li>{@code Domains} - Shows the full list of hosts whose web links this app handles, using
  blank spaces as delimiters.
  </li>
  <li>{@code Status} - Shows the current link-handling setting for this app. An app that has
  passed verification, and whose manifest contains {@code android:autoVerify="true"}, shows a status
  of {@code always}. The hexadecimal number after this status is related to the Android system's
  record of the user’s app linkage preferences. This value does not indicate whether verification
  succeeded.
  </li>
</ul>

<p class="note">
  <strong>Note:</strong> If a user changes the app link settings for an app before verification
  is complete, you may see a false positive for a successful verification, even though
  verification has failed. This verification failure, however, does not matter if the user
  explicitly enabled the app to open supported links without asking. This is because
  user preferences take precedence over programmatic verification (or lack of it). As a result,
  the link goes directly to your app, without showing a dialog, just as if verification had
  succeeded.
</p>



<h3 id="test-example">Test example</h3>

<p>
  For app link verification to succeed, the system must be able to verify your app with all of
  the websites that you specify in your app’s intent filters, and that meet the criteria for app
  links. The following example shows a manifest configuration with several app links defined:
</p>

<pre>
&lt;application&gt;

    &lt;activity android:name=”MainActivity”&gt;
        &lt;intent-filter <strong>android:autoVerify="true"</strong>&gt;
            &lt;action android:name="android.intent.action.VIEW" /&gt;
            &lt;category android:name="android.intent.category.DEFAULT" /&gt;
            &lt;category android:name="android.intent.category.BROWSABLE" /&gt;
            &lt;data android:scheme="http" android:host="www.example.com" /&gt;
            &lt;data android:scheme="https" android:host="mobile.example.com" /&gt;
        &lt;/intent-filter&gt;
        &lt;intent-filter&gt;
            &lt;action android:name="android.intent.action.VIEW" /&gt;
            &lt;category android:name="android.intent.category.BROWSABLE" /&gt;
            &lt;data android:scheme="http" android:host="www.example2.com" /&gt;
        &lt;/intent-filter&gt;
    &lt;/activity&gt;

    &lt;activity android:name=”SecondActivity”&gt;
        &lt;intent-filter&gt;
            &lt;action android:name="android.intent.action.VIEW" /&gt;
            &lt;category android:name="android.intent.category.DEFAULT" /&gt;
            &lt;category android:name="android.intent.category.BROWSABLE" /&gt;
            &lt;data android:scheme="http" android:host="account.example.com" /&gt;
        &lt;/intent-filter&gt;
    &lt;/activity&gt;

      &lt;activity android:name=”ThirdActivity”&gt;
        &lt;intent-filter&gt;
            &lt;action android:name="android.intent.action.VIEW" /&gt;
            &lt;category android:name="android.intent.category.DEFAULT" /&gt;
            &lt;data android:scheme="http" android:host="map.example.com" /&gt;
        &lt;/intent-filter&gt;
        &lt;intent-filter&gt;
            &lt;action android:name="android.intent.action.VIEW" /&gt;
            &lt;category android:name="android.intent.category.BROWSABLE" /&gt;
            &lt;data android:scheme="market" android:host="example.com" /&gt;
        &lt;/intent-filter&gt;
      &lt;/activity&gt;

&lt;/application&gt;
</pre>

<p>
  The list of hosts that the platform would attempt to verify from the above manifest is:
</p>

<pre>
www.example.com
mobile.example.com
www.example2.com
account.example.com
</pre>

<p>
  The list of hosts that the platform would not attempt to verify from the above manifest is:
</p>

<pre>
map.example.com (it does not have android.intent.category.BROWSABLE)
market://example.com (it does not have either an “http” or “https” scheme)
</pre>