docs/html/preview/features/app-linking.jd

page.title=App Links

@jd:body


<div id="qv-wrapper">
  <div id="qv">
    <h2>In this document</h2>
      <ol>
        <li><a href="#web-assoc">Declare a Website Association</a></li>
        <li><a href="#verfy-links">Request App Link Verification</a></li>
        <li><a href="#user-manage">Managing App Link Settings</a></li>
      </ol>
  </div>
</div>

<p>
  The Android Intent system is a flexible mechanism to enable apps to handle content and requests.
  Multiple apps may declare matching URI patterns in their intent filters. When a user clicks on a
  web link that does not have default launch handler, the platform may show a dialog for the user
  to select from a list of apps that have declared matching intent filters.
</p>

<p>
  The Android M Developer Preview introduces support for App Links, which improves upon existing
  link handling by allowing app developers to associate an app with a web domain they own. When
  developers create this association, the platform can automatically determine the default app used
  to handle a particular web link and skip asking users.
</p>


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

<p>
  Website owners must declare associations with apps to establish an app link. The site owner
  declares the relationship to an app by hosting a JSON file, named {@code statements.json}, at the
  well-known location on the domain:
</p>

<pre>http://&lt;domain&gt;:&lt;optional port&gt;/.well-known/statements.json</pre>

<p class="note">
  <strong>Note:</strong>
  During the M Developer Preview period, the JSON file is verified via http protocol. For
  the official release of the platform, the file is verified over encrypted, https protocol.
</p>

<p>
  This JSON file indicates the Android app that should be used as the default handler for the URLs
  under this domain. It identifies the app based on these fields:
</p>

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

  <li>{@code sha256_cert_fingerprints}: The SHA256 fingerprint of your app’s signing certificate.
    You can use the Java keytool to generate the fingerprint using the following command:
    <pre>keytool -list -v -keystore my-release-key.keystore</pre>
  </li>
</ul>

<p>
  The following file listing shows an example of the contents and format of a
  {@code statements.json} file:
</p>

<pre>
[{
  "relation": ["delegate_permission/common.handle_all_urls"],
  "target": {
    "namespace": "android_app",
    "package_name": "<strong>&lt;package name&gt;</strong>",
    "sha256_cert_fingerprints": ["<strong>6C:EC:C5:0E:34:AE....EB:0C:9B</strong>"]
  }
}]
</pre>


<h2 id="verfy-links">Request App Link Verification</h2>

<p>
  An app can request that the platform automatically verify any app links defined by the host names
  in the data elements of its intent filters against the {@code statements.json} files hosted on
  the respective web domains. To request app link verification, add an {@code android:autoVerify}
  attribute to each desired intent filter in the 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 in an app manifest, the platform
  attempts to verify app links when the app is installed. If the platform cannot successfully
  verify the app links, the app is not set as the preferred app to handle the web links. The next
  time a user opens one of the links, the platform falls back to presenting the user with a
  dialog.
</p>

<p class="note">
  <strong>Note:</strong> In testing, there is a potential for a false positive if verfication
  fails, but the user has explicitly enabled the app to open supported links without asking, using
  the system Settings app. In this case, no dialog is shown and the link goes directly to your
  app, but only because of the user setting, and not because verification succeeded.
</p>


<h2 id="user-manage">Managing App Link Settings</h2>

<p>
  Users can change app link settings so URLs are handled the way they prefer. You can review and
  manage app links in the system Settings app, under <strong>Settings &gt; Apps &gt; App Info &gt;
  Open by default</strong>.
</p>