docs/html/training/sync-adapters/creating-authenticator.jd

page.title=Creating a Stub Authenticator

trainingnavtop=true
@jd:body


<div id="tb-wrapper">
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<h2>This lesson teaches you to</h2>
<ol>
    <li>
        <a href="#CreateAuthenticator">Add a Stub Authenticator Component</a>
    </li>
    <li>
        <a href="#CreateAuthenticatorService">Bind the Authenticator to the Framework</a>
    </li>
    <li>
        <a href="#CreateAuthenticatorFile">Add the Authenticator Metadata File</a>
    </li>
    <li>
        <a href="#DeclareAuthenticator">Declare the Authenticator in the Manifest</a>
    </li>
</ol>

<h2>You should also read</h2>
<ul>
    <li>
        <a href="{@docRoot}guide/components/bound-services.html">Bound Services</a>
    </li>
</ul>

<h2>Try it out</h2>

<div class="download-box">
 <a href="http://developer.android.com/shareables/training/BasicSyncAdapter.zip" class="button">Download the sample</a>
 <p class="filename">BasicSyncAdapter.zip</p>
</div>

</div>
</div>
<p>
    The sync adapter framework assumes that your sync adapter transfers data between device storage
    associated with an account and server storage that requires login access. For this reason, the
    framework expects you to provide a component called an authenticator as part of your sync
    adapter. This component plugs into the Android accounts and authentication framework and
    provides a standard interface for handling user credentials such as login information.
</p>
<p>
    Even if your app doesn't use accounts, you still need to provide an authenticator component.
    If you don't use accounts or server login, the information handled by the authenticator is
    ignored, so you can provide an authenticator component that contains stub method
    implementations. You also need to provide a bound {@link android.app.Service} that
    allows the sync adapter framework to call the authenticator's methods.
</p>
<p>
    This lesson shows you how to define all the parts of a stub authenticator that you need to
    satisfy the requirements of the sync adapter framework. If you need to provide a real
    authenticator that handles user accounts, read the reference documentation for
    {@link android.accounts.AbstractAccountAuthenticator}.
</p>

<h2 id="CreateAuthenticator">Add a Stub Authenticator Component</h2>
<p>
    To add a stub authenticator component to your app, create a class that extends
    {@link android.accounts.AbstractAccountAuthenticator}, and then stub out the required methods,
    either by returning {@code null} or by throwing an exception.
</p>
<p>
    The following snippet shows an example of a stub authenticator class:
</p>
<pre>
/*
 * Implement AbstractAccountAuthenticator and stub out all
 * of its methods
 */
public class Authenticator extends AbstractAccountAuthenticator {
    // Simple constructor
    public Authenticator(Context context) {
        super(context);
    }
    // Editing properties is not supported
    &#64;Override
    public Bundle editProperties(
            AccountAuthenticatorResponse r, String s) {
        throw new UnsupportedOperationException();
    }
    // Don't add additional accounts
    &#64;Override
    public Bundle addAccount(
            AccountAuthenticatorResponse r,
            String s,
            String s2,
            String[] strings,
            Bundle bundle) throws NetworkErrorException {
        return null;
    }
    // Ignore attempts to confirm credentials
    &#64;Override
    public Bundle confirmCredentials(
            AccountAuthenticatorResponse r,
            Account account,
            Bundle bundle) throws NetworkErrorException {
        return null;
    }
    // Getting an authentication token is not supported
    &#64;Override
    public Bundle getAuthToken(
            AccountAuthenticatorResponse r,
            Account account,
            String s,
            Bundle bundle) throws NetworkErrorException {
        throw new UnsupportedOperationException();
    }
    // Getting a label for the auth token is not supported
    &#64;Override
    public String getAuthTokenLabel(String s) {
        throw new UnsupportedOperationException();
    }
    // Updating user credentials is not supported
    &#64;Override
    public Bundle updateCredentials(
            AccountAuthenticatorResponse r,
            Account account,
            String s, Bundle bundle) throws NetworkErrorException {
        throw new UnsupportedOperationException();
    }
    // Checking features for the account is not supported
    &#64;Override
    public Bundle hasFeatures(
        AccountAuthenticatorResponse r,
        Account account, String[] strings) throws NetworkErrorException {
        throw new UnsupportedOperationException();
    }
}
</pre>
<h2 id="CreateAuthenticatorService">Bind the Authenticator to the Framework</h2>
<p>
    In order for the sync adapter framework to access your authenticator, you must create a bound
    Service for it. This service provides an Android binder object that allows the framework
    to call your authenticator and pass data between the authenticator and the framework.
</p>
<p>
    Since the framework starts this {@link android.app.Service} the first time it needs to
    access the authenticator, you can also use the service to instantiate the authenticator,
    by calling the authenticator constructor in the
    {@link android.app.Service#onCreate Service.onCreate()} method of the service.
</p>
<p>
    The following snippet shows you how to define the bound {@link android.app.Service}:
</p>
<pre>
/**
 * A bound Service that instantiates the authenticator
 * when started.
 */
public class AuthenticatorService extends Service {
    ...
    // Instance field that stores the authenticator object
    private Authenticator mAuthenticator;
    &#64;Override
    public void onCreate() {
        // Create a new authenticator object
        mAuthenticator = new Authenticator(this);
    }
    /*
     * When the system binds to this Service to make the RPC call
     * return the authenticator's IBinder.
     */
    &#64;Override
    public IBinder onBind(Intent intent) {
        return mAuthenticator.getIBinder();
    }
}
</pre>

<h2 id="CreateAuthenticatorFile">Add the Authenticator Metadata File</h2>
<p>
    To plug your authenticator component into the sync adapter and account frameworks, you need to
    provide these framework with metadata that describes the component. This metadata declares the
    account type you've created for your sync adapter and declares user interface elements
    that the system displays if you want to make your account type visible to the user. Declare this
    metadata in a XML file stored in the {@code /res/xml/} directory in your app project.
    You can give any name to the file, although it's usually called {@code authenticator.xml}.
</p>
<p>
    This XML file contains a single element <code>&lt;account-authenticator&gt;</code> that
    has the following attributes:
</p>
<dl>
    <dt>
        <code>android:accountType</code>
    </dt>
    <dd>
        The sync adapter framework requires each sync adapter to have an account type, in the form
        of a domain name. The framework uses the account type as part of the sync adapter's
        internal identification. For servers that require login, the account type along with a
        user account is sent to the server as part of the login credentials.
    <p>
        If your server doesn't require login, you still have to provide an account type. For the
        value, use a domain name that you control. While the framework uses it to manage your
        sync adapter, the value is not sent to your server.
    </p>
    </dd>
    <dt>
        <code>android:icon</code>
    </dt>
    <dd>
        Pointer to a <a href="{@docRoot}guide/topics/resources/drawable-resource.html">Drawable</a>
        resource containing an icon. If you make the sync adapter visible by specifying the
        attribute <code>android:userVisible="true"</code> in <code>res/xml/syncadapter.xml</code>,
        then you must provide this icon resource. It appears in the <b>Accounts</b> section of
        the system's Settings app.
    </dd>
    <dt>
        <code>android:smallIcon</code>
    </dt>
    <dd>
        Pointer to a <a href="{@docRoot}guide/topics/resources/drawable-resource.html">Drawable</a>
        resource containing a small version of the icon. This resource may be used instead of
        <code>android:icon</code> in the <b>Accounts</b> section of the system's Settings app,
        depending on the screen size.
    </dd>
    <dt>
        <code>android:label</code>
    </dt>
    <dd>
        Localizable string that identifies the account type to users. If you make the sync adapter
        visible by specifying the attribute <code>android:userVisible="true"</code> in
        <code>res/xml/syncadapter.xml</code>, then you should provide this string. It appears in the
        <b>Accounts</b> section of the system's Settings app, next to the icon you define for the
        authenticator.
    </dd>
</dl>
<p>
    The following snippet shows the XML file for the authenticator you created previously:
</p>
<pre>
&lt;?xml version="1.0" encoding="utf-8"?&gt;
&lt;account-authenticator
        xmlns:android="http://schemas.android.com/apk/res/android"
        android:accountType="example.com"
        android:icon="&#64;drawable/ic_launcher"
        android:smallIcon="&#64;drawable/ic_launcher"
        android:label="&#64;string/app_name"/&gt;
</pre>

<h2 id="DeclareAuthenticator">Declare the Authenticator in the Manifest</h2>
<p>
    In a previous step, you created a bound {@link android.app.Service} that links the authenticator
    to the sync adapter framework. To identify this service to the system, declare it in your app
    manifest by adding the following
    <code><a href="{@docRoot}guide/topics/manifest/service-element.html">&lt;service&gt;</a></code>
    element as a child element of
<code><a href="{@docRoot}guide/topics/manifest/application-element.html">&lt;application&gt;</a></code>:
</p>
<pre>
    &lt;service
            android:name="com.example.android.syncadapter.AuthenticatorService"&gt;
        &lt;intent-filter&gt;
            &lt;action android:name="android.accounts.AccountAuthenticator"/&gt;
        &lt;/intent-filter&gt;
        &lt;meta-data
            android:name="android.accounts.AccountAuthenticator"
            android:resource="@xml/authenticator" /&gt;
    &lt;/service&gt;
</pre>
<p>
    The
<code><a href="{@docRoot}guide/topics/manifest/intent-filter-element.html">&lt;intent-filter&gt;</a></code>
    element sets up a filter that's triggered by the intent action
    {@code android.accounts.AccountAuthenticator}, which sent by the system to run the
    authenticator. When the filter is triggered, the system starts {@code AuthenticatorService},
    the bound {@link android.app.Service} you have provided to wrap the authenticator.
</p>
<p>
    The
<code><a href="{@docRoot}guide/topics/manifest/meta-data-element.html">&lt;meta-data&gt;</a></code>
    element declares the metadata for the authenticator. The
<code><a href="{@docRoot}guide/topics/manifest/meta-data-element.html#nm">android:name</a></code>
    attribute links the meta-data to the authentication framework. The
<code><a href="{@docRoot}guide/topics/manifest/meta-data-element.html#rsrc">android:resource</a></code>
    element specifies the name of the authenticator metadata file you created previously.
</p>
<p>
    Besides an authenticator, a sync adapter also requires a content provider. If your app doesn't
    use a content provider already, go to the next lesson to learn how to create a stub content
    provider; otherwise, go to the lesson <a href="creating-sync-adapter.html"
    >Creating a Sync Adapter</a>.
</p>