DOC: Sync Adapters Android Training

page.title=Creating a Stub Authenticator

trainingnavtop=true

@jd:body

<div id="tb-wrapper">

<div id="tb">

<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

    @Override

    public Bundle editProperties(

            AccountAuthenticatorResponse r, String s) {

        throw new UnsupportedOperationException();

    }

    // Don't add additional accounts

    @Override

    public Bundle addAccount(

            AccountAuthenticatorResponse r,

            String s,

            String s2,

            String[] strings,

            Bundle bundle) throws NetworkErrorException {

        return null;

    }

    // Ignore attempts to confirm credentials

    @Override

    public Bundle confirmCredentials(

            AccountAuthenticatorResponse r,

            Account account,

            Bundle bundle) throws NetworkErrorException {

        return null;

    }

    // Getting an authentication token is not supported

    @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

    @Override

    public String getAuthTokenLabel(String s) {

        throw new UnsupportedOperationException();

    }

    // Updating user credentials is not supported

    @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

    @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;

    @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.

     */

    @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>the

<?xml version="1.0" encoding="utf-8"?>

<account-authenticator

        xmlns:android="http://schemas.android.com/apk/res/android"

        android:accountType="example.com"

        android:icon="@drawable/ic_launcher"

        android:smallIcon="@drawable/ic_launcher"

        android:label="@string/app_name"/>

</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>

    <service

            android:name="com.example.android.syncadapter.AuthenticatorService">

        <intent-filter>

            <action android:name="android.accounts.AccountAuthenticator"/>

        </intent-filter>

        <meta-data

            android:name="android.accounts.AccountAuthenticator"

            android:resource="@xml/authenticator" />

    </service>

</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>

page.title=Creating a Stub Content Provider

trainingnavtop=true

@jd:body

<div id="tb-wrapper">

<div id="tb">

<h2>This lesson teaches you to</h2>

<ol>

    <li>

        <a href="#CreateProvider">Add a Stub Content Provider</a>

    </li>

    <li>

        <a href="#DeclareProvider">Declare the Provider in the Manifest</a>

    </li>

</ol>

<h2>You should also read</h2>

<ul>

    <li>

        <a href="{@docRoot}guide/topics/providers/content-provider-basics.html"

        >Content Provider Basics</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 is designed to work with device data managed by the flexible and

    highly secure content provider framework. For this reason, the sync adapter framework expects

    that an app that uses the framework has already defined a content provider for its local data.

    If the sync adapter framework tries to run your sync adapter, and your app doesn't have a

    content provider, your sync adapter crashes.

</p>

<p>

    If you're developing a new app that transfers data from a server to the device, you should

    strongly consider storing the local data in a content provider. Besides their importance for

    sync adapters, content providers offer a variety of security benefits and are specifically

    designed to handle data storage on Android systems. To learn more about creating a content

    provider, see <a href="{@docRoot}guide/topics/providers/content-provider-creating.html"

    >Creating a Content Provider</a>.

</p>

<p>

    However, if you're already storing local data in another form, you can still use a sync

    adapter to handle data transfer. To satisfy the sync adapter framework requirement for a

    content provider, add a stub content provider to your app. A stub provider implements the

    content provider class, but all of its required methods return {@code null} or {@code 0}. If you

    add a stub provider, you can then use a sync adapter to transfer data from any storage

    mechanism you choose.

</p>

<p>

    If you already have a content provider in your app, you don't need a stub content provider.

    In that case, you can skip this lesson and proceed to the lesson

    <a href="creating-sync-adapter.html">Creating a Sync Adapter</a>. If you don't yet have a

    content provider, this lesson shows you how to add a stub content provider that allows you to

    plug your sync adapter into the framework.

</p>

<h2 id="CreateProvider">Add a Stub Content Provider</h2>

<p>

    To create a stub content provider for your app, extend the class

    {@link android.content.ContentProvider} and stub out its required methods. The following

    snippet shows you how to create the stub provider:

</p>

<pre>

/*

 * Define an implementation of ContentProvider that stubs out

 * all methods

 */

public class StubProvider extends ContentProvider {

    /*

     * Always return true, indicating that the

     * provider loaded correctly.

     */

    @Override

    public boolean onCreate() {

        return true;

    }

    /*

     * Return an empty String for MIME type

     */

    @Override

    public String getType() {

        return new String();

    }

    /*

     * query() always returns no results

     *

     */

    @Override

    public Cursor query(

            Uri uri,

            String[] projection,

            String selection,

            String[] selectionArgs,

            String sortOrder) {

        return null;

    }

    /*

     * insert() always returns null (no URI)

     */

    @Override

    public Uri insert(Uri uri, ContentValues values) {

        return null;

    }

    /*

     * delete() always returns "no rows affected" (0)

     */

    @Override

    public int delete(Uri uri, String selection, String[] selectionArgs) {

        return 0;

    }

    /*

     * update() always returns "no rows affected" (0)

     */

    public int update(

            Uri uri,

            ContentValues values,

            String selection,

            String[] selectionArgs) {

        return 0;

    }

}

</pre>

<h2 id="DeclareProvider">Declare the Provider in the Manifest</h2>

<p>

    The sync adapter framework verifies that your app has a content provider by checking that your

    app has declared a provider in its app manifest. To declare the stub provider in the

    manifest, add a <code><a href="{@docRoot}guide/topics/manifest/provider-element.html"

    >&lt;provider&gt;</a></code> element with  the following attributes:

</p>

<dl>

    <dt>

        <code>android:name="com.example.android.datasync.provider.StubProvider"</code>

    </dt>

    <dd>

        Specifies the fully-qualified name of the class that implements the stub content provider.

    </dd>

    <dt>

        <code>android:authorities="com.example.android.datasync.provider"</code>

    </dt>

    <dd>

        A URI authority that identifies the stub content provider. Make this value your app's

        package name with the string ".provider" appended to it. Even though you're declaring your

        stub provider to the system, nothing tries to access the provider itself.

   </dd>

    <dt>

        <code>android:exported="false"</code>

    </dt>

    <dd>

        Determines whether other apps can access the content provider. For your stub content

        provider, set the value to {@code false}, since there's no need to allow other apps to see

        the provider. This value doesn't affect the interaction between the sync adapter framework

        and the content provider.

    </dd>

    <dt>

        <code>android:syncable="true"</code>

    </dt>

    <dd>

        Sets a flag that indicates that the provider is syncable. If you set this flag to

        {@code true}, you don't have to call {@link android.content.ContentResolver#setIsSyncable

        setIsSyncable()} in your code. The flag allows the sync adapter framework to make data

        transfers with the content provider, but transfers only occur if you do them explicitly.

    </dd>

</dl>

<p>

    The following snippet shows you how to add the

    <code><a href="{@docRoot}guide/topics/manifest/provider-element.html"

    >&lt;provider&gt;</a></code> element to the app manifest:

</p>

<pre>

<manifest xmlns:android="http://schemas.android.com/apk/res/android"

    package="com.example.android.network.sync.BasicSyncAdapter"

    android:versionCode="1"

    android:versionName="1.0" >

    <application

        android:allowBackup="true"

        android:icon="@drawable/ic_launcher"

        android:label="@string/app_name"

        android:theme="@style/AppTheme" >

    ...

    <provider

        android:name="com.example.android.datasync.provider.StubProvider"

        android:authorities="com.example.android.datasync.provider"

        android:export="false"

        android:syncable="true"/>

    ...

    </application>

</manifest>

</pre>

<p>

    Now that you have created the dependencies required by the sync adapter framework, you can

    create the component that encapsulates your data transfer code. This component is called a

    sync adapter. The next lesson shows you how to add this component to your app.

</p>