page.title=User Notifications
@jd:body
<div id="qv-wrapper">
<div id="qv">
<h2>Quickview</h2>
<ul>
<li>Learn how to send a single message to multiple devices owned by a single user.</li>
</ul>
<h2>In this document</h2>
<ol class="toc">
<li><a href="#gen-server">Generate a Notification Key on the Server</a></li>
<li><a href="#gen-client">Generate a Notification Key on the Client</a></li>
<li><a href="#add">Add Registration IDs</a></li>
<li><a href="#remove">Remove Registration IDs</a></li>
<li><a href="#upstream">Send Upstream Messages</a></li>
<li><a href="#response">Response Formats</a>
<ol class="toc">
<li><a href="#response-create">Create/add/remove operations</a>
<li><a href="#response-send">Send operations</a>
</ol>
</li>
</ol>
<h2>See Also</h2>
<ol class="toc">
<li><a href="{@docRoot}google/gcm/gs.html">Getting Started</a></li>
</ol>
</div>
</div>
<p>With user notifications, 3rd-party app servers can send a single message to
multiple instance of an app running on devices owned by a single user. This feature
is called <em>user notifications</em>. User notifications make it possible for every
app instance that a user owns to reflect the latest messaging state. For example:</p>
<ul>
<li>If a message has been handled on one device, the GCM message on the other
devices are dismissed. For example, if a user has handled a calendar notification
on one device, the notification will go away on the user's other devices.</li>
<li>If a message has not been delivered yet to a device and but it has been handled,
the GCM server removes it from the unsent queue for the other devices.</li>
<li>Likewise, a device can send messages to the {@code notification_key}, which
is the token that GCM uses to fan out notifications to all devices whose
registration IDs are associated with the key.</li>
</ul>
<p>The way this works is that during registration, the 3rd-party server requests
a {@code notification_key}. The {@code notification_key} maps a particular user
to all of the user's associated registration IDs (a regID represents a particular
Android application running on a particular device). Then instead of sending one
message to one regID at a time, the 3rd-party server can send a message to to the
{@code notification_key}, which then sends the message to all of the user's regIDs.</p>
<p class="note"><strong>Note:</strong> A notification dismissal message is like any
other upstream message, meaning that it will be delivered to the other devices that
belong to the specified {@code notification_key}. You should design your app to
handle cases where the app receives a dismissal message, but has not yet displayed
the notification that is being dismissed. You can solve this by caching the dismissal
and then reconciling it with the corresponding notification.
</p>
<p>You can use this feature with either the <a href="ccs.html">XMPP</a> (CCS) or
<a href="http.html">HTTP</a> connection server.</p>
<p>You can generate notification keys in two different ways: on the server, and on
the client, if the user has a Google account. All of the associated registration IDs
can be mapped to a single user.</p>
<p>The examples below show you how to perform generate/add/remove operations,
and how to send upstream messages. For generate/add/remove operations, the
message body is JSON.</p>
<h2 id="gen-server">Generate a Notification Key on the Server</h2>
<p>To generate a notification key on the server, you create a new
create a new <code>notification_key</code> and map it to a
<code>notification_key_name</code>.</p>
<p>This example shows how to create a new <code>notification_key</code> for a
<code>notification_key_name</code> called <code>appUser-Chris</code>.
The {@code notification_key_name} is a name or identifier (it can be a username for
a 3rd-party app) that is unique to a given user. It is used by third parties to
group together registration IDs for a single user. Note that <code>notification_key_name</code>
and <code>notification_key</code> are unique to a group of registration IDs. It is also
important that <code>notification_key_name</code> be uniquely named per app in case
you have multiple apps for the same project ID. This ensures that notifications
only go to the intended target app.</p>
<p>A create operation returns a token (<code>notification_key</code>). Third parties
must save this token (as well as its mapping to the <code>notification_key_name</code>)
to use in subsequent operations:</p>
<pre>request:
{
"operation": "create",
"notification_key_name": "appUser-Chris",
"registration_ids": ["4", "8", "15", "16", "23", "42"]
}</pre>
<h3 id="request-server">Request format</h3>
<p>To send a message in cases where your notification key is generated on the server,
the application server issues a POST request to
<code>https://android.googleapis.com/gcm/notification</code>.</p>
<p>Here is the HTTP request header you should use for all server side create/add/remove operations:</p>
<pre>content-type: "application/json"
Header : "project_id": <projectID>
Header: "Authorization", "key=API_KEY"
</pre>
<h2 id="gen-client">Generate a Notification Key on the Client</h2>
<p>Generating a notification key on the client is useful for cases where a server is unavailable.
To generate a notification key on the client, the device must have at least one
Google account. Note that the process for generating a notification key on the client is significantly
different from the server process described above.</p>
<p>To generate a notification key on the client:</p>
<ol>
<li>Open your project in the <a href="https://cloud.google.com/console">Google Developers Console</a>.</li>
<li>Click <strong>APIS & AUTH > Credentials</strong>.</li>
<li>Under OAuth, click <strong>Create new Client ID</strong>.</li>
<li>In the <strong>Create Client ID</strong> dialog, select <strong>Web Application</strong> as
the application type, and click <strong>Create Client ID</strong>.</li>
<li>Copy the value from <strong>Client ID for web application > Client ID</strong>.
This client ID represents a Google account "scope" that you will use to generate an {@code id_token}.</li>
</ol>
<p>Once you've followed the above steps and gotten a client ID from Google Developers Console,
you're ready to add this feature to your app. First check the device for the presence of a Google
account. For example:</p>
<pre>// This snippet takes the simple approach of using the first returned Google account,
// but you can pick any Google account on the device.
public String getAccount() {
Account[] accounts = AccountManager.get(getActivity()).
getAccountsByType("com.google");
if (accounts.length == 0) {
return null;
}
return accounts[0].name;
}</pre>
<p>Next, get an authentication token ({@code id_token}) by using the <code><a href=
"http://developer.android.com/reference/com/google/android/gms/auth/GoogleAuthUtil.html">GoogleAuthUtil</a></code>
class. For example:</p>
<pre>String accountName = getAccount();
// Initialize the scope using the client ID you got from the Console.
final String scope = "audience:server:client_id:"
+ "1262xxx48712-9qs6n32447mcj9dirtnkyrejt82saa52.apps.googleusercontent.com";
String id_token = null;
try {
id_token = GoogleAuthUtil.getToken(context, accountName, scope);
} catch (Exception e) {
log("exception while getting id_token: " + e);
}
...</pre>
<p>Now use <code>id_token</code> to authenticate your request.
This add operation returns a {@code notification_key}.
Third parties must save this {@code notification_key} (as well as its mapping to the
<code>notification_key_name</code>)
to use in subsequent operations. Note that a client request only takes a single regID.
The only operations supported on the client side are add/remove.</p>
<pre>request:
{
"operation": "add",
"notification_key_name": "appUser-Chris",
"registration_ids": ["4"]
"id_token": "id_token"
}</pre>
<h3 id="request-client">Request format</h3>
<p>To send a message in cases where your notification key is generated on the client,
the application server issues a POST request to
<code>https://android.googleapis.com/gcm/googlenotification</code>.</p>
<p>Here is the HTTP request header you should use for all add/remove operations. The
client side doesn't support the create operation;
the add operation has the effect of creating the notification key if it doesn't already
exist:</p>
<pre>content-type: "application/json"
Header : "project_id": <projectID>
</pre>
<p>Note that the authentication token is passed in the JSON body as shown above, not the header.
This is different from the server case.</p>
<h2 id="add">Add Registration IDs</h2>
<p>This example shows how to add registration IDs for a given notification key.
The maximum number of members allowed for a {@code notification_key} is 20.</p>
<p>Note that the <code>notification_key_name</code> is not strictly required for
adding/removing regIDs. But including it protects you against accidentally using
the incorrect <code>notification_key</code>.</p>
<pre>request:
{
"operation": "add",
"notification_key_name": "appUser-Chris",
"notification_key": "aUniqueKey"
"registration_ids": ["4", "8", "15", "16", "23", "42"]
}</pre>
<h2 id="remove">Remove Registration IDs</h2>
<p>This example shows how to remove registration IDs for a given notification key:</p>
<pre>request:
{
"operation": "remove",
"notification_key_name": "appUser-Chris",
"notification_key": "aUniqueKey"
"registration_ids": ["4", "8", "15", "16", "23", "42"]
}</pre>
<h2 id="upstream">Send Upstream Messages</h2>
<p>To send an upstream (device-to-cloud) message, you must use the
<a href="{@docRoot}reference/com/google/android/gms/gcm/GoogleCloudMessaging.html">
{@code GoogleCloudMessaging}</a> API. Specifying a {@code notification_key} as the target
for an upstream message allows a user on one device to send a message to other
devices in the notification group—for example, to dismiss a notification.
Here is an example that shows targeting a {@code notification_key}:</p>
<pre>GoogleCloudMessaging gcm = GoogleCloudMessaging.get(context);
String to = NOTIFICATION_KEY;
AtomicInteger msgId = new AtomicInteger();
String id = Integer.toString(msgId.incrementAndGet());
Bundle data = new Bundle();
data.putString("hello", "world");
gcm.send(to, id, data);
</pre>
<p>This call generates the necessary XMPP stanza for sending the message. The
Bundle data consists of a key-value pair.</p>
<p>For a complete example, see <a href="client.html">Implementing GCM Client</a>.
<h2 id="response">Response Formats</h2>
<p>This section shows examples of the responses that can be returned for
notification key operations.</p>
<h3 id="response-create">Create/add/remove operations</h3>
<p>When you make a request to create a {@code notification_key} or to add/remove its
regIDs, a successful response always returns the <code>notification_key</code>.
his is the {@code notification_key} you will use for sending messages:</p>
<pre>HTTP status: 200
{
"notification_key": "aUniqueKey", // to be used for sending
}</pre>
<h3 id="response-send">Send operations</h3>
<p>For a send operation that has a {@code notification_key} as its target, the
possible responses are success, partial success, and failure.</p>
<p>Here is an example of "success"—the {@code notification_key} has 2 regIDs
associated with it, and the message was successfully sent to both of them:</p>
<pre>{
"success": 2,
"failure": 0
}</pre>
<p>Here is an example of "partial success"—the {@code notification_key} has
3 regIDs associated with it. The message was successfully send to 1 of the regIDs,
but not to the other 2. The response message lists the regIDs that failed to
receive the message:</p>
<pre>{
"success":1,
"failure":2,
"failed_registration_ids":[
"regId1",
"regId2"
]
}</pre>
<p>In the case of failure, the response has HTTP code 503 and no JSON. When a message
fails to be delivered to one or more of the regIDs associated with a {@code notification_key},
the 3rd-party server should retry.</p>