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diff --git a/docs/html/training/wearables/data-layer/messages.jd b/docs/html/training/wearables/data-layer/messages.jd new file mode 100644 index 0000000..a9dec75 --- /dev/null +++ b/docs/html/training/wearables/data-layer/messages.jd @@ -0,0 +1,99 @@ +page.title=Sending and Receiving Messages + +@jd:body + +<div id="tb-wrapper"> +<div id="tb"> + +<h2>This lesson teaches you to</h2> +<ol> + <li><a href="#SendMessage">Send a Message</a></li> + <li><a href="#ReceiveMessage">Receive a Message</a></li> +</ol> +</div> +</div> + +<p>You send messages using the +<a href="{@docRoot}reference/com/google/android/gms/wearable/MessageApi.html"><code>MessageApi</code></a> +and attach the following items to the message:</p> + +<ul> + <li>An arbitrary payload (optional)</li> + <li>A path that uniquely identifies the message's action</li> +</ul> +<p> +Unlike data items, there is no syncing between the handheld and wearable apps. +Messages are a one-way communication mechanism that's meant for +"fire-and-forget" tasks, such as sending a message to the wearable +to start an activity. You can also use messages in request/response model +where one side of the connection sends a message, does some work, +sends back a response message.</p> + +<h2 id="SendMessage">Send a Message</h2> + +<p>The following example shows how to send a message that indicates to the other +side of the connect to start an activity. +This call is made synchronously, which blocks until the message +is received or when the request times out: +</p> + +<p class="note"><b>Note:</b> Read more about asynchronous and synchronous calls +to Google Play services and when to use each in +<a href="google/auth/api-client.html#Communicating">Communicate with Google Play Services</a>. +</p> + +<pre> +Node node; // the connected device to send the message to +GoogleApiClient mGoogleApiClient; +public static final START_ACTIVITY_PATH = "/start/MainActivity"; +... + + SendMessageResult result = Wearable.MessageApi.sendMessage( + mGoogleApiClient, node, START_ACTIVITY_PATH, null).await(); + if (!result.getStatus().isSuccess()) { + Log.e(TAG, "ERROR: failed to send Message: " + result.getStatus()); + } +</pre> + +<p> +Here's a simple way to get a list of connected nodes that you can potentially +send messages to:</p> + +<pre> +private Collection<String> getNodes() { + HashSet <String>results= new HashSet<String>(); + NodeApi.GetConnectedNodesResult nodes = + Wearable.NodeApi.getConnectedNodes(mGoogleApiClient).await(); + for (Node node : nodes.getNodes()) { + results.add(node.getId()); + } + return results; +} +</pre> + +<h2 id="ReceiveMessage">Receiving a Message</h2> + +<p> + +To be notified of received messages, you implement a listener for message events. +This example shows how you might do this by checking the <code>START_ACTIVITY_PATH</code> +that the previous example used to send the message. If this condition is <code>true</code>, +a specific activity is started. +</p> + +<pre> +@Override +public void onMessageReceived(MessageEvent messageEvent) { + if (messageEvent.getPath().equals(START_ACTIVITY_PATH)) { + Intent startIntent = new Intent(this, MainActivity.class); + startIntent.addFlags(Intent.FLAG_ACTIVITY_NEW_TASK); + startActivity(startIntent); + } +} +</pre> + +<p> +This is just a snippet that requires more implementation details. Learn about +how to implement a full listener service or activity in +<a href="#listening">Listening for Data Layer Events</a>. +</p>
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