docs/html/training/wearables/data-layer/accessing.jd

page.title=Accessing the Wearable Data Layer

@jd:body

<div id="tb-wrapper">
<div id="tb">

<h2>This lesson teaches you to</h2>
<ol>
  <li>Set up a Google Play services client to use the Wearable Data Layer APIs</li>
</ol>

<h2>Dependencies and Prerequisites</h2>
<ol>
  <li><a href="{@docRoot}training/wearables/apps/creating.html#SetupEmulator">Creating
  Wearable Apps > Set Up an Android Wear Emulator or Device</a></li>
  <li><a href="{@docRoot}training/wearables/apps/creating.html#CreateProject">Creating
    Wearable Apps > Creating a Project</a></li>
</ol>
</div>
</div>

<p>To call the Data Layer API, create an instance of
<a href="{@docRoot}reference/com/google/android/gms/common/api/GoogleApiClient.html"><code>GoogleApiClient</code></a>,
the main entry point for any of the Google Play services APIs.
</p>

<p>
<a href="{@docRoot}reference/com/google/android/gms/common/api/GoogleApiClient.html"><code>GoogleApiClient</code></a>
provides a builder that makes it easy to create an instance of the client.
A minimal <a href="{@docRoot}reference/com/google/android/gms/common/api/GoogleApiClient.html"><code>GoogleApiClient</code></a> looks like this:
</p>

<p class="note"><b>Note:</b> For now, this minimal client is enough to get started. However, see
<a href="{@docRoot}google/auth/api-client.html">Accessing Google Play services APIs</a>
for more information about creating a <a href="{@docRoot}reference/com/google/android/gms/common/api/GoogleApiClient.html"><code>GoogleApiClient</code></a>,
implementing its callbacks, and handling error cases.</p>

<pre style="clear:right">
GoogleApiClient mGoogleApiClient = new GoogleApiClient.Builder(this)
        .addConnectionCallbacks(new ConnectionCallbacks() {
                &#64;Override
                public void onConnected(Bundle connectionHint) {
                    Log.d(TAG, "onConnected: " + connectionHint);
                    // Now you can use the Data Layer API
                }
                &#64;Override
                public void onConnectionSuspended(int cause) {
                    Log.d(TAG, "onConnectionSuspended: " + cause);
                }
        })
        .addOnConnectionFailedListener(new OnConnectionFailedListener() {
                &#64;Override
                public void onConnectionFailed(ConnectionResult result) {
                    Log.d(TAG, "onConnectionFailed: " + result);
                }
            })
        // Request access only to the Wearable API
        .addApi(Wearable.API)
        .build();
</pre>

<p class="caution">
<strong>Important:</strong> To avoid client connection errors on devices that do not have the
<a href="https://play.google.com/store/apps/details?id=com.google.android.wearable.app&hl=en">Android
Wear app</a> installed, use a separate <a
href="{@docRoot}reference/com/google/android/gms/common/api/GoogleApiClient.html">{@code
GoogleApiClient}</a> instance to access only the <a
href="{@docRoot}reference/com/google/android/gms/wearable/Wearable.html">{@code
Wearable}</a> API. For more information, see <a
href="{@docRoot}google/auth/api-client.html#WearableApi">Access the Wearable API</a>.</p>

<p>Before you use the data layer API, start a connection on your client by calling the
<a href="{@docRoot}reference/com/google/android/gms/common/api/GoogleApiClient.html#connect()">
<code>connect()</code></a>
method, as described in
<a href="{@docRoot}google/auth/api-client.html#Starting">Start a Connection</a>.
When the system invokes the
<a href="{@docRoot}reference/com/google/android/gms/common/api/GoogleApiClient.ConnectionCallbacks.html#onConnected(android.os.Bundle)">
<code>onConnected()</code></a> callback for your client, you're ready to use the Data Layer API.</p>