page.title=Accessing Google APIs
page.tags="oauth 2.0","GoogleAuthUtil"

trainingnavtop=true
startpage=true

@jd:body

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

<h2>In this document</h2>
<ol>
  <li><a href="#Starting">Start a Connection</a>
    <ol>
      <li><a href="#HandlingFailures">Handle connection failures</a></li>
      <li><a href="#MaintainingState">Maintain state while resolving an error</a></li>
      <li><a href="#WearableApi">Access the Wearable API</a></li>
    </ol>
  </li>
  <li><a href="#Communicating">Communicate with Google Services</a>
    <ol>
      <li><a href="#Async">Using asynchronous calls</a></li>
      <li><a href="#Sync">Using synchronous calls</a></li>
    </ol>
  </li>
</ol>
</div>
</div>


<p>When you want to make a connection to one of the Google APIs provided in the Google Play services
library (such as Google+, Games, or Drive), you need to create an instance of <a
href="{@docRoot}reference/com/google/android/gms/common/api/GoogleApiClient.html">{@code
GoogleApiClient}</a> ("Google API Client"). The Google API Client provides a common entry point to all
the Google Play services and manages the network connection between the user's device and each
Google service.</p>

<div class="sidebox" style="clear:right;width:190px">
<h2>Connecting to REST APIs</h2>
<p>If the Google API you want to use is not included in the Google Play services library, you can
connect using the appropriate REST API, but you must obtain an OAuth 2.0 token. For more
information, read <a href="{@docRoot}google/auth/http-auth.html">Authorizing with Google
for REST APIs</a>.</p>
</div>

<p>This guide shows how you can use Google API Client to:</p>
<ul>
<li>Connect to one or more Google Play services asynchronously and handle failures.</li>
<li>Perform synchronous and asynchronous API calls to any of the Google Play services.</li>
</ul>

<p class="note">
<strong>Note:</strong> If you have an existing app that connects to Google Play services with a
subclass of {@code GooglePlayServicesClient}, you should migrate to <a
href="{@docRoot}reference/com/google/android/gms/common/api/GoogleApiClient.html">{@code
GoogleApiClient}</a> as soon as possible.</p>


<img src="{@docRoot}images/google/GoogleApiClient@2x.png" width="464px" alt="" />
<p class="img-caption">
<strong>Figure 1.</strong> An illustration showing how the Google API Client provides an
interface for connecting and making calls to any of the available Google Play services such as
Google Play Games and Google Drive.</p>


<p>To get started, you must first install the Google Play services library (revision 15 or higher) for
your Android SDK. If you haven't done so already, follow the instructions in <a
href="{@docRoot}google/play-services/setup.html">Set Up Google
Play Services SDK</a>.</p>


<h2 id="Starting">Start a Connection</h2>

<p>Once your project is linked to the Google Play services library, create an instance of <a
href="{@docRoot}reference/com/google/android/gms/common/api/GoogleApiClient.html">{@code
GoogleApiClient}</a> using the <a
href="{@docRoot}reference/com/google/android/gms/common/api/GoogleApiClient.Builder.html">{@code
GoogleApiClient.Builder}</a> APIs in your activity's {@link
android.app.Activity#onCreate onCreate()} method. The <a
href="{@docRoot}reference/com/google/android/gms/common/api/GoogleApiClient.Builder.html">{@code
GoogleApiClient.Builder}</a> class
provides methods that allow you to specify the Google APIs you want to use and your desired OAuth
2.0 scopes. For example, here's a <a
href="{@docRoot}reference/com/google/android/gms/common/api/GoogleApiClient.html">{@code
GoogleApiClient}</a> instance that connects with the Google
Drive service:</p>
<pre>
GoogleApiClient mGoogleApiClient = new GoogleApiClient.Builder(this)
    .addApi(Drive.API)
    .addScope(Drive.SCOPE_FILE)
    .build();
</pre>

<p>You can add multiple APIs and multiple scopes to the same <a
href="{@docRoot}reference/com/google/android/gms/common/api/GoogleApiClient.html">{@code
GoogleApiClient}</a> by appending
additional calls to
<a href="{@docRoot}reference/com/google/android/gms/common/api/GoogleApiClient.Builder.html#addApi(com.google.android.gms.common.api.Api<? extends com.google.android.gms.common.api.Api.ApiOptions.NotRequiredOptions>)"
>{@code addApi()}</a> and
<a href="{@docRoot}reference/com/google/android/gms/common/api/GoogleApiClient.Builder.html#addScope(com.google.android.gms.common.api.Scope)"
>{@code addScope()}</a>.</p>

<p class="caution">
<strong>Important:</strong> If you are adding multiple APIs to a
<a href="{@docRoot}reference/com/google/android/gms/common/api/GoogleApiClient.html"><code>GoogleApiClient</code></a>,
you may run into 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. To avoid connection errors, call the
<a href="{@docRoot}reference/com/google/android/gms/common/api/GoogleApiClient.Builder.html#addApiIfAvailable(com.google.android.gms.common.api.Api<? extends com.google.android.gms.common.api.Api.ApiOptions.NotRequiredOptions>, com.google.android.gms.common.api.Scope...)">{@code addApiIfAvailable()}</a>
method and pass in the <a
href="{@docRoot}reference/com/google/android/gms/wearable/Wearable.html">{@code
Wearable}</a> API to indicate that your client should gracefully handle the missing API.
For more information, see <a
href="{@docRoot}google/auth/api-client.html#WearableApi">Access the Wearable API</a>.</p>

<p>Before you can begin a connection by calling <a
href="{@docRoot}reference/com/google/android/gms/common/api/GoogleApiClient.html#connect()"
>{@code connect()}</a> on the <a
href="{@docRoot}reference/com/google/android/gms/common/api/GoogleApiClient.html">{@code
GoogleApiClient}</a>, you must specify an implementation for the callback interfaces, <a
href="{@docRoot}reference/com/google/android/gms/common/api/GoogleApiClient.ConnectionCallbacks.html"
>{@code ConnectionCallbacks}</a> and <a
href="{@docRoot}reference/com/google/android/gms/common/api/GoogleApiClient.OnConnectionFailedListener.html"
>{@code OnConnectionFailedListener}</a>. These interfaces receive callbacks in
response to the asynchronous <a
href="{@docRoot}reference/com/google/android/gms/common/api/GoogleApiClient.html#connect()"
>{@code connect()}</a> method when the connection to Google Play services
succeeds, fails, or becomes suspended.</p>

<p>For example, here's an activity that implements the callback interfaces and adds them to the Google
API Client:</p>

<pre>
import com.google.android.gms.common.api.GoogleApiClient;
import com.google.android.gms.common.api.GoogleApiClient.ConnectionCallbacks;
import com.google.android.gms.common.api.GoogleApiClient.OnConnectionFailedListener;
import gms.drive.*;
import android.support.v4.app.FragmentActivity;

public class MyActivity extends FragmentActivity
        implements ConnectionCallbacks, OnConnectionFailedListener {
    private GoogleApiClient mGoogleApiClient;

    &#64;Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);

        // Create a GoogleApiClient instance
        mGoogleApiClient = new GoogleApiClient.Builder(this)
                .addApi(Drive.API)
                .addScope(Drive.SCOPE_FILE)
                .addConnectionCallbacks(this)
                .addOnConnectionFailedListener(this)
                .build();
        ...
    }

    &#64;Override
    public void onConnected(Bundle connectionHint) {
        // Connected to Google Play services!
        // The good stuff goes here.
    }

    &#64;Override
    public void onConnectionSuspended(int cause) {
        // The connection has been interrupted.
        // Disable any UI components that depend on Google APIs
        // until onConnected() is called.
    }

    &#64;Override
    public void onConnectionFailed(ConnectionResult result) {
        // This callback is important for handling errors that
        // may occur while attempting to connect with Google.
        //
        // More about this in the next section.
        ...
    }
}
</pre>

<p>With the callback interfaces defined, you're ready to call <a
href="{@docRoot}reference/com/google/android/gms/common/api/GoogleApiClient.html#connect()"
>{@code connect()}</a>. To gracefully manage
the lifecycle of the connection, you should call <a
href="{@docRoot}reference/com/google/android/gms/common/api/GoogleApiClient.html#connect()"
>{@code connect()}</a> during the activity's {@link
android.app.Activity#onStart onStart()} (unless you want to connect later), then call <a
href="{@docRoot}reference/com/google/android/gms/common/api/GoogleApiClient.html#disconnect()"
>{@code disconnect()}</a> during the {@link android.app.Activity#onStop onStop()} method. For example:</p>
<pre>
    &#64;Override
    protected void onStart() {
        super.onStart();
        if (!mResolvingError) {  // more about this later
            mGoogleApiClient.connect();
        }
    }

    &#64;Override
    protected void onStop() {
        mGoogleApiClient.disconnect();
        super.onStop();
    }
</pre>

<p>However, if you run this code, there's a good chance it will fail and your app will receive a call
to <a
href="{@docRoot}reference/com/google/android/gms/common/api/GoogleApiClient.OnConnectionFailedListener.html#onConnectionFailed(com.google.android.gms.common.ConnectionResult)"
>{@code onConnectionFailed()}</a> with the <a
href="{@docRoot}reference/com/google/android/gms/common/ConnectionResult.html#SIGN_IN_REQUIRED"
>{@code SIGN_IN_REQUIRED}</a> error because the user account
has not been specified. The next section shows how to handle this error and others.</p>


<h3 id="HandlingFailures">Handle connection failures</h3>

<p>When you receive a call to the
<a href="{@docRoot}reference/com/google/android/gms/common/api/GoogleApiClient.OnConnectionFailedListener.html#onConnectionFailed(com.google.android.gms.common.ConnectionResult)">
{@code onConnectionFailed()}</a> callback, you should call <a
href="{@docRoot}reference/com/google/android/gms/common/ConnectionResult.html#hasResolution()"
>{@code hasResolution()}</a> on the provided <a
href="{@docRoot}reference/com/google/android/gms/common/ConnectionResult.html"
>{@code ConnectionResult}</a> object. If it returns true, you can
request the user take immediate action to resolve the error by calling <a
href="{@docRoot}reference/com/google/android/gms/common/ConnectionResult.html#startResolutionForResult(android.app.Activity, int)">{@code startResolutionForResult()}</a> on the <a
href="{@docRoot}reference/com/google/android/gms/common/ConnectionResult.html"
>{@code ConnectionResult}</a> object. The <a
href="{@docRoot}reference/com/google/android/gms/common/ConnectionResult.html#startResolutionForResult(android.app.Activity, int)"
>{@code startResolutionForResult()}</a> behaves the same as {@link
android.app.Activity#startActivityForResult startActivityForResult()} and launches the
appropriate activity for the user
to resolve the error (such as an activity to select an account).</p>

<p>If <a
href="{@docRoot}reference/com/google/android/gms/common/ConnectionResult.html#hasResolution()"
>{@code hasResolution()}</a> returns false, you should instead call <a
href="{@docRoot}reference/com/google/android/gms/common/GooglePlayServicesUtil.html#getErrorDialog(int, android.app.Activity, int)"
>{@code GooglePlayServicesUtil.getErrorDialog()}</a>, passing it the error code. This returns a {@link
android.app.Dialog} provided by Google Play services that's appropriate for the given error. The
dialog may simply provide a message explaining the error, but it may also provide an action to
launch an activity that can resolve the error (such as when the user needs to install a newer
version of Google Play services).</p>

<p>For example, your
<a
href="{@docRoot}reference/com/google/android/gms/common/api/GoogleApiClient.OnConnectionFailedListener.html#onConnectionFailed(com.google.android.gms.common.ConnectionResult)"
>{@code onConnectionFailed()}</a> callback method should now look like this:</p>

<pre>
public class MyActivity extends FragmentActivity
        implements ConnectionCallbacks, OnConnectionFailedListener {

    // Request code to use when launching the resolution activity
    private static final int REQUEST_RESOLVE_ERROR = 1001;
    // Unique tag for the error dialog fragment
    private static final String DIALOG_ERROR = "dialog_error";
    // Bool to track whether the app is already resolving an error
    private boolean mResolvingError = false;

    ...

    &#64;Override
    public void onConnectionFailed(ConnectionResult result) {
        if (mResolvingError) {
            // Already attempting to resolve an error.
            return;
        } else if (result.hasResolution()) {
            try {
                mResolvingError = true;
                result.startResolutionForResult(this, REQUEST_RESOLVE_ERROR);
            } catch (SendIntentException e) {
                // There was an error with the resolution intent. Try again.
                mGoogleApiClient.connect();
            }
        } else {
            // Show dialog using GooglePlayServicesUtil.getErrorDialog()
            showErrorDialog(result.getErrorCode());
            mResolvingError = true;
        }
    }

    // The rest of this code is all about building the error dialog

    /* Creates a dialog for an error message */
    private void showErrorDialog(int errorCode) {
        // Create a fragment for the error dialog
        ErrorDialogFragment dialogFragment = new ErrorDialogFragment();
        // Pass the error that should be displayed
        Bundle args = new Bundle();
        args.putInt(DIALOG_ERROR, errorCode);
        dialogFragment.setArguments(args);
        dialogFragment.show(getSupportFragmentManager(), "errordialog");
    }

    /* Called from ErrorDialogFragment when the dialog is dismissed. */
    public void onDialogDismissed() {
        mResolvingError = false;
    }

    /* A fragment to display an error dialog */
    public static class ErrorDialogFragment extends DialogFragment {
        public ErrorDialogFragment() { }

        &#64;Override
        public Dialog onCreateDialog(Bundle savedInstanceState) {
            // Get the error code and retrieve the appropriate dialog
            int errorCode = this.getArguments().getInt(DIALOG_ERROR);
            return GooglePlayServicesUtil.getErrorDialog(errorCode,
                    this.getActivity(), REQUEST_RESOLVE_ERROR);
        }

        &#64;Override
        public void onDismiss(DialogInterface dialog) {
            ((MainActivity)getActivity()).onDialogDismissed();
        }
    }
}
</pre>

<p>Once the user completes the resolution provided by <a
href="{@docRoot}reference/com/google/android/gms/common/ConnectionResult.html#startResolutionForResult(android.app.Activity, int)"
>{@code startResolutionForResult()}</a> or <a
href="{@docRoot}reference/com/google/android/gms/common/GooglePlayServicesUtil.html#getErrorDialog(int, android.app.Activity, int)"
>{@code GooglePlayServicesUtil.getErrorDialog()}</a>, your activity receives the {@link
android.app.Activity#onActivityResult onActivityResult()} callback with the {@link
android.app.Activity#RESULT_OK}
result code. You can then call <a
href="{@docRoot}reference/com/google/android/gms/common/api/GoogleApiClient.html#connect()"
>{@code connect()}</a> again. For example:</p>

<pre>
&#64;Override
protected void onActivityResult(int requestCode, int resultCode, Intent data) {
    if (requestCode == REQUEST_RESOLVE_ERROR) {
        mResolvingError = false;
        if (resultCode == RESULT_OK) {
            // Make sure the app is not already connected or attempting to connect
            if (!mGoogleApiClient.isConnecting() &&
                    !mGoogleApiClient.isConnected()) {
                mGoogleApiClient.connect();
            }
        }
    }
}
</pre>

<p>In the above code, you probably noticed the boolean, {@code mResolvingError}. This keeps track of
the app state while the user is resolving the error to avoid repetitive attempts to resolve the
same error. For instance, while the account picker dialog is showing to resolve the <a
href="{@docRoot}reference/com/google/android/gms/common/ConnectionResult.html#SIGN_IN_REQUIRED"
>{@code SIGN_IN_REQUIRED}</a> error, the user may rotate the screen. This recreates your activity and causes
your {@link android.app.Activity#onStart onStart()} method to be called again, which then calls <a
href="{@docRoot}reference/com/google/android/gms/common/api/GoogleApiClient.html#connect()"
>{@code connect()}</a> again. This results in another call to <a
href="{@docRoot}reference/com/google/android/gms/common/ConnectionResult.html#startResolutionForResult(android.app.Activity, int)"
>{@code startResolutionForResult()}</a>, which
creates another account picker dialog in front of the existing one.</p>

<p>This boolean is effective only
if retained across activity instances, though. The next section explains further.</p>


<h3 id="MaintainingState">Maintain state while resolving an error</h3>

<p>To avoid executing the code in
<a href="{@docRoot}reference/com/google/android/gms/common/api/GoogleApiClient.OnConnectionFailedListener.html#onConnectionFailed(com.google.android.gms.common.ConnectionResult)">
{@code onConnectionFailed()}</a> while a previous attempt to resolve an
error is ongoing, you need to retain a boolean that tracks whether your app is already attempting
to resolve an error.</p>

<p>As shown in the code above, you should set a boolean to {@code true} each time you call <a
href="{@docRoot}reference/com/google/android/gms/common/ConnectionResult.html#startResolutionForResult(android.app.Activity, int)"
>{@code startResolutionForResult()}</a> or display the dialog from <a
href="{@docRoot}reference/com/google/android/gms/common/GooglePlayServicesUtil.html#getErrorDialog(int, android.app.Activity, int)"
>{@code GooglePlayServicesUtil.getErrorDialog()}</a>. Then when you
receive {@link android.app.Activity#RESULT_OK} in the {@link android.app.Activity#onActivityResult
onActivityResult()} callback, set the boolean to {@code false}.</p>

<p>To keep track of the boolean across activity restarts (such as when the user rotates the screen),
save the boolean in the activity's saved instance data using {@link
android.app.Activity#onSaveInstanceState onSaveInstanceState()}:</p>

<pre>
private static final String STATE_RESOLVING_ERROR = "resolving_error";

&#64;Override
protected void onSaveInstanceState(Bundle outState) {
    super.onSaveInstanceState(outState);
    outState.putBoolean(STATE_RESOLVING_ERROR, mResolvingError);
}
</pre>

<p>Then recover the saved state during {@link android.app.Activity#onCreate onCreate()}:</p>

<pre>
&#64;Override
protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);

    ...
    mResolvingError = savedInstanceState != null
            && savedInstanceState.getBoolean(STATE_RESOLVING_ERROR, false);
}
</pre>

<p>Now you're ready to safely run your app and connect to Google Play services.
How you can perform read and write requests to any of the Google Play services
using <a
href="{@docRoot}reference/com/google/android/gms/common/api/GoogleApiClient.html">{@code
GoogleApiClient}</a> is discussed in the next section.</p>

<p>For more information about each services's APIs available once you're connected,
consult the corresponding documentation, such as for
<a href="{@docRoot}google/play-services/games.html">Google Play Games</a> or
<a href="{@docRoot}google/play-services/drive.html">Google Drive</a>.
</p>


<h3 id="WearableApi">Access the Wearable API</h3>

<p>The Wearable API provides a communication channel for your handheld and wearable apps. The API
consists of a set of data objects that the system can send and synchronize over the wire and
listeners that notify your apps of important events with the data layer. The
<a href="{@docRoot}reference/com/google/android/gms/wearable/Wearable.html">{@code Wearable}</a>
API is available on devices running Android 4.3 (API level 18) or higher when a wearable device is
connected. The API is not available under the following conditions:
</p>

<ul>
<li>Devices running Android 4.2 (API level 17) or earlier.</li>
<li><a href="https://play.google.com/store/apps/details?id=com.google.android.wearable.app&hl=en">Android
Wear companion app</a> is not installed on the device.</li>
<li>Android Wear device is not connected.</li>
</ul>

<h4 id="OnlyWearableApi">Using only the Wearable API</h4>

<p>If your app uses the
<a href="{@docRoot}reference/com/google/android/gms/wearable/Wearable.html">{@code Wearable}</a>
API but not other Google APIs, you can add this API by calling the
<a href="{@docRoot}reference/com/google/android/gms/common/api/GoogleApiClient.Builder.html#addApi(com.google.android.gms.common.api.Api<? extends com.google.android.gms.common.api.Api.ApiOptions.NotRequiredOptions>)"
>{@code addApi()}</a> method. The following example shows how to add the
<a href="{@docRoot}reference/com/google/android/gms/wearable/Wearable.html">{@code Wearable}</a>
API to your <a
href="{@docRoot}reference/com/google/android/gms/common/api/GoogleApiClient.html">{@code
GoogleApiClient}</a> instance:</p>

<pre>
GoogleApiClient mGoogleApiClient = new GoogleApiClient.Builder(this)
    .addApi(Wearable.API)
    .build();
</pre>

<p>In situations where the
<a href="{@docRoot}reference/com/google/android/gms/wearable/Wearable.html">{@code Wearable}</a>
API is not available, connection requests that include the <a
href="{@docRoot}reference/com/google/android/gms/wearable/Wearable.html">{@code
Wearable}</a> API fail with the <a
href="{@docRoot}reference/com/google/android/gms/common/ConnectionResult.html#API_UNAVAILABLE">
<code>API_UNAVAILABLE</code></a> error code.</p>

<p>
The following example shows how to determine whether the
<a href="{@docRoot}reference/com/google/android/gms/wearable/Wearable.html">{@code Wearable}</a>
API is available:
</p>

<pre>
// Connection failed listener method for a client that only
// requests access to the Wearable API
&#64;Override
public void onConnectionFailed(ConnectionResult result) {
    if (result.getErrorCode() == ConnectionResult.API_UNAVAILABLE) {
        // The Wearable API is unavailable
    }
    ...
}
</pre>


<h4 id="WearableApiWithOthers">Using the Wearable API with other APIs</h4>

<p>
If your app uses the
<a href="{@docRoot}reference/com/google/android/gms/wearable/Wearable.html">{@code Wearable}</a>
API in addition to other Google APIs, call the
<a href="{@docRoot}reference/com/google/android/gms/common/api/GoogleApiClient.Builder.html#addApiIfAvailable(com.google.android.gms.common.api.Api<? extends com.google.android.gms.common.api.Api.ApiOptions.NotRequiredOptions>, com.google.android.gms.common.api.Scope...)">addApiIfAvailable()</a>
method and pass in the
<a href="{@docRoot}reference/com/google/android/gms/wearable/Wearable.html">{@code Wearable}</a>
API to indicate that your client should gracefully handle the missing API.</p>

<p>The following example shows how to access the
<a href="{@docRoot}reference/com/google/android/gms/wearable/Wearable.html">{@code Wearable}</a>
API along with the
<a href="{@docRoot}reference/com/google/android/gms/drive/DriveApi.html">{@code Drive}</a>
API:</p>

<pre>
// Create a GoogleApiClient instance
mGoogleApiClient = new GoogleApiClient.Builder(this)
        .addApi(Drive.API)
        .addApiIfAvailable(Wearable.API)
        .addScope(Drive.SCOPE_FILE)
        .addConnectionCallbacks(this)
        .addOnConnectionFailedListener(this)
        .build();
</pre>

<p>In the example above, the
<a href="{@docRoot}reference/com/google/android/gms/common/api/GoogleApiClient.html">{@code GoogleApiClient}</a>
can successfully connect with the Google Drive service without connecting to the
<a href="{@docRoot}reference/com/google/android/gms/wearable/Wearable.html">{@code Wearable}</a>
API if it is unavailable. After you connect your
<a href="{@docRoot}reference/com/google/android/gms/common/api/GoogleApiClient.html">{@code GoogleApiClient}</a>
instance, ensure that the
<a href="{@docRoot}reference/com/google/android/gms/wearable/Wearable.html">{@code Wearable}</a>
API is available before making the API calls:
</p>

<pre>
mGoogleApiClient.hasConnectedApi(Wearable.API);
</pre>


<h2 id="Communicating">Communicate with Google Services</h2>

<p>Once connected, your client can make read and write calls using the service-specific APIs for which
your app is authorized, as specified by the APIs and scopes you added to your <a
href="{@docRoot}reference/com/google/android/gms/common/api/GoogleApiClient.html">{@code
GoogleApiClient}</a> instance.</p>

<p class="note">
<strong>Note:</strong> Before making calls to specific Google services, you may first need to
register your app in the Google Developer Console. For specific instructions, refer to the
appropriate getting started guide for the API you're using, such as <a href=
"https://developers.google.com/drive/android/get-started">Google Drive</a> or <a href=
"https://developers.google.com/+/mobile/android/getting-started">Google+</a>.</p>

<p>When you perform a read or write request using Google API Client, the immediate result is returned
as a <a href="{@docRoot}reference/com/google/android/gms/common/api/PendingResult.html">{@code
PendingResult}</a> object. This is an object representing the request, which hasn't yet
been delivered to the Google service.</p>

<p>For example, here's a request to read a file from Google Drive that provides a
<a href="{@docRoot}reference/com/google/android/gms/common/api/PendingResult.html">{@code
PendingResult}</a> object:</p>

<pre>
Query query = new Query.Builder()
        .addFilter(Filters.eq(SearchableField.TITLE, filename));
PendingResult result = Drive.DriveApi.query(mGoogleApiClient, query);
</pre>

<p>Once you have the
<a href="{@docRoot}reference/com/google/android/gms/common/api/PendingResult.html">{@code
PendingResult}</a>, you can continue by making the request either asynchronous
or synchronous.</p>


<h3 id="Async">Using asynchronous calls</h3>

<p>To make the request asynchronous, call <a
href="{@docRoot}reference/com/google/android/gms/common/api/PendingResult.html#setResultCallback(com.google.android.gms.common.api.ResultCallback<R>)"
>{@code setResultCallback()}</a> on the
<a href="{@docRoot}reference/com/google/android/gms/common/api/PendingResult.html">{@code
PendingResult}</a> and
provide an implementation of the <a
href="{@docRoot}reference/com/google/android/gms/common/api/ResultCallback.html"
>{@code ResultCallback}</a> interface. For example, here's the request
executed asynchronously:</p>

<pre>
private void loadFile(String filename) {
    // Create a query for a specific filename in Drive.
    Query query = new Query.Builder()
            .addFilter(Filters.eq(SearchableField.TITLE, filename))
            .build();
    // Invoke the query asynchronously with a callback method
    Drive.DriveApi.query(mGoogleApiClient, query)
            .setResultCallback(new ResultCallback&lt;DriveApi.MetadataBufferResult>() {
        &#64;Override
        public void onResult(DriveApi.MetadataBufferResult result) {
            // Success! Handle the query result.
            ...
        }
    });
}
</pre>

<p>When your app receives a <a
href="{@docRoot}reference/com/google/android/gms/common/api/Result.html">{@code Result}</a>
object in the <a
href="{@docRoot}reference/com/google/android/gms/common/api/ResultCallback.html#onResult(R)"
>{@code onResult()}</a> callback, it is delivered as an instance of the
appropriate subclass as specified by the API you're using, such as <a
href="{@docRoot}reference/com/google/android/gms/drive/DriveApi.MetadataBufferResult.html"
>{@code DriveApi.MetadataBufferResult}</a>.</p>


<h3 id="Sync">Using synchronous calls</h3>

<p>If you want your code to execute in a strictly defined order, perhaps because the result of one
call is needed as an argument to another, you can make your request synchronous by calling <a
href="{@docRoot}reference/com/google/android/gms/common/api/PendingResult.html#await()"
>{@code await()}</a> on the
<a href="{@docRoot}reference/com/google/android/gms/common/api/PendingResult.html">{@code
PendingResult}</a>. This blocks the thread and returns the <a
href="{@docRoot}reference/com/google/android/gms/common/api/Result.html">{@code Result}</a> object
when the request completes, which is delivered as an instance of the
appropriate subclass as specified by the API you're using, such as <a
href="{@docRoot}reference/com/google/android/gms/drive/DriveApi.MetadataBufferResult.html"
>{@code DriveApi.MetadataBufferResult}</a>.</p>

<p>Because calling <a
href="{@docRoot}reference/com/google/android/gms/common/api/PendingResult.html#await()"
>{@code await()}</a> blocks the thread until the result arrives, it's important that you
never perform this call on the UI thread. So, if you want to perform synchronous requests to a
Google Play service, you should create a new thread, such as with {@link android.os.AsyncTask} in
which to perform the request. For example, here's how to perform the same file request to Google
Drive as a synchronous call:</p>

<pre>
private void loadFile(String filename) {
    new GetFileTask().execute(filename);
}

private class GetFileTask extends AsyncTask&lt;String, Void, Void> {
    protected void doInBackground(String filename) {
        Query query = new Query.Builder()
                .addFilter(Filters.eq(SearchableField.TITLE, filename))
                .build();
        // Invoke the query synchronously
        DriveApi.MetadataBufferResult result =
                Drive.DriveApi.query(mGoogleApiClient, query).await();

        // Continue doing other stuff synchronously
        ...
    }
}
</pre>

<p class="note">
<strong>Tip:</strong> You can also enqueue read requests while not connected to Google Play
services. For example, execute a method to read a file from Google Drive regardless of whether your
Google API Client is connected yet. Then once a connection is established, the read requests
execute and you'll receive the results. Any write requests, however, will generate an error if you
call them while your Google API Client is not connected.</p>