You can use the GoogleApiClient
("Google API Client")
object to access the Google APIs provided in the Google Play services library
(such as Google Sign-In, Games, and Drive). The Google API Client provides a
common entry point to Google Play services and manages the network
connection between the user's device and each Google service.
However, the newer GoogleApi
interface and its implementations are easier to
use and are the preferred way to access Play services APIs.
See Accessing Google APIs.
This guide shows how you can:
- Automatically manage your connection to Google Play services.
- Perform synchronous and asynchronous API calls to any of the Google Play services.
- Manually manage your connection to Google Play services in those rare cases where this is necessary. To learn more, see Manually managed connections.
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 Set Up Google Play Services SDK.
Start an automatically managed connection
After your project is linked to the Google Play services library, create an instance of
GoogleApiClient
using the
GoogleApiClient.Builder
APIs in your activity's
onCreate()
method. The
GoogleApiClient.Builder
class provides methods that allow you to specify the Google APIs you want to use and your desired
OAuth 2.0 scopes. Here is a code example that creates a
GoogleApiClient
instance that connects with the Google Drive service:
GoogleApiClient mGoogleApiClient = new GoogleApiClient.Builder(this) .enableAutoManage(this /* FragmentActivity */, this /* OnConnectionFailedListener */) .addApi(Drive.API) .addScope(Drive.SCOPE_FILE) .build();
You can add multiple APIs and multiple scopes to the same
GoogleApiClient
by appending additional calls to addApi()
and addScope()
.
Important: If you are adding the Wearable
API together with other APIs to a
GoogleApiClient
, you may run into client connection errors on devices that do
not have the Wear OS app installed. To
avoid connection errors, call the addApiIfAvailable()
method and pass in
the Wearable
API to allow your client to gracefully handle the missing
API. For more information, see Access the Wearable API.
To begin an automatically managed connection, you must specify an
implementation for the OnConnectionFailedListener
interface to receive unresolvable connection errors. When your auto-managed
GoogleApiClient
instance attempts to connect to Google APIs, it will automatically
display UI to attempt to fix any resolvable connection failures (for example, if
Google Play services needs to be updated). If an error occurs that cannot be
resolved, you will receive a call to
onConnectionFailed()
.
You may also specify an optional implementation for the ConnectionCallbacks
interface if your app needs to know when the
automatically managed connection is established or suspended. For example if
your app makes calls to write data to Google APIs, these should be invoked
only after the onConnected()
method has been called.
Here is an example activity that implements the callback interfaces and adds them to the Google API Client:
import com.google.android.gms.common.api.GoogleApiClient; import com.google.android.gms.common.api.GoogleApiClient.OnConnectionFailedListener; import gms.drive.*; import android.support.v4.app.FragmentActivity; public class MyActivity extends FragmentActivity implements OnConnectionFailedListener { private GoogleApiClient mGoogleApiClient; @Override protected void onCreate(Bundle savedInstanceState) { super.onCreate(savedInstanceState); // Create a GoogleApiClient instance mGoogleApiClient = new GoogleApiClient.Builder(this) .enableAutoManage(this /* FragmentActivity */, this /* OnConnectionFailedListener */) .addApi(Drive.API) .addScope(Drive.SCOPE_FILE) .build(); // ... } @Override public void onConnectionFailed(ConnectionResult result) { // An unresolvable error has occurred and a connection to Google APIs // could not be established. Display an error message, or handle // the failure silently // ... } }
Your GoogleApiClient
instance will automatically connect after your activity
calls onStart()
and disconnect after calling onStop()
.
Your app can immediately begin making
read requests to Google APIs after building GoogleApiClient
, without
waiting for the connection to complete.
Communicate with Google Services
After connecting, 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
GoogleApiClient
instance.
Note: Before making calls to specific Google services, you may first need to register your app in the Google Developer Console. For instructions, refer to the appropriate getting started guide for the API you're using, such as Google Drive or Google Sign-In.
When you perform a read or write request using GoogleApiClient
, the API client returns a PendingResult
object that represents the request.
This occurs immediately, before the request is delivered to the Google service that your app is calling.
For example, here's a request to read a file from Google Drive that provides a
PendingResult
object:
Query query = new Query.Builder() .addFilter(Filters.eq(SearchableField.TITLE, filename)); PendingResult<DriveApi.MetadataBufferResult> result = Drive.DriveApi.query(mGoogleApiClient, query);
After your app has a PendingResult
object,
your app can then specify whether the request is handled as an asynchronous call or as a synchronous call.
Tip: Your app can enqueue read requests while not connected to Google Play services. For
example, your app can call methods to read a file from Google Drive regardless of whether your GoogleApiClient
instance is connected yet. After a connection is established, enqueued read requests execute. Write requests generate an error if your app calls
Google Play services write methods while your Google API Client is not connected.
Using asynchronous calls
To make the request asynchronous, call
setResultCallback()
on the PendingResult
and provide an
implementation of the
ResultCallback
interface. For
example, here's the request executed asynchronously:
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<DriveApi.MetadataBufferResult>() { @Override public void onResult(DriveApi.MetadataBufferResult result) { // Success! Handle the query result. // ... } }); }
When your app receives a Result
object in
the onResult()
callback,
it is delivered as an instance of the appropriate subclass as specified by the API you're using,
such as
DriveApi.MetadataBufferResult
.
Using synchronous calls
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
await()
on the
PendingResult
. This blocks the thread
and returns the Result
object when the
request completes. This object is delivered as an instance of the appropriate subclass as specified by
the API you're using, for example
DriveApi.MetadataBufferResult
.
Because calling await()
blocks the thread until the result arrives, your app should never make synchronous requests to Google APIs on the
UI thread. Your app can create a new thread using an AsyncTask
object, and use that thread to make the synchronous request.
The following example shows how to make a file request to Google Drive as a synchronous call:
private void loadFile(String filename) { new GetFileTask().execute(filename); } private class GetFileTask extends AsyncTask<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 // ... } }
Access the Wearable API
The Wearable API provides a communication channel for apps that run on handheld and wearable devices. The API consists of a set of data objects that the system can send and synchronize, and listeners that notify your apps of important events using a data layer. The Wearable API is available on devices running Android 4.3 (API level 18) or higher when a wearable device is connected and the Wear OS companion app is installed on the device.
Using the Wearable API stand-alone
If your app uses the Wearable API but not other Google APIs, you can add this API by
calling the addApi()
method. The following example shows how to add the
Wearable API to your GoogleApiClient
instance:
GoogleApiClient mGoogleApiClient = new GoogleApiClient.Builder(this) .enableAutoManage(this /* FragmentActivity */, this /* OnConnectionFailedListener */) .addApi(Wearable.API) .build();
In situations where the Wearable API is not available, connection requests that
include the Wearable API fail with the
API_UNAVAILABLE
error code.
The following example shows how to determine whether the Wearable API is available:
// Connection failed listener method for a client that only // requests access to the Wearable API @Override public void onConnectionFailed(ConnectionResult result) { if (result.getErrorCode() == ConnectionResult.API_UNAVAILABLE) { // The Wearable API is unavailable } // ... }
Using the Wearable API with other Google APIs
If your app uses the Wearable API in addition to other Google APIs, call the
addApiIfAvailable()
method and pass in the Wearable API to check whether it is available. You can use this check to help your app to gracefully handle cases where the API is unavailable.
The following example shows how to access the Wearable API along with the Drive API:
// Create a GoogleApiClient instance mGoogleApiClient = new GoogleApiClient.Builder(this) .enableAutoManage(this /* FragmentActivity */, this /* OnConnectionFailedListener */) .addApi(Drive.API) .addApiIfAvailable(Wearable.API) .addScope(Drive.SCOPE_FILE) .build();
In the example above, the GoogleApiClient
can successfully connect with
Google Drive without connecting to the Wearable API if it is unavailable. After
you connect your GoogleApiClient
instance, ensure that the Wearable API is available before making the API calls:
boolean wearAvailable = mGoogleApiClient.hasConnectedApi(Wearable.API);
Ignoring API Connection Failures
If you call addApi()
and the GoogleApiClient
is unable to
connect successfully to that API, the entire connection operation for that client fails and
triggers the onConnectionFailed()
callback.
You can register an API connection failure to be ignored by using
addApiIfAvailable()
. If an API added with
addApiIfAvailable()
fails to connect due to a non-recoverable error
(like API_UNAVAILABLE
for Wear),
that API is dropped from your GoogleApiClient
and the client proceeds to
connect to other APIs. However, if any API connection fails with a recoverable error (like an
OAuth consent resolution intent), the client connect operation fails. When
using an automatically managed connection the GoogleApiClient
will attempt
to resolve such errors when possible. When using a manually managed connection
a ConnectionResult
containing a resolution intent is
delivered to the onConnectionFailed()
callback. API
connection failures are ignored only if there is no resolution for the failure
and the API was added
with addApiIfAvailable()
.
To learn how to implement manual connection failure
handling, see Handle connection failures.
Because APIs added with
addApiIfAvailable()
may not always be present in the connected
GoogleApiClient
instance, you should guard calls to these APIs by adding a check
using hasConnectedApi()
. To find out why a
particular API failed to connect when the entire connection operation succeeded for the client, call
getConnectionResult()
and get the error code from the
ConnectionResult
object. If your client calls an API when it is not
connected to the client, the call fails with the
API_NOT_AVAILABLE
status code.
If the API you are adding through addApiIfAvailable()
requires one or
more scopes, add those scopes as parameters in your
addApiIfAvailable()
method call rather than by using the
addScope()
method. Scopes added using this approach may not be requested if the API
connection fails before getting OAuth consent, whereas scopes added with
addScope()
are always requested.
Manually managed connections
The majority of this guide shows you how to use the
enableAutoManage
method to initiate an
automatically managed connection with automatically resolved errors. In almost
all cases, this is the best and easiest way to connect to Google APIs from your
Android app. However, there are some situations where you would want to use a
manually managed connection to Google APIs in your app:
- To access Google APIs outside of an activity or retain control of the API connection
- To customize connection error handling and resolution
This section provides examples of these and other advanced use cases.
Start a manually managed connection
To initiate a manually managed connection to GoogleApiClient
, you must
specify an implementation for the callback interfaces,
ConnectionCallbacks
and OnConnectionFailedListener
.
These interfaces receive callbacks in response to the asynchronous
connect()
method when the
connection to Google Play services succeeds, fails, or becomes suspended.
mGoogleApiClient = new GoogleApiClient.Builder(this) .addApi(Drive.API) .addScope(Drive.SCOPE_FILE) .addConnectionCallbacks(this) .addOnConnectionFailedListener(this) .build()
When managing a connection manually you will need to call the
connect()
and
disconnect()
methods at the right points in your app's lifecycle. In an activity
context the best practice is to call connect()
in your activity's onStart()
method and disconnect()
in your activity's onStop()
method.
The connect()
and
disconnect()
methods
are called automatically when using an automatically managed connection.
If you are using GoogleApiClient
to connect to APIs that require
authentication, like Google Drive or Google Play Games, there's a good chance
your first connection attempt will fail and your app will receive a call
to onConnectionFailed()
with the SIGN_IN_REQUIRED
error because the user account was not specified.
Handle connection failures
When your app receives a call to the onConnectionFailed()
callback, you should call hasResolution()
on the provided ConnectionResult
object. If it returns true, your app can request that the user take immediate action to resolve the error by
calling startResolutionForResult()
on the ConnectionResult
object.
The startResolutionForResult()
method
behaves the same as startActivityForResult()
in this situation,
and launches an activity appropriate to the context that helps the user to resolve the error (such as an activity that helps the user to
select an account).
If hasResolution()
returns false, your app should call
GoogleApiAvailability.getErrorDialog()
,
passing the error code to this method. This returns a
Dialog
provided by Google Play
services that's appropriate to the error. The dialog may simply provide a message explaining
the error, or 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).
For example, your
onConnectionFailed()
callback method should now look like this:
public class MyActivity extends Activity 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; // ... @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 GoogleApiAvailability.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() { } @Override public Dialog onCreateDialog(Bundle savedInstanceState) { // Get the error code and retrieve the appropriate dialog int errorCode = this.getArguments().getInt(DIALOG_ERROR); return GoogleApiAvailability.getInstance().getErrorDialog( this.getActivity(), errorCode, REQUEST_RESOLVE_ERROR); } @Override public void onDismiss(DialogInterface dialog) { ((MyActivity) getActivity()).onDialogDismissed(); } } }
After the user completes the dialog provided by
startResolutionForResult()
or dismisses the message provided by GoogleApiAvailability.getErrorDialog()
,
your activity receives the
onActivityResult()
callback with the
RESULT_OK
result code.
Your app can then call
connect()
again.
For example:
@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(); } } } }
In the above code, you probably noticed the boolean, 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 example, while the account picker dialog is displayed to help the user to resolve the
SIGN_IN_REQUIRED
error, the user may rotate the screen. This recreates your activity and causes your
onStart()
method to be
called again, which then calls
connect()
again. This
results in another call to
startResolutionForResult()
,
which creates another account picker dialog in front of the existing one.
This boolean serves its intended purpose only if it persists across activity instances. The next section explains how to maintain the error handling state of your app despite other user actions or events that occur on the device.
Maintain state while resolving an error
To avoid executing the code in
onConnectionFailed()
while a previous attempt to resolve an error is in progress, you need to retain a boolean that
tracks whether your app is already attempting to resolve an error.
As shown in the code example above, your app should set a boolean to true
each time it calls
startResolutionForResult()
or displays the dialog from
GoogleApiAvailability.getErrorDialog()
.
Then, when your app receives
RESULT_OK
in the
onActivityResult()
callback, set the boolean to false
.
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
onSaveInstanceState()
:
private static final String STATE_RESOLVING_ERROR = "resolving_error"; @Override protected void onSaveInstanceState(Bundle outState) { super.onSaveInstanceState(outState); outState.putBoolean(STATE_RESOLVING_ERROR, mResolvingError); }
Then recover the saved state during
onCreate()
:
@Override protected void onCreate(Bundle savedInstanceState) { super.onCreate(savedInstanceState); // ... mResolvingError = savedInstanceState != null && savedInstanceState.getBoolean(STATE_RESOLVING_ERROR, false); }
Now you're ready to safely run your app and manually connect to Google Play services.