page.title=Authorization page.tags=AccountManager,oauth2 @jd:body

In this document

  1. Choosing an Account
  2. Obtaining an Access Token
  3. Handling Exceptions
  4. Using the Access Token

Google Play services offers a standard authorization flow for all Google APIs and all components of Google Play services. In addition, you can leverage the authorization portion of the Google Play services SDK to gain authorization to services that are not yet supported in the Google Play services platform by using the access token to manually make API requests or using a client library provided by the service provider.

For implementation details, see the sample in <android-sdk>/extras/google-play-services/samples/auth, which shows you how to carry out these basic steps for obtaining an access token.

Choosing an Account

Google Play services leverage existing accounts on an Android-powered device to gain authorization to the services that you want to use. To obtain an access token, a valid Google account is required and it must exist on the device. You can ask your users which account they want to use by enumerating the Google accounts on the device or using the built-in {@code AccountPicker} class to display a standard account picker view. You'll need the {@link android.Manifest.permission#GET_ACCOUNTS} permission set in your manifest file for both methods.

For example, here's how to gather all of the Google accounts on a device and return them in an array. When obtaining an access token, only the email address of the account is needed, so that is what the array stores: 

private String[] getAccountNames() {
    mAccountManager = AccountManager.get(this);
    Account[] accounts = mAccountManager.getAccountsByType(
            GoogleAuthUtil.GOOGLE_ACCOUNT_TYPE);
    String[] names = new String[accounts.length];
    for (int i = 0; i < names.length; i++) {
        names[i] = accounts[i].name;
    }
    return names;
}

Obtaining an Access Token

With an email address and the service scope you can now obtain an access token.

Note: Specify "oauth2:scope" for a single scope or "oauth2:scope1 scope2 scope3" for multiple scopes.

There are two general ways to get a token:

Using getToken()

The following code snippet obtains an access token with an email address, the scope that you want to use for the service, and a {@link android.content.Context}: 
HelloActivity mActivity;
String mEmail;
String mScope;
String token;

...
try {
    token = GoogleAuthUtil.getToken(mActivity, mEmail, mScope);
} catch {
    ...
}

Call this method off of the main UI thread since it executes network transactions. An easy way to do this is in an {@link android.os.AsyncTask}. The sample in the Google Play services SDK shows you how to wrap this call in an AsyncTask. If authorization is successful, the token is returned. If not, the exceptions described in Handling Exceptions are thrown that you can catch and handle appropriately.

Using getTokenWithNotification()

If you are obtaining access tokens in a background service or sync adapter, there are three overloaded {@code getTokenWithNotification()} methods that you can use:

See the sample in <android-sdk>/extras/google-play-services/samples/auth for implementation details.

Handling Exceptions

When requesting an access token with {@code GoogleAuthUtil.getToken()}, the following exceptions can be thrown:

For more information on how to handle these exceptions and code snippets, see the reference documentation for the {@code GoogleAuthUtil} class.

Using the Access Token

Once you have successfully obtained a token, you can use it to access Google services. Many Google services provide client libraries, so it is recommended that you use these when possible, but you can make raw HTTP requests as well with the token. The following example shows you how to do this and handle HTTP error and success responses accordingly: 

URL url = new URL("https://www.googleapis.com/oauth2/v1/userinfo?access_token="
        + token);
HttpURLConnection con = (HttpURLConnection) url.openConnection();
int serverCode = con.getResponseCode();
//successful query
if (serverCode == 200) {
    InputStream is = con.getInputStream();
    String name = getFirstName(readResponse(is));
    mActivity.show("Hello " + name + "!");
    is.close();
    return;
//bad token, invalidate and get a new one
} else if (serverCode == 401) {
    GoogleAuthUtil.invalidateToken(mActivity, token);
    onError("Server auth error, please try again.", null);
    Log.e(TAG, "Server auth error: " + readResponse(con.getErrorStream()));
    return;
//unknown error, do something else
} else {
    Log.e("Server returned the following error code: " + serverCode, null);
    return;
}

Notice that you must manually invalidate the token if the response from the server signifies an authorization error (401). This could mean the access token being used is invalid for the service's scope or the token may have expired. If this is the case, obtain a new token using {@code GoogleAuthUtil.getToken()}.