google_sign_in | Flutter Package

A Flutter plugin for Google Sign In.

AndroidiOSWebSupportSDK 16+iOS 11+Any

Platform integration #

Android integration #

To access Google Sign-In, you’ll need to make sure to
register your application.

You don’t need to include the google-services.json file in your app unless you
are using Google services that require it. You do need to enable the OAuth APIs
that you want, using the
Google Cloud Platform API manager. For
example, if you want to mimic the behavior of the Google Sign-In sample app,
you’ll need to enable the
Google People API.

Make sure you’ve filled out all required fields in the console for
OAuth consent screen.
Otherwise, you may encounter APIException errors.

iOS integration #

1. First register your application.
2. Make sure the file you download in step 1 is named
   GoogleService-Info.plist.
3. Move or copy GoogleService-Info.plist into the [my_project]/ios/Runner
   directory.
4. Open Xcode, then right-click on Runner directory and select
   Add Files to "Runner".
5. Select GoogleService-Info.plist from the file manager.
6. A dialog will show up and ask you to select the targets, select the Runner
   target.
7. If you need to authenticate to a backend server you can add a
   SERVER_CLIENT_ID key value pair in your GoogleService-Info.plist.

   <key>SERVER_CLIENT_ID</key>
   <string>[YOUR SERVER CLIENT ID]</string>
   

8. Then add the CFBundleURLTypes attributes below into the
   [my_project]/ios/Runner/Info.plist file.

<!-- Put me in the [my_project]/ios/Runner/Info.plist file -->
<!-- Google Sign-in Section -->
<key>CFBundleURLTypes</key>
<array>
	<dict>
		<key>CFBundleTypeRole</key>
		<string>Editor</string>
		<key>CFBundleURLSchemes</key>
		<array>
			<!-- TODO Replace this value: -->
			<!-- Copied from GoogleService-Info.plist key REVERSED_CLIENT_ID -->
			<string>com.googleusercontent.apps.861823949799-vc35cprkp249096uujjn0vvnmcvjppkn</string>
		</array>
	</dict>
</array>
<!-- End of the Google Sign-in Section -->

As an alternative to adding GoogleService-Info.plist to your Xcode project,
you can instead configure your app in Dart code. In this case, skip steps 3 to 7
and pass clientId and serverClientId to the GoogleSignIn constructor:

GoogleSignIn _googleSignIn = GoogleSignIn(
  ...
  // The OAuth client id of your app. This is required.
  clientId: ...,
  // If you need to authenticate to a backend server, specify its OAuth client. This is optional.
  serverClientId: ...,
);

Note that step 8 is still required.

iOS additional requirement

Note that according to
https://developer.apple.com/sign-in-with-apple/get-started, starting June 30,
2020, apps that use login services must also offer a “Sign in with Apple” option
when submitting to the Apple App Store.

Consider also using an Apple sign in plugin from pub.dev.

The Flutter Favorite
sign_in_with_apple plugin could
be an option.

Web integration #

The new SDK used by the web has fully separated Authentication from Authorization,
so signIn and signInSilently no longer authorize OAuth scopes.

Flutter apps must be able to detect what scopes have been granted by their users,
and if the grants are still valid.

Read below about Working with scopes, and incremental authorization for
general information about changes that may be needed on an app, and for more
specific web integration details, see the
google_sign_in_web package.

Import the package #

To use this plugin, follow the
plugin installation instructions.

Use the plugin #

Add the following import to your Dart code:

import 'package:google_sign_in/google_sign_in.dart';

Initialize GoogleSignIn with the scopes you want:

GoogleSignIn _googleSignIn = GoogleSignIn(
  scopes: [
    'email',
    'https://www.googleapis.com/auth/contacts.readonly',
  ],
);

Full list of available scopes.

You can now use the GoogleSignIn class to authenticate in your Dart code, e.g.

Future<void> _handleSignIn() async {
  try {
    await _googleSignIn.signIn();
  } catch (error) {
    print(error);
  }
}

In the web, you should use the Google Sign In button (and not the signIn method)
to guarantee that your user authentication contains a valid idToken.

For more details, take a look at the
google_sign_in_web package.

Working with scopes, and incremental authorization. #

If your app supports both mobile and web, read this section!

Checking if scopes have been granted #

Users may (or may not) grant all the scopes that an application requests at
Sign In. In fact, in the web, no scopes are granted by signIn, silentSignIn
or the renderButton widget anymore.

Applications must be able to:

• Detect if the authenticated user has authorized the scopes they need.
• Determine if the scopes that were granted a few minutes ago are still valid.

There’s a new method that enables the checks above, canAccessScopes:

final bool isAuthorized = await _googleSignIn.canAccessScopes(scopes);

(Only implemented in the web platform, from version 6.1.0 of this package)

Requesting more scopes when needed #

If an app determines that the user hasn’t granted the scopes it requires, it
should initiate an Authorization request. (Remember that in the web platform,
this request must be initiated from an user interaction, like a button press).

Future<void> _handleAuthorizeScopes() async {
  final bool isAuthorized = await _googleSignIn.requestScopes(scopes);
  if (isAuthorized) {
    // Do things that only authorized users can do!
    _handleGetContact(_currentUser!);
  }
}

The requestScopes returns a boolean value that is true if the user has
granted all the requested scopes or false otherwise.

Once your app determines that the current user isAuthorized to access the
services for which you need scopes, it can proceed normally.

Authorization expiration #

In the web, the accessToken is no longer refreshed. It expires after 3600
seconds (one hour), so your app needs to be able to handle failed REST requests,
and update its UI to prompt the user for a new Authorization round.

This can be done by combining the error responses from your REST requests with
the canAccessScopes and requestScopes methods described above.

For more details, take a look at the
google_sign_in_web package.

Does an app always need to check canAccessScopes? #

The new web SDK implicitly grant access to the email, profile and openid
scopes when users complete the sign-in process (either via the One Tap UX or the
Google Sign In button).

If an app only needs an idToken, or only requests permissions to any/all of
the three scopes mentioned above
(OpenID Connect scopes),
it won’t need to implement any additional scope handling.

If an app needs any scope other than email, profile and openid, it must
implement a more complete scope handling, as described above.

Find the example wiring in the
Google sign-in example application.