Google APIs

Contents

The Google APIs package exposes dozens of Google services that you can use from Dart projects.

This page describes how to use APIs that interact with end-user data by using Google authentication.

Examples of user-data APIs include Calendar, Gmail, and YouTube.

Overview

To use Google APIs, follow these steps.

  1. Pick the desired API
  2. Enable the API
  3. Authenticate user with the required scopes
  4. Obtain an authenticated HTTP client
  5. Create and use the desired API class

1. Pick the desired API

The documentation for package:googleapis lists each API as a separate Dart library – in a name.version format. Let’s look at youtube.v3 as an example.

Each library may provide many types, but there is one root class that ends in Api. For YouTube, it’s YouTubeApi.

Not only is the Api class the one you need to instantiate – see step 3 – but it also exposes the scopes that represent the permissions needed to use the API. Look under the Constants section of the YouTubeApi class and you’ll see the available scopes. To request access to simply read (but not write) an end-users YouTube data, use the youtubeReadonlyScope when authenticating the user.

/// Provides the `YouTubeApi` class.
import 'package:googleapis/youtube/v3.dart';

2. Enable the API

To use Google APIs you must have a Google account and a Google project. You also need to enable your desired API.

In this example, you’d enable YouTube Data API v3.

For details, see the getting started instructions.

3. Authenticate the user with the required scopes

Use the google_sign_in package to authenticate users with their Google identity. You will have to configure signin for each platform you want to support.

/// Provides the `GoogleSignIn` class
import 'package:google_sign_in/google_sign_in.dart';

When you instantiate the GoogleSignIn class, you provide the desired scopes as discussed in the previous section.

final _googleSignIn = GoogleSignIn(
  scopes: <String>[YouTubeApi.youtubeReadonlyScope],
);

Follow the instructions provided by package:google_sign_in to allow a user to authenticate.

Once authenticated, you must obtain an authenticated HTTP client.

4. Obtain an authenticated HTTP client

The extension_google_sign_in_as_googleapis_auth package provides an extension method on GoogleSignIn: authenticatedClient.

import 'package:extension_google_sign_in_as_googleapis_auth/extension_google_sign_in_as_googleapis_auth.dart';

You can listen to onCurrentUserChanged. When event value is not null, you can create an authenticated client.

var httpClient = (await _googleSignIn.authenticatedClient())!;

This Client instance includes the nessesary credentials when invoking Google API classes.

5. Create and use the desired API class

Use the API to create the desired API type and call methods, for instance:

var youTubeApi = YouTubeApi(httpClient);

var favorites = await youTubeApi.playlistItems.list(
  ['snippet'],
  playlistId: 'LL', // Liked List
);

More information