A month of Flutter: configure Firebase Auth for Sign in with Google on Android

Yesterday I added the sign-in button. Now let's make it do something.

First I'll create a new Firebase project that will be used in development. Once I get ready to publish the app I'll create a production project.

creating Firebase development project

Once the project is created, I'm going to enable Google as a sign-in provider for Firebase Auth. Enabling Google requires an app name and an email address. The email address can be a Google Group mailing list. I made sure the group is configured so that anyone can post but nobody can join and only members can read.

enable Google auth

There are a number of alternatives to Google if Twitter or email/password is more appropriate for the app's target user.

list of Firebase Auth providers

Within android/app/build.gradle I will replace the default com.example.<name> applicationId with app.birb. An application ID should be a domain that you own with the parts in reverse order.

Sign in with Google requires that API clients be authenticated. This basically means that you must use a certificate when accessing some Google APIs. Since the Birb app is currently using the development Firebase project, I will use the Android Studio debug certificate now and generate a production certificate in the future.

To get the debug certificate fingerprint, the keytool program is used. This is installed with Android Studio but may not be available in your system path. I used flutter doctor -v to find where the Java bins were located.

$ /usr/local/android-studio/jre/bin/keytool -list -v -alias androiddebugkey -keystore ~/.android/debug.keystore
Enter keystore password:  
Alias name: androiddebugkey
Creation date: Oct 22, 2018
Entry type: PrivateKeyEntry
Certificate chain length: 1
Certificate[1]:
Owner: C=US, O=Android, CN=Android Debug
Issuer: C=US, O=Android, CN=Android Debug
Serial number: 1
Valid from: Mon Oct 22 18:57:30 CDT 2018 until: Wed Oct 14 18:57:30 CDT 2048
Certificate fingerprints:
	 MD5:  32:B6:A3:75:EA:76:C7:AB:4A:A5:D4:48:AD:F3:09:52
	 SHA1: 0C:DC:5F:08:F0:45:EF:F0:7B:5C:CA:F2:76:52:CC:EA:16:3F:94:08
	 SHA256: 36:33:30:07:40:12:A4:30:2A:DD:9F:8C:FD:BE:92:62:F2:FB:C3:37:09:6F:DB:62:C9:60:7C:5E:8A:F8:21:59
	 Signature algorithm name: SHA1withRSA
	 Version: 1

With the SHA-1 fingerprint, 0C:DC:5F:08:F0:45:EF:F0:7B:5C:CA:F2:76:52:CC:EA:16:3F:94:08, at the ready, it's back to Firebase. I'll add an Android app to the project I created earlier. In the future I will also create an iOS app.

adding Android app to Firebase project

With the package name and fingerprint configured, Firebase will now prompt to download a google-services.json file. This contains various Google Cloud and Firebase service details and should be put in the android/app directory. There isn't any sensitive information in the file but for an open source project it will need to be different for every developer so I'm adding it to .gitignore.

adding Android app to Firebase project

Now I'll add a couple of dependencies to the Android app and to Flutter.

adding Android app to Firebase project

com.google.gms:google-services gets added to android/build.gradle.

buildscript {
    dependencies {
        // Add this line
        classpath 'com.google.gms:google-services:4.2.0'
    }
}

In android/app/build.gradle there are two additions.

dependencies {
  // Add this line
  implementation 'com.google.firebase:firebase-core:16.0.6'
}

// Add to the bottom of the file
apply plugin: 'com.google.gms.google-services'

In pubspec.yaml require the google_sign_in package and the firebase_auth package.

adding Android app to Firebase project

Well the Sign in with Google button still doesn't do anything but maybe tomorrow it will.

Code changes

Posts in this series

  • A month of Flutter
  • A month of Flutter: create the app
  • A month of Flutter: configuring continuous integration
  • A month of Flutter: continuous linting
  • A month of Flutter: upgrading to 1.0
  • A month of Flutter: initial theme
  • A month of Flutter: no content widget
  • A month of Flutter: a list of posts
  • A month of Flutter: extract post item widget
  • A month of Flutter: post model and mock data
  • A month of Flutter: rendering a ListView with StreamBuilder
  • A month of Flutter: Stream transforms and failing tests
  • A month of Flutter: real faker data
  • A month of Flutter: rendering network images
  • A month of Flutter: FABulous authentication
  • A month of Flutter: configure Firebase Auth for Sign in with Google on Android
  • A month of Flutter: configure Firebase Auth for Sign in with Google on iOS
  • A month of Flutter: Sign in with Google
  • A month of Flutter: mocking Firebase Auth in tests
  • A month of Flutter: delicious welcome snackbar
  • A month of Flutter: navigate to user registration
  • A month of Flutter: user registration form
  • A month of Flutter: testing forms
  • A month of Flutter: setting up Firebase Firestore
  • A month of Flutter: awesome adaptive icons
  • A month of Flutter: set up Firestore rules tests
  • A month of Flutter: Firestore create user rules and tests
  • A month of Flutter: WIP save users to Firestore
  • A month of Flutter: user registration refactor with reactive scoped model
  • A month of Flutter: the real hero animation
  • A month of Flutter: a look back