Debug School

rakesh kumar
rakesh kumar

Posted on • Edited on

Google Sign In With Flutter using Firebase

google-sign-in-with-flutter
Social Authentication
https://blog.codemagic.io/firebase-authentication-google-sign-in-using-flutter/
client-auth
Video
firebase-authentication

Goal (what will change)

✅ You will still use Google Sign-In UI
✅ But authentication will be handled by FirebaseAuth (so you get a real Firebase user session)
✅ You will optionally send idToken to backend later (recommended), but not required if your backend only needs email/name

Step 1: Create Firebase project

Open Firebase Console

Add project → create project

After project created → go to Build → Authentication

Click Get started

Go to Sign-in method

Enable Google provider → Save

Go here inside the same project:

Firebase Console →

Build → Authentication → Get started → Sign-in method
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Then:

Click Google

Toggle Enable

Select Project support email

Save

Step 2: Add Android app in Firebase


> Task :shared_preferences_android:signingReport
Variant: debugAndroidTest
Config: debug
Store: C:\Users\rakes\.android\debug.keystore
Alias: AndroidDebugKey
MD5: 57:6B:8F:7A:03:D3:13:78:64:BC:68:C4:53:EB:4D:C8
SHA1: 9C:88:41:89:E5:3F:15:8D:0E:BD:AA:BE:90:39:56:D2:80:58:F0:54
SHA-256: 04:96:E4:EA:14:83:C7:13:CE:57:1A:1B:BA:8E:81:84:08:DB:31:53:D3:A0:81:63:7B:A7:F0:AD:C0:45:83:EF
Valid until: Monday, 8 November, 2055
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Paste SHA in Google Play Console (only for RELEASE / production)

Step 1

Open Google Play Console → select your app

Step 2

Go to:
Setup → App integrity

Step 3

Find section: App signing

Step 4

You will see:

App signing key certificate

Upload key certificate

Step 5

Copy:

SHA-1

SHA-256

Now go back to Firebase Console and paste these release SHA values also (same place as above).


NOTE:IMPORTANT
verify in google play console is it auto created or not for corresponding sha1 ,othere wise google login would not work in production it same sha1 which is firebase must be auto created by google play console if it is there in google ply console then download googlr.service.json from firebase and ckeck in certificate hash present in json file

google.service.json

STEP 3: Re-download google-services.json

After adding SHA:

Click google-services.json download again
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Replace file here (exact path):

android/app/google-services.json
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(Old file may not contain OAuth config)

STEP 4: Verify Android Gradle (Quick Check)
android/app/build.gradle

Make sure this line exists at BOTTOM:

apply plugin: 'com.google.gms.google-services'
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android/build.gradle

Ensure:

classpath 'com.google.gms:google-services:4.4.2'
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buildscript {
    repositories {
        google()
        mavenCentral()
    }
    dependencies {
        classpath 'com.google.gms:google-services:4.4.2'
    }
}
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Also ensure:

gradle

allprojects {
    repositories {
        google()
        mavenCentral()
    }
}
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android/app/build.gradle (App level)

Open: android/app/build.gradle

At top ensure:

apply plugin: 'com.android.application'
apply plugin: 'com.google.gms.google-services'
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Inside android {} ensure minSdkVersion is at least 21:

defaultConfig {
    minSdkVersion 21
}
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STEP 5: Flutter packages (verify)

In pubspec.yaml you should have:

dependencies:
  firebase_core: ^3.0.0
  firebase_auth: ^5.0.0
  google_sign_in: ^6.2.1
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Then:

flutter clean
flutter pub get
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STEP 6: Firebase initialized? (critical)

In main.dart:


void main() async {
  WidgetsFlutterBinding.ensureInitialized();
  await Firebase.initializeApp();
  runApp(const MyApp());
}
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If this is missing → app will crash or login won’t start.

STEP 7: Use Firebase Google login code

You already asked earlier and I gave you correct code.

You should now be using:

FirebaseGoogleAuthService

FirebaseAuth.instance.signInWithCredential()
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✅ Your backend login_emails() logic stays unchanged.

Where is SHA-1 in google-services.json?
✅ This line is the SHA-1 (certificate hash):

"certificate_hash": "9c884189e53f158d0ebdaabe903956d28058f054"
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This appears under:

"oauth_client": [
  {
    "client_type": 1,
    "android_info": {
      "package_name": "com.cotocus.motoshare.partner",
      "certificate_hash": "9c884189e53f158d0ebdaabe903956d28058f054"
    }
  }
]
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Step 8: Create Firebase Google Auth Service (NEW)

Create file:

✅ lib/services/firebase_google_auth_service.dart

import 'package:firebase_auth/firebase_auth.dart';
import 'package:google_sign_in/google_sign_in.dart';

class FirebaseGoogleAuthService {
  final FirebaseAuth _firebaseAuth = FirebaseAuth.instance;
  final GoogleSignIn _googleSignIn = GoogleSignIn(scopes: ['email', 'profile']);

  /// Sign in with Google + Firebase
  Future<UserCredential?> signInWithGoogle() async {
    try {
      // Always start with clean state to avoid old account confusion
      await _googleSignIn.signOut();

      final GoogleSignInAccount? googleUser = await _googleSignIn.signIn();
      if (googleUser == null) {
        // user cancelled
        return null;
      }

      final GoogleSignInAuthentication googleAuth = await googleUser.authentication;

      final credential = GoogleAuthProvider.credential(
        accessToken: googleAuth.accessToken,
        idToken: googleAuth.idToken,
      );

      final UserCredential userCred =
          await _firebaseAuth.signInWithCredential(credential);

      final user = userCred.user;
      if (user != null) {
        print('[FIREBASE] UID: ${user.uid}');
        print('[FIREBASE] Email: ${user.email}');
        print('[FIREBASE] Name: ${user.displayName}');
        print('[FIREBASE] idToken: ${await user.getIdToken()}');
      }

      return userCred;
    } catch (e) {
      print('[FIREBASE] Google Sign-In Error: $e');
      return null;
    }
  }

  Future<void> signOut() async {
    await _firebaseAuth.signOut();
    await _googleSignIn.signOut();
  }

  User? currentUser() => _firebaseAuth.currentUser;
}
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Step 9: Update your existing _handleGoogleSignIn() (minimal change)

You currently rely on GoogleSignInAccount.
Now you will rely on Firebase User.

Replace your method with this version:

Future<void> _handleGoogleSignIn() async {
  setState(() => _isLoading = true);

  try {
    final userCred = await FirebaseGoogleAuthService().signInWithGoogle();

    if (userCred == null || userCred.user == null) {
      ScaffoldMessenger.of(context).showSnackBar(
        const SnackBar(content: Text('Sign in canceled or failed')),
      );
      return;
    }

    final user = userCred.user!;
    final email = (user.email ?? '').trim();
    final name = (user.displayName ?? '').trim();

    print('Firebase Email: $email');
    print('Firebase Name: $name');

    if (email.isEmpty) {
      ScaffoldMessenger.of(context).showSnackBar(
        const SnackBar(content: Text('Email not received from Google')),
      );
      return;
    }

    final loginViewModel = Provider.of<LoginViewModel>(context, listen: false);

    // Keep your backend call as-is
    bool success = await loginViewModel.login_emails(
      email,
      name.isEmpty ? 'User' : name,
      context,
    );

    if (success) {
      Navigator.pushReplacement(
        context,
        MaterialPageRoute(
          builder: (context) => DashboardScreen(email: email),
        ),
      );
    } else {
      Navigator.push(
        context,
        MaterialPageRoute(
          builder: (context) => UpdateProfile(
            dialCode: dial_code,
            googleEmail: email,
            googleDisplayName: name,
          ),
        ),
      );
    }
  } catch (error) {
    ScaffoldMessenger.of(context).showSnackBar(
      SnackBar(content: Text('Error signing in: $error')),
    );
  } finally {
    setState(() => _isLoading = false);
  }
}
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