In this article, we will learn about Authentication- integrating Google SignIn in Android Application using firebase. If you want to integrate Google SignIn into your Android app, you’ve come to the right place.
People seem to hate filling out forms and remembering passwords, so including a Google SignIn in your Android application is a great idea. So, if you have a Google SignIn option in your Android app, it makes it easier for your users to SignUp.

If you don’t know what is firebase then please refer to What is Firebase | All about Firebase.

Output:

Step by step exaplanation:

Step 1: Go to the Main menu and select “Tools” and after that select “Firebase”.

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Step 2: Select Authentication as shown in above figure.

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Step 3: Select the option- “Authentication using Google SignIn Kotlin”.

Step 4: Connect your app to firebase: First.

• After that Add the Firebase Authentication SDK to your app as shown in figure given below:

Step 5: Go to Firebase console: Enable Google Authentication as shown in below:

Step 6: Enable it, select a email address and click save as shown in figure below:

Step 7: Open General setting and paste SHA key as shown below:

To generate SHA key : Go to the Android Studio Project and press ctrl 2 times and Run Anything pop up in this pop-up type – signingReport and Enter.

dependency required in Google Signin

Step 8: Add this to your file build.gradle(Module:app) :

//Firebase implementation platform(‘com.google.firebase:firebase-bom:28.4.0’) implementation ‘com.google.firebase:firebase-auth-ktx’ implementation ‘com.google.android.gms:play-services-auth:19.2.0’ // we use Coroutines also in this project to improve performance. implementation ‘org.jetbrains.kotlinx:kotlinx-coroutines-play-services:1.1.1’ implementation ‘org.jetbrains.kotlinx:kotlinx-coroutines-core:1.3.8’ implementation ‘org.jetbrains.kotlinx:kotlinx-coroutines-android:1.5.0’

Plugin required in Google Sign in

Add this to your file build.gradle(Module:app):

id ‘com.google.gms.google-services’

Add dependencies in build.gradle(Project:app)

classpath ‘com.google.gms:google-services:4.3.10’

Finally, your build.gradle(Module:app) file code look like:

plugins {
    id 'com.android.application'
    id 'kotlin-android'
    id 'com.google.gms.google-services'
}

android {
    compileSdkVersion 30
    buildToolsVersion "30.0.3"

    defaultConfig {
        applicationId "com.sagar.googlesignup"
        minSdkVersion 16
        targetSdkVersion 30
        versionCode 1
        versionName "1.0"
        multiDexEnabled true

        testInstrumentationRunner "androidx.test.runner.AndroidJUnitRunner"
    }

    buildTypes {
        release {
            minifyEnabled false
            proguardFiles getDefaultProguardFile('proguard-android-optimize.txt'), 'proguard-rules.pro'
        }
    }
    compileOptions {
        sourceCompatibility JavaVersion.VERSION_1_8
        targetCompatibility JavaVersion.VERSION_1_8
    }
    kotlinOptions {
        jvmTarget = '1.8'
    }
}

dependencies {

    implementation "org.jetbrains.kotlin:kotlin-stdlib:$kotlin_version"
    implementation 'androidx.core:core-ktx:1.6.0'
    implementation 'androidx.appcompat:appcompat:1.3.1'
    implementation 'com.google.android.material:material:1.4.0'
    implementation 'androidx.constraintlayout:constraintlayout:2.1.0'
    implementation 'com.google.firebase:firebase-auth-ktx:21.0.1'
    testImplementation 'junit:junit:4.+'
    androidTestImplementation 'androidx.test.ext:junit:1.1.3'
    androidTestImplementation 'androidx.test.espresso:espresso-core:3.4.0'

    //Firebase
    implementation platform('com.google.firebase:firebase-bom:28.4.0')
    implementation 'com.google.firebase:firebase-auth-ktx'
    implementation 'com.google.android.gms:play-services-auth:19.2.0'

    //Coroutines
    implementation 'org.jetbrains.kotlinx:kotlinx-coroutines-play-services:1.1.1'
    implementation 'org.jetbrains.kotlinx:kotlinx-coroutines-core:1.3.8'
    implementation 'org.jetbrains.kotlinx:kotlinx-coroutines-android:1.5.0'
}

and build.gradle(Project:app) code look like:

// Top-level build file where you can add configuration options common to all sub-projects/modules.
buildscript {
    ext.kotlin_version = "1.5.10"
    repositories {
        google()
        mavenCentral()
    }
    dependencies {
        classpath "com.android.tools.build:gradle:4.2.2"
        classpath "org.jetbrains.kotlin:kotlin-gradle-plugin:$kotlin_version"
        classpath 'com.google.gms:google-services:4.3.10'

        // NOTE: Do not place your application dependencies here; they belong
        // in the individual module build.gradle files
    }
}

allprojects {
    repositories {
        google()
        mavenCentral()
        jcenter() // Warning: this repository is going to shut down soon
    }
}

task clean(type: Delete) {
    delete rootProject.buildDir
}

Step 9: In activity_main.xml file add the code given below:

<?xml version="1.0" encoding="utf-8"?>
<androidx.constraintlayout.widget.ConstraintLayout xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:app="http://schemas.android.com/apk/res-auto"
    xmlns:tools="http://schemas.android.com/tools"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    tools:context=".SignIn">

    <TextView
        android:id="@+id/textView"
        android:layout_width="0dp"
        android:layout_height="wrap_content"
        android:text="DevelopersDome"
        android:textSize="30sp"
        android:textAlignment="center"
        app:layout_constraintBottom_toBottomOf="parent"
        app:layout_constraintEnd_toEndOf="parent"
        app:layout_constraintStart_toStartOf="parent"
        app:layout_constraintTop_toTopOf="parent"
        android:gravity="center_horizontal" />

</androidx.constraintlayout.widget.ConstraintLayout>

Step 10: In MainActivity.kt file keep it is as default:

package com.sagar.googlesignup

import android.os.Bundle
import androidx.appcompat.app.AppCompatActivity


class MainActivity : AppCompatActivity() {
    override fun onCreate(savedInstanceState: Bundle?) {
        super.onCreate(savedInstanceState)
        setContentView(R.layout.activity_main)

    }
}

Step 11: Create a New Activity(Empty activity) and name it SignIn and add the code given below in your activity_sign_in.xml file.

<?xml version="1.0" encoding="utf-8"?>
<androidx.constraintlayout.widget.ConstraintLayout xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:app="http://schemas.android.com/apk/res-auto"
    xmlns:tools="http://schemas.android.com/tools"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:background="@color/white"
    tools:context=".MainActivity">

    <ImageView
        android:id="@+id/imageView"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_marginTop="116dp"
        android:src="@drawable/download"
        app:layout_constraintEnd_toEndOf="parent"
        app:layout_constraintStart_toStartOf="parent"
        app:layout_constraintTop_toTopOf="parent" />

    <com.google.android.gms.common.SignInButton
        android:id="@+id/signInButton"
        android:layout_width="0dp"
        android:layout_height="wrap_content"
        android:layout_marginBottom="115dp"
        app:layout_constraintBottom_toBottomOf="parent"
        app:layout_constraintEnd_toEndOf="parent"
        app:layout_constraintStart_toStartOf="parent" />

    <ProgressBar
        android:id="@+id/progressBar"
        style="?android:attr/progressBarStyle"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_marginBottom="71dp"
        android:visibility="gone"
        app:layout_constraintBottom_toTopOf="@+id/signInButton"
        app:layout_constraintEnd_toEndOf="parent"
        app:layout_constraintStart_toStartOf="parent" />

</androidx.constraintlayout.widget.ConstraintLayout>

Step 12: In SignIn.kt file add the code given below:

package com.sagar.googlesignup

import android.content.Intent
import android.os.Bundle
import android.util.Log
import android.view.View
import android.widget.ProgressBar
import androidx.appcompat.app.AppCompatActivity
import com.google.android.gms.auth.api.signin.GoogleSignIn
import com.google.android.gms.auth.api.signin.GoogleSignInAccount
import com.google.android.gms.auth.api.signin.GoogleSignInClient
import com.google.android.gms.auth.api.signin.GoogleSignInOptions
import com.google.android.gms.common.SignInButton
import com.google.android.gms.common.api.ApiException
import com.google.android.gms.tasks.Task
import com.google.firebase.auth.FirebaseAuth
import com.google.firebase.auth.FirebaseUser
import com.google.firebase.auth.GoogleAuthProvider
import com.google.firebase.auth.ktx.auth
import com.google.firebase.ktx.Firebase
import kotlinx.coroutines.Dispatchers
import kotlinx.coroutines.GlobalScope
import kotlinx.coroutines.launch
import kotlinx.coroutines.tasks.await
import kotlinx.coroutines.withContext

class SignIn : AppCompatActivity() {
    private val RC_SIGN_IN: Int = 123
    private val TAG = "DevelopersDome"
    private lateinit var auth: FirebaseAuth
    private lateinit var googleSignInClient: GoogleSignInClient
    override fun onCreate(savedInstanceState: Bundle?) {
        super.onCreate(savedInstanceState)
        setContentView(R.layout.activity_sign_in)
        val gso = GoogleSignInOptions.Builder(GoogleSignInOptions.DEFAULT_SIGN_IN)
            .requestIdToken(getString(R.string.default_web_client_id))
            .requestEmail()
            .build()

        googleSignInClient = GoogleSignIn.getClient(this, gso)
        auth = Firebase.auth

        findViewById<SignInButton>(R.id.signInButton).setOnClickListener {
            signIn()
        }

    }

    private fun signIn() {
        val signInIntent = googleSignInClient.signInIntent
        startActivityForResult(signInIntent, RC_SIGN_IN)
    }

    override fun onActivityResult(requestCode: Int, resultCode: Int, data: Intent?) {
        super.onActivityResult(requestCode, resultCode, data)

        // Result returned from launching the Intent from GoogleSignInApi.getSignInIntent(...);
        if (requestCode == RC_SIGN_IN) {
            val task = GoogleSignIn.getSignedInAccountFromIntent(data)
            handleSignInResult(task)
        }
    }

    private fun handleSignInResult(completedTask: Task<GoogleSignInAccount>) {
        try {
            val account =
                completedTask.getResult(ApiException::class.java)!!
            Log.d(TAG, "firebaseAuthWithGoogle:" + account.id)
            firebaseAuthWithGoogle(account.idToken!!)
        } catch (e: ApiException) {
            Log.w(TAG, "signInResult:failed code=" + e.statusCode)

        }
    }

    private fun firebaseAuthWithGoogle(idToken: String) {
        val credential = GoogleAuthProvider.getCredential(idToken, null)
        findViewById<SignInButton>(R.id.signInButton).visibility = View.GONE
        findViewById<ProgressBar>(R.id.progressBar).visibility = View.VISIBLE
        GlobalScope.launch(Dispatchers.IO) {
            val auth = auth.signInWithCredential(credential).await()
            val firebaseUser = auth.user
            withContext(Dispatchers.Main) {
                updateUI(firebaseUser!!)
            }
        }

    }


    private fun updateUI(firebaseUser: FirebaseUser?) {
        if (firebaseUser != null) {
            val mainActivityIntent = Intent(this, MainActivity::class.java)
            startActivity(mainActivityIntent)
            finish()
        } else {
            findViewById<SignInButton>(R.id.signInButton).visibility = View.VISIBLE
            findViewById<ProgressBar>(R.id.progressBar).visibility = View.GONE
        }
    }
}

Run the application now. You will get the output shown in the output section.

Source Code:

We’ve completed the development of Google SignIn using Firebase in the Android application. You can get the Source code from the given below button.

• We hope that this guide will assist you in understanding all about the concepts of Google SignIn using firebase in android application. We have concentrated on making a basic, meaningful and easy-to -learn guide to the concepts of Google SignIn using firebase with suitable examples. Still if you have any problems regarding this, please post them in the comments section, we will be glad to assist you.