Unresolved reference for import com.google.android.gms.auth.api.Auth

Question

I'm learning how to develop an app with Google sign-in options and I am following this tutorial. However, my activity, however, is not registering import com.google.android.gms.auth.api.Auth and colors Auth in red on the import.

package nus.is3261.kotlinapp

import android.support.v7.app.AppCompatActivity
import android.os.Bundle
import android.util.Log
import android.view.View
import android.widget.Toast
import kotlinx.android.synthetic.main.activity_google_signin.*
import com.google.android.gms.auth.api.Auth
import com.google.android.gms.common.api.GoogleApiClient
import com.google.firebase.auth.FirebaseAuth
import com.google.android.gms.auth.api.signin.GoogleSignInOptions
import com.google.android.gms.common.ConnectionResult
import com.google.firebase.auth.FirebaseUser
import android.content.Intent
import com.google.android.gms.auth.api.signin.GoogleSignInAccount
import com.google.firebase.auth.GoogleAuthProvider

class GoogleSigninActivity : AppCompatActivity(), View.OnClickListener, GoogleApiClient.OnConnectionFailedListener {

    private val TAG = "JSAGoogleSignIn"
    private val REQUEST_CODE_SIGN_IN = 1234
    private val WEB_CLIENT_ID = "xxxxxx.apps.googleusercontent.com"

    private var mAuth: FirebaseAuth? = null

    private var mGoogleApiClient: GoogleApiClient? = null

    override fun onCreate(savedInstanceState: Bundle?) {
        super.onCreate(savedInstanceState)
        setContentView(R.layout.activity_google_signin)

        btn_sign_in.setOnClickListener(this)
        btn_sign_out.setOnClickListener(this)
        btn_disconnect.setOnClickListener(this)

        val gso = GoogleSignInOptions.Builder(GoogleSignInOptions.DEFAULT_SIGN_IN)
                .requestIdToken(WEB_CLIENT_ID)
                .requestEmail()
                .build()

        mGoogleApiClient = GoogleApiClient.Builder(this)
                .enableAutoManage(this /* FragmentActivity */, this /* OnConnectionFailedListener */)
                .addApi(Auth.GOOGLE_SIGN_IN_API, gso)
                .build()

        mAuth = FirebaseAuth.getInstance()
    }

    override fun onStart() {
        super.onStart()

        // Check if user is signed in (non-null) and update UI accordingly.
        val currentUser = mAuth!!.currentUser
        updateUI(currentUser)
    }

    override fun onClick(v: View?) {
        val i = v!!.id

        when (i) {
            R.id.btn_sign_in -> signIn()
            R.id.btn_sign_out -> signOut()
            R.id.btn_disconnect -> revokeAccess()
        }
    }

    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 == REQUEST_CODE_SIGN_IN) {
            val result = Auth.GoogleSignInApi.getSignInResultFromIntent(data)
            if (result.isSuccess) {
                // successful -> authenticate with Firebase
                val account = result.signInAccount
                firebaseAuthWithGoogle(account!!)
            } else {
                // failed -> update UI
                updateUI(null)
                Toast.makeText(applicationContext, "SignIn: failed!",
                        Toast.LENGTH_SHORT).show()
            }
        }
    }

    private fun firebaseAuthWithGoogle(acct: GoogleSignInAccount) {
        Log.e(TAG, "firebaseAuthWithGoogle():" + acct.id!!)

        val credential = GoogleAuthProvider.getCredential(acct.idToken, null)
        mAuth!!.signInWithCredential(credential)
                .addOnCompleteListener(this) { task ->
                    if (task.isSuccessful) {
                        // Sign in success
                        Log.e(TAG, "signInWithCredential: Success!")
                        val user = mAuth!!.currentUser
                        updateUI(user)
                    } else {
                        // Sign in fails
                        Log.w(TAG, "signInWithCredential: Failed!", task.exception)
                        Toast.makeText(applicationContext, "Authentication failed!",
                                Toast.LENGTH_SHORT).show()
                        updateUI(null)
                    }
                }
    }

    override fun onConnectionFailed(connectionResult: ConnectionResult) {
        Log.e(TAG, "onConnectionFailed():" + connectionResult);
        Toast.makeText(applicationContext, "Google Play Services error.", Toast.LENGTH_SHORT).show();
    }

    private fun signIn() {
        val intent = Auth.GoogleSignInApi.getSignInIntent(mGoogleApiClient)
        startActivityForResult(intent, REQUEST_CODE_SIGN_IN)
    }

    private fun signOut() {
        // sign out Firebase
        mAuth!!.signOut()

        // sign out Google
        Auth.GoogleSignInApi.signOut(mGoogleApiClient).setResultCallback { updateUI(null) }
    }

    private fun revokeAccess() {
        // sign out Firebase
        mAuth!!.signOut()

        // revoke access Google
        Auth.GoogleSignInApi.revokeAccess(mGoogleApiClient).setResultCallback { updateUI(null) }
    }

    private fun updateUI(user: FirebaseUser?) {
        if (user != null) {
            tvStatus.text = "Google User email: " + user.email!!
            tvDetail.text = "Firebase User ID: " + user.uid

            btn_sign_in.visibility = View.GONE
            layout_sign_out_and_disconnect.visibility = View.VISIBLE
        } else {
            tvStatus.text = "Signed Out"
            tvDetail.text = null

            btn_sign_in.visibility = View.VISIBLE
            layout_sign_out_and_disconnect.visibility = View.GONE
        }
    }
}

I feel like this is a dependency issue but I'm not sure as to where the issue is.

apply plugin: 'com.android.application'

apply plugin: 'kotlin-android'

apply plugin: 'kotlin-android-extensions'
apply plugin: 'com.google.gms.google-services'

android {
    compileSdkVersion 28
    defaultConfig {
        applicationId "nus.is3261.kotlinapp"
        minSdkVersion 21
        targetSdkVersion 28
        versionCode 1
        versionName "1.0"
        testInstrumentationRunner "android.support.test.runner.AndroidJUnitRunner"
    }
    buildTypes {
        release {
            minifyEnabled false
            proguardFiles getDefaultProguardFile('proguard-android.txt'), 'proguard-rules.pro'
        }
    }
}

dependencies {
    implementation fileTree(dir: 'libs', include: ['*.jar'])
    implementation "org.jetbrains.kotlin:kotlin-stdlib-jdk7:$kotlin_version"
    implementation 'com.android.support:appcompat-v7:28.0.0'
    implementation 'com.android.support.constraint:constraint-layout:1.1.3'
    implementation 'com.android.support:support-v4:28.0.0'
    implementation 'com.android.support:design:28.0.0'
    testImplementation 'junit:junit:4.12'
    androidTestImplementation 'com.android.support.test:runner:1.0.2'
    androidTestImplementation 'com.android.support.test.espresso:espresso-core:3.0.2'
    implementation 'com.google.firebase:firebase-auth:16.0.5'
    implementation 'com.google.firebase:firebase-core:16.0.4'

}

Here are my gradle files

buildscript {
    ext.kotlin_version = '1.2.70'
    repositories {
        google()
        jcenter()
    }
    dependencies {
        classpath 'com.android.tools.build:gradle:3.2.1'
        classpath "org.jetbrains.kotlin:kotlin-gradle-plugin:$kotlin_version"
        classpath 'com.google.gms:google-services:4.1.0'

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

    }
}

allprojects {
    repositories {
        google()
        jcenter()
    }
}

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

Answer 1

Inside the dependencies add:

implementation 'com.google.android.gms:play-services-auth:16.0.1'

and then at the bottom of the app/build.gradle file, add (required for firebase):

apply plugin: 'com.google.gms.google-services'