MainActivity.java

package com.alfianyusufabdullah.firebaseauthwithgoogle;

import android.content.Intent;
import android.support.annotation.NonNull;
import android.support.v4.app.FragmentActivity;
import android.support.v7.app.AppCompatActivity;
import android.os.Bundle;
import android.util.Log;
import android.view.View;
import android.widget.Button;
import android.widget.TextView;

import com.google.android.gms.auth.api.Auth;
import com.google.android.gms.auth.api.signin.GoogleSignInAccount;
import com.google.android.gms.auth.api.signin.GoogleSignInOptions;
import com.google.android.gms.auth.api.signin.GoogleSignInResult;
import com.google.android.gms.common.ConnectionResult;
import com.google.android.gms.common.SignInButton;
import com.google.android.gms.common.api.Api;
import com.google.android.gms.common.api.GoogleApiClient;
import com.google.android.gms.common.api.PendingResult;
import com.google.android.gms.common.api.ResultCallback;
import com.google.android.gms.common.api.Status;
import com.google.android.gms.tasks.OnCompleteListener;
import com.google.android.gms.tasks.Task;
import com.google.firebase.auth.AuthCredential;
import com.google.firebase.auth.AuthResult;
import com.google.firebase.auth.FirebaseAuth;
import com.google.firebase.auth.FirebaseUser;
import com.google.firebase.auth.GoogleAuthCredential;
import com.google.firebase.auth.GoogleAuthProvider;

import java.io.FileDescriptor;
import java.io.PrintWriter;
import java.util.concurrent.TimeUnit;

public class MainActivity extends AppCompatActivity {

    TextView authUsename, authEmail, authProfilPic, authToken;
    Button btnLogout;
    SignInButton btnSingIn;

    public static final int RequestSignInCode = 7;
    public FirebaseAuth firebaseAuth;
    public GoogleApiClient googleApiClient;


    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);

        authUsename = findViewById(R.id.authUsername);
        authEmail = findViewById(R.id.authEmail);
        authProfilPic = findViewById(R.id.authProfilPic);
        authToken = findViewById(R.id.authToken);

        btnLogout = findViewById(R.id.btnLogout);
        btnLogout.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {

                firebaseAuth.signOut();
                Auth.GoogleSignInApi.signOut(googleApiClient).setResultCallback(new ResultCallback<Status>() {
                    @Override
                    public void onResult(@NonNull Status status) {
                        authUsename.setText("Username");
                        authEmail.setText("Email");
                        authProfilPic.setText("Profil Pic");
                        authToken.setText("Token");
                    }
                });


            }
        });


        btnSingIn = findViewById(R.id.btnSignin);
        btnSingIn.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {

                Intent auth = Auth.GoogleSignInApi.getSignInIntent(googleApiClient);
                startActivityForResult(auth, RequestSignInCode);
            }
        });

        TextView textView = (TextView) btnSingIn.getChildAt(0);
        textView.setText("Masuk Dengan Google");

        firebaseAuth = FirebaseAuth.getInstance();

        GoogleSignInOptions googleSignInOptions = new GoogleSignInOptions.Builder(GoogleSignInOptions.DEFAULT_SIGN_IN)
                .requestIdToken("idtoken")
                .requestEmail()
                .build();

        googleApiClient = new GoogleApiClient.Builder(this)
                .enableAutoManage(this, new GoogleApiClient.OnConnectionFailedListener() {
                    @Override
                    public void onConnectionFailed(@NonNull ConnectionResult connectionResult) {
                        Log.i("MAINACTIVITY", "onConnectionFailed: " + connectionResult.getErrorMessage());
                    }
                })
                .addApi(Auth.GOOGLE_SIGN_IN_API, googleSignInOptions)
                .build();
    }

    @Override
    protected void onActivityResult(int requestCode, int resultCode, Intent data) {
        super.onActivityResult(requestCode, resultCode, data);

        if (requestCode == RequestSignInCode) {

            GoogleSignInResult result = Auth.GoogleSignInApi.getSignInResultFromIntent(data);
            if (result.isSuccess()) {

                GoogleSignInAccount account = result.getSignInAccount();

                if (account != null) {
                    AuthCredential credential = GoogleAuthProvider.getCredential(account.getIdToken(), null);

                    firebaseAuth.signInWithCredential(credential).addOnCompleteListener(new OnCompleteListener<AuthResult>() {
                        @Override
                        public void onComplete(@NonNull Task<AuthResult> task) {

                            if (task.isSuccessful()) {

                                FirebaseUser user = firebaseAuth.getCurrentUser();
                                if (user != null) {
                                    authUsename.setText(user.getDisplayName());
                                    authEmail.setText(user.getEmail());
                                    authToken.setText(user.getUid());

                                    if (user.getPhotoUrl() != null)
                                        authProfilPic.setText(user.getPhotoUrl().getEncodedPath());
                                }
                            }
                        }
                    });
                }
            } else {
                Log.i("MAINACTIVITY", "Login Status " + result.getStatus().getStatusMessage());
            }
        }
    }
}