Sign-In with Facebook using Firebase and get user information using Facebook Graph API.

activity_facebook.xml

<?xml version="1.0" encoding="utf-8"?>
<RelativeLayout 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:id="@+id/activity_facebook"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:paddingBottom="@dimen/activity_vertical_margin"
    android:paddingLeft="@dimen/activity_horizontal_margin"
    android:paddingRight="@dimen/activity_horizontal_margin"
    android:paddingTop="@dimen/activity_vertical_margin"
    tools:context="com.example.harshil.firebasebasic.facebook">

    <ProgressBar
        android:id="@+id/progressBar2"
        style="?android:attr/progressBarStyle"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_centerHorizontal="true"
        android:layout_centerVertical="true" />

    <TextView
        android:id="@+id/textView"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_below="@+id/progressBar2"
        android:layout_centerHorizontal="true"
        android:layout_marginTop="18dp"
        android:text="Handshaking with Facebook..."
        android:textColor="@color/colorAccent"
        android:textStyle="normal|bold" />

    <com.facebook.login.widget.LoginButton
        android:id="@+id/button_facebook_login"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_alignParentBottom="true"
        android:layout_centerHorizontal="true"
        android:visibility="invisible" />
</RelativeLayout>

facebook.java

package com.example.harshil.firebasebasic;

import android.content.Intent;
import android.os.Bundle;
import android.support.annotation.NonNull;
import android.support.v7.app.AppCompatActivity;
import android.util.Log;
import android.widget.Toast;

import com.facebook.AccessToken;
import com.facebook.CallbackManager;
import com.facebook.FacebookCallback;
import com.facebook.FacebookException;
import com.facebook.FacebookSdk;
import com.facebook.GraphRequest;
import com.facebook.GraphResponse;
import com.facebook.login.LoginResult;
import com.facebook.login.widget.LoginButton;
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.FacebookAuthProvider;
import com.google.firebase.auth.FirebaseAuth;

import org.json.JSONException;
import org.json.JSONObject;

import java.util.Arrays;

public class facebook extends AppCompatActivity {

    private static final String TAG = "FacebookLogin";
    private FirebaseAuth mAuth;
    private FirebaseAuth.AuthStateListener mAuthListener;
    private CallbackManager mCallbackManager;
    private String email, first_name, last_name, gender, birthday;

    @Override
    public void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        FacebookSdk.sdkInitialize(getApplicationContext());
        setContentView(R.layout.activity_facebook);

        mAuth = FirebaseAuth.getInstance();
        mAuthListener = new FirebaseAuth.AuthStateListener() {
            @Override
            public void onAuthStateChanged(@NonNull FirebaseAuth firebaseAuth) {
                if (firebaseAuth.getCurrentUser() != null) {
                    Intent intent = new Intent(facebook.this, AccountActivity.class);
                    intent.putExtra("email", email);
                    intent.putExtra("first_name", first_name);
                    intent.putExtra("last_name", last_name);
                    intent.putExtra("gender", gender);
                    intent.putExtra("birthday", birthday);
                    intent.putExtra("provider", "facebook");
                    intent.putExtra("avatar", firebaseAuth.getCurrentUser().getPhotoUrl().toString());
                    startActivity(intent);
                }
            }
        };

        mCallbackManager = CallbackManager.Factory.create();
        final LoginButton loginButton = (LoginButton) findViewById(R.id.button_facebook_login);
        loginButton.setReadPermissions(Arrays.asList("email", "user_birthday"));

        loginButton.registerCallback(mCallbackManager, new FacebookCallback<LoginResult>() {
            @Override
            public void onSuccess(LoginResult loginResult) {
                Log.d("Access Token", loginResult.getAccessToken().toString());
                Log.d(TAG, "facebook:onSuccess:" + loginResult);

                GraphRequest request = GraphRequest.newMeRequest(
                        loginResult.getAccessToken(),
                        new GraphRequest.GraphJSONObjectCallback() {
                            @Override
                            public void onCompleted(
                                    JSONObject object,
                                    GraphResponse response) {
                                final JSONObject jsonObject = response.getJSONObject();
                                try {
                                    email = jsonObject.getString("email");
                                    first_name = jsonObject.getString("first_name");
                                    last_name = jsonObject.getString("last_name");
                                    gender = jsonObject.getString("gender");
                                    birthday = jsonObject.getString("birthday");
                                } catch (JSONException e) {
                                    e.printStackTrace();
                                }
                            }
                        });
                Bundle parameters = new Bundle();
                parameters.putString("fields", "email,first_name,last_name,gender,birthday");
                request.setParameters(parameters);
                request.executeAsync();

                handleFacebookAccessToken(loginResult.getAccessToken());
            }

            @Override
            public void onCancel() {
                Log.d(TAG, "facebook:onCancel");
            }

            @Override
            public void onError(FacebookException error) {
                Log.d(TAG, "facebook:onError", error);
            }
        });
    }

    @Override
    public void onStart() {
        super.onStart();
        mAuth.addAuthStateListener(mAuthListener);
    }

    @Override
    public void onStop() {
        super.onStop();
        if (mAuthListener != null) {
            mAuth.removeAuthStateListener(mAuthListener);
        }
    }

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

    private void handleFacebookAccessToken(AccessToken token) {
        Log.d(TAG, "handleFacebookAccessToken:" + token);

        AuthCredential credential = FacebookAuthProvider.getCredential(token.getToken());
        mAuth.signInWithCredential(credential)
                .addOnCompleteListener(this, new OnCompleteListener<AuthResult>() {
                    @Override
                    public void onComplete(@NonNull Task<AuthResult> task) {
                        Log.d(TAG, "signInWithCredential:onComplete:" + task.isSuccessful());
                        if (!task.isSuccessful()) {
                            Log.w(TAG, "signInWithCredential", task.getException());
                            Toast.makeText(facebook.this, "Authentication failed.",
                                    Toast.LENGTH_SHORT).show();
                        }
                    }
                });
    }
}