How to instantiate the Firebase object to my URL, Help with the Error below

Question

package br.com.netcriativa.umadeb.activity;

import android.app.ProgressDialog;
import android.content.Intent;
import android.os.Bundle;
import android.support.annotation.NonNull;
import android.support.v7.app.AppCompatActivity;
import android.support.v7.widget.Toolbar;
import android.text.TextUtils;
import android.util.Log;
import android.view.View;
import android.widget.EditText;
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.login.LoginResult;
import com.facebook.login.widget.LoginButton;
import com.firebase.client.Firebase;
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 com.google.firebase.auth.FirebaseUser;

import br.com.netcriativa.umadeb.R;
import br.com.netcriativa.umadeb.model.User;

/**
 * Created by AndroidBash on 10/07/16
 */

public class LoginActivity extends AppCompatActivity {

    private static final String TAG = "AndroidBash";
    public User user;
    private EditText email;
    private EditText password;
    private FirebaseAuth mAuth;
    private FirebaseAuth.AuthStateListener mAuthListener;
    private ProgressDialog mProgressDialog;

    //Add YOUR Firebase Reference URL instead of the following URL
    Firebase mRef = new   Firebase("https://aplicativoumadeb.firebaseio.com/users/");

    //FaceBook callbackManager
    private CallbackManager callbackManager;
    //

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_login);
        Toolbar toolbar = (Toolbar) findViewById(R.id.toolbar);
        setSupportActionBar(toolbar);

        mAuth = FirebaseAuth.getInstance();

        FirebaseUser mUser = mAuth.getCurrentUser();
        if (mUser != null) {
            // User is signed in
            Intent intent = new Intent(getApplicationContext(), MainActivity.class);
            String uid = mAuth.getCurrentUser().getUid();
            String image=mAuth.getCurrentUser().getPhotoUrl().toString();
            intent.putExtra("user_id", uid);
            if(image!=null || image!=""){
                intent.putExtra("profile_picture",image);
            }
            startActivity(intent);
            finish();
            Log.d(TAG, "onAuthStateChanged:signed_in:" + mUser.getUid());
        }

        mAuthListener = new FirebaseAuth.AuthStateListener() {
            @Override
            public void onAuthStateChanged(@NonNull FirebaseAuth firebaseAuth) {
                FirebaseUser mUser = firebaseAuth.getCurrentUser();
                if (mUser != null) {
                    // User is signed in
                    Log.d(TAG, "onAuthStateChanged:signed_in:" + mUser.getUid());
                } else {
                    // User is signed out
                    Log.d(TAG, "onAuthStateChanged:signed_out");
                }

            }
        };

        //FaceBook
        FacebookSdk.sdkInitialize(getApplicationContext());
        callbackManager = CallbackManager.Factory.create();
        LoginButton loginButton = (LoginButton) findViewById(R.id.button_facebook_login);
        loginButton.setReadPermissions("email", "public_profile");
        loginButton.registerCallback(callbackManager, new FacebookCallback<LoginResult>() {
            @Override
            public void onSuccess(LoginResult loginResult) {
                Log.d(TAG, "facebook:onSuccess:" + loginResult);
                signInWithFacebook(loginResult.getAccessToken());
            }

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

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

    }

    @Override
    protected void onStart() {
        super.onStart();
        email = (EditText) findViewById(R.id.edit_text_email_id);
        password = (EditText) findViewById(R.id.edit_text_password);
        mAuth.addAuthStateListener(mAuthListener);
    }

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


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

    protected void setUpUser() {
        user = new User();
        user.setEmail(email.getText().toString());
        user.setPassword(password.getText().toString());
    }

    public void onSignUpClicked(View view) {
        Intent intent = new Intent(this, SignUpActivity.class);
        startActivity(intent);
    }

    public void onLoginClicked(View view) {
        setUpUser();
        signIn(email.getText().toString(), password.getText().toString());
    }

    private void signIn(String email, String password) {
        Log.d(TAG, "signIn:" + email);
        if (!validateForm()) {
            return;
        }

        showProgressDialog();

        mAuth.signInWithEmailAndPassword(email, password)
                .addOnCompleteListener(this, new OnCompleteListener<AuthResult>() {
                    @Override
                    public void onComplete(@NonNull Task<AuthResult> task) {
                        Log.d(TAG, "signInWithEmail:onComplete:" + task.isSuccessful());

                        // If sign in fails, display a message to the user. If sign in succeeds
                        // the auth state listener will be notified and logic to handle the
                        // signed in user can be handled in the listener.
                        if (!task.isSuccessful()) {
                            Log.w(TAG, "signInWithEmail", task.getException());
                            Toast.makeText(LoginActivity.this, "Authentication failed.",
                                    Toast.LENGTH_SHORT).show();
                        } else {
                            Intent intent = new Intent(getApplicationContext(), MainActivity.class);
                            String uid = mAuth.getCurrentUser().getUid();
                            intent.putExtra("user_id", uid);
                            startActivity(intent);
                            finish();
                        }

                        hideProgressDialog();
                    }
                });
        //
    }

    private boolean validateForm() {
        boolean valid = true;

        String userEmail = email.getText().toString();
        if (TextUtils.isEmpty(userEmail)) {
            email.setError("Required.");
            valid = false;
        } else {
            email.setError(null);
        }

        String userPassword = password.getText().toString();
        if (TextUtils.isEmpty(userPassword)) {
            password.setError("Required.");
            valid = false;
        } else {
            password.setError(null);
        }

        return valid;
    }


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

        showProgressDialog();


        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 sign in fails, display a message to the user. If sign in succeeds
                        // the auth state listener will be notified and logic to handle the
                        // signed in user can be handled in the listener.
                        if (!task.isSuccessful()) {
                            Log.w(TAG, "signInWithCredential", task.getException());
                            Toast.makeText(LoginActivity.this, "Authentication failed.",
                                    Toast.LENGTH_SHORT).show();
                        }else{
                            String uid=task.getResult().getUser().getUid();
                            String name=task.getResult().getUser().getDisplayName();
                            String email=task.getResult().getUser().getEmail();
                            String image=task.getResult().getUser().getPhotoUrl().toString();

                            //Create a new User and Save it in Firebase database
                            User user = new User(uid,name,null,email,null);

                            mRef.child(uid).setValue(user);

                            Intent intent = new Intent(getApplicationContext(), MainActivity.class);
                            intent.putExtra("user_id",uid);
                            intent.putExtra("profile_picture",image);
                            startActivity(intent);
                            finish();
                        }

                        hideProgressDialog();
                    }
                });
    }


    public void showProgressDialog() {
        if (mProgressDialog == null) {
            mProgressDialog = new ProgressDialog(this);
            mProgressDialog.setMessage(getString(R.string.loading));
            mProgressDialog.setIndeterminate(true);
        }

        mProgressDialog.show();
    }

    public void hideProgressDialog() {
        if (mProgressDialog != null && mProgressDialog.isShowing()) {
            mProgressDialog.dismiss();
        }
    }


}

Below is Error Forneido by Android Logcat

Caused by: java.lang.RuntimeException: You need to set the Android context using Firebase.setAndroidContext() before using Firebase.