Sign up new users to firebase

Firebase signUp.java

package com.example.bahaaibrahim.firebasetest;

import android.content.Intent;
import android.os.Bundle;
import android.support.annotation.NonNull;
import android.support.design.widget.FloatingActionButton;
import android.support.design.widget.Snackbar;
import android.support.v7.app.AppCompatActivity;
import android.support.v7.widget.Toolbar;
import android.text.TextUtils;
import android.view.Menu;
import android.view.MenuItem;
import android.view.View;
import android.widget.Button;
import android.widget.EditText;
import android.widget.Toast;

import com.google.android.gms.tasks.OnCompleteListener;
import com.google.android.gms.tasks.Task;
import com.google.firebase.auth.AuthResult;
import com.google.firebase.auth.FirebaseAuth;
import com.google.firebase.auth.FirebaseUser;

public class MainActivity extends AppCompatActivity {

    public EditText signUpText;
    public EditText password;
    public Button signUpBotton;
    public FirebaseAuth mAuth;
    public FirebaseAuth.AuthStateListener mAuthListener;
    public String email_s;
    public String password_s;


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

        signUpText = (EditText) findViewById(R.id.email);
        password = (EditText) findViewById(R.id.password);
        signUpBotton = (Button) findViewById(R.id.signup);


        mAuth = FirebaseAuth.getInstance();

        mAuthListener = new FirebaseAuth.AuthStateListener() {
            @Override
            public void onAuthStateChanged(@NonNull FirebaseAuth firebaseAuth) {
                FirebaseUser user = firebaseAuth.getCurrentUser();
                if (user != null) {
                    startActivity(new Intent(MainActivity.this, ProfileActivity.class));
                } else {
                    // User is signed out
                }
                // ...
            }
        };


        signUpBotton.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View view) {
                onSignUp();
            }
        });


        
   


    public void onSignUp() {
        email_s = signUpText.getText().toString();
        password_s = password.getText().toString();

        if (TextUtils.isEmpty(email_s) || TextUtils.isEmpty(password_s)) {
            Toast.makeText(getApplicationContext(), "Invalid Email / Password", Toast.LENGTH_LONG).show();
        } else {
            mAuth.createUserWithEmailAndPassword(email_s, password_s)
                    .addOnCompleteListener(this, new OnCompleteListener<AuthResult>() {
                        @Override
                        public void onComplete(@NonNull Task<AuthResult> task) {
                            if (task.isSuccessful()) {
                                Toast.makeText(getApplicationContext(), "Signed Up!", Toast.LENGTH_LONG).show();
                            }
                        }
                    });
        }
    }
}