Android user registration in firebase using authnetication and it should display that data in realtime database

1 You have to design 2 screens. 
a) Registration screen 
b) Dashboard screen 

2) Registration screen should contain below fields: 
a) First Name 
b) Last Name 
c) Email 
d) Mobile Number 
e) Password 
f) Confirm Password

3) Registration Form should have standard validation like:

a) User can enter max 50 characters for First Name 
b) User can enter max 100 characters for Last Name 
c) Email standard validation (xx@xx.xx) 
d) Password should be in hidden 
e) Users can enter max 20 characters for Passwords. 

4) Registration screen records should be inserted into the Firebase Realtime Database. 

5) After submitting a record on the Registration screen, the user should redirect to the Dashboard screen. 

6) On Dashboard Screen, Get all the users data from database and display list of users.

I have done the authentication is working fine but not showing in realtime database.

Package com.example.registration;

import androidx.annotation.NonNull;
import androidx.appcompat.app.AppCompatActivity;

import android.content.Intent;
import android.os.Bundle;
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.crashlytics.buildtools.reloc.org.apache.http.util.TextUtils;
import com.google.firebase.database.DataSnapshot;
import com.google.firebase.database.DatabaseError;
import com.google.firebase.database.DatabaseReference;
import com.google.firebase.database.FirebaseDatabase;
import com.google.firebase.database.ValueEventListener;

public class MainActivity extends AppCompatActivity {

            private EditText  edfname,edlname,edemail,edpassword,edcpassword,edphone;
            private Button btregister;

            FirebaseAuth fAuth;

        // creating a variable for our
        // Firebase Database.
        FirebaseDatabase firebaseDatabase;

        // creating a variable for our Database
        // Reference for Firebase.
        DatabaseReference databaseReference;

        // creating a variable for
        // our object class

        RegisterInfo registerInfo;

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

        // initializing our edittext and button
        edfname = findViewById(R.id.edfname);
        edlname = findViewById(R.id.edlname);
        edemail = findViewById(R.id.edemail);
        edpassword = findViewById(R.id.edpassword);
        edcpassword = findViewById(R.id.edcpassword);
        edphone = findViewById(R.id.edphone);

        // below line is used to get the
        // instance of our FIrebase database.
        firebaseDatabase = FirebaseDatabase.getInstance();

        // below line is used to get reference for our database.
        databaseReference = firebaseDatabase.getReference("RegisterInfo");

        // initializing our object
        // class variable.
        registerInfo = new RegisterInfo();

        btregister = findViewById(R.id.btregister);

        // adding on click listener for our button.
        btregister.setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View v) {

        // getting text from our edittext fields.
        String fname = edfname.getText().toString().trim();
        String lname = edlname.getText().toString().trim();
        String email= edemail.getText().toString().trim();
        String password = edpassword.getText().toString().trim();
        String cpassword = edcpassword.getText().toString().trim();
        String phone = edphone.getText().toString().trim();




        fAuth.createUserWithEmailAndPassword(email,password).addOnCompleteListener(new OnCompleteListener<AuthResult>() {
                @Override
                public void onComplete(@NonNull Task<AuthResult> task) {

                        if(task.isSuccessful()){
                                Toast.makeText(MainActivity.this, "User created", Toast.LENGTH_SHORT).show();
                                startActivity(new Intent(getApplicationContext(),Dashboard.class));
                        }
                        else{
                                Toast.makeText(MainActivity.this, "Error !" + task.getException().getMessage(), Toast.LENGTH_SHORT).show();

                        }
                }
        });

        // below line is for checking weather the
        // edittext fields are empty or not.
        if (TextUtils.isEmpty(fname) && TextUtils.isEmpty(lname) && TextUtils.isEmpty(email) && TextUtils.isEmpty(password) && TextUtils.isEmpty(cpassword)&& TextUtils.isEmpty(phone) ) {
        // if the text fields are empty
        // then show the below message.
        Toast.makeText(MainActivity.this, "Please add some data.", Toast.LENGTH_SHORT).show();
        } else {
        // else call the method to add
        // data to our database.
        addDatatoFirebase(fname,lname,email,password,cpassword,phone);
        }
        }
        });
        }

private void addDatatoFirebase(String fname, String lname, String email,String password, String cpassword, String phone) {
        // below 3 lines of code is used to set
        // data in our object class.
        registerInfo.setRfname(fname);
        registerInfo.setRlanme(lname);
        registerInfo.setRemail(email);
        registerInfo.setRpassword(password);
        registerInfo.setRcpassword(cpassword);
        registerInfo.setRphone(phone);

        // we are use add value event listener method
        // which is called with database reference.
        databaseReference.addValueEventListener(new ValueEventListener() {
@Override



public void onDataChange(@NonNull DataSnapshot snapshot) {
        // inside the method of on Data change we are setting
        // our object class to our database reference.
        // data base reference will sends data to firebase.
        databaseReference.setValue(registerInfo);

        // after adding this data we are showing toast message.
        Toast.makeText(MainActivity.this, "data added", Toast.LENGTH_SHORT).show();
        }

@Override
public void onCancelled(@NonNull DatabaseError error) {
        // if the data is not added or it is cancelled then
        // we are displaying a failure toast message.
        Toast.makeText(MainActivity.this, "Fail to add data " + error, Toast.LENGTH_SHORT).show();
        }
        });
        }
        }