FirebaseDemo | Firebase Realtime Database for Android demo application | Authentication library

package com.pradeephr.firebasedemo;

import android.os.Bundle;
import android.util.Log;
import android.view.View;
import android.widget.Button;
import android.widget.EditText;
import android.widget.TextView;
import android.widget.Toast;

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

import com.google.firebase.database.ChildEventListener;
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.pradeephr.firebasedemo.model.Person;

public class MainActivity extends AppCompatActivity {
    private EditText editText;
    private EditText editText1;
    private TextView textView;
    private Button buttonSend;
    private Button buttonRead;

    private FirebaseDatabase mDatabase;
    private DatabaseReference mRef;

    private ChildEventListener mchildEventListener;



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

        initViews();
        mDatabase=FirebaseDatabase.getInstance();
        mRef=mDatabase.getReference("user");

        this.buttonSend.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                sendData();

            }
        });
        this.buttonRead.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                readData();
            }
        });

        mchildEventListener=new ChildEventListener() {
            @Override
            public void onChildAdded(@NonNull DataSnapshot snapshot, @Nullable String previousChildName) {
                Person p=snapshot.getValue(Person.class);
                Log.d("TAG",p.getName()+" "+p.getAge());
            }

            @Override
            public void onChildChanged(@NonNull DataSnapshot snapshot, @Nullable String previousChildName) {

            }

            @Override
            public void onChildRemoved(@NonNull DataSnapshot snapshot) {

            }

            @Override
            public void onChildMoved(@NonNull DataSnapshot snapshot, @Nullable String previousChildName) {

            }

            @Override
            public void onCancelled(@NonNull DatabaseError error) {

            }
        };
        mRef.addChildEventListener(mchildEventListener);


    }

    private void sendData(){
        String dataName=editText.getText().toString();
        int dataAge=Integer.parseInt(editText1.getText().toString());
        String key=mRef.push().getKey();

        // when class is present in package
        Person person=new Person(dataAge,dataName);
        assert key != null;
        mRef.child(key).setValue(person);

        Toast.makeText(MainActivity.this,"Data inserted...",Toast.LENGTH_SHORT).show();
    }
    private void readData(){

    }

    private void initViews() {
        editText=findViewById(R.id.editTextName);
        textView=findViewById(R.id.text);
        buttonSend=findViewById(R.id.btn_send);
        buttonRead=findViewById(R.id.btn_read);
        editText1=findViewById(R.id.editTextAge);
    }
}