MainActivity.java

package com.application.brainfit;

import android.content.Intent;
import android.os.Bundle;
import android.support.v7.app.AlertDialog;
import android.support.v7.app.AppCompatActivity;
import android.view.View;
import android.widget.Button;
import android.widget.EditText;
import android.widget.TextView;

import com.android.volley.RequestQueue;
import com.android.volley.Response;
import com.android.volley.toolbox.Volley;

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


public class MainActivity extends AppCompatActivity {

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

        final EditText etusername = (EditText) findViewById(R.id.username);
        final EditText etpassword = (EditText) findViewById(R.id.password);
        final Button login = (Button) findViewById(R.id.loginbtn);
        final TextView register = (TextView) findViewById(R.id.register);

        register.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                Intent i = new Intent(getApplicationContext(), RegisterActivity.class);
                startActivity(i);
            }
        });

        login.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                final String username = etusername.getText().toString();
                final String password = etpassword.getText().toString();


                // Response received from the server
                Response.Listener<String> responseListener = new Response.Listener<String>() {
                    @Override
                    public void onResponse(String response) {
                        try {
                            JSONObject jsonResponse = new JSONObject(response);
                            boolean success = jsonResponse.getBoolean("success");

                            if (success) {
                                String name = jsonResponse.getString("name");
                                String age = jsonResponse.getString("age");

                                Intent intent = new Intent(MainActivity.this, HomeActivity.class);
                                intent.putExtra("age",age);
                                intent.putExtra("name", name);

                                MainActivity.this.startActivity(intent);
                            } else {
                                AlertDialog.Builder builder = new AlertDialog.Builder(MainActivity.this);
                                builder.setMessage("Login Failed")
                                        .setNegativeButton("Retry", null)
                                        .create()
                                        .show();
                            }

                        } catch (JSONException e) {
                            e.printStackTrace();
                        }
                    }
                };

                LoginRequest loginRequest = new LoginRequest(username, password, responseListener);
                RequestQueue queue = Volley.newRequestQueue(MainActivity.this);
                queue.add(loginRequest);
            }
        });



    }
}