package com.example.pc.loginregister;_
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.Response;
import org.json.JSONException;
import org.json.JSONObject;

public class LoginActivity extends AppCompatActivity {

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

    final EditText etUsername=(EditText) findViewById(R.id.login);
    final EditText etPassword=(EditText) findViewById(R.id.password);
    final Button bLogin=(Button) findViewById(R.id.loginbutton);

    bLogin.setOnClickListener(new View.OnClickListener() {
        @Override
        public void onClick(View v) {
            final String login=etUsername.getText().toString();
            final String password=etPassword.getText().toString();

            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");
                            Intent intent=new Intent(LoginActivity.this, UserAreaActivity.class);
                            intent.putExtra("name",name);
                            intent.putExtra("login",login);
                            intent.putExtra("password",password);
                            LoginActivity.this.startActivity(intent);
                        }

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

                        }
                    } catch (JSONException e) {
                        e.printStackTrace();
                    }
                }
            };
            LoginRequest loginRequest=new LoginRequest(login,password,responseListener);
        }
    });
  }
}

package com.example.pc.loginregister;
import com.android.volley.Response;
import com.android.volley.toolbox.StringRequest;

import java.util.HashMap;
import java.util.Map;

public class LoginRequest extends StringRequest {
private static final String LOGIN_REQUEST_URL="http://10.0.2.2/attendance/Login.php";
private Map<String, String> params;

public LoginRequest(String login, String password, Response.Listener<String> listener)
{
    super(Method.POST, LOGIN_REQUEST_URL, listener, null);
    params=new HashMap<>();
    params.put("login",login);
    params.put("password",password);
}

@Override
public Map<String, String> getParams() {
    return params;
}
}

<?xml version="1.0" encoding="utf-8"?>
<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
xmlns:app="http://schemas.android.com/apk/res-auto"
xmlns:tools="http://schemas.android.com/tools"
android:id="@+id/activity_main"
android:layout_width="match_parent"
android:layout_height="match_parent"
android:paddingTop="16dp"
android:paddingBottom="16dp"
android:paddingLeft="16dp"
android:paddingRight="16dp"
android:orientation="vertical"
android:background="@color/white"
tools:context="com.example.pc.loginregister.LoginActivity">

<LinearLayout
    android:orientation="vertical"
    android:layout_centerHorizontal="true"
    android:layout_centerVertical="true"
    android:layout_width="match_parent"
    android:layout_height="match_parent">

    <ImageView
        android:layout_width="match_parent"
        android:layout_height="0dp"
        android:layout_weight="1"
        android:layout_marginTop="20dp"
        android:layout_marginLeft="10dp"
        android:layout_marginBottom="10dp"
        android:layout_marginRight="10dp"
        android:src="@drawable/papl"
        android:id="@+id/imageView"/>

    <EditText
        android:id="@+id/login"
        android:inputType="textEmailAddress"
        android:hint="Email"
        style="@style/edittext_style"/>

    <EditText
        android:id="@+id/password"
        android:inputType="textPassword"
        android:hint="Password"
        style="@style/edittext_style"/>

    <Button
        android:id="@+id/loginbutton"
        android:text="Login"
        style="@style/button_style" />

</LinearLayout>

</RelativeLayout>

<?xml version="1.0" encoding="utf-8"?>
<manifest xmlns:android="http://schemas.android.com/apk/res/android"
package="com.example.pc.loginregister">
<uses-permission android:name="android.permssion.INTERNET"/>

<application
    android:allowBackup="true"
    android:icon="@mipmap/ic_launcher"
    android:label="@string/app_name"
    android:roundIcon="@mipmap/ic_launcher_round"
    android:supportsRtl="true"
    android:theme="@style/AppTheme">
    <activity android:name=".LoginActivity">
        <intent-filter>
            <action android:name="android.intent.action.MAIN" />

            <category android:name="android.intent.category.LAUNCHER" />
        </intent-filter>
    </activity>
    <activity android:name=".UserAreaActivity"></activity>
</application>

</manifest>

<?php
$conn=mysqli_connect("localhost","root","","loginregister");

if (!$conn) {
printf("Connect failed: %sn", mysqli_connect_error());
exit();
}

$login=$_POST[""];
$password=$_POST[""];

$stmt=mysqli_prepare($conn,"SELECT * FROM user WHERE login=? AND password=?");
mysqli_stmt_bind_param($stmt,"ss",$login,$password);
mysqli_stmt_execute($stmt);

mysqli_stmt_store_result($stmt);
mysqli_stmt_bind_result($stmt,$emp_id,$name,$login,$password);

$response=array();
$response["success"]=false;

while(mysqli_stmt_fetch($stmt))
{
    $response["success"]=true;
    $response["emp_id"]=$emp_id;
    $response["name"]=$name;
    $response["login"]=$login;
    $response["password"]=$password;
}

echo json_encode($response);

?>