Android payment XML and Java code

Payment activity xml

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:orientation="vertical"
    android:padding="16dp">

    <EditText
        android:id="@+id/etCardNumber"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:hint="Card Number"
        android:inputType="number" />

    <EditText
        android:id="@+id/etCardHolder"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:hint="Card Holder Name" />

    <EditText
        android:id="@+id/etExpiry"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:hint="MM/YY" />

    <EditText
        android:id="@+id/etCVV"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:hint="CVV"
        android:inputType="numberPassword" />

    <Button
        android:id="@+id/btnPay"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:text="Pay Now"
        android:layout_marginTop="20dp" />

</LinearLayout>

Payment Activity Java

package com.example.paymentapp;

import android.os.Bundle;
import android.widget.Button;
import android.widget.EditText;
import android.widget.Toast;

import androidx.appcompat.app.AppCompatActivity;

public class PaymentActivity extends AppCompatActivity {

    EditText etCardNumber, etCardHolder, etExpiry, etCVV;
    Button btnPay;

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

        etCardNumber = findViewById(R.id.etCardNumber);
        etCardHolder = findViewById(R.id.etCardHolder);
        etExpiry = findViewById(R.id.etExpiry);
        etCVV = findViewById(R.id.etCVV);
        btnPay = findViewById(R.id.btnPay);

        btnPay.setOnClickListener(v -> {

            String cardNumber = etCardNumber.getText().toString().trim();
            String cardHolder = etCardHolder.getText().toString().trim();
            String expiry = etExpiry.getText().toString().trim();
            String cvv = etCVV.getText().toString().trim();

            if (cardNumber.isEmpty() || cardHolder.isEmpty()
                    || expiry.isEmpty() || cvv.isEmpty()) {

                Toast.makeText(this,
                        "Please fill all fields",
                        Toast.LENGTH_SHORT).show();
            } else {

                // Call your payment gateway API here
                Toast.makeText(this,
                        "Payment Processing...",
                        Toast.LENGTH_SHORT).show();
            }
        });
    }
}