flutter razorpay integration code

# add this package "razorpay_flutter: ^1.2.2" in the pubspec.yaml file

import 'package:flutter/material.dart';
import 'package:razorpay_flutter/razorpay_flutter.dart';

class PaymentScreen extends StatefulWidget {
  @override
  _PaymentScreenState createState() => _PaymentScreenState();
}

class _PaymentScreenState extends State<PaymentScreen> {
  var _razorpay = Razorpay();

  var options;

  @override
  void initState() {
    _razorpay.on(Razorpay.EVENT_PAYMENT_SUCCESS, _handlePaymentSuccess);
    _razorpay.on(Razorpay.EVENT_PAYMENT_ERROR, _handlePaymentError);
    _razorpay.on(Razorpay.EVENT_EXTERNAL_WALLET, _handleExternalWallet);

    options = {
      'key': '<Generate and Add Your Key here https://dashboard.razorpay.com/app/keys>',
      'amount': 100 * 100,
      'name': 'Sai Gopi YT',
      'description': 'Course Free',
      'prefill': {'contact': '7981686394', 'email': 'test@razorpay.com'}
    };

    super.initState();
  }

  void _handlePaymentSuccess(PaymentSuccessResponse response) {
    // Do something when payment succeeds

    print("_handlePaymentSuccess payment is success " + response.paymentId);
  }

  void _handlePaymentError(PaymentFailureResponse response) {
    // Do something when payment fails
    print("_handlePaymentError payment is failed " + response.message);
  }

  void _handleExternalWallet(ExternalWalletResponse response) {
    // Do something when an external wallet was selected
  }

  @override
  Widget build(BuildContext context) {
    return Scaffold(
      appBar: AppBar(
        title: Text("Payment Gateway"),
      ),
      body: Center(
        child: RaisedButton(
            onPressed: () {
              _razorpay.open(options);
            },
            child: Text("Start payment")),
      ),
    );
  }
}