如何在Flutter中使用Razorpay Orders API？

dependencies:
  flutter:
    sdk: flutter
  razorpay_flutter: ^1.2.6

import 'package:razorpay_flutter/razorpay_flutter.dart';

Razorpay _razorpay;

@override
void initState() {
  super.initState();
  
  _razorpay = Razorpay();
  
  // 初始化Razorpay
  _razorpay.on(Razorpay.EVENT_PAYMENT_SUCCESS, _handlePaymentSuccess);
  _razorpay.on(Razorpay.EVENT_PAYMENT_ERROR, _handlePaymentError);
  _razorpay.on(Razorpay.EVENT_EXTERNAL_WALLET, _handleExternalWallet);
}

@override
void dispose() {
  super.dispose();
  
  // 释放Razorpay资源
  _razorpay.clear();
}

void _startPayment() {
  var options = {
    'key': 'YOUR_RAZORPAY_API_KEY',
    'amount': 100, // 订单金额，以最小货币单位为单位（例如100表示1.00 INR）
    'name': 'Merchant Name',
    'description': 'Product Description',
    'prefill': {'contact': '1234567890', 'email': 'example@example.com'},
  };

  try {
    _razorpay.open(options);
  } catch (e) {
    print(e.toString());
  }
}

void _handlePaymentSuccess(PaymentSuccessResponse response) {
  // 处理支付成功
}

void _handlePaymentError(PaymentFailureResponse response) {
  // 处理支付错误
}

void _handleExternalWallet(ExternalWalletResponse response) {
  // 处理外部钱包支付
}