Flutter Web3交互插件dart_web3gas的使用

dart_web3gas 是一个基于 Dart 语言计算区块链 Gas 的库（参考 Metamask 的计算逻辑）。为了防止 web3dart 的代码更新过快，部分代码被包含并进行了修改。

web3dart

在 pubspec.yaml 文件中添加以下依赖：

dependencies:
  web3dart: ^2.6.1

可以在 pub.dev 上找到更多关于 web3dart 的信息。

示例代码

以下是一个完整的示例代码，展示了如何使用 dart_web3gas 插件进行 Web3 交互。

import 'dart:io';
import 'package:dart_web3gas/web3dart/web3dart.dart';
import 'package:dart_web3gas/dart_web3gas.dart';

Future<void> main() async {
  var http = HttpClient();
  http.connectionTimeout = const Duration(seconds: 2);

  // 创建 Web3 客户端实例
  var web3 = Web3Client.custom(
      JsonRPCHttp('https://polygon-mumbai-bor.publicnode.com', http));

  // 获取 Gas 费用估计数据
  var gas = await GasFeeController.fetchGasFeeEstimateData(web3);
  var max = gas?.gasFeeEstimates?.medium.suggestedMaxFeePerGas;
  var priority = gas?.gasFeeEstimates?.medium.suggestedMaxPriorityFeePerGas;

  // 打印钱包地址
  final wallet = EthPrivateKey.fromHex(
      'ae349e5dc27fe2b001ebbfe865c871e15a84929dbf42a9391941f3f7bc8f42fb');
  print('${wallet.address.hex} ');

  // 创建交易对象
  var transaction = Transaction(
    from: wallet.address,
    to: EthereumAddress.fromHex('0x7459e6df1f70820788809d5d25882acd3f9be3c3'),
    value: EtherAmount.fromBigInt(EtherUnit.finney, BigInt.one),
  );

  // 估算 Gas
  var basefee = await web3.estimateGas(
    sender: transaction.from,
    to: transaction.to,
    value: transaction.value,
  );

  if (max != null && priority != null) {
    print('basefee: $basefee');
    print(
        'max:${double.parse(max) * basefee.toDouble()} pri:${double.parse(priority) * basefee.toDouble()}');
  }

  // 获取当前 Gas 价格
  var gasprice = await web3.getGasPrice();
  print('gasprice: $gasprice');

  // 创建 EIP-1559 交易对象
  final transaction0 = transaction.copyWith(
    maxFeePerGas: BigInt.from(
        double.parse(eip1559GasFee.suggestedMaxFeePerGas) *
            BigInt.from(10).pow(9).toDouble()),
    maxPriorityFeePerGas: BigInt.from(
        double.parse(eip1559GasFee.suggestedMaxPriorityFeePerGas) *
            BigInt.from(10).pow(9).toDouble()),
    gasPrice: gasprice,
  );

  // 计算总 Gas 费用
  var total = getGasFee(transaction0, gas, basefee);
  print('total:$total');
  
  // 发送交易
  await web3.sendTransaction(wallet, transaction0, chainId: 80001);

  // 创建基础交易对象
  final transaction1 = transaction.copyWith(
    from: wallet.address,
    to: EthereumAddress.fromHex('0x7459e6df1f70820788809d5d25882acd3f9be3c3'),
    value: EtherAmount.fromBigInt(EtherUnit.finney, BigInt.one),
    maxGas: basefee,
    gasPrice: EtherAmount.fromBigInt(EtherUnit.gwei, BigInt.from(30)).getInWei,
  );

  // 计算总 Gas 费用
  total = getGasFee(transaction1, gas, basefee);
  print('total:$total');
  
  // 发送交易
  await web3.sendTransaction(wallet, transaction1, chainId: 80001);
}

// 计算 Gas 费用
BigInt getGasFee(
    Transaction? transaction, GasFeeCalculations? gasFee, BigInt? maxFee) {
  final gasPrice = transaction?.gasPrice;
  final gasLimit = transaction?.maxGas;
  if (gasPrice != null && gasLimit != null) {
    return (gasPrice * gasLimit);
  }
  return _getEip1159EthGasFee(gasFee, maxFee);
}

// 计算 EIP-1559 Gas 费用
BigInt _getEip1159EthGasFee(GasFeeCalculations? gasFee, BigInt? maxFee) {
  ///  (base fee + priority fee) x units of gas used
  BigInt total = BigInt.zero;
  BigInt? gasPrice = gasFee?.gasPrice;

  Eip1559GasFee? eip1559Gas = gasFee?.gasFeeEstimates?.medium;
  if (eip1559Gas != null) {
    double baseFee = double.parse(eip1559Gas.suggestedMaxFeePerGas);
    double priorityFee = double.parse(eip1559Gas.suggestedMaxPriorityFeePerGas);
    gasPrice = BigInt.from(
        (baseFee + priorityFee) * BigInt.from(10).pow(9).toDouble());
    print('==== base:$baseFee priority:$priorityFee  max:$maxFee');
  }

  if (gasPrice != null && maxFee != null) {
    total += gasPrice * maxFee;
  }

  return total;
}