Flutter调用Ganache合约报RPCError: Invalid signature v value错误求助

我是Flutter和Web3新手，尝试在按钮点击时调用智能合约的setter方法，将交易发送到本地区块链网络Ganache，使用Truffle管理和部署合约，但运行时出现错误：

flutter: RPCError: got code -32700 with msg "Invalid signature v value"

相关代码文件如下：

truffle-config.js #

module.exports = {
  networks: {
    development: {
      host: "127.0.0.1",     // Localhost (default: none)
      port: 7545,            // Standard Ethereum port (default: none)
      network_id: "*",       // Any network (default: none)
    }
  },

  mocha: {
    // timeout: 100000
  },
  contracts_build_directory: "./contracts",
  compilers: {
    solc: {
      version: "0.8.19",
      settings: {
        optimizer: {
          enabled: false,
          runs: 200
        },
      }
    }
  },
  db: {
    enabled: false
  }
};

MyContract.sol #

// SPDX-License-Identifier: MIT
pragma solidity 0.8.19;

contract MyContract {
    string public sentence = "Default Sentence Value";

    function set(string memory x) public {
        sentence = x;
    }

    function get() public view returns (string memory) {
        return sentence;
    }
}

main.dart #

import 'package:flutter/material.dart';
import 'package:flutter_app/contract_provider.dart';
import 'package:flutter_app/my_app.dart';
import 'package:provider/provider.dart';

void main() {
  runApp(const MainApp());
}

class MainApp extends StatelessWidget {
  const MainApp({super.key});

  @override
  Widget build(BuildContext context) {
    return ChangeNotifierProvider(
      create: (_) => ContractProvider(context),
      child: MaterialApp(
        title: 'Flutter Practice App',
        theme: ThemeData(
          useMaterial3: true,
        ),
        home: const HomeScreen(title: 'HomeScreen Title'),
      ),
    );
  }
}

my_app.dart #

import 'package:flutter/material.dart';
import 'package:flutter_app/contract_provider.dart';
import 'package:provider/provider.dart';

class HomeScreen extends StatefulWidget {
  const HomeScreen({super.key, required this.title});

  final String title;

  @override
  State<HomeScreen> createState() => _HomeScreenState();
}

class _HomeScreenState extends State<HomeScreen> {
  @override
  Widget build(BuildContext context) {
    TextEditingController inputController = TextEditingController();
    final contractProvider = Provider.of<ContractProvider>(context);
    return Scaffold(
        appBar: AppBar(title: Text(widget.title)),
        body: Consumer<ContractProvider>(builder: (context, model, child) {
          return Center(
              child: model.isLoading
                  ? const CircularProgressIndicator()
                  : Column(
                      mainAxisAlignment: MainAxisAlignment.center,
                      children: [
                        Text(
                            'Current value of the sentence: ${model.sentence.toString()}'),
                        const SizedBox(
                          height: 30,
                        ),
                        SizedBox(
                          width: 200,
                          child: TextFormField(
                            controller: inputController,
                            keyboardType: TextInputType.text,
                            decoration: const InputDecoration(
                                labelText: 'Please set a sentence!'),
                          ),
                        ),
                        const SizedBox(
                          height: 30,
                        ),
                        ElevatedButton(
                            onPressed: () async {
                              try {
                                await contractProvider.setSentence(
                                    inputController.text.toString());
                              } catch (e) {
                                print(e);
                              } finally {
                                inputController.clear();
                              }
                            },
                            child: const Text('Set'))
                      ],
                    ));
        }));
  }
}

contract_provider.dart #

import 'dart:convert';

import 'package:flutter/material.dart';
import 'package:http/http.dart';
import 'package:web3dart/web3dart.dart';
import 'package:web_socket_channel/io.dart';

class ContractProvider extends ChangeNotifier {
  static const String contract_name = "MyContract";
  static const String ganache_host = "127.0.0.1";
  static const String ganache_port = "7545";

  final String _rpcURL = "http://$ganache_host:$ganache_port";
  final String _wsURL = "wss://$ganache_host:$ganache_port";
  final String _privateKey =
      "0x67e633f41624a1d742d753fe52bcdfe96b54fe3d91a87ce5260101605fced7fb";

  late Web3Client _client;
  late Credentials _credentials;
  late DeployedContract _deployedContract;
  late ContractFunction _getSentence, _setSentence;
  String? sentence;
  bool isLoading = true;

  ContractProvider(context) {
    initialize(context);
  }

  initialize(context) async {
    _client = Web3Client(_rpcURL, Client(), socketConnector: () {
      return IOWebSocketChannel.connect(_wsURL).cast<String>();
    });

    final abiStringFile = await DefaultAssetBundle.of(context)
        .loadString('build/contracts/MyContract.json');
    final abiJson = jsonDecode(abiStringFile);
    final abi = jsonEncode(abiJson["abi"]);

    final contractAddress =
        EthereumAddress.fromHex(abiJson["networks"]["5777"]["address"]);

    _credentials = EthPrivateKey.fromHex(_privateKey);

    _deployedContract = DeployedContract(
        ContractAbi.fromJson(abi, contract_name), contractAddress);

    _getSentence = _deployedContract.function("get");
    _setSentence = _deployedContract.function("set");

    getSentence();
  }

  Future<void> getSentence() async {
    final result = await _client
        .call(contract: _deployedContract, function: _getSentence, params: []);
    sentence = result[0];
    isLoading = false;
    notifyListeners();
  }

  Future<void> setSentence(String value) async {
    isLoading = true;
    notifyListeners();
    await _client.sendTransaction(
        _credentials,
        Transaction.callContract(
            contract: _deployedContract,
            function: _setSentence,
            parameters: [value]));

    getSentence();
  }
}

问题排查与解决 #

这个错误核心原因是交易签名的网络标识不匹配，或者WebSocket协议配置错误，导致Ganache拒绝无效签名。以下是具体修复步骤：

1. 修正WebSocket协议 #

Ganache本地节点默认不启用加密WebSocket（wss），需将协议改为ws://：

// 在contract_provider.dart中修改
final String _wsURL = "ws://$ganache_host:$ganache_port";

2. 指定交易的Chain ID #

web3dart发送交易时需明确指定Ganache的Chain ID（默认是5777），确保签名使用正确的网络标识：

// 修改setSentence方法中的sendTransaction调用
await _client.sendTransaction(
    _credentials,
    Transaction.callContract(
        contract: _deployedContract,
        function: _setSentence,
        parameters: [value],
        chainId: 5777 // 添加Chain ID参数
    ),
    fetchChainIdFromNetworkId: false, // 强制使用指定的Chain ID
);

3. 验证私钥有效性 #

确认_privateKey是Ganache界面中生成的账户私钥，且该账户有足够ETH支付Gas费用。

4. 优化Provider初始化逻辑 #

原构造函数中直接调用异步方法可能导致初始化不完整，改为工厂方法+私有初始化：

// 修改contract_provider.dart中的构造函数和初始化方法
factory ContractProvider(BuildContext context) {
  final provider = ContractProvider._();
  provider._initialize(context);
  return provider;
}

ContractProvider._();

void _initialize(BuildContext context) async {
  // 原initialize方法的代码
}

完成以上修改后，重新运行项目即可正常调用智能合约的setter方法。

内容的提问来源于stack exchange，提问作者mr-possible