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# Web3Dart Library

The primary Ethereum library for Dart and Flutter ecosystems, providing comprehensive blockchain interaction capabilities.

import 'package:web3dart/web3dart.dart';
import 'package:http/http.dart';

class EthereumService {
  final Web3Client client;

  EthereumService(String rpcUrl) : client = Web3Client(rpcUrl, Client());

  Future<EtherAmount> getBalance(String address) async {
    final addr = EthereumAddress.fromHex(address);
    return await client.getBalance(addr);
  }

  Future<String> sendTransaction({
    required Credentials credentials,
    required String to,
    required BigInt amount,
  }) async {
    final transaction = await client.sendTransaction(
      credentials,
      Transaction(
        to: EthereumAddress.fromHex(to),
        value: EtherAmount.fromBigInt(EtherUnit.wei, amount),
      ),
    );
    return transaction;
  }
}

GitHub: web3dart
Pub.dev: web3dart package
Features:
- Flutter support for cross-platform mobile dApps
- Seamless integration with Flutter widgets
- Complete contract interaction capabilities
- Secure transaction signing and verification
- HD wallet integration with BIP-39/44 support
- ENS resolution and integration
- ERC-20 and ERC-721 token standards support
- Gas estimation and optimization

Important Note: Always specify a gas limit when creating transactions to prevent unexpected transaction failures. The Web3Dart library will attempt to estimate gas but explicit values are recommended for production applications.

# Flutter Integration Examples

Example of a Flutter widget using Web3Dart to display wallet balance:

import 'package:flutter/material.dart';
import 'package:web3dart/web3dart.dart';

class WalletWidget extends StatefulWidget {
  @override
  _WalletWidgetState createState() => _WalletWidgetState();
}

class _WalletWidgetState extends State<WalletWidget> {
  final ethereum = EthereumService('YOUR_ETHEREUM_NODE_URL');
  EtherAmount? balance;

  Future<void> updateBalance() async {
    final newBalance = await ethereum.getBalance('YOUR_ADDRESS');
    setState(() {
      balance = newBalance;
    });
  }

  @override
  Widget build(BuildContext context) {
    return Card(
      child: Padding(
        padding: EdgeInsets.all(16.0),
        child: Column(
          children: [
            Text('Balance: ${balance?.getValueInUnit(EtherUnit.ether)} ETH'),
            ElevatedButton(
              onPressed: updateBalance,
              child: Text('Refresh Balance'),
            ),
          ],
        ),
      ),
    );
  }
}

Performance Tip: For production Flutter apps, consider implementing caching mechanisms and background refresh patterns to avoid excessive RPC calls that might impact app responsiveness.

# Smart Contract Integration

Working with smart contracts in Dart with complete type safety:

class SmartContractService {
  final Web3Client client;
  final DeployedContract contract;

  SmartContractService(String rpcUrl, String contractAddress, String abi)
      : client = Web3Client(rpcUrl, Client()),
        contract = DeployedContract(
          ContractAbi.fromJson(abi, 'YourContract'),
          EthereumAddress.fromHex(contractAddress),
        );

  Future<List<dynamic>> callFunction(
    String functionName,
    List<dynamic> params,
  ) async {
    final function = contract.function(functionName);
    final result = await client.call(
      contract: contract,
      function: function,
      params: params,
    );
    return result;
  }
}

Security Note: When handling private keys in Flutter applications, use secure storage solutions like flutter_secure_storage to protect sensitive credentials. Never hardcode private keys in your application code.

# Error Handling and Utilities

Proper error handling in Dart for robust Ethereum applications:

class EthereumException implements Exception {
  final String message;
  final dynamic originalError;

  EthereumException(this.message, [this.originalError]);

  @override
  String toString() => 'EthereumException: $message';
}

extension EtherAmountExtension on EtherAmount {
  String formatEther([int decimals = 4]) {
    return getValueInUnit(EtherUnit.ether).toStringAsFixed(decimals);
  }
}

Dart & Flutter Tools for Ethereum

# Web3Dart Library

# Flutter Integration Examples

# Smart Contract Integration

# Error Handling and Utilities

See also