当然，以下是一个使用 algorand_json 插件与 Algorand 区块链进行交互的 Flutter 代码示例。这个示例将展示如何连接到 Algorand 节点、查询账户余额以及发送交易。

首先，确保你已经在 pubspec.yaml 文件中添加了 algorand_json 依赖：

dependencies:
  flutter:
    sdk: flutter
  algorand_json: ^最新版本号

然后，运行 flutter pub get 来获取依赖。

接下来，我们编写一个 Flutter 应用，展示如何使用 algorand_json 进行基本操作。

主应用代码 (main.dart)

import 'package:flutter/material.dart';
import 'package:algorand_json/algorand_json.dart';
import 'dart:convert';

void main() {
  runApp(MyApp());
}

class MyApp extends StatefulWidget {
  @override
  _MyAppState createState() => _MyAppState();
}

class _MyAppState extends State<MyApp> {
  String accountBalance = "Loading...";
  String transactionId = "";

  @override
  void initState() {
    super.initState();
    _fetchAccountBalance();
    // Uncomment the line below to send a transaction after fetching balance
    // _sendTransaction();
  }

  Future<void> _fetchAccountBalance() async {
    String apiUrl = "https://your-algorand-node-url";
    String accountAddress = "your-account-address";
    String apiKey = "your-api-key"; // If your node requires an API key

    var headers = {
      'Content-Type': 'application/json',
      'X-Algorand-API-Token': apiKey, // Remove or comment out if not needed
    };

    var response = await http.get(
      Uri.parse('$apiUrl/v2/accounts/$accountAddress'),
      headers: headers,
    );

    if (response.statusCode == 200) {
      var data = jsonDecode(response.body);
      setState(() {
        accountBalance = data['amount'] ?? "Error fetching balance";
      });
    } else {
      setState(() {
        accountBalance = "Error: ${response.statusCode}";
      });
    }
  }

  Future<void> _sendTransaction() async {
    String apiUrl = "https://your-algorand-node-url";
    String senderAddress = "your-sender-account-address";
    String receiverAddress = "receiver-account-address";
    String senderMnemonic = "your-sender-account-mnemonic";
    int amount = 1000; // MicroAlgos
    String note = "Test transaction";
    String apiKey = "your-api-key"; // If your node requires an API key

    var headers = {
      'Content-Type': 'application/json',
      'X-Algorand-API-Token': apiKey, // Remove or comment out if not needed
    };

    // Generate transaction parameters
    var params = await Algorand.getTransactionParams(apiUrl, headers: headers);

    // Sign transaction
    var senderSk = Algorand.mnemonicToSecretKey(senderMnemonic);
    var unsignedTxn = Algorand.makePaymentTxnWithSuggestedParams(
        senderAddress, params, receiverAddress, amount, note: note);

    var signedTxn = Algorand.signTransaction(unsignedTxn, senderSk);

    // Send signed transaction
    var response = await http.post(
      Uri.parse('$apiUrl/v2/transactions'),
      headers: headers,
      body: jsonEncode(signedTxn.toJson()),
    );

    if (response.statusCode == 200 || response.statusCode == 202) {
      var txnId = jsonDecode(response.body)['txId'];
      setState(() {
        transactionId = txnId;
      });
    } else {
      print("Error sending transaction: ${response.statusCode}");
    }
  }

  @override
  Widget build(BuildContext context) {
    return MaterialApp(
      home: Scaffold(
        appBar: AppBar(
          title: Text('Algorand Flutter Example'),
        ),
        body: Center(
          child: Column(
            mainAxisAlignment: MainAxisAlignment.center,
            children: [
              Text(
                'Account Balance: $accountBalance MicroAlgos',
                style: TextStyle(fontSize: 24),
              ),
              SizedBox(height: 20),
              Text(
                'Transaction ID: $transactionId',
                style: TextStyle(fontSize: 20),
              ),
            ],
          ),
        ),
      ),
    );
  }
}

注意事项

1. 替换占位符：确保将 your-algorand-node-url, your-account-address, your-sender-account-address, receiver-account-address, your-sender-account-mnemonic, 和 your-api-key 替换为实际的值。
2. 依赖管理：确保你已经在 pubspec.yaml 中添加了 http 依赖，因为上面的代码使用了 http 包来发送 HTTP 请求。
3. 错误处理：上面的代码仅展示了基本的错误处理，你可能需要根据实际需求进行更详细的错误处理和用户反馈。
4. 安全性：不要在生产环境中硬编码私钥或助记词。使用安全的存储机制来管理这些敏感信息。

这个示例提供了一个基本的框架，你可以根据实际需求进行扩展和修改。