Dart中如何将API返回JSON数组的HEX格式SSID转为UTF-8/UTF-16

我是Dart新手，目前通过Future从API的JSON响应构建ListView，请求代码如下：

Future<List<Job>> _fetchJobs() async {
    final response = await http.get(
        Uri.parse('http://10.10.10.254/httpapi.asp?command=wlanGetApListEx'));
    if (response.statusCode == 200) {
      final List jsonResponse = json.decode(response.body)['aplist'] as List;
     print(jsonResponse);
      return jsonResponse.map((job) => new Job.fromJson(job)).toList();
    } else {
      throw Exception('Failed to load jobs from API');
    }
  }

API返回的JSON数据（已修正语法错误）如下：

[
   {
      "ssid":"444A446F626C65615F322E34",
      "bssid":"80:3f:5d:ed:cd:f9",
      "rssi":42,
      "channel":8,
      "auth":"WPA2PSK",
      "encry":"AES",
      "extch":0
   },
   {
      "ssid":"426172696369632D322E3447",
      "bssid":"b0:76:1b:f4:55:80",
      "rssi":18,
      "channel":1,
      "auth":"WPA2PSK",
      "encry":"AES",
      "extch":0
   },
   {
      "ssid":"46616D696C69615F65737061727A61",
      "bssid":"60:32:b1:71:ce:46",
      "rssi":0,
      "channel":5,
      "auth":"WPA2PSK",
      "encry":"AES",
      "extch":0
   },
   {
      "ssid":"43617361204C756369616E61",
      "bssid":"20:ab:48:86:17:58",
      "rssi":0,
      "channel":11,
      "auth":"WPA2PSK",
      "encry":"AES",
      "extch":0
   }
]

可以看到返回的SSID值为HEX格式，我需要将其转换为UTF-8或UTF-16格式。我尝试使用hex包，但不知道如何在这类JSON数组上实现转换。

1. 添加hex包依赖 #

在pubspec.yaml的dependencies区块中添加：

dependencies:
  hex: ^0.2.0 # 可替换为最新版本

执行flutter pub get（Flutter项目）或dart pub get（纯Dart项目）完成依赖安装。

2. 编写十六进制转UTF-8的工具函数 #

创建通用解码函数，处理十六进制字符串到UTF-8的转换：

import 'dart:convert';
import 'package:hex/hex.dart';

String hexToUtf8(String hexStr) {
  try {
    List<int> bytes = HEX.decode(hexStr);
    return utf8.decode(bytes);
  } catch (e) {
    // 解码失败时返回原字符串，也可自定义提示文本
    return hexStr;
  }
}

3. 在JSON解析流程中处理SSID #

有两种实现方式，按需选择：

方式一：在列表映射时处理

修改_fetchJobs方法，在转换每个JSON对象前先解码SSID：

import 'dart:convert';
import 'package:http/http.dart' as http;
import 'package:hex/hex.dart';

Future<List<Job>> _fetchJobs() async {
  final response = await http.get(
    Uri.parse('http://10.10.10.254/httpapi.asp?command=wlanGetApListEx'));
  
  if (response.statusCode == 200) {
    final List jsonResponse = json.decode(response.body)['aplist'] as List;
    return jsonResponse.map((jobJson) {
      // 替换解码后的SSID
      Map<String, dynamic> processedData = {
        ...jobJson,
        'ssid': hexToUtf8(jobJson['ssid'])
      };
      return Job.fromJson(processedData);
    }).toList();
  } else {
    throw Exception('Failed to load jobs from API');
  }
}

方式二：在Job类的构造函数中处理

直接在Job.fromJson里完成SSID解码，保持数据流程内聚：

class Job {
  final String ssid;
  final String bssid;
  final int rssi;
  final int channel;
  final String auth;
  final String encry;
  final int extch;

  Job({
    required this.ssid,
    required this.bssid,
    required this.rssi,
    required this.channel,
    required this.auth,
    required this.encry,
    required this.extch,
  });

  factory Job.fromJson(Map<String, dynamic> json) {
    return Job(
      ssid: hexToUtf8(json['ssid']),
      bssid: json['bssid'],
      rssi: json['rssi'],
      channel: json['channel'],
      auth: json['auth'],
      encry: json['encry'],
      extch: json['extch'],
    );
  }
}

4. 验证转换效果 #

以第一个SSID444A446F626C65615F322E34为例，解码后会得到DJDoublea_2.4，符合预期。

内容的提问来源于stack exchange，提问作者Alejandro Carrasquero