在Flutter开发中，网络请求是必不可少的功能。为了简化代码、提高开发效率，我们通常会封装一个网络请求工具类。本文基于Dio库，详细介绍如何封装一个高效、灵活、易用的网络请求工具类，支持以下功能：

1. 单例模式：确保全局只有一个Dio实例，避免资源浪费。
2. 动态配置：支持运行时动态修改baseUrl、headers等配置。
3. 拦截器：内置日志拦截器，并支持添加自定义拦截器。
4. 错误处理：提供详细的错误信息，支持自定义错误处理逻辑。
5. 文件上传和下载：封装了文件上传和下载功能。
6. 取消请求：支持取消正在进行的请求。
7. 模块化设计：代码结构清晰，便于维护和扩展。

通过本文，你将学会如何封装一个功能强大的网络请求工具类，并直接应用到你的Flutter项目中。

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代码实现

import 'package:dio/dio.dart';
import 'package:flutter/foundation.dart';class HttpUtil {// 单例模式static final HttpUtil _instance = HttpUtil._internal();factory HttpUtil() => _instance;HttpUtil._internal() {_init();}late Dio _dio;final List<Interceptor> _interceptors = []; // 自定义拦截器列表CancelToken _cancelToken = CancelToken(); // 用于取消请求// 初始化void _init() {_dio = Dio(BaseOptions(baseUrl: 'https://your-api-url.com', // 默认基础地址connectTimeout: const Duration(seconds: 5), // 连接超时时间receiveTimeout: const Duration(seconds: 5), // 接收数据超时时间headers: {'Content-Type': 'application/json; charset=UTF-8',},));// 添加默认拦截器_dio.interceptors.add(InterceptorsWrapper(onRequest: (options, handler) {if (kDebugMode) {print('Request: ${options.method} ${options.path}');}return handler.next(options);},onResponse: (response, handler) {if (kDebugMode) {print('Response: ${response.statusCode} ${response.data}');}return handler.next(response);},onError: (DioException e, handler) {if (kDebugMode) {print('Error: ${e.message}');}return handler.next(e);},));// 添加自定义拦截器for (var interceptor in _interceptors) {_dio.interceptors.add(interceptor);}}// 添加自定义拦截器void addInterceptor(Interceptor interceptor) {_interceptors.add(interceptor);_dio.interceptors.add(interceptor);}// 动态更新基础配置void updateBaseConfig({String? baseUrl,Duration? connectTimeout,Duration? receiveTimeout,Map<String, dynamic>? headers,}) {_dio.options.baseUrl = baseUrl ?? _dio.options.baseUrl;_dio.options.connectTimeout = connectTimeout ?? _dio.options.connectTimeout;_dio.options.receiveTimeout = receiveTimeout ?? _dio.options.receiveTimeout;_dio.options.headers = headers ?? _dio.options.headers;}// GET请求Future<Response> get(String path, {Map<String, dynamic>? queryParameters,Options? options,CancelToken? cancelToken,}) async {return _request(path,method: 'GET',queryParameters: queryParameters,options: options,cancelToken: cancelToken,);}// POST请求Future<Response> post(String path, {dynamic data,Map<String, dynamic>? queryParameters,Options? options,CancelToken? cancelToken,}) async {return _request(path,method: 'POST',data: data,queryParameters: queryParameters,options: options,cancelToken: cancelToken,);}// PUT请求Future<Response> put(String path, {dynamic data,Map<String, dynamic>? queryParameters,Options? options,CancelToken? cancelToken,}) async {return _request(path,method: 'PUT',data: data,queryParameters: queryParameters,options: options,cancelToken: cancelToken,);}// DELETE请求Future<Response> delete(String path, {dynamic data,Map<String, dynamic>? queryParameters,Options? options,CancelToken? cancelToken,}) async {return _request(path,method: 'DELETE',data: data,queryParameters: queryParameters,options: options,cancelToken: cancelToken,);}// 文件上传Future<Response> upload(String path, {required String filePath,Map<String, dynamic>? data,Map<String, dynamic>? queryParameters,Options? options,CancelToken? cancelToken,}) async {final formData = FormData.fromMap({...data ?? {},'file': await MultipartFile.fromFile(filePath),});return _request(path,method: 'POST',data: formData,queryParameters: queryParameters,options: options,cancelToken: cancelToken,);}// 文件下载Future<Response> download(String urlPath,String savePath, {Map<String, dynamic>? queryParameters,Options? options,CancelToken? cancelToken,}) async {try {final response = await _dio.download(urlPath,savePath,queryParameters: queryParameters,options: options,cancelToken: cancelToken ?? _cancelToken,);return response;} on DioException catch (e) {throw _handleError(e);}}// 通用请求方法Future<Response> _request(String path, {required String method,dynamic data,Map<String, dynamic>? queryParameters,Options? options,CancelToken? cancelToken,}) async {try {final response = await _dio.request(path,data: data,queryParameters: queryParameters,options: Options(method: method),cancelToken: cancelToken ?? _cancelToken,);return response;} on DioException catch (e) {throw _handleError(e);}}// 取消请求void cancelRequests({CancelToken? cancelToken}) {if (cancelToken == null) {_cancelToken.cancel('Request cancelled');_cancelToken = CancelToken(); // 重置CancelToken} else {cancelToken.cancel('Request cancelled');}}// 错误处理String _handleError(DioException e) {switch (e.type) {case DioExceptionType.connectionTimeout:return '连接超时';case DioExceptionType.sendTimeout:return '发送请求超时';case DioExceptionType.receiveTimeout:return '接收数据超时';case DioExceptionType.badResponse:return '服务器返回错误: ${e.response?.statusCode}';case DioExceptionType.cancel:return '请求已取消';case DioExceptionType.unknown:return '未知错误: ${e.message}';default:return '网络错误: ${e.message}';}}
}

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使用示例

void fetchData() async {try {final response = await HttpUtil().get('/api/data');print('Data: ${response.data}');} catch (e) {print('Error: $e');}
}void uploadFile() async {try {final response = await HttpUtil().upload('/api/upload',filePath: '/path/to/file',);print('Upload Response: ${response.data}');} catch (e) {print('Error: $e');}
}void cancelRequest() {HttpUtil().cancelRequests();
}

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总结

通过封装这样一个网络请求工具类，我们可以显著提高Flutter项目的开发效率，减少重复代码，同时增强代码的可维护性和扩展性。希望本文对你有所帮助