1. Dio

dio是一个强大的Dart Http请求库，支持Restful API、FormData、拦截器、请求取消、Cookie管理、文件上传/下载、超时、自定义适配器等...

1.1 Dio 引入

Dio 引入

dependencies:
  dio: ^x.x.x #请使用pub上的最新版本

执行 flutter pub get命令，即可导入dio三方库

导入并创建dio实例：

import 'package:dio/dio.dart';
Dio dio =  Dio();

注意，一个dio实例可以发起多个http请求，一般来说，APP只有一个http数据源时，dio应该使用单例模式。

1.2 基本使用

Get

  final dio = Dio();
  dio.get("https://httpbin.org/get").then((res) {
    print(res);
  });

  final dio = Dio();
  var res = await dio.get("https://httpbin.org/get");
  print(res);

Post

  final dio = Dio();
  dio.post("https://httpbin.org/post").then((res) {
    print(res);
  });

  final dio = Dio();
  var res = await dio.post("https://httpbin.org/post");
  print(res);

发起多个并发请求:

  final dio = Dio();
  var res = await Future.wait([
    dio.post("https://httpbin.org/post"),
    dio.get("https://httpbin.org/get")
  ]);
  print(res);

下载文件

response=await dio.download("https://www.google.com/",_savePath);

发送 FormData:

FormData formData = FormData.from({
   "name": "wendux",
   "age": 25,
});
response = await dio.post("/info", data: formData)

如果发送的数据是FormData，则dio会将请求header的contentType设为“multipart/form-data”。

通过FormData上传多个文件:

var formData = FormData.fromMap({
  'name': 'wendux',
  'age': 25,
  'file': await MultipartFile.fromFile('./text.txt', filename: 'upload.txt'),
  'files': [
    await MultipartFile.fromFile('./text1.txt', filename: 'text1.txt'),
    await MultipartFile.fromFile('./text2.txt', filename: 'text2.txt'),
  ]
});
var response = await dio.post('/info', data: formData);

监听上传进度

response = await dio.post(
  'http://www.dtworkroom.com/doris/1/2.0.0/test',
  data: {'aa': 'bb' * 22},
  onSendProgress: (int sent, int total) {
    print('$sent $total');
  },
);

设置代理、请求认证、证书校验

dio内部仍然使用HttpClient发起的请求，所以代理、请求认证、证书校验等和HttpClient是相同的，我们可以在onHttpClientCreate回调中设置，例如：

  dio.httpClientAdapter = DefaultHttpClientAdapter();
  (dio.httpClientAdapter as DefaultHttpClientAdapter).onHttpClientCreate =
      (client) {
    // config the http client
    client.findProxy = (uri) {
      //proxy all request to localhost:8888
      return 'PROXY localhost:8888';
    };

    client.badCertificateCallback =
        (X509Certificate cert, String host, int port) {
      if (cert.pem == "PEM") {
        return true; //证书一致，则允许发送数据
      }
      return false;
    };
  };

注意: onHttpClientCreate会在当前dio实例内部需要创建HttpClient时调用，所以通过此回调配置HttpClient会对整个dio实例生效，如果你想针对某个应用请求单独的代理或证书校验策略，可以创建一个新的dio实例即可。

拦截器 InterceptorsWrapper

    Interceptor dInter = InterceptorsWrapper(onRequest: (options, handler) {
      print("拦截配置");
      return handler.next(options);
    }, onResponse: (res, handler) {
      print("拦截数据");
      return handler.next(res);
    }, onError: (err, handler) {
      print("拦截错误");
      return handler.next(err);
    });

自定义拦截器

class CustomInterceptors extends Interceptor {
  @override
  void onRequest(RequestOptions options, RequestInterceptorHandler handler) {
    print('REQUEST[${options.method}] => PATH: ${options.path}');
    return super.onRequest(options, handler);
  }

  @override
  void onResponse(Response response, ResponseInterceptorHandler handler) {
    print(
        'RESPONSE[${response.statusCode}] => PATH: ${response.requestOptions.path}');
    return super.onResponse(response, handler);
  }

  @override
  void onError(DioError err, ErrorInterceptorHandler handler) {
    print(
        'ERROR[${err.response?.statusCode}] => PATH: ${err.requestOptions.path}');
    return super.onError(err, handler);
  }
}

1.3 示例

import 'package:dio/dio.dart';
import 'config.dart';

class HttpRequest {
  static final BaseOptions baseOptions = BaseOptions(
      baseUrl: HttpConfig.baseURL, connectTimeout: HttpConfig.timeout);
  static final Dio dio = Dio(baseOptions);

  static Future<T> request<T>(String url,
      {String method = "get",
      Map<String, dynamic>? params,
      Interceptor? inter}) async {
    // 1.创建单独配置
    final Options specialOptions = Options(method: method);
    // 拦截器
    Interceptor dInter = InterceptorsWrapper(onRequest: (options, handler) {
      print("拦截配置");
      return handler.next(options);
    }, onResponse: (res, handler) {
      print("拦截数据");
      return handler.next(res);
    }, onError: (err, handler) {
      print("拦截错误");
      return handler.next(err);
    });

    // 自定义Interceptor
    CustomInterceptors cInter = CustomInterceptors();

    List<Interceptor> inters = [cInter];

    if (inter != null) {
      inters.add(inter);
    }

    dio.interceptors.addAll(inters);

    // 发送网络请求
    try {
      Response resp = await dio.request(url,
          queryParameters: params, options: specialOptions);
      return resp.data;
    } on DioError catch (e) {
      return Future.error(e);
    }
  }
}

class CustomInterceptors extends Interceptor {
  @override
  void onRequest(RequestOptions options, RequestInterceptorHandler handler) {
    print('REQUEST[${options.method}] => PATH: ${options.path}');
    return super.onRequest(options, handler);
  }

  @override
  void onResponse(Response response, ResponseInterceptorHandler handler) {
    print(
        'RESPONSE[${response.statusCode}] => PATH: ${response.requestOptions.path}');
    return super.onResponse(response, handler);
  }

  @override
  void onError(DioError err, ErrorInterceptorHandler handler) {
    print(
        'ERROR[${err.response?.statusCode}] => PATH: ${err.requestOptions.path}');
    return super.onError(err, handler);
  }
}


class HttpConfig {
  static const String baseURL = "https://httpbin.org/";
  static const int timeout = 5000;
}

https://book.flutterchina.club/chapter11/dio.html