Android Retrofit2.1.0设置编码格式GBK

设置接口如下：

public interface IHttpService {

    /**
     * 获取userId
     * @param params
     * @return
     */
    @FormUrlEncoded
    @POST("user/userid.do")
    Call<UserIdBean> getUserById(@FieldMap(encoded = true) Map<String, String>params);

    /**
     * 获取userId
     * @param params
     * @return
     */
    @FormUrlEncoded
    @POST("user/login.do")
    Call<UserBean> login(@FieldMap(encoded = true) Map<String, String>params);

}

retrofit中@FormUrlEncoded的默认编码方式为UTF-8，这个没法改变（目前本人所知，如有误请赐教，那么可以通过MediaType进行设置

 /** 

     * 添加统一header,超时时间,http日志打印
     * @return
     */
    public static OkHttpClient genericClient() {
        HttpLoggingInterceptor logging = new HttpLoggingInterceptor();
        logging.setLevel(HttpLoggingInterceptor.Level.BODY);
        OkHttpClient httpClient = new OkHttpClient.Builder()
                .addInterceptor(new Interceptor() {
                    @Override
                    public okhttp3.Response intercept(Chain chain) throws IOException {
                        Request request = chain.request();
                        Request.Builder requestBuilder = request.newBuilder();
                        request = requestBuilder.post(RequestBody.create(MediaType.parse("application/x-www-form-urlencoded;charset=GBK"),
                                URLDecoder.decode(bodyToString(request.body()), "UTF-8")))
                                .build();
                        return chain.proceed(request);
                    }
                })
                .addInterceptor(logging)
                .connectTimeout(DEFAULT_TIMEOUT, TimeUnit.SECONDS)
                .writeTimeout(DEFAULT_TIMEOUT, TimeUnit.SECONDS)
                .readTimeout(DEFAULT_TIMEOUT, TimeUnit.SECONDS)
                .build();
              return httpClient;
           }

如上设置了

 "application/x-www-form-urlencoded;charset=GBK"

但是request.body()获取到的是已经是经过@FormUrlEncoded编码（UTF-8）过的，因此要先用UTF-8解码，再用GBK编码

bodyToString()的实现

private static String bodyToString(final RequestBody request) {
        try {
            final RequestBody copy = request;
            final Buffer buffer = new Buffer();
            if (copy != null)
                copy.writeTo(buffer);
            else
                return "";
            return buffer.readUtf8();
        } catch (final IOException e) {
            return "did not work";
        }
    }