为Retrofit统一添加post请求的默认参数的方法

APP_FORM_URLENCODED("application/x-www-form-urlencoded"),
 APP_JSON("application/json"),
 APP_OCTET_STREAM("application/octet-stream"),
 MULTIPART_FORM_DATA("multipart/form-data"),
 TEXT_HTML("text/html"),
 TEXT_PLAIN("text/plain"),

public interface Apis {
 
 @POST("user/login")
 Observable<Entity<User>> login(@Body RequestBody body);//构造一个RequestBody对象
 
 @POST("user/login")
 Observable<Entity<User>> login(@Body LoginInfo loginInfo);//构造一个实体对象
 
 }

Retrofit mRetrofit = new Retrofit.Builder()
    .baseUrl(HttpConfig.BASE_URL)
    .addConverterFactory(GsonConverterFactory.create())//添加gson转换器
    .addCallAdapterFactory(RxJava2CallAdapterFactory.create())//添加rxjava转换器
    .client(new OkHttpClient.Builder().build())
    .build();
Apis mAPIFunction = mRetrofit.create(Apis.class);
Map<String, Object> params = new LinkedHashMap<>();
 params.put("name", "吴彦祖");
 params.put("request", "123456");
RequestBody requestBody = RequestBody.create(MediaType.parse("application/json; charset=utf-8"), JsonHelper.toJSONString(params));
mAPIFunction.login(RequestBody.create(requestBody))

public static RequestBody getRequestBody(HashMap<String, Object> hashMap) {
  Map<String, Object> params = new LinkedHashMap<>();
  params.put("auth", getBaseParams());
  params.put("request", hashMap);
  return RequestBody.create(MediaType.parse("application/json; charset=utf-8"), JsonHelper.toJSONString(params));
 }

@Override
 public Response intercept(Chain chain) throws IOException {
  Request request = chain.request();
  if (request.method().equals("POST")) {
  if (request.body() instanceof FormBody) {
   FormBody.Builder bodyBuilder = new FormBody.Builder();
   FormBody formBody = (FormBody) request.body();
   //把原来的参数添加到新的构造器，（因为没找到直接添加，所以就new新的）
   for (int i = 0; i < formBody.size(); i++) {
    bodyBuilder.addEncoded(formBody.encodedName(i), formBody.encodedValue(i));
   }
   formBody = bodyBuilder
     .addEncoded("clienttype", "1")
     .addEncoded("imei", "imei")
     .addEncoded("version", "VersionName")
     .addEncoded("timestamp", String.valueOf(System.currentTimeMillis()))
     .build();

   request = request.newBuilder().post(formBody).build();
  }
   return chain.proceed(request);
  }

public class PostJsonBody extends RequestBody {

 private static final MediaType JSON = MediaType.parse("application/json; charset=utf-8");
 private static final Charset charset = Util.UTF_8;

 private String content;

 public PostJsonBody(@NonNull String content) {
  this.content = content;
 }

 public String getContent() {
  return content;
 }

 @Nullable
 @Override
 public MediaType contentType() {
  return JSON;
 }

 @Override
 public void writeTo(@NonNull BufferedSink sink) throws IOException {
  byte[] bytes = content.getBytes(charset);
  if (bytes == null) throw new NullPointerException("content == null");
  Util.checkOffsetAndCount(bytes.length, 0, bytes.length);
  sink.write(bytes, 0, bytes.length);
 }

 public static RequestBody create(@NonNull String content) {
  return new PostJsonBody(content);
 }
}

@Override
 public Response intercept(@NonNull Chain chain) throws IOException {
  Request originalRequest = chain.request();
  Request.Builder builder = originalRequest.newBuilder();
  if (originalRequest.method().equals("POST")) {
   RequestBody requestBody = originalRequest.body();
   if (requestBody instanceof PostJsonBody) {
    String content = ((PostJsonBody) requestBody).getContent();
    HashMap<String, Object> hashMap = JsonHelper.fromJson(content, HashMap.class);
    builder.post(RequestBodyFactory.getRequestBody(hashMap));
   }
  }
  return chain.proceed(builder.build());
 }

RequestBody requestBody =
 RequestBody.create(MediaType.parse("application/json;charset=utf-8"),JsonHelper.toJSONString(params));