Retrofit: @Body parameters cannot be used with form or multi-part encoding. (parameter #2)

[Yexi]

I m trying to make a request in which I want to include a Header , a form-urlencoded field and a json body. My Retrofit interface is as follows

@FormUrlEncoded
@POST("/api/register")
Observable<RegisterResponse> register(
    @Header("Authorization") String authorization, 
    @Field("grant_type") String grantType, 
    @Body RegisterBody body
);

When I make this request I get back exception @Body parameters cannot be used with form or multi-part encoding.
I have also tried with the @Multipart annotation:

@Multipart
@FormUrlEncoded
@POST("/api/register")
Observable<RegisterResponse> register(
    @Header("Authorization") String authorization, 
    @Part("grant_type") TypedString grantType, 
    @Body RegisterBody body
);

and I get an IllegalArgumentException and only one encoding annotation is allowed.

[JakeWharton]

You can use two @Part parameters with the @Multipart encoding. One for the form encoded parts and the other for the JSON body. Retrofit will run @Parts through the converters, so make sure you're using the appropriate parameter types. In Retrofit 2 you'd want to use RequestBody (and then create the argument using FormBody.Builder) and then your JSON object type for the two.

[jemshit]

What if parameter count is dynamic, i can send 5 to 10 parameters to same service according to condition. How can i write interface for that without @Body MyModel ?

[DeathsKnights]

上传接口()
@Multipart
@POST(Urls.FILE_RECEIVE)
Observable CommitUpload(@Part("params") RequestBody params , @Part MultipartBody.Part file);
后台提供的接口 是 参数是 String params ,File file 这样可以么

[yerimaSI]

You can solve it by deleting this annotation @FormUrlEncoded