Retrofit 2.0 throwing "IllegalArgumentException: @Field parameters can only be used with form encoding". How to do right API query and fix it?

you just missed @FormUrlEncoded above your Rest method call.

Your request is not encoded right, but are postman, so do change that :

@FormUrlEncoded@PUT("/api/register")    Call<AuthRegisterUserModel> getStatus(            @Field("username") String username,            @Field("email") String email,            @Field("password") String password,            @Field("fbID") String fbID,            @Field("gmailID") String gmailID,            @Field("twitID") String twitID,            @Field("gender") String gender,            @Field("birthDate") String birthDate,            @Field("location") String location,            @Field("longitude") String longitude,            @Field("latitude") String latitude,            @Field("profileImage") String profileImage);

Tell me if it's ok.

The problem was because I try to PUT e.g. longitude \ latitude \ location with no value - empty String.

I mean - there was a problem on API side. So to avoid that I changed method to this:

@FormUrlEncoded@PUT(ApiConstants.REGISTER_URL_PART)Call<RegisterModel> registerUser(        @Field("username") String username,        @Field("email") String email,        @Field("password") String password,        @Field("fbID") String fbID,        @Field("gmailID") String gmailID,        @Field("twitID") String twitID,        @Field("gender") String gender,        @Field("birthDate") String birthDate,        @Nullable @Field("location") String location,        @Nullable @Field("longitude") String longitude,        @Nullable @Field("latitude") String latitude,        @Field("profileImage") String profileImage);

Now, when I go no value for one of them, I simply don't enclose this field.