Retrofit 2.0 + GSON Unable to invoke no-args constructor for interface

Question

I'm using Retrofit 2.0 in my app. Everything was quite good, but when I started request with no args, GSON returns:

Unable to invoke no-args constructor for interface
com.example.project.API.GetPhones. Register an InstanceCreator
with Gson for this type may fix this problem.

Here's my API interface:

public interface GetPhones {
    @GET("phones.php")
    Call<ArrayList<GetPhones>> getPhones();
}

and model class:

public class GetPhones {
    int id;
    char[] iso;
    String name;
    String phone_1;
    String phone_2;
    String phone_3;
}

and code in fragment:

Retrofit retrofit = new Retrofit.Builder()
         .baseUrl(URL_API)
         .client(SSLSuppressClient.trustcert())
         .addConverterFactory(GsonConverterFactory.create())
         .build();
GetPhones getPhonesInfo = retrofit.create(GetPhones.class);
Call<GetPhones> call = getPhonesInfo.getPhones();
call.enqueue(new Callback<GetPhones>() {
    @Override
    public void onResponse(Response<GetPhones> response, Retrofit retrofit) {
        Toast.makeText(getActivity(), "Success!", Toast.LENGTH_SHORT).show();
    }

    @Override
    public void onFailure(Throwable t) {
        Toast.makeText(getActivity(), "Failure!", Toast.LENGTH_SHORT).show();
        Log.d("LOG", t.getMessage());
                }
    });

I've tried to make no-args constructor for GetPhones.class, but it doesn't change anything.

Daniel Wilson · Answer 1 · 2019-11-14T12:09:41.327

53

If anyone in 2019 comes across this and is using Kotlin, coroutines and at least Retrofit 2.6.0, returning a Call<MyObject> instance while the api method is suspended, produces the same error message, which is a little confusing.

The solution is to replace Call<MyObject> with MyObject in the interface definition, and remove ?.execute()?.body() (or equivalent) at the call site.

EDIT:

The reason I think most people will stumble across this is that they want to wrap their suspended Retrofit responses in something to handle errors in a seamless way.

There is an issue on this located here, perhaps Retrofit will deal with this in the future. I ended up using the kind solution provided here.

edited Nov 14 '19 at 12:09

answered Sep 05 '19 at 17:03

Daniel Wilson

18,838
12
85
135

2

Thank you so much. I was facing the same issue. This worked!! – Hitesh Bisht Oct 08 '19 at 07:23
2

Not all heroes wear capes. Thank you! – Mark Kazakov Oct 15 '19 at 11:57
Hello Daniel I was using a convertor to Call to ResultWrapper and I was using the execute method, now how it works? Since I do not have the execute method – StuartDTO Oct 19 '19 at 16:02
You're my hero, pal! – Danilo Lemes Nov 05 '19 at 11:23
I was frustrated by the lack of access to the full response for error handling, then I spotted in the release note (Retrofit's docs are not great) to return `Response` . This seems to work fine. – Simon Featherstone Nov 13 '19 at 13:22
Thanks @SimonFeatherstone! Change return `Call` to `Response` works here! – João Eudes Lima Apr 17 '20 at 19:01

score 4 · Accepted Answer · answered Nov 17 '15 at 07:52

You have the same name for interface (interface GetPhones) and model class (class GetPhones).

I think you are using interface in this line:

Call<ArrayList<GetPhones>> getPhones();

But it should be your model class. Check import section for it or rename model class to be sure that you are not mixing it.

Anant Raman · Answer 3 · 2020-05-07T16:07:37.660

1

This was really helpful. I had the same issue and it worked by replacing Call<MyObject> with MyObject in the interface where we write the function for the API call request followed by removing .enque at the call site.

edited May 07 '20 at 16:07

answered May 07 '20 at 15:58

Anant Raman

63
1
1
7

Retrofit 2.0 + GSON Unable to invoke no-args constructor for interface

3 Answers3

Linked