expected begin array but was begin object

Question

I a very new in retrofit.I want to fetch some data from server.but I am unable to do this. Please help me.when I call api then show me an error "expected begin array but was begin object".

 private void getCatagories(){
    Retrofit retrofit = new Retrofit.Builder()
            .baseUrl(Api.BASE_URL)
            .addConverterFactory(GsonConverterFactory.create()) //Here we are using the GsonConverterFactory to directly convert json data to object
            .build();

    Api api = retrofit.create(Api.class);
    Call<List<Catagoty>> call = api.getCatagories();
    Log.e("this",Api.BASE_URL+"");
    call.enqueue(new Callback<List<Catagoty>>() {
        @Override
        public void onResponse(Call<List<Catagoty>> call, Response<List<Catagoty>> response) {
            List<Catagoty> catagotiesList = response.body();
            //Creating an String array for the ListView
            String[] heroes = new String[catagotiesList.size()];

            //looping through all the heroes and inserting the names inside the string array
            for (int i = 0; i < catagotiesList.size(); i++) {
                heroes[i] = catagotiesList.get(i).getSubCatagoryDescription();
            }


            //displaying the string array into listview
            listView.setAdapter(new ArrayAdapter<String>(getApplicationContext(), android.R.layout.simple_list_item_1, heroes));

        }

        @Override
        public void onFailure(Call<List<Catagoty>> call, Throwable t) {
            Toast.makeText(getApplicationContext(), t.getMessage(), Toast.LENGTH_SHORT).show();
        }
    });
}

Answer 1

As you are expecting a List then when GSON does the conversion it is expecting a JSON array of Catagoty so it can convert this to a list of Catagoty.

The error you are getting is caused by the first character of the JSON response starting with a { to denote an object, but you are expecting a [ to denote a JSON array

What the JSON response should probably be is something like below. It seems like the api response is actually returning a Catagoty object and not a list or perhaps it's a top level JSON object which wraps an array of Catagoty object

[
  {
  "Id": 1,
  "SubCatagoryDescription": "Description 1"
 },
 {
  "Id": 2,
  "SubCatagoryDescription": "Description 2"
 }
]