How to grab JSON Array and use gson to parse each json object? (Retrofit)

Question

I am returning an array of results with my json Objects, and I am trying to use my customObjectResponse class to pull out each of the fields within each of the objects... the problem it is expecting an object so how do I edit my class to allow it to take in an array of object to be able to then call the fields of each object... I am confused as to what needs to be added:

Here is a response example of what is being passed to be used:

[
  {
    itemId: 'dfsdfsdf343434',
    name: 'tests',
    picture: '6976-7jv8h5.jpg',
    description: 'testy.',
    dateUpdated: 1395101819,

  }
]

Here is my response Object Class:

public class ObjResponse{
    private String itemId;
    private String name;
    private String picture;

    private String description;

    private String location;
    private int dateUpdated;

    private String msg;




    //gridview constructor
    public ObjResponse(String picture) {
        this.picture = picture;
    }

    //public constructor
    public ObjResponse() {

    }

    public String getItemId() {
        return itemId;
    }

    public void setItemId(String itemId) {
        this.itemId = itemId;
    }

    public String getName() {
        return name;
    }

    public void setName(String name) {
        this.name = name;
    }

    public String getPicture() {
        return picture;
    }

    public void setPicture(String picture) {
        this.picture = picture;
    }


    public String getLocation() {
        return location;
    }

    public void setLocation(String location) {
        this.location = location;
    }


    public String getDescription() {
        return description;
    }

    public void setDescription(String description) {
        this.description = description;
    }



    public int getDateUpdated() {
        return dateUpdated;
    }

    public void setDateUpdated(int dateUpdated) {
        this.dateUpdated = dateUpdated;
    }




    public String getMsg() {
        return msg;
    }

}

what I am trying, but is not working, even if I separate the classes into their own files:

Data passed in:
items: [{obj1: "A", obj2: ["c", "d"]}, {etc...}]


public class Response {

        public class List<Custom> {
                private List<Custom> items;
        }

        public class Custom {
                private String obj1;
                private List<Obj2> obj2;
        }

        public Class Obj2 {
                private String letters;
        }
}

Answer 1

I ended up just calling in the callback a list of the customObject and it did the job...

new Callback<List<ObjResponse>>() {

Answer 2

I originally had trouble getting an idea of how the OP solved his problem but, after days of debugging I have finally figured out how to solve this issue.

So you essentially have data in the format like so (JSON Array of JSON Objects):

[
    {
      ...
    }
] 

Your class that models the data and contains the getter and setter methods are nothing more than your typical POJO.

public class Person implements Serializable {
    @SerializedName("Exact format of your json field name goes here")
    private String firstName;

    // Getters and Setters....
}

In your interface that contains your RESTful annotations you want to convert your call from:

Before:

public interface APInterface {
    @GET("SOME URL TO YOUR JSON ARRAY")
    Call<Person>(...)
}

After:

public interface APInterface {
    @GET("SOME URL TO YOUR JSON ARRAY")
    Call<List<Person>>(...)
}

In your android activity you want to convert all calls in the form of Call<Person> to Call<List<Person>>

Finally when making the initial asynchronous request call, you will want to convert your callbacks like so.

call.enqueue(new Callback<List<Person>>() {
    @Override
    public void onResponse(Call<List<Person>> call, Response<List<Person>> response) {

        if(response.isSuccessful()){
            List<Person> person = response.body();

           // Can iterate through list and grab Getters from POJO
           for(Person p: person){...}


        } else {
            // Error response...
        }

    }

    @Override
    public void onFailure(Call<List<Person>> call, Throwable t) {...}
});

Hope this helps others whom are lost from the accepted answer above.

Answer 3

This can also work by just passing an array of response objects. So if this is your response object:

public class CustomUserResponse {
    public String firstName;
    public String lastName;
    ...
}

You can use related syntax, depending on how you use the callbacks. Such as:

new Callback<CustomUserResponse[]>(){
    @Override
    public void success(CustomUserResponse[] customUserResponses, Response rawResponse) {

    }

    @Override
    public void failure(RetrofitError error) {

    }
};

OR

public class GetUserCommand implements Callback<CustomUserResponse[]> { ...

Put simply, in every place where you normally replace T with a response class, replace it with an array, instead as in CustomUserResponse[].

---

NOTE: to avoid confusing errors, be sure to also use an array in the Retrofit interface definition:

@POST ( "/users" )
public void listUsers(@Body GetUsersRequest request, Callback<CustomUserResponse[]> callback);

Answer 4

You could try something like this

JSONObject jsonObject = new JSONObject(<your JSON string result>);
JSONArray jsonArray = jsonObject.getJSONArray();

//use GSON to parse
if (jsonArray != null) {
   Gson gson = new Gson();
   ObjResponse[] objResponse = gson.fromJson(jsonArray.toString(), ObjResponse[].class);
   List<ObjResponse> objResponseList = Arrays.asList(objResponse);
}

This should definitely work.