Retrofit GSON Returning null

Question

I am trying to make a simple app using the Retrofit that will parse the JSON Array and will fetch some data such as latitude and longitude but the problem is that is is returning null. I am new to Retrofit. Please explain whatever you post the solution

Here is my code

MainActivity.java

package com.example.akshay.retrofitgsonjsonarray;

import android.os.Bundle;
import android.support.v7.app.AppCompatActivity;
import android.widget.Toast;

import retrofit.Callback;
import retrofit.RestAdapter;
import retrofit.RetrofitError;
import retrofit.client.Response;

public class MainActivity extends AppCompatActivity {
    public final String URL = "https://roads.googleapis.com/v1";

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);

        RestAdapter restAdapter = new RestAdapter.Builder().setEndpoint(URL).setLogLevel(RestAdapter.LogLevel.FULL).build();
        api api = restAdapter.create(api.class);
        api.getData(new Callback<SnappedPoints>() {
            @Override
            public void success(SnappedPoints snappedPoints, Response response) {
                Toast.makeText(MainActivity.this ,String.valueOf(snappedPoints.location.getLatitude()) , Toast.LENGTH_LONG ).show();
            }

            @Override
            public void failure(RetrofitError error) {
                Toast.makeText(MainActivity.this, "Something went wrong", Toast.LENGTH_LONG).show();
            }
        });
    }


}

Snappedpoints.java

package com.example.akshay.retrofitgsonjsonarray;

import com.google.gson.annotations.Expose;
import com.google.gson.annotations.SerializedName;

/**
 * Created by Akshay on 9/14/2015.
 */
public class SnappedPoints {

    @SerializedName("location")
            @Expose
    Location location;


    public void setLocation(Location location)
    {
        this.location = location;

    }
    public Location getLocation()
    {
        return location;
    }
}

Location.java

package com.example.akshay.retrofitgsonjsonarray;

import com.google.gson.annotations.Expose;
import com.google.gson.annotations.SerializedName;

/**
 * Created by Akshay on 9/14/2015.
 */
public class Location {


    @SerializedName("latitude")
    @Expose
    Double latitude;
    @SerializedName("longitude")
    @Expose
    Double longitude;

    public void setLatitude(Double latitude) {
        this.latitude = latitude;
    }

    public Double getLatitude() {
        return latitude;
    }

    public void setLongitude(Double longitude) {
        this.longitude = longitude;
    }

    public Double getLongitude() {
        return longitude;
    }
}

api.java

package com.example.akshay.retrofitgsonjsonarray;
import retrofit.Callback;
import retrofit.http.GET;

/**
 * Created by Akshay on 9/8/2015.
 */
public interface api {
    @GET("/snapToRoads?path=-35.27801,149.12958&interpolate=true&key=KEY")
    public void getData( Callback<SnappedPoints> response);
}

I am Trying to get latitude and longitude out of it but I am not getting any result

Here is my Logcat:

09-14 14:53:15.820  19592-19636/com.example.akshay.retrofitgsonjsonarray D/Retrofit﹕ <--- HTTP 200 https://roads.googleapis.com/v1/snapToRoads?path=-35.27801,149.12958&interpolate=true&key=KEYHERE_Ihavechangedthis (1901ms)
09-14 14:53:15.820  19592-19636/com.example.akshay.retrofitgsonjsonarray D/Retrofit﹕ : HTTP/1.1 200 OK
09-14 14:53:15.820  19592-19636/com.example.akshay.retrofitgsonjsonarray D/Retrofit﹕ Alt-Svc: quic=":443"; p="1"; ma=604800
09-14 14:53:15.820  19592-19636/com.example.akshay.retrofitgsonjsonarray D/Retrofit﹕ Alternate-Protocol: 443:quic,p=1
09-14 14:53:15.820  19592-19636/com.example.akshay.retrofitgsonjsonarray D/Retrofit﹕ Cache-Control: private
09-14 14:53:15.820  19592-19636/com.example.akshay.retrofitgsonjsonarray D/Retrofit﹕ Content-Type: application/json; charset=UTF-8
09-14 14:53:15.820  19592-19636/com.example.akshay.retrofitgsonjsonarray D/Retrofit﹕ Date: Mon, 14 Sep 2015 09:23:17 GMT
09-14 14:53:15.820  19592-19636/com.example.akshay.retrofitgsonjsonarray D/Retrofit﹕ Server: ESF
09-14 14:53:15.820  19592-19636/com.example.akshay.retrofitgsonjsonarray D/Retrofit﹕ Transfer-Encoding: chunked
09-14 14:53:15.820  19592-19636/com.example.akshay.retrofitgsonjsonarray D/Retrofit﹕ Vary: Origin
09-14 14:53:15.820  19592-19636/com.example.akshay.retrofitgsonjsonarray D/Retrofit﹕ Vary: X-Origin
09-14 14:53:15.820  19592-19636/com.example.akshay.retrofitgsonjsonarray D/Retrofit﹕ Vary: Referer
09-14 14:53:15.820  19592-19636/com.example.akshay.retrofitgsonjsonarray D/Retrofit﹕ X-Android-Received-Millis: 1442222595815
09-14 14:53:15.820  19592-19636/com.example.akshay.retrofitgsonjsonarray D/Retrofit﹕ X-Android-Response-Source: NETWORK 200
09-14 14:53:15.820  19592-19636/com.example.akshay.retrofitgsonjsonarray D/Retrofit﹕ X-Android-Sent-Millis: 1442222595304
09-14 14:53:15.820  19592-19636/com.example.akshay.retrofitgsonjsonarray D/Retrofit﹕ X-Content-Type-Options: nosniff
09-14 14:53:15.820  19592-19636/com.example.akshay.retrofitgsonjsonarray D/Retrofit﹕ X-Frame-Options: SAMEORIGIN
09-14 14:53:15.820  19592-19636/com.example.akshay.retrofitgsonjsonarray D/Retrofit﹕ X-XSS-Protection: 1; mode=block
09-14 14:53:15.820  19592-19636/com.example.akshay.retrofitgsonjsonarray D/Retrofit﹕ {
    "snappedPoints": [
    {
    "location": {
    "latitude": -35.278005228392438,
    "longitude": 149.12953569405369
    },
    "originalIndex": 0,
    "placeId": "ChIJp47M1mdNFmsRcF5UbW7qABM"
    }
    ]
    }
09-14 14:53:15.820  19592-19636/com.example.akshay.retrofitgsonjsonarray D/Retrofit﹕ <--- END HTTP (224-byte

body)

Answer 1

You have to define a container to meet the definition of your JSON:

public class SnappedPointsContainer {

@SerializedName("snappedPoints")
        @Expose
List<SnappedPoints> snappedPoints;

// TODO Getter & Setter

}

and change your Retrofit-Interface to :

public interface api {
    @GET("/snapToRoads?path=-35.27801,149.12958&interpolate=true&key=KEY")
    public void getData( Callback<SnappedPointsContainer> response);
}

Define your callback this way:

api.getData(new Callback<SnappedPointsContainer>() {
    @Override
    public void success(SnappedPointsContainer snappedPointsContainer, Response response) {
        // TODO Process e.g. snappedPointsContainer.getSnappedPoints()
    }

    @Override
    public void failure(RetrofitError error) {
        Toast.makeText(MainActivity.this, "Something went wrong", Toast.LENGTH_LONG).show();
    }
});

Answer 2

I have no clue about retrofit, but it looks like your api is returning an array of values but you are trying to get it as scalar.

Try the following:

    RestAdapter restAdapter = new RestAdapter.Builder().setEndpoint(URL).setLogLevel(RestAdapter.LogLevel.FULL).build();
    api api = restAdapter.create(api.class);
    api.getData(new Callback<SnappedPoints[]>() {
        @Override
        public void success(SnappedPoints[] snappedPoints, Response response) {

            Toast.makeText(MainActivity.this ,String.valueOf(snappedPoints[0].location.getLatitude()) , Toast.LENGTH_LONG ).show();
        }

        @Override
        public void failure(RetrofitError error) {
            Toast.makeText(MainActivity.this, "Something went wrong", Toast.LENGTH_LONG).show();
        }
    });