AsyncResponse.java

/**
 * Created by todor.kostov on 6/25/2016.
 */
public interface AsyncResponse {
    void processFinish(String output);
}

CommonData.java

import android.os.AsyncTask;

import com.squareup.okhttp.OkHttpClient;
import com.squareup.okhttp.Request;
import com.squareup.okhttp.Response;

import java.io.IOException;
import java.util.concurrent.TimeUnit;

public class CommonData extends AsyncTask<String, Void, String> {
    public AsyncResponse delegate = null;
    private static final String URL = "https://httpbin.org/get";


    @Override
    protected String doInBackground(String... params) {
        OkHttpClient client = new OkHttpClient();
        client.setConnectTimeout(120, TimeUnit.SECONDS);
        client.setWriteTimeout(120, TimeUnit.SECONDS);
        client.setReadTimeout(120, TimeUnit.SECONDS);

        Request request = new Request.Builder()
                .url(URL)
                .build();

        try {
            Response response = client.newCall(request).execute();
            if(response.isSuccessful()) {
                return response.body().string();
            }
        } catch (IOException e) {
            e.printStackTrace();

        }
        return null;
    }


    @Override
    protected void onPostExecute(String result) {
        delegate.processFinish(result);
    }
}

MainActivity.java

import android.app.Activity;
import android.os.Bundle;
import android.util.Log;
import android.view.View;
import android.widget.Button;

/**
 * Created by todor.kostov on 6/25/2016.
 */
public class MainActivity extends Activity implements AsyncResponse{
    Button b;
    CommonData commonData;

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

        b = (Button) findViewById(R.id.btnProceed);

        commonData = new CommonData();
        commonData.delegate = this;

        b.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                commonData.execute();
            }
        });
    }

    @Override
    public void processFinish(String output) {
        Log.e("MainActivity", "Heelloooooo");
    }
}

Hello, what dependencies do I need in my build.gradle to use AsyncResponse?