Example.java

package com.supinfo.dondusang.task;

import android.os.AsyncTask;
import android.util.Log;
import com.google.gson.Gson;
import com.supinfo.dondusang.helper.UrlHelper;
import com.supinfo.dondusang.model.gift.Center;
import com.supinfo.dondusang.model.gift.CenterMapUrl;
import com.supinfo.dondusang.model.gift.CenterResult;
import org.apache.commons.io.IOUtils;

import java.io.BufferedReader;
import java.io.IOException;
import java.io.InputStreamReader;
import java.net.HttpURLConnection;
import java.net.URL;
import java.util.List;

/**
 * @author Lukasz Piliszczuk <lukasz.pili AT gmail.com>
 */
public class CenterLocationTask extends AsyncTask<Void, Void, List<Center>> {

    private CenterMapUrl centerMapUrl;

    private Gson gson;

    private Listener listener;

    public CenterLocationTask(CenterMapUrl centerMapUrl, Gson gson, Listener listener) {
        this.centerMapUrl = centerMapUrl;
        this.gson = gson;
        this.listener = listener;
    }

    @Override
    protected void onPreExecute() {
        listener.onStart();
    }

    @Override
    protected List<Center> doInBackground(Void... voids) {

        URL url = UrlHelper.getUrl(centerMapUrl.getUrl());

        CenterResult centerResult = null;

        BufferedReader bufferedReader = null;
        HttpURLConnection urlConnection = null;

        try {
            urlConnection = (HttpURLConnection) url.openConnection();
            urlConnection.setConnectTimeout(15 * 1000);

            Log.d(getClass().getName(), "Connection opened to : " + centerMapUrl.getUrl());

            long time = System.currentTimeMillis();

            bufferedReader = new BufferedReader(new InputStreamReader(urlConnection.getInputStream()));
            centerResult = gson.fromJson(bufferedReader, CenterResult.class);

            Log.d(getClass().getName(), "Content downloaded and parsed in " + (System.currentTimeMillis() - time) + " ms");

        } catch (IOException e) {
            Log.w(getClass().getName(), "Error during reading connection stream", e);
            return null;

        } finally {

            IOUtils.closeQuietly(bufferedReader);

            if (null != urlConnection) {
                urlConnection.disconnect();
            }
        }

        if (null == centerResult) {
            return null;
        }

        return centerResult.getCenters();
    }

    @Override
    protected void onPostExecute(List<Center> centers) {

        if (null == centers) {
            listener.onFailure();
        } else {
            listener.onSuccess(centers);
        }

        listener.onStop();
    }

    @Override
    protected void onCancelled(List<Center> centers) {
        Log.d(getClass().getName(), "Task cancelled");
        listener.onStop();
    }

    public interface Listener {

        void onSuccess(List<Center> centers);

        void onFailure();

        void onStart();

        void onStop();
    }
}