Android Open Source - Sunshine Fetch Weather Task

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License

The source code is released under:

Apache License

Java Source Code

package br.com.santhyago.udacity.sunshine.app;
//w w w.j  a va2s  . c o m
import android.content.Context;
import android.content.SharedPreferences;
import android.net.Uri;
import android.os.AsyncTask;
import android.preference.PreferenceManager;
import android.util.Log;
import android.widget.ArrayAdapter;

import org.json.JSONArray;
import org.json.JSONException;
import org.json.JSONObject;

import java.io.BufferedReader;
import java.io.IOException;
import java.io.InputStream;
import java.io.InputStreamReader;
import java.net.HttpURLConnection;
import java.net.URL;
import java.text.SimpleDateFormat;
import java.util.Date;

/**
 * Created by san on 11/23/14.
 */
public class FetchWeatherTask extends AsyncTask<String, Void, String[]> {

  private final String LOG_TAG = FetchWeatherTask.class.getSimpleName();

  private ArrayAdapter<String> mForecastAdapter;
  private final Context mContext;

  public FetchWeatherTask(Context context, ArrayAdapter<String> forecastAdapter) {
    mContext = context;
    mForecastAdapter = forecastAdapter;
  }

  /* The date/time conversion code is going to be moved outside the asynctask later,
   * so for convenience we're breaking it out into its own method now.
   */
  private String getReadableDateString(long time){
    // Because the API returns a unix timestamp (measured in seconds),
    // it must be converted to milliseconds in order to be converted to valid date.
    Date date = new Date(time * 1000);
    SimpleDateFormat format = new SimpleDateFormat("E, MMM d");
    return format.format(date).toString();
  }

  /**
   * Prepare the weather high/lows for presentation.
   */
  private String formatHighLows(double high, double low) {
    // Data is fetched in Celsius by default.
    // If user prefers to see in Fahrenheit, convert the values here.
    // We do this rather than fetching in Fahrenheit so that the user can
    // change this option without us having to re-fetch the data once
    // we start storing the values in a database.
    SharedPreferences sharedPrefs =
        PreferenceManager.getDefaultSharedPreferences(mContext);
    String unitType = sharedPrefs.getString(
        mContext.getString(R.string.pref_units_key),
        mContext.getString(R.string.pref_units_metric));

    if (unitType.equals(mContext.getString(R.string.pref_units_imperial))) {
      high = (high * 1.8) + 32;
      low = (low * 1.8) + 32;
    } else if (!unitType.equals(mContext.getString(R.string.pref_units_metric))) {
      Log.d(LOG_TAG, "Unit type not found: " + unitType);
    }

    // For presentation, assume the user doesn't care about tenths of a degree.
    long roundedHigh = Math.round(high);
    long roundedLow = Math.round(low);

    String highLowStr = roundedHigh + "/" + roundedLow;
    return highLowStr;
  }

  /**
   * Take the String representing the complete forecast in JSON Format and
   * pull out the data we need to construct the Strings needed for the wireframes.
   *
   * Fortunately parsing is easy:  constructor takes the JSON string and converts it
   * into an Object hierarchy for us.
   */
  private String[] getWeatherDataFromJson(String forecastJsonStr, int numDays,
                                          String locationSetting)
      throws JSONException {

    // These are the names of the JSON objects that need to be extracted.

    // Location information
    final String OWM_CITY = "city";
    final String OWM_CITY_NAME = "name";
    final String OWM_COORD = "coord";
    final String OWM_COORD_LAT = "lat";
    final String OWM_COORD_LONG = "lon";

    // Weather information.  Each day's forecast info is an element of the "list" array.
    final String OWM_LIST = "list";

    final String OWM_DATETIME = "dt";
    final String OWM_PRESSURE = "pressure";
    final String OWM_HUMIDITY = "humidity";
    final String OWM_WINDSPEED = "speed";
    final String OWM_WIND_DIRECTION = "deg";

    // All temperatures are children of the "temp" object.
    final String OWM_TEMPERATURE = "temp";
    final String OWM_MAX = "max";
    final String OWM_MIN = "min";

    final String OWM_WEATHER = "weather";
    final String OWM_DESCRIPTION = "main";
    final String OWM_WEATHER_ID = "id";

    JSONObject forecastJson = new JSONObject(forecastJsonStr);
    JSONArray weatherArray = forecastJson.getJSONArray(OWM_LIST);

    JSONObject cityJson = forecastJson.getJSONObject(OWM_CITY);
    String cityName = cityJson.getString(OWM_CITY_NAME);
    JSONObject coordJSON = cityJson.getJSONObject(OWM_COORD);
    double cityLatitude = coordJSON.getLong(OWM_COORD_LAT);
    double cityLongitude = coordJSON.getLong(OWM_COORD_LONG);

    Log.v(LOG_TAG, cityName + ", with coord: " + cityLatitude + " " + cityLongitude);

    // Insert the location into the database.
    // The function referenced here is not yet implemented, so we've commented it out for now.
//        long locationID = addLocation(locationSetting, cityName, cityLatitude, cityLongitude);

    String[] resultStrs = new String[numDays];
    for(int i = 0; i < weatherArray.length(); i++) {
      // For now, using the format "Day, description, hi/low"
      String day;
      String description;
      String highAndLow;

      // Get the JSON object representing the day
      JSONObject dayForecast = weatherArray.getJSONObject(i);

      // The date/time is returned as a long.  We need to convert that
      // into something human-readable, since most people won't read "1400356800" as
      // "this saturday".
      long dateTime = dayForecast.getLong(OWM_DATETIME);
      day = getReadableDateString(dateTime);

      // description is in a child array called "weather", which is 1 element long.
      JSONObject weatherObject = dayForecast.getJSONArray(OWM_WEATHER).getJSONObject(0);
      description = weatherObject.getString(OWM_DESCRIPTION);

      // Temperatures are in a child object called "temp".  Try not to name variables
      // "temp" when working with temperature.  It confuses everybody.
      JSONObject temperatureObject = dayForecast.getJSONObject(OWM_TEMPERATURE);
      double high = temperatureObject.getDouble(OWM_MAX);
      double low = temperatureObject.getDouble(OWM_MIN);

      highAndLow = formatHighLows(high, low);
      resultStrs[i] = day + " - " + description + " - " + highAndLow;
    }
    return resultStrs;
  }

  @Override
  protected String[] doInBackground(String... params) {

    // If there's no zip code, there's nothing to look up.  Verify size of params.
    if (params.length == 0) {
      return null;
    }
    String locationQuery = params[0];

    // These two need to be declared outside the try/catch
    // so that they can be closed in the finally block.
    HttpURLConnection urlConnection = null;
    BufferedReader reader = null;

    // Will contain the raw JSON response as a string.
    String forecastJsonStr = null;

    String format = "json";
    String units = "metric";
    int numDays = 14;

    try {
      // Construct the URL for the OpenWeatherMap query
      // Possible parameters are avaiable at OWM's forecast API page, at
      // http://openweathermap.org/API#forecast
      final String FORECAST_BASE_URL =
          "http://api.openweathermap.org/data/2.5/forecast/daily?";
      final String QUERY_PARAM = "q";
      final String FORMAT_PARAM = "mode";
      final String UNITS_PARAM = "units";
      final String DAYS_PARAM = "cnt";

      Uri builtUri = Uri.parse(FORECAST_BASE_URL).buildUpon()
          .appendQueryParameter(QUERY_PARAM, params[0])
          .appendQueryParameter(FORMAT_PARAM, format)
          .appendQueryParameter(UNITS_PARAM, units)
          .appendQueryParameter(DAYS_PARAM, Integer.toString(numDays))
          .build();

      URL url = new URL(builtUri.toString());

      // Create the request to OpenWeatherMap, and open the connection
      urlConnection = (HttpURLConnection) url.openConnection();
      urlConnection.setRequestMethod("GET");
      urlConnection.connect();

      // Read the input stream into a String
      InputStream inputStream = urlConnection.getInputStream();
      StringBuffer buffer = new StringBuffer();
      if (inputStream == null) {
        // Nothing to do.
        return null;
      }
      reader = new BufferedReader(new InputStreamReader(inputStream));

      String line;
      while ((line = reader.readLine()) != null) {
        // Since it's JSON, adding a newline isn't necessary (it won't affect parsing)
        // But it does make debugging a *lot* easier if you print out the completed
        // buffer for debugging.
        buffer.append(line + "\n");
      }

      if (buffer.length() == 0) {
        // Stream was empty.  No point in parsing.
        return null;
      }
      forecastJsonStr = buffer.toString();
    } catch (IOException e) {
      Log.e(LOG_TAG, "Error ", e);
      // If the code didn't successfully get the weather data, there's no point in attemping
      // to parse it.
      return null;
    } finally {
      if (urlConnection != null) {
        urlConnection.disconnect();
      }
      if (reader != null) {
        try {
          reader.close();
        } catch (final IOException e) {
          Log.e(LOG_TAG, "Error closing stream", e);
        }
      }
    }

    try {
      return getWeatherDataFromJson(forecastJsonStr, numDays, locationQuery);
    } catch (JSONException e) {
      Log.e(LOG_TAG, e.getMessage(), e);
      e.printStackTrace();
    }
    // This will only happen if there was an error getting or parsing the forecast.
    return null;
  }

  @Override
  protected void onPostExecute(String[] result) {
    if (result != null) {
      mForecastAdapter.clear();
      for(String dayForecastStr : result) {
        mForecastAdapter.add(dayForecastStr);
      }
      // New data is back from the server.  Hooray!
    }
  }
}

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