Java tutorial
/* * Copyright (C) 2014 The Android Open Source Project * * Licensed under the Apache License, Version 2.0 (the "License"); * you may not use this file except in compliance with the License. * You may obtain a copy of the License at * * http://www.apache.org/licenses/LICENSE-2.0 * * Unless required by applicable law or agreed to in writing, software * distributed under the License is distributed on an "AS IS" BASIS, * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. * See the License for the specific language governing permissions and * limitations under the License. */ package org.krackedeggs.sunshine; import android.content.Context; import android.content.ContentUris; import android.content.ContentValues; import android.database.Cursor; import android.net.Uri; import android.os.AsyncTask; import android.text.format.Time; import android.util.Log; import org.krackedeggs.sunshine.data.WeatherContract; import org.krackedeggs.sunshine.data.WeatherContract.WeatherEntry; 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.util.Vector; public class FetchWeatherTask extends AsyncTask<String, Void, Void> { private final String LOG_TAG = FetchWeatherTask.class.getSimpleName(); private final Context mContext; public FetchWeatherTask(Context context) { mContext = context; } private boolean DEBUG = true; /** * Helper method to handle insertion of a new location in the weather database. * * @param locationSetting The location string used to request updates from the server. * @param cityName A human-readable city name, e.g "Mountain View" * @param lat the latitude of the city * @param lon the longitude of the city * @return the row ID of the added location. */ long addLocation(String locationSetting, String cityName, double lat, double lon) { // Students: First, check if the location with this city name exists in the db // If it exists, return the current ID // Otherwise, insert it using the content resolver and the base URI String[] projection = new String[] { WeatherContract.LocationEntry._ID, WeatherContract.LocationEntry.COLUMN_CITY_NAME }; String whereclause = WeatherContract.LocationEntry.TABLE_NAME + "." + WeatherContract.LocationEntry.COLUMN_CITY_NAME + " = ? "; String[] whereclauseArgs = new String[] { cityName }; // WeatherProvider weatherProvider = new WeatherProvider(); // weatherProvider.getWritePermission(); // if (weatherProvider.onCreate()) { Cursor cursor = mContext.getContentResolver().query(WeatherContract.LocationEntry.CONTENT_URI, projection, whereclause, whereclauseArgs, null); if (cursor.moveToFirst()) // check if city exists { return cursor.getLong(cursor.getColumnIndex(WeatherContract.LocationEntry._ID)); } // } ContentValues row = new ContentValues(); row.put(WeatherContract.LocationEntry.COLUMN_LOCATION_SETTING, locationSetting); row.put(WeatherContract.LocationEntry.COLUMN_CITY_NAME, cityName); row.put(WeatherContract.LocationEntry.COLUMN_COORD_LAT, lat); row.put(WeatherContract.LocationEntry.COLUMN_COORD_LONG, lon); Uri locationUri = mContext.getContentResolver().insert(WeatherContract.LocationEntry.CONTENT_URI, row); return ContentUris.parseId(locationUri); } /** * 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 void getWeatherDataFromJson(String forecastJsonStr, String locationSetting) throws JSONException { // Now we have a String representing the complete forecast in JSON Format. // Fortunately parsing is easy: constructor takes the JSON string and converts it // into an Object hierarchy for us. // 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"; // Location coordinate final String OWM_LATITUDE = "lat"; final String OWM_LONGITUDE = "lon"; // Weather information. Each day's forecast info is an element of the "list" array. final String OWM_LIST = "list"; 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"; try { 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 cityCoord = cityJson.getJSONObject(OWM_COORD); double cityLatitude = cityCoord.getDouble(OWM_LATITUDE); double cityLongitude = cityCoord.getDouble(OWM_LONGITUDE); long locationId = addLocation(locationSetting, cityName, cityLatitude, cityLongitude); // Insert the new weather information into the database Vector<ContentValues> cVVector = new Vector<ContentValues>(weatherArray.length()); // OWM returns daily forecasts based upon the local time of the city that is being // asked for, which means that we need to know the GMT offset to translate this data // properly. // Since this data is also sent in-order and the first day is always the // current day, we're going to take advantage of that to get a nice // normalized UTC date for all of our weather. Time dayTime = new Time(); dayTime.setToNow(); // we start at the day returned by local time. Otherwise this is a mess. int julianStartDay = Time.getJulianDay(System.currentTimeMillis(), dayTime.gmtoff); // now we work exclusively in UTC dayTime = new Time(); for (int i = 0; i < weatherArray.length(); i++) { // These are the values that will be collected. long dateTime; double pressure; int humidity; double windSpeed; double windDirection; double high; double low; String description; int weatherId; // Get the JSON object representing the day JSONObject dayForecast = weatherArray.getJSONObject(i); // Cheating to convert this to UTC time, which is what we want anyhow dateTime = dayTime.setJulianDay(julianStartDay + i); pressure = dayForecast.getDouble(OWM_PRESSURE); humidity = dayForecast.getInt(OWM_HUMIDITY); windSpeed = dayForecast.getDouble(OWM_WINDSPEED); windDirection = dayForecast.getDouble(OWM_WIND_DIRECTION); // Description is in a child array called "weather", which is 1 element long. // That element also contains a weather code. JSONObject weatherObject = dayForecast.getJSONArray(OWM_WEATHER).getJSONObject(0); description = weatherObject.getString(OWM_DESCRIPTION); weatherId = weatherObject.getInt(OWM_WEATHER_ID); // 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); high = temperatureObject.getDouble(OWM_MAX); low = temperatureObject.getDouble(OWM_MIN); ContentValues weatherValues = new ContentValues(); weatherValues.put(WeatherEntry.COLUMN_LOC_KEY, locationId); weatherValues.put(WeatherEntry.COLUMN_DATE, dateTime); weatherValues.put(WeatherEntry.COLUMN_HUMIDITY, humidity); weatherValues.put(WeatherEntry.COLUMN_PRESSURE, pressure); weatherValues.put(WeatherEntry.COLUMN_WIND_SPEED, windSpeed); weatherValues.put(WeatherEntry.COLUMN_DEGREES, windDirection); weatherValues.put(WeatherEntry.COLUMN_MAX_TEMP, high); weatherValues.put(WeatherEntry.COLUMN_MIN_TEMP, low); weatherValues.put(WeatherEntry.COLUMN_SHORT_DESC, description); weatherValues.put(WeatherEntry.COLUMN_WEATHER_ID, weatherId); cVVector.add(weatherValues); } int inserted = 0; // add to database int size = cVVector.size(); if (size > 0) { // Student: call bulkInsert to add the weatherEntries to the database here ContentValues[] cvArray = new ContentValues[size]; cVVector.toArray(cvArray); inserted = mContext.getContentResolver().bulkInsert(WeatherEntry.CONTENT_URI, cvArray); } Log.d(LOG_TAG, "FetchWeatherTask Complete. " + inserted + " Inserted"); } catch (JSONException e) { Log.e(LOG_TAG, e.getMessage(), e); e.printStackTrace(); } } @Override protected Void 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 APPID = "a7949c037a98d94368b92e0fcdba010d"; final String QUERY_PARAM = "q"; final String FORMAT_PARAM = "mode"; final String UNITS_PARAM = "units"; final String DAYS_PARAM = "cnt"; final String APPID_PARAM = "appid"; 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)) .appendQueryParameter(APPID_PARAM, APPID).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(); getWeatherDataFromJson(forecastJsonStr, locationQuery); } catch (IOException e) { Log.e(LOG_TAG, "Error ", e); // If the code didn't successfully get the weather data, there's no point in attempting // to parse it. } catch (JSONException e) { Log.e(LOG_TAG, e.getMessage(), e); e.printStackTrace(); } finally { if (urlConnection != null) { urlConnection.disconnect(); } if (reader != null) { try { reader.close(); } catch (final IOException e) { Log.e(LOG_TAG, "Error closing stream", e); } } } return null; } }