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 city.uk.co.sunshine; import android.net.Uri; import android.os.AsyncTask; import android.os.Bundle; import android.support.v4.app.Fragment; import android.text.format.Time; import android.util.Log; import android.view.LayoutInflater; import android.view.Menu; import android.view.MenuInflater; import android.view.MenuItem; import android.view.View; import android.view.ViewGroup; import android.widget.ArrayAdapter; import android.widget.ListView; 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.ArrayList; import java.util.Arrays; import java.util.List; /** * Encapsulates fetching the forecast and displaying it as a {@link ListView} layout. */ public class ForecastFragment extends Fragment { private ArrayAdapter<String> mForecastAdapter; public ForecastFragment() { } @Override public void onCreate(Bundle savedInstanceState) { super.onCreate(savedInstanceState); // Add this line in order for this fragment to handle menu events. setHasOptionsMenu(true); } @Override public void onCreateOptionsMenu(Menu menu, MenuInflater inflater) { inflater.inflate(R.menu.forecastfragment, menu); } @Override public boolean onOptionsItemSelected(MenuItem item) { // Handle action bar item clicks here. The action bar will // automatically handle clicks on the Home/Up button, so long // as you specify a parent activity in AndroidManifest.xml. int id = item.getItemId(); if (id == R.id.action_refresh) { FetchWeatherTask weatherTask = new FetchWeatherTask(); weatherTask.execute("94043"); return true; } return super.onOptionsItemSelected(item); } @Override public View onCreateView(LayoutInflater inflater, ViewGroup container, Bundle savedInstanceState) { // Create some dummy data for the ListView. Here's a sample weekly forecast String[] data = { "Mon 6/23- Sunny - 31/17", "Tue 6/24 - Foggy - 21/8", "Wed 6/25 - Cloudy - 22/17", "Thurs 6/26 - Rainy - 18/11", "Fri 6/27 - Foggy - 21/10", "Sat 6/28 - TRAPPED IN WEATHERSTATION - 23/18", "Sun 6/29 - Sunny - 20/7" }; List<String> weekForecast = new ArrayList<String>(Arrays.asList(data)); // Now that we have some dummy forecast data, create an ArrayAdapter. // The ArrayAdapter will take data from a source (like our dummy forecast) and // use it to populate the ListView it's attached to. mForecastAdapter = new ArrayAdapter<String>(getActivity(), // The current context (this activity) R.layout.list_item_forecast, // The name of the layout ID. R.id.list_item_forecast_textview, // The ID of the textview to populate. weekForecast); View rootView = inflater.inflate(R.layout.fragment_main, container, false); // Get a reference to the ListView, and attach this adapter to it. ListView listView = (ListView) rootView.findViewById(R.id.listview_forecast); listView.setAdapter(mForecastAdapter); return rootView; } public class FetchWeatherTask extends AsyncTask<String, Void, String[]> { private final String LOG_TAG = FetchWeatherTask.class.getSimpleName(); /* 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. SimpleDateFormat shortenedDateFormat = new SimpleDateFormat("EEE MMM dd"); return shortenedDateFormat.format(time); } /** * Prepare the weather high/lows for presentation. */ private String formatHighLows(double high, double low) { // 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) throws JSONException { // These are the names of the JSON objects that need to be extracted. final String OWM_LIST = "list"; final String OWM_WEATHER = "weather"; final String OWM_TEMPERATURE = "temp"; final String OWM_MAX = "max"; final String OWM_MIN = "min"; final String OWM_DESCRIPTION = "main"; JSONObject forecastJson = new JSONObject(forecastJsonStr); JSONArray weatherArray = forecastJson.getJSONArray(OWM_LIST); // 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(); 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; // Cheating to convert this to UTC time, which is what we want anyhow dateTime = dayTime.setJulianDay(julianStartDay + i); 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; } for (String s : resultStrs) { Log.v(LOG_TAG, "Forecast entry: " + s); } return resultStrs; } @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! } } @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; } // 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 = 7; 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()); Log.v(LOG_TAG, "Built URI " + 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(); Log.v(LOG_TAG, "Forecast string: " + forecastJsonStr); } 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); } 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; } } }