I am trying to build an app following a tutorial. I have a "Refresh" button that's supposed to populate a ListView (through and ArrayAdaptor)with an array of day from an API call but when I press the "Refresh" button. The buttons is supposed to run updateWeather() method to load the ListView with some weather data that looks like this (This data appears in my Log actually):
Can someone please help with this. Can't seem to get my head around it.
05-10 23:23:23.921: V/FetchWeatherTask(2037): Forecast entry: Sun May 10 - Clouds - 10/8
05-10 23:23:23.921: V/FetchWeatherTask(2037): Forecast entry: Mon May 11 - Clear - 17/5
05-10 23:23:23.921: V/FetchWeatherTask(2037): Forecast entry: Tue May 12 - Rain - 21/8
05-10 23:23:23.921: V/FetchWeatherTask(2037): Forecast entry: Wed May 13 - Rain - 15/10
05-10 23:23:23.921: V/FetchWeatherTask(2037): Forecast entry: Thu May 14 - Rain - 20/15
05-10 23:23:23.922: V/FetchWeatherTask(2037): Forecast entry: Fri May 15 - Rain - 13/11
05-10 23:23:23.922: V/FetchWeatherTask(2037): Forecast entry: Sat May 16 - Rain - 13/8
ForecastFragment.java
package com.example.siaw.sunshine;
import ...
public class ForecastFragment extends Fragment {
private ArrayAdapter<String> forecastAdaptor;
public ForecastFragment() {
}
@Override
public void onCreate(Bundle savedInstanceState){
super.onCreate(savedInstanceState);
setHasOptionsMenu(true);
}
@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){
updateWeather();
return true;
}
return super.onOptionsItemSelected(item);
}
@Override
public View onCreateView(LayoutInflater inflater, ViewGroup container,
Bundle savedInstanceState) {
View rootView = inflater.inflate(R.layout.fragment_main, container, false);
forecastAdaptor = new ArrayAdapter<String>(getActivity(),R.layout.list_item_forecast,
R.id.list_item_forecast_textview, new ArrayList<String>());
ListView listView = (ListView) rootView.findViewById(R.id.listview_forecast);
listView.setAdapter(forecastAdaptor);
listView.setOnItemClickListener(new AdapterView.OnItemClickListener() {
@Override
public void onItemClick(AdapterView<?> parent, View view, int position, long id) {
String forecast = forecastAdaptor.getItem(position);
Intent intent = new Intent(getActivity(), DetailActivity.class)
.putExtra(Intent.EXTRA_TEXT, forecast);
startActivity(intent);
}
});
return rootView;
}
private void updateWeather() {
FetchWeatherTask weatherTask = new FetchWeatherTask();
SharedPreferences prefs = PreferenceManager.getDefaultSharedPreferences(getActivity());
String location = prefs.getString(getString(R.string.pref_location_key),
getString(R.string.pref_location_default));
weatherTask.execute(location);
}
@Override
public void onStart() {
super.onStart();
updateWeather();
}
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 String[] doInBackground(String... params){
// These two need to be declared outside the try/catch
// so that they can be closed in the finally block.
if (params.length == 0){
return null;
}
HttpURLConnection urlConnection = null;
//TODO: track and remove.
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 {
final String FORECAST_BASE_URL = "http://ift.tt/1jqKpkt?";
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();
StringBuilder buffer = new StringBuilder();
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("ForecastFragment", "Error", e);
// If the code didn't successfully get the weather data, there's no point in attempting
// to parse it.
return null;
} finally{
if (urlConnection != null) {
urlConnection.disconnect();
}
if (reader != null) {
try {
reader.close();
} catch (final IOException e) {
Log.e("ForecastFragment", "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/parsing the forecast.
return null;
}
@Override
protected void onPostExecute(String[] result) {
if (result != null) {
forecastAdaptor.clear();
for (String dayForecastStr : result) {
forecastAdaptor.add(dayForecastStr);
}
// New data is back from the server. Hooray!
}
}
}
}
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