Develop Reference

Android Fragments, Json Parsing, return statement in doInBackground() method

I am having problem when developing a weather app using Android Studio. The doInBackGround() method requires a return statement, but it shows error when I am returning forecastJsonStr (line no.181) . It says i need to return String[] and not String value. Similar return statement is asked in line 283. It says return statement missing.
import android.net.Uri;
import android.os.AsyncTask;
import android.os.Bundle;
import android.support.annotation.Nullable;
import android.support.v4.app.Fragment;
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.ListAdapter;
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.sql.Time;
import java.text.SimpleDateFormat;
import java.util.ArrayList;
import java.util.Arrays;
import java.util.List;
import android.text.format.Time;
import static com.github.afrin14.sunshine.R.id.container;
public class ForecastFragment extends Fragment {
public ForecastFragment() {
}
#Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setHasOptionsMenu(true);
}
#Override
public void onCreateOptionsMenu(Menu menu, MenuInflater inflater) {
inflater.inflate(R.menu.forecastfragment, menu);
}
#Override
public boolean onOptionsItemSelected(MenuItem item) {
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) {
String[] forecastArray = {
"Today - Sunny - 88/63",
"Tomorrow - Foggy - 70/40",
"Wed - Cloudy - 72/63",
"Thurs - Asteroids - 75/65",
"Fri - Heavy Rain - 65/56",
"Sat - HELP TRAPPED IN WEATHERSTATION 60/51",
"Sun - Sunny - 80/68",
};
List<String> weekForecast = new ArrayList<String>
(Arrays.asList(forecastArray));
ListAdapter mForecastAdapter = new ArrayAdapter<String>(
getActivity(),
R.layout.list_item_forecast,
R.id.list_item_forecast_textview,
weekForecast);
View rootView = inflater.inflate(R.layout.fragment_main,
container, false);
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();
#Override
protected String[] doInBackground(String... 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 forecastsonStr = 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("http://api.openweathermap.org/data/2.5/forecast/daily?q=94043&mode=json&units=metric&cnt=7");
Log.v(LOG_TAG, "Buit 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 JSON 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();
}
return forecastJsonStr;
}
/* 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;
}
return resultStrs;
}
#Override
protected String[] doInBackground(String... params){
if(params.length == 0){
return null;
}
}
}
}

The first generic of your AsyncTask is defining what is returned in the doInBackground method. If you want to return a String instead of a String array (String[]) than change the async task to extend:
AsyncTask<String, Void, String>
and change the doInBackground Method to return String. If you don´t want it to return anything change it to "Void".
In your second AsyncTask doInBackground method (Why do you even have two of them?) the problem is that the method only returns something (null) when your if clause is true, otherwise nothing is returned. You should also return something in the else case.
To fully understand what the generics and return types are for I recommend you to read the AsyncTask docummentation

You have initialized Async task with return type String array.
public class FetchWeatherTask extends AsyncTask<String, Void, String[]>
Change the initialization as below to String to make it work.
public class FetchWeatherTask extends AsyncTask<String, Void, String>
change the method like below
#Override
protected String doInBackground(String... params)
Now you won't get this error. Hope it helps :)

You have to call postExecute method to get result from your http call. I have edited your code completely. This will work as you expected.
Your code should be like this.
public class ForecastFragment extends Fragment {
public ForecastFragment() {
}
#Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setHasOptionsMenu(true);
}
#Override
public void onCreateOptionsMenu(Menu menu, MenuInflater inflater) {
inflater.inflate(R.menu.forecastfragment, menu);
}
#Override
public boolean onOptionsItemSelected(MenuItem item) {
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) {
String[] forecastArray = {
"Today - Sunny - 88/63",
"Tomorrow - Foggy - 70/40",
"Wed - Cloudy - 72/63",
"Thurs - Asteroids - 75/65",
"Fri - Heavy Rain - 65/56",
"Sat - HELP TRAPPED IN WEATHERSTATION 60/51",
"Sun - Sunny - 80/68",
};
List<String> weekForecast = new ArrayList<String>
(Arrays.asList(forecastArray));
ListAdapter mForecastAdapter = new ArrayAdapter<String>(
getActivity(),
R.layout.list_item_forecast,
R.id.list_item_forecast_textview,
weekForecast);
View rootView = inflater.inflate(R.layout.fragment_main,
container, false);
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();
private int numDays = 7;
#Override
protected String doInBackground(String... params) {
if (params.length == 0) {
return null;
}
HttpURLConnection urlConnection = null;
BufferedReader reader = null;
String forecastJsonStr = null;
String format = "json";
String units = "metric";
try {
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("http://api.openweathermap.org/data/2.5/forecast/daily?q=94043&mode=json&units=metric&cnt=7");
Log.v(LOG_TAG, "Buit URI " + builtUri.toString());
urlConnection = (HttpURLConnection) url.openConnection();
urlConnection.setRequestMethod("GET");
urlConnection.connect();
InputStream inputStream = urlConnection.getInputStream();
StringBuilder builder = new StringBuilder();
if (inputStream == null)
return null;
reader = new BufferedReader(new InputStreamReader(inputStream));
String line;
while ((line = reader.readLine()) != null) {
builder.append(line).append("\n");
}
if (builder.length() == 0)
return null;
forecastJsonStr = builder.toString();
Log.v(LOG_TAG, "Forecast JSON String: " + forecastJsonStr);
} catch (IOException e) {
Log.e(LOG_TAG, "Error ", e);
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);
}
}
}
return forecastJsonStr;
}
#Override
protected void onPostExecute(String s) {
super.onPostExecute(s);
try{
String[] weatherDataFromJson = getWeatherDataFromJson(s);
// do whatever you want with the output.
}catch(JSONException e){
Log.e(LOG_TAG, e.getMessage(), e);
e.printStackTrace();
}
}
private String getReadableDateString(long time) {
SimpleDateFormat shortenedDateFormat = new SimpleDateFormat("EEE MMM dd");
return shortenedDateFormat.format(time);
}
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;
}
private String[] getWeatherDataFromJson(String forecastJsonStr) 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);
Time dayTime = new Time();
dayTime.setToNow();
int julianStartDay = Time.getJulianDay(System.currentTimeMillis(),
dayTime.gmtoff);
dayTime = new Time();
String[] resultStrs = new String[numDays];
for (int i = 0; i < weatherArray.length(); i++) {
String day;
String description;
String highAndLow;
JSONObject dayForecast = weatherArray.getJSONObject(i);
long dateTime;
dateTime = dayTime.setJulianDay(julianStartDay + i);
day = getReadableDateString(dateTime);
JSONObject weatherObject =
dayForecast.getJSONArray(OWM_WEATHER).getJSONObject(0);
description = weatherObject.getString(OWM_DESCRIPTION);
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;
}
}
}
Hope this help:)

Data not showing in the Listview

Its not showing any errors but its not updating the correct data on the app which I'm running it in the emulator. Any ideas? Its the MainFragment Class of the SunShine App whose video lectures are made by udacity(if it helps!)...Thanks
public class MainActivityFragment extends Fragment {
private ArrayAdapter<String> mForecast;
public MainActivityFragment() {
}
#Override
public void onCreate(#Nullable Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setHasOptionsMenu(true);
}
#Override
public void onCreateOptionsMenu(Menu menu, MenuInflater inflater) {
inflater.inflate(R.menu.fragment_forecast,menu);
}
#Override
public boolean onOptionsItemSelected(MenuItem item) {
int id = item.getItemId();
if (id== R.id.action_refresh){
FetchWeatherTask weatherTask = new FetchWeatherTask();
weatherTask.execute("London");
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);
String[] forecastArray = {
"Today - Sunny - 88/63",
"Tomorrow - Sunny - 88/63",
"Today - Sunny - 88/63",
"Today - Sunny - 88/63",
"Today - Sunny - 88/63",
"Today - Sunny - 88/63",
"Today - Sunny - 88/63"
};
List<String> weekForecast = new ArrayList<String>(
Arrays.asList(forecastArray));
mForecast = new ArrayAdapter<String>(getActivity(),R.layout.list_item_forecast,R.id.list_item_forecast_textview,weekForecast);
ListView listView = (ListView)rootView.findViewById(R.id.listview_forecast);
listView.setAdapter(mForecast);
return rootView;
}
public class FetchWeatherTask extends AsyncTask<String,Void,String[]>{
private String getReadableDateString(long time){
Date date = new Date(time*1000);
SimpleDateFormat dateFormat = new SimpleDateFormat("E,MMM d");
return dateFormat.format(date).toString();
}
private String formatHighLows(double high, double low){
long roundedHigh = Math.round(high);
long roundedLow = Math.round(low);
String highLowStr = roundedHigh+"/"+roundedLow;
return highLowStr;
}
private String[] getWeatherDataFromJson(String forecastJsonStr, int numDays) throws JSONException{
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_DATETIME = "dt";
final String OWM_DESCRIPTION = "main";
JSONObject forecastJSON = new JSONObject(forecastJsonStr);
JSONArray weatherArray = forecastJSON.getJSONArray(OWM_LIST);
String[] resultsStr = new String[numDays];
for (int i=0;i<weatherArray.length();i++){
String day,description,highAndLow;
JSONObject dayForecast = weatherArray.getJSONObject(i);
long dateTime = dayForecast.getLong(OWM_DATETIME);
day = getReadableDateString(dateTime);
JSONObject weatherObject = dayForecast.getJSONArray(OWM_WEATHER).getJSONObject(0);
description = weatherObject.getString(OWM_DESCRIPTION);
JSONObject temperatureObject = dayForecast.getJSONObject(OWM_TEMPERATURE);
double high = temperatureObject.getDouble(OWM_MAX);
double low = temperatureObject.getDouble(OWM_MIN);
highAndLow = formatHighLows(high,low);
resultsStr[i] = day+" - "+description+" - "+ highAndLow;
}
return resultsStr;
}
#Override
protected String[] doInBackground(String... params) {
if (params.length==0){
return null;
}
HttpURLConnection URLConnection = null;
BufferedReader reader = null;
String forecastJSONstring = null;
String format = "json";
String units = "metric";
int numDays = 7;
String app_id = "c24632b5cc62e50ba9d325cf251bad1d";
try {
final String FORECAST_BASE_URL = "http://api.openweathermap.org/data/2.5/forecast?";
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,app_id).build();
URL url = new URL(builtUri.toString());
URLConnection = (HttpURLConnection)url.openConnection();
URLConnection.setRequestMethod("GET");
URLConnection.connect();
InputStream inputStream = URLConnection.getInputStream();
StringBuffer buffer = new StringBuffer();
if (inputStream == null){
return null;
}
reader =new BufferedReader( new InputStreamReader(inputStream));
String line;
while ((line = reader.readLine())!= null){
buffer.append(line+"\n");
}
if (buffer.length()==0){
return null;
}
forecastJSONstring = buffer.toString();
}catch (IOException e){
forecastJSONstring=null;
e.printStackTrace();
}finally {
if (URLConnection!=null){
URLConnection.disconnect();
}
if (reader!=null){
try {
reader.close();
}catch (final IOException e){
e.printStackTrace();
}
}
}
try {
return getWeatherDataFromJson(forecastJSONstring,numDays);
}catch (JSONException e){
e.printStackTrace();
}
return null;
}
#Override
protected void onPostExecute(String[] results) {
if (results != null){
mForecast.clear();
for(String i:results) {
mForecast.add(i);
}
}
}
}
}

Any time the data backing your Adapter changes, you must call notifyDataSetChanged() (from the UI thread) in order to see the new data.
I haven't checked all of your networking/parsing code, but I suspect that you can just add this line to the end of your onPostExecute() method:
mForecast.notifyDataSetChanged();

getting AndroidRuntime: FATAL EXCEPTION: AsyncTask #1

I want to use AsyncTask to parse JSON data For that I have Created constructor of FetchWeatherTask in ForecastFragment
ForecastFragment.java
public class ForecastFragment extends Fragment {
private ArrayAdapter<String> mForecastAdapter;
public ForecastFragment() {
}
#Override
public void onCreate(#Nullable 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) {
updateWeather();
return true;
}
return super.onOptionsItemSelected(item);
}
#Override
public View onCreateView(LayoutInflater inflater, ViewGroup container,
Bundle savedInstanceState) {
// The ArrayAdapter will take data from a source 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.tv_list_item_forecast, new ArrayList<String>()); // The ID of the textview to populate.
// Log.e("weekForecast", "forecastArray: " + forecastArray + "/n" + weekForecast);
View rootView = inflater.inflate(R.layout.fragment_main, container, false);
ListView listView = (ListView) rootView.findViewById(R.id.listview_forecast);
listView.setAdapter(mForecastAdapter);
listView.setOnItemClickListener(new AdapterView.OnItemClickListener() {
#Override
public void onItemClick(AdapterView<?> adapterView, View view, int position, long l) {
String forecast = mForecastAdapter.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();
FetchWeatherTask weatherTask = new FetchWeatherTask(getActivity(), mForecastAdapter);
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();
}
FetchWeatherTask.java
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;
}
private boolean DEBUG = true;
/* 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);
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;
}
/**
* 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) {
long locationId;
// First, check if the location with this city name exists in the db
Cursor locationCursor = mContext.getContentResolver().query(
WeatherContract.LocationEntry.CONTENT_URI,
new String[]{WeatherContract.LocationEntry._ID},
WeatherContract.LocationEntry.COLUMN_LOCATION_SETTING + " = ?",
new String[]{locationSetting},
null);
if (locationCursor.moveToFirst()) {
int locationIdIndex = locationCursor.getColumnIndex(WeatherContract.LocationEntry._ID);
locationId = locationCursor.getLong(locationIdIndex);
} else {
// Now that the content provider is set up, inserting rows of data is pretty simple.
// First create a ContentValues object to hold the data you want to insert.
ContentValues locationValues = new ContentValues();
// Then add the data, along with the corresponding name of the data type,
// so the content provider knows what kind of value is being inserted.
locationValues.put(WeatherContract.LocationEntry.COLUMN_CITY_NAME, cityName);
locationValues.put(WeatherContract.LocationEntry.COLUMN_LOCATION_SETTING, locationSetting);
locationValues.put(WeatherContract.LocationEntry.COLUMN_COORD_LAT, lat);
locationValues.put(WeatherContract.LocationEntry.COLUMN_COORD_LONG, lon);
// Finally, insert location data into the database.
Uri insertedUri = mContext.getContentResolver().insert(
WeatherContract.LocationEntry.CONTENT_URI,
locationValues
);
// The resulting URI contains the ID for the row. Extract the locationId from the Uri.
locationId = ContentUris.parseId(insertedUri);
}
locationCursor.close();
// Wait, that worked? Yes!
return locationId;
}
/*
Students: This code will allow the FetchWeatherTask to continue to return the strings that
the UX expects so that we can continue to test the application even once we begin using
the database.
*/
String[] convertContentValuesToUXFormat(Vector<ContentValues> cvv) {
// return strings to keep UI functional for now
String[] resultStrs = new String[cvv.size()];
for (int i = 0; i < cvv.size(); i++) {
ContentValues weatherValues = cvv.elementAt(i);
String highAndLow = formatHighLows(
weatherValues.getAsDouble(WeatherEntry.COLUMN_MAX_TEMP),
weatherValues.getAsDouble(WeatherEntry.COLUMN_MIN_TEMP));
resultStrs[i] = getReadableDateString(
weatherValues.getAsLong(WeatherEntry.COLUMN_DATE)) +
" - " + weatherValues.getAsString(WeatherEntry.COLUMN_SHORT_DESC) +
" - " + highAndLow;
}
return resultStrs;
}
/**
* 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.
* <p/>
* Fortunately parsing is easy: constructor takes the JSON string and converts it
* into an Object hierarchy for us.
*/
private String[] 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);
}
// add to database
if (cVVector.size() > 0) {
ContentValues[] cvArray = new ContentValues[cVVector.size()];
cVVector.toArray(cvArray);
mContext.getContentResolver().bulkInsert(WeatherEntry.CONTENT_URI, cvArray);
}
// Sort order: Ascending, by date.
String sortOrder = WeatherEntry.COLUMN_DATE + " ASC";
Uri weatherForLocationUri = WeatherEntry.buildWeatherLocationWithStartDate(
locationSetting, System.currentTimeMillis());
// Students: Uncomment the next lines to display what what you stored in the bulkInsert
Cursor cur = mContext.getContentResolver().query(weatherForLocationUri,
null, null, null, sortOrder);
cVVector = new Vector<ContentValues>(cur.getCount());
if (cur.moveToFirst()) {
do {
ContentValues cv = new ContentValues();
DatabaseUtils.cursorRowToContentValues(cur, cv);
cVVector.add(cv);
} while (cur.moveToNext());
}
Log.d(LOG_TAG, "FetchWeatherTask Complete. " + cVVector.size() + " Inserted");
String[] resultStrs = convertContentValuesToUXFormat(cVVector);
return resultStrs;
} catch (JSONException e) {
Log.e(LOG_TAG, e.getMessage(), e);
e.printStackTrace();
}
return null;
}
#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";
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, BuildConfig.OPEN_WEATHER_MAP_API_KEY)
.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, 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 != null) {
mForecastAdapter.clear();
for (String dayForecastStr : result) {
mForecastAdapter.add(dayForecastStr);
}
// New data is back from the server. Hooray!
}
}}
Though I have created constructor of FetchWeatherTask and initialized the values but still I am getting Following error:
http://i.stack.imgur.com/6elr4.png

Your
locationCursor
is null in
addLocation
method

Cannot find symbol getActivity()?

I am learning android from Udacity's course on developing Android apps.
In that they show us how to develop weather app, but I am stuck in the code where we add the code for changing the temperature units.
My question is why can't i use getActivity() method in following code:
Its in the first line of the very first function.
class FetchWeatherTask extends AsyncTask<String ,Void,String []>
{
public String formatHighLows(double high, double low) {
SharedPreferences sharedPrefs=PreferenceManager.getDefaultSharedPreferences(getActivity());
String unitType=sharedPrefs.getString(getString(R.string.pref_units_key),getString(R.string.pref_units_metric));
if(unitType.equals(getString(R.string.pref_units_imperial)))
{
high=(high*1.8)+32;
low=(low*1.8)+32;
}
else if(!unitType.equals(getString(R.string.pref_units_metric)))
{
Toast.makeText(getActivity(),"invalid unit",Toast.LENGTH_SHORT).show();
}
long roundedHigh = Math.round(high);
long roundedLow = Math.round(low);
String str= roundedHigh+"/"+roundedLow;
return str;
}
#Override
protected String [] doInBackground(String []params)
{ 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 {
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());
http://api.openweathermap.org/data/2.5/forecast/daily?q=94043&mode=json&units=metric&cnt=7
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("PlaceholderFragment", "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("PlaceholderFragment", "Error closing stream", e);
}
}
}
try
{
return getWeatherDataFromJson(forecastJsonStr,numDays);
}
catch(JSONException e)
{
}
return null;
}
protected void onPostExecute(String[] result) {
/*RECEIVES THE STRING ARRAY FROM THE DOINBACKGROUND METHOD. THE RESULT IS BY DEFAULT RETURNED TO THE ONPOST EXECUTE
* AND WE CAN ACCESS THE ARRAYLIST OF WEATHER WHICH POPULATES THE LISTVIEW BECAUSE WE HAVE MADE THAT STATIC.*/
if (result != null) {
MainActivityFragment.weather_adapter.clear();
for(String dayForecastStr : result) {
MainActivityFragment.weather_adapter.add(dayForecastStr);
}
// New data is back from the server. Hooray!
}
}
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.
*/
/**
* 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";/*it will contain the weather data for seven days, it is an array*/
/*every element of the list has a one element long array called weather which contains weather details of corresponding
day.
*/
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";/*this will contain the weather description main title like clear
/*The json object is created from the string which contains data in json format*/
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.
// We are doing this because we have to associate date with each forecast entry.
Time dayTime = new Time();
dayTime.setToNow();
// we start at the day returned by local time. Otherwise this is a mess.
// julian day returns the number of days that have passed since the julian period.
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.it contains the description of the
/*weather for the corresponding day in the form of string*/
/*weatherObject is the corresponding object of the ith day*/
JSONObject weatherObject = dayForecast.getJSONArray(OWM_WEATHER).getJSONObject(0);
/*OWM_DESCRIPTION contains the "main" description like clear*/
description = weatherObject.getString(OWM_DESCRIPTION);
// Temperatures are in a child object called "temp".It contains the max and min temperatures
// in double format with the keys mentioned OWM_MAX and OWM_MIN 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);
resultStrs[i] = day + " - " + description + " - " +Math.round(high)+" / "+Math.round(low);
}
return resultStrs;
}
}

Get Context and save in member variable of this class :
class FetchWeatherTask extends AsyncTask<String ,Void,String []> {
private Context mContext;
public FetchWeatherTask(Context context) {
this.mContext = context;
}
// use context as this.mContext everywhere you want
}
You should call above class using :
new FetchWeatherTask(context).execute(/* String parameters */);

You are inside a AsyncTask which which does not recognize getActivity(). Try to define a context at the top level activity. in onCreate() :
context = this.
Then inside AsyncTask you can use
context.getActivity();

class FetchWeatherTask extends AsyncTask<String ,Void,String>
{
private Context mContext;
String str1, str2, str3;
String finalStr="";
public FetchWeatherTask(Context context)
{ this.mContext = context;}
#Override
protected String doInBackground(String... params)
{
str1 = params[0];
str2 = params[1];
str3 = params[2];
finalStr = str1 + str2 + str3;
return finalStr;
}
#Override
protected void onPostExecute(String result) {
Log.d("rs", result);
}
}
And in your activity:
new FetchWeatherTask(this).execute(new String[]{"a", "b","c"});

not able to return data after doInBackground Method

Here is my code. In it onPostExecute() method is getting result as null but I am returning the value from doInBackground() method.
doInBackground() is calling the method getWeatherDataFromJson(). I am getting return arrary resultStrs in LOG(see code) but in onPostExecute() result is null.
public class ForecastFragment extends Fragment {
public ForecastFragment(){
}
#Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setHasOptionsMenu(true);
}
#Override
public void onCreateOptionsMenu(Menu menu, MenuInflater inflater) {
// Inflate the menu; this adds items to the action bar if it is present.
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("600001");
return true;
}
return super.onOptionsItemSelected(item);
}
private ArrayAdapter<String> mForecastAdapter;
#Override
public View onCreateView(LayoutInflater inflater, ViewGroup container,
Bundle savedInstanceState) {
View rootView = inflater.inflate(R.layout.fragment_main, container, false);
FetchWeatherTask weatherTask = new FetchWeatherTask();
weatherTask.execute("600001");
// Will contain the raw JSON response as a string.
String[] forecastArray = {
"Today - Sunny - 88/64",
"Tomorrow - Foggy - 78/64",
"Wed - Cloudy - 72/64",
"Thurs - Asteroids - 75/55",
"Fri - Heavy Rain - 67/44",
"Sat - Sunny - 88/76",
"Today - Light Rain - 81/69",
};
List<String> weekForecast = new ArrayList<String>(
Arrays.asList(forecastArray)
);
mForecastAdapter =
new ArrayAdapter<String>(
// the current context
getActivity(),
//id of list item layout
R.layout.list_item_forecast,
// id of text view to populate
R.id.list_item_forecast_textview,
// array data
weekForecast);
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 String[] doInBackground(String... params) {
// 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 BASE_URL = "http://api.openweathermap.org/data/2.5/forecast/daily?";
final String QUERY_PARAMS = "q";
final String FORMAT_PARAMS = "mode";
final String UNIT_PARAMS = "units";
final String DAYS_PARAMS = "cnt";
Uri builtUri = Uri.parse(BASE_URL).buildUpon()
.appendQueryParameter(QUERY_PARAMS, params[0])
.appendQueryParameter(FORMAT_PARAMS, format)
.appendQueryParameter(UNIT_PARAMS, units)
.appendQueryParameter(DAYS_PARAMS, Integer.toString(numDays))
.build();
URL url = new URL(builtUri.toString());
Log.v(LOG_TAG, "Built 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.
//forecastJsonStr = null;
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.
//forecastJsonStr = null;
return null;
}
forecastJsonStr = buffer.toString();
try {
return getWeatherDataFromJson(forecastJsonStr, numDays);
} catch (JSONException e) {
Log.e(LOG_TAG,e.getMessage());
e.printStackTrace();
}
} 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;
//forecastJsonStr = null;
//return forecastJsonStr;
} finally{
if (urlConnection != null) {
urlConnection.disconnect();
return null;
}
if (reader != null) {
try {
reader.close();
} catch (final IOException e) {
Log.e("PlaceholderFragment", "Error closing stream", e);
}
}
}
return null;
}
#Override
protected void onPostExecute(String[] result) {
if (result != null) {
Log.v(LOG_TAG,"dfgihuffhuffuhgfufdhuidfhudfuhli");
mForecastAdapter.clear();
for (String dayForecastStr : result) {
mForecastAdapter.add(dayForecastStr);
}
}else {
Log.v(LOG_TAG, "errprdvdfdffd");
}
}
}
}

I think that, previous way which you were using to return at last 'return getWeatherDataFromJson(forecastJsonStr, numDays);' is nice approach. But that was not happening because I think your finally block get executed and your urlconnection object is not null. so it executed 'if' condition and returns null. and last return statement never get called.
As Secondary option, 'numDays' are fixed so if you can send a 'forecastJSONString' as param in the onPost(String resStr). so you can perform next operation inside onPost() method and it will more simpler.