我的应用程序遇到了困难。当我选择刷新按钮时，服务器没有数据通过。我知道我错过了一些关键的东西，但似乎无法找到我出错的地方。
希望你们能帮忙。
public class ForecastFragment extends Fragment {
private ArrayAdapter<String> mForecastAdapter;
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.forcastfragment, 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();
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[] data = {
"Today - Sunny - 88/63",
"Tomorrow - Foggy - 70/45",
"Weds - Cloudy - 72/63",
"Thurs - Rainy - 64/51",
"Fri - Foggy - 70/46",
"Sat - WHAT - 76/68"
};
List<String> weekForcast = new ArrayList<String>(Arrays.asList(data));
mForecastAdapter = new ArrayAdapter<String>(getActivity(), R.layout.list_item_forecast,
R.id.list_item_forecast_textview, weekForcast);
ListView listView = (ListView) rootView.findViewById(R.id.listview_forecast);
listView.setAdapter(mForecastAdapter);
return rootView;
}
public class FetchWeatherTask extends AsyncTask<String, Void, String[]> {
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) {
// 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_DATETIME = "dt";
final String OWM_DESCRIPTION = "main";
JSONObject forecastJson = new JSONObject(forecastJsonStr);
JSONArray weatherArray = forecastJson.getJSONArray(OWM_LIST);
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;
}
private final String LOG_TAG = FetchWeatherTask.class.getSimpleName();
@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";
int numDays = 7;
try {
final String FORECAST_BASE_URL = "http://api.openweathermap.org/data/2.5/weather?q=Christchurch,nz";
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());
urlConnection = (HttpURLConnection) url.openConnection();
urlConnection.setRequestMethod("GET");
urlConnection.connect();
//Read the input stream into 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) {
buffer.append(line = "\n");
}
if (buffer.length() == 0) {
forecastJsonStr = null;
}
} catch (IOException e) {
Log.e("PlaceholderFragment", "Error", e);
//If the placeholder doesn't get the weather data there is no point parsing it
forecastJsonStr = null;
} finally {
if (urlConnection != null) {
urlConnection.disconnect();
}
if (reader != null) {
try {
reader.close();
} catch (final IOException e) {
Log.e("PlacementHolderFragment", "Error closing stream", e);
}
}
}
try {
return getWeatherDataFromJson(forecastJsonStr, numDays);
}
catch (JSONException e) {
Log.e(LOG_TAG, e.getMessage(), e);
e.printStackTrace();
}
return doInBackground();
}
@Override
protected void onPostExecute(String[] result) {
if(result != null) {
mForecastAdapter.clear();
for (String dayForecasterStr : result) {
mForecastAdapter.add(dayForecasterStr);
}
//New Data is back from the server! :)
}
}
}
}