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我已成功實施android陽光應用程序進行天氣預報。它工作正常。Android陽光應用程序（udacity）空白列表視圖
我通過更新應用程序進行了一些更新和我目前的版本是：6.7.1.0(KHJMICH)和操作系統是4.4.4KTU84P和我的手機是redmii 2
現在一個問題就是快到了，我完全不知道這是怎麼發生。每當我運行我的應用程序，就會出現一個空白的列表視圖。
所以基本上我使用發送到openweathermap的http查詢獲取json格式的天氣預報，然後填充listview。
我沒有對我的源代碼進行修改，它是相同的。這是什麼讓我最困惑
這是填充listview的代碼。 for循環之後
package com.example.hp.weather_app;
import android.content.Context;
import android.content.Intent;
import android.content.SharedPreferences;
import android.net.Uri;
import android.os.AsyncTask;
import android.os.Bundle;
import android.preference.PreferenceManager;
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.AdapterView;
import android.widget.ArrayAdapter;
import android.widget.ListView;
import android.widget.Toast;
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;
/**
* Created by hp on 20-06-2015.
*/
public class MainActivityFragment extends Fragment {
static ArrayAdapter<String> weather_adapter;
public MainActivityFragment() {
}
public void onCreate(Bundle savedInstanceState)
{
super.onCreate(savedInstanceState);
setHasOptionsMenu(true);
}
@Override
public View onCreateView(LayoutInflater inflater, ViewGroup container,
Bundle savedInstanceState) {
View rootview = inflater.inflate(R.layout.fragment_main, container, false);
ArrayList<String> x = new ArrayList<String>();
weather_adapter = new ArrayAdapter<String>(getActivity(), R.layout.list_item_forecast, R.id.list_item_forecast_textview, x);
final ListView listview = (ListView) rootview.findViewById(R.id.list_view_forecast);
listview.setAdapter(weather_adapter);
listview.setOnItemClickListener(new AdapterView.OnItemClickListener()
{
public void onItemClick(AdapterView<?> adapterView,View view,int i,long l)
{
String msg=(String)listview.getItemAtPosition(i);
Intent it=new Intent(getActivity(),Detail_Activity.class).putExtra(Intent.EXTRA_TEXT,msg);
startActivity(it);
}
});
return rootview;
}
public void onCreateOptionsMenu(Menu menu,MenuInflater inflater)
{
inflater.inflate(R.menu.forecast_fragment, menu);
}
public void onStart()
{
super.onStart();
updateweather();
}
private void updateweather()
{
FetchWeatherTask w=new FetchWeatherTask(getActivity());
SharedPreferences prefs= PreferenceManager.getDefaultSharedPreferences(getActivity());
String location = prefs.getString(getString(R.string.pref_location_key),
getString(R.string.pref_location_default));
w.execute(location);
}
public boolean onOptionsItemSelected(MenuItem item)
{
int id=item.getItemId();
if(id==R.id.action_refresh) {
FetchWeatherTask w=new FetchWeatherTask(getActivity());
SharedPreferences prefs= PreferenceManager.getDefaultSharedPreferences(getActivity());
String location = prefs.getString(getString(R.string.pref_location_key),
getString(R.string.pref_location_default));
w.execute(location);
return true;
}
if (id == R.id.action_settings) {
startActivity(new Intent(getActivity(), SettingsActivity.class));
return true;
}
return super.onOptionsItemSelected(item);
}
}
class FetchWeatherTask extends AsyncTask<String ,Context,String []>
{private Context mContext;
public FetchWeatherTask(Context context) {
this.mContext = context;
}
@Override
protected String [] doInBackground(String []params)
{
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/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());
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;
}
forecastJsonStr = buffer.toString();
} catch (IOException e) {
Log.e("PlaceholderFragment", "Error ", e);
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) {
if (result != null) {
MainActivityFragment.weather_adapter.clear();
for(String dayForecastStr : result) {
MainActivityFragment.weather_adapter.add(dayForecastStr);
}
}
}
private String getReadableDateString(long time){
SimpleDateFormat shortenedDateFormat = new SimpleDateFormat("EEE MMM dd");
return shortenedDateFormat.format(time);
}
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_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);
String HL=formatHighLows(high,low);
resultStrs[i] = day + " - " + description + " - " +HL;
}
return resultStrs;
}
public String formatHighLows(double high, double low) {
MainActivityFragment obj=new MainActivityFragment();
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)))
{
Toast.makeText(mContext,"invalid unit",Toast.LENGTH_SHORT).show();
}
long roundedHigh = Math.round(high);
long roundedLow = Math.round(low);
String str= roundedHigh+"/"+roundedLow;
return str;
}
}
非常感謝。你也可以告訴我如何獲得鑰匙？ –
這裏是鏈接[link]（http://openweathermap.org/appid）。您可以免費註冊並從註冊後的頁面複製密鑰。 –