無法在AsycTask中返回字符串數組

Question

如果我更改爲字符串，則返回字符串值。但我不明白爲什麼它不返回字符串值。我檢查所有仍然無法得到它。

我的錯誤在哪裏？提前致謝。

public class FetchWeatherTask extends AsyncTask<String, Void, String[]> { 
private final String LOG_TAG=FetchWeatherTask.class.getSimpleName(); 

private String[] getWeatherDataFromJson(String forecastJsonStr) 
      throws JSONException { 

     // These are the names of the JSON objects that need to beextracted. 
final String OWM_LIST = "list"; 
final String OWM_WEATHER = "weather"; 
final String OWM_TEMPERATURE = "temp"; 
final String OWM_MAX = "temp_max"; 
final String OWM_MIN = "temp_min"; 
final String OWM_DESCRIPTION = "main"; 

JSONObject forecastJson = new JSONObject(forecastJsonStr); 
JSONArray weatherArray = forecastJson.getJSONArray(OWM_LIST); 
JSONObject city=forecastJson.getJSONObject("city"); 
String name=city.getString("name"); 

String[] resultStrs = null; 
for(int i = 0; i < weatherArray.length(); i++) { 
    // For now, using the format "Day, description, hi/low" 
String description; 

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_DESCRIPTION); 
      double high = temperatureObject.getDouble(OWM_MAX); 
      double low = temperatureObject.getDouble(OWM_MIN); 

      highAndLow = formatHighLows(high, low); 
      //resultStrs[i] = description + " - " + highAndLow; 
      resultStrs[i]=name; 
     } 

     for (String s : resultStrs) { 
      Log.v(LOG_TAG, "Forecast entry: " + s); 
     } 
     return resultStrs; 


    } 

doinbackground也串[]

@Override 
    protected String[] doInBackground(String... params) { 


     //if there is no zip code nothing to look it 
     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 appid = "bc1"; 


     try { 
      // Construct the URL for the OpenWeatherMap query 
      // Possible parameters are available 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 = "id"; 
      final String APPID = "APPID"; 


      Uri builturi = Uri.parse(FORECAST_BASE_URL).buildUpon() 
        .appendQueryParameter(QUERY_PARAM, params[0]) 
        .appendQueryParameter(APPID, appid) 
        .build(); 
      URL URl; 
      URl = new URL(builturi.toString()); 
      Log.v(LOG_TAG, "BUILT URI" + builturi.toString()); 


      // URL url = new URL("http://api.openweathermap.org/data/2.5/forecast/city?id=524901&APPID=bc16214cbb434f8386d9b0c3d7eebc17"); 

      // 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; 

      } 
      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; 
      } 
      if (buffer.length()!=0){forecastJsonStr = buffer.toString();} 

     } catch (ProtocolException e) { 
      e.printStackTrace(); 
     } catch (MalformedURLException e) { 
      e.printStackTrace(); 
     } catch (IOException e) { 
      Log.e("PlaceholderFragment", "Error ", e); 
      // If the code didn't successfully get the weather data, there's no point in attempting 
      // to parse it. 
      //forecastJsonStr = 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); 
     } catch (JSONException e) { 
      e.printStackTrace(); 
     } 
     //this will happen if there was an error getting or parsing the document 
     return null; 
    } 

    @Override 
    protected void onPostExecute(String[] result) { 
     if (result!=null){ 
      Toast.makeText(getActivity(),"working", Toast.LENGTH_LONG).show(); 
      arrayAdapter.clear(); 
      for (String dayforcast:result){ 
       arrayAdapter.add(dayforcast); 
      } 
     } 
    //i used to figure out it is working or not 
    // not much significance 
if (result==null){ 
Toast.makeText(getActivity(),"not working", Toast.LENGTH_LONG).show(); 
     } 
    } 
} 
    //Onpost in string[],asyctask also string[],dolnbackground also string[] 

Answer 1

試圖調用notifyDataSetChanged在onPostExecute你arrayadapter您添加後所有的dayforcast元素;-)