应用程序未连接到主机？

Question

我正在尝试连接我的应用程序与主机，我得到所有的代码，但它没有连接 给我在logcat冗长的消息，当我点击模拟器中的Menu按钮，当这个消息，当我点击Refresh按钮

这里是MainActivity.java类：

public class MainActivity extends ActionBarActivity { 

    @Override 
    protected void onCreate(Bundle savedInstanceState) { 
     super.onCreate(savedInstanceState); 
     setContentView(R.layout.activity_main); 
     if (savedInstanceState == null) 
     { 
      getSupportFragmentManager().beginTransaction() 
       .add(R.id.container, new ForecastFragment() 
         .Commit()); 
      } 
     } 

    @Override 
    public boolean onCreateOptionsMenu(Menu menu) { 
     // Inflate the menu; this adds items to the action bar if it is present. 
     getMenuInflater().inflate(R.menu.main, menu); 
     return 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_settings) { 
      return true; 
     } 
     return super.onOptionsItemSelected(item); 
    } 

    /** 
    * A placeholder fragment containing a simple view. 
    */ 
    public ForecastFragment Commit() { 
     return null; 
    } 

      HttpURLConnection urlConnection = null; 
      BufferedReader reader = null; 

      String forecastJsonStr = null; 
    } 

这里是ForecastFragment.java类：

public class ForecastFragment extends Fragment 
{ 
    private ArrayAdapter<String> mForecastAdapter; 
    public ForecastFragment() 
    { 
    } 

    @Override 
    public void onCreate(Bundle savedInstanceState) 
    { 
     super.onCreate(savedInstanceState); 
     setHasOptionsMenu(true); 
    } 


    public void onCreateOptionMenu(Menu menu, MenuInflater inflater) 
    { 
     inflater.inflate(R.menu.forecastfragment, menu); 
    } 


    public boolean onOptionItemSelected(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[] data = 
     { 
       "Today - Sunny - 88/63", 
       "Tomorrow - foggy - 70/46", 
       "weds - Cloudy - 72/63", 
       "Thurs - Rainy - 64/51", 
       "Fri - Foggy - 70/46", 
       "Sat - Sunny - 76/68" 
     }; 

     List<String> weekForecast = new ArrayList<String>(
       Arrays.asList(data)); 


     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 ForecastFragment Commit() { 
     return null; 
    } 

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


     private String getReadableDateString(long time) 
     { 
      Date date = new Date(time * 1000); 
      SimpleDateFormat format = new SimpleDateFormat("E, MMM d"); 
      return format.format(date).toString(); 
     } 


     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[] 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 = 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); 
       resultStrs[i] = day + " - " + description + " - " + highAndLow; 
      } 

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

     } 


     @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/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, format) 
         .appendQueryParameter(DAYS_param, Integer.toString(numDays)) 
         .build(); 

       URL url = new URL(builtUri.toString()); 
       Log.v(LOG_TAG, "Built Uri " + 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(); 
       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); 
        } 
       } 
      } 
      try 
      { 
       return getWeatherDataFromJson(forecastJsonStr, numDays); 
      } 
      catch (JSONException e) 
      { 
       Log.e(LOG_TAG, e.getMessage(), e); 
       e.printStackTrace(); 
      } 
        return null; 
     } 

      @Override 
     protected void onPostExecute(String[] result) 
      { 
       if (result != null) 
       { 

        mForecastAdapter.clear(); 
        for (String dayForecastStr : result) 
        { 
         mForecastAdapter.add(dayForecastStr); 
        } 
       } 
      } 
    } 

    private String formatHighLows(double high, double low) { 
     return null; 
    } 


} 

现在我得到了所有的错误并记录ForecastFragment.java类中的代码，那么为什么它没有连接到给我同样错误的主机？

Answer 1

你doInBackground()是空的：

@Override 
protected Void doInBackground(String... params) { 
    return null; 
} 

有一个在其他doInBackGround()方法名称的拼写错误（应该有小写g）。删除空方法并用代码重命名另一个，以便可以运行AsyncTask。