FATAL EXCEPTION: AsyncTask # 1 Произошла ошибка во время выполнения doInBackground()

Question

Я пытаюсь сделать приложение в android, наблюдая пример с Android app development weather app. Теперь у меня есть это фатальное исключение, и я понятия не имею, почему это происходит, потому что я использую JSON и api в первый раз.
мой журнал ошибок следующее:

01-27 03:01:40.622: E/AndroidRuntime(514): FATAL EXCEPTION: AsyncTask #1 
01-27 03:01:40.622: E/AndroidRuntime(514): java.lang.RuntimeException: An error occured  while executing doInBackground() 
01-27 03:01:40.622: E/AndroidRuntime(514): at android.os.AsyncTask$3.done(AsyncTask.java:200) 
01-27 03:01:40.622: E/AndroidRuntime(514): at java.util.concurrent.FutureTask$Sync.innerSetException(FutureTask.java:274) 
01-27 03:01:40.622: E/AndroidRuntime(514): at java.util.concurrent.FutureTask.setException(FutureTask.java:125) 
01-27 03:01:40.622: E/AndroidRuntime(514): at java.util.concurrent.FutureTask$Sync.innerRun(FutureTask.java:308) 
01-27 03:01:40.622: E/AndroidRuntime(514): at java.util.concurrent.FutureTask.run(FutureTask.java:138) 
01-27 03:01:40.622: E/AndroidRuntime(514): at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1088) 
01-27 03:01:40.622: E/AndroidRuntime(514): at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:581) 
01-27 03:01:40.622: E/AndroidRuntime(514): at java.lang.Thread.run(Thread.java:1019) 
01-27 03:01:40.622: E/AndroidRuntime(514): Caused by: java.lang.NullPointerException 
01-27 03:01:40.622: E/AndroidRuntime(514): at org.json.JSONTokener.nextCleanInternal(JSONTokener.java:112) 
01-27 03:01:40.622: E/AndroidRuntime(514): at org.json.JSONTokener.nextValue(JSONTokener.java:90) 
01-27 03:01:40.622: E/AndroidRuntime(514): at org.json.JSONObject.<init>(JSONObject.java:154) 
01-27 03:01:40.622: E/AndroidRuntime(514): at org.json.JSONObject.<init>(JSONObject.java:171) 
01-27 03:01:40.622: E/AndroidRuntime(514): at com.example.secondtime.JSONWeatherParser.getWeather(JSONWeatherParser.java:24) 
01-27 03:01:40.622: E/AndroidRuntime(514): at com.example.secondtime.MainActivity$JSONWeatherTask.doInBackground(MainActivity.java:96) 
01-27 03:01:40.622: E/AndroidRuntime(514): at com.example.secondtime.MainActivity$JSONWeatherTask.doInBackground(MainActivity.java:1) 
01-27 03:01:40.622: E/AndroidRuntime(514): at android.os.AsyncTask$2.call(AsyncTask.java:185) 
01-27 03:01:40.622: E/AndroidRuntime(514): at java.util.concurrent.FutureTask$Sync.innerRun(FutureTask.java:306) 
01-27 03:01:40.622: E/AndroidRuntime(514): ... 4 more 

Это мой Основной класс деятельности:

package com.example.secondtime; 

import com.survivingwithandroid.weatherapp.R; 
import java.io.BufferedReader; 
import java.io.InputStream; 
import java.io.InputStreamReader; 
import java.net.HttpURLConnection; 
import java.net.URL; 

import org.json.JSONArray; 
import org.json.JSONException; 
import org.json.JSONObject; 

import com.example.secondtime.DailyForecastPageAdapter; 
import com.example.secondtime.Location; 
import com.example.secondtime.Weather; 
import com.example.secondtime.WeatherForecast; 

import android.os.AsyncTask; 
import android.os.Bundle; 
import android.app.Activity; 
import android.graphics.Bitmap; 
import android.graphics.BitmapFactory; 
import android.support.v4.app.FragmentActivity; 
import android.support.v4.view.ViewPager; 
import android.view.Menu; 
import android.widget.ImageView; 
import android.widget.TextView; 

public class MainActivity extends FragmentActivity { 


     private TextView cityText; 
     private TextView condDescr; 
     private TextView temp; 
     private TextView press; 
     private TextView windSpeed; 
     private TextView windDeg; 
     private TextView unitTemp; 

     private TextView hum; 
     private ImageView imgView; 

     private static String forecastDaysNum = "3"; 
     private ViewPager pager; 

     @Override 
     protected void onCreate(Bundle savedInstanceState) { 
       super.onCreate(savedInstanceState); 
       setContentView(R.layout.activity_main); 
       String city = "London, UK"; 
       String lang = "en"; 

       cityText = (TextView) findViewById(R.id.cityText); 
       temp = (TextView) findViewById(R.id.temp); 
       unitTemp = (TextView) findViewById(R.id.unittemp); 
       unitTemp.setText("°C"); 
       condDescr = (TextView) findViewById(R.id.skydesc); 

       pager = (ViewPager) findViewById(R.id.pager); 
       imgView = (ImageView) findViewById(R.id.condIcon); 




       JSONWeatherTask task = new JSONWeatherTask(); 
       task.execute(new String[]{city,lang}); 

       JSONForecastWeatherTask task1 = new JSONForecastWeatherTask(); 
       task1.execute(new String[]{city,lang, forecastDaysNum}); 
     } 

     @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; 
     } 


     private class JSONWeatherTask extends AsyncTask<String, Void, Weather> { 

       @Override 
       protected Weather doInBackground(String... params) { 
         Weather weather = new Weather(); 
         String data = ((new WeatherHttpClient()).getWeatherData(params[0], params[1])); 

         try { 
           weather = JSONWeatherParser.getWeather(data); 
           System.out.println("Weather ["+weather+"]"); 

           weather.iconData = ((new WeatherHttpClient()).getImage(weather.currentCondition.getIcon())); 

         } catch (JSONException e) {         
           e.printStackTrace(); 
         } 
         return weather; 

     } 


     @Override 
     protected void onPostExecute(Weather weather) {       
         super.onPostExecute(weather); 

         if (weather.iconData != null && weather.iconData.length > 0) { 
           Bitmap img = BitmapFactory.decodeByteArray(weather.iconData, 0, weather.iconData.length); 
           imgView.setImageBitmap(img); 
         } 


         cityText.setText(weather.location.getCity() + "," + weather.location.getCountry()); 
         temp.setText("" + Math.round((weather.temperature.getTemp() - 275.15))); 
         condDescr.setText(weather.currentCondition.getCondition() + "(" + weather.currentCondition.getDescr() + ")"); 


       } 



    } 


     private class JSONForecastWeatherTask extends AsyncTask<String, Void, WeatherForecast> { 

       @Override 
       protected WeatherForecast doInBackground(String... params) { 

         String data = ((new WeatherHttpClient()).getForecastWeatherData(params[0], params[1], params[2])); 
         WeatherForecast forecast = new WeatherForecast(); 
         try { 
           forecast = JSONWeatherParser.getForecastWeather(data); 
           System.out.println("Weather ["+forecast+"]"); 


         } catch (JSONException e) {         
           e.printStackTrace(); 
         } 
         return forecast; 

     } 




     @Override 
       protected void onPostExecute(WeatherForecast forecastWeather) {       
         super.onPostExecute(forecastWeather); 

         DailyForecastPageAdapter adapter = new DailyForecastPageAdapter(Integer.parseInt(forecastDaysNum), getSupportFragmentManager(), forecastWeather); 

         pager.setAdapter(adapter); 
       } 



    } 
} 

Еще один это это моя основная деятельность XML-файл:

<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android" 
    xmlns:tools="http://schemas.android.com/tools" 
    android:layout_width="match_parent" 
    android:layout_height="wrap_content" 
    android:paddingBottom="@dimen/activity_vertical_margin" 
    android:paddingLeft="@dimen/activity_horizontal_margin" 
    android:paddingRight="@dimen/activity_horizontal_margin" 
    android:paddingTop="@dimen/activity_vertical_margin" 
    tools:context=".MainActivity" 
    android:orientation="vertical" > 

    <RelativeLayout 
     android:layout_width="290dp" 
     android:layout_height="wrap_content" 
     android:paddingBottom="@dimen/activity_vertical_margin" 
     android:paddingLeft="@dimen/activity_horizontal_margin" 
     android:paddingRight="@dimen/activity_horizontal_margin" 
     android:paddingTop="@dimen/activity_vertical_margin" 
     tools:context=".MainActivity" > 

    <TextView 
     android:id="@+id/cityText" 
     style="?android:attr/textAppearanceMedium" 
     android:layout_width="wrap_content" 
     android:layout_height="wrap_content" 
     android:layout_alignParentLeft="true">   
    </TextView> 

    <TextView 
     android:id="@+id/temp" 
     android:layout_width="wrap_content" 
     android:layout_height="wrap_content" 
     android:layout_below="@id/cityText" 
     android:layout_centerHorizontal="true">   
    </TextView> 
    <TextView 
     android:id="@+id/unittemp"   
     android:layout_width="wrap_content" 
     style="?android:attr/textAppearanceMedium" 
     android:layout_height="wrap_content" 
     android:layout_below="@id/cityText" 
     android:layout_toRightOf="@id/temp" 
     android:layout_alignBaseline="@id/temp">   
    </TextView> 
    <TextView 
     android:id="@+id/skydesc"   
     android:layout_width="wrap_content" 
     style="?android:attr/textAppearanceMedium" 
     android:layout_height="wrap_content" 
     android:layout_below="@id/temp"   
     android:layout_alignStart="@id/temp" 
     android:layout_toRightOf="@id/temp"> 
    </TextView> 

    <!-- Image weather condition --> 
    <ImageView android:id="@+id/condIcon" 
       android:layout_height="wrap_content" 
       android:layout_width="wrap_content" 
       android:layout_alignTop="@id/temp" 
       android:layout_toRightOf="@id/temp"/> 

</RelativeLayout> 

<android.support.v4.view.ViewPager 

    android:id="@+id/pager" 
    android:layout_width="match_parent" 
    android:layout_height="match_parent" 
    android:layout_weight="6" > 

    <android.support.v4.view.PagerTitleStrip 
     android:id="@+id/pager_title_strip" 
     android:layout_width="match_parent" 
     android:layout_height="wrap_content" 
     android:layout_gravity="top" 
     android:background="#E6E6E6" 
     android:paddingBottom="4dp" 
     android:paddingTop="4dp" 
     android:textColor="#fff" /> 

     </android.support.v4.view.ViewPager> 
</LinearLayout> 

Любая помощь на этом будет здорово. Спасибо заранее и извините за мой плохой английский и грамматик.

Answer 1

Вы должны проверить возвращаемый data за не null..Try добавить там контрольную точку, и вы увидите ..

if(data != null){ 
    //do the parsing stuff 
}else{ 
    //something wrong happened during the download.. 

} 

Согласно StackTrace, у вас есть NullPointerException здесь:

JSONWeatherParser.getWeather(data) 

Когда вы смотрите на код метода

public String getWeatherData(String location, String lang) { 
      HttpURLConnection con = null ; 
      InputStream is = null; 

      try { 
        String url = BASE_URL + location; 
        if (lang != null) 
          url = url + "&lang=" + lang; 

        con = (HttpURLConnection) (new URL(url)).openConnection(); 
        con.setRequestMethod("GET"); 
        con.setDoInput(true); 
        con.setDoOutput(true); 
        con.connect(); 

        // Let's read the response 
        StringBuffer buffer = new StringBuffer(); 
        is = con.getInputStream(); 
        BufferedReader br = new BufferedReader(new InputStreamReader(is)); 
        String line = null; 
        while ( (line = br.readLine()) != null) 
          buffer.append(line + "\r\n"); 

        is.close(); 
        con.disconnect(); 

        return buffer.toString(); 
     } 
      catch(Throwable t) { 
        t.printStackTrace(); 
      } 
      finally { 
        try { is.close(); } catch(Throwable t) {} 
        try { con.disconnect(); } catch(Throwable t) {} 
      } 

      return null; 

    } 

йо u может видеть, что в последней строке он возвращает null. Это происходит, когда во время загрузки возникает ошибка. Поэтому вам обязательно нужно проверить, есть ли там nullpointer, чтобы сэкономить ваш код.