title: HTTP Request Android - Attempt to invoke virtual method
body: <p>So I have a problem. I have been trying to get an http request to work for quite a while now, and I have made a new thread so that the request never runs on the main thread. I have successfully made it so that the HTTP Request occurs and in the request thread I have made it so it logs the data that it has grabbed from the http request. Now if I ever want to use this jsonObject outside the method it gives me errors. Help?</p>
  
  <p>LogCat:</p>
  
  <pre><code>02-23 22:48:08.612    4239-4239/com.tamrefrank.www.listviewandroidstudio E/AndroidRuntime﹕ FATAL EXCEPTION: main
      Process: com.tamrefrank.www.listviewandroidstudio, PID: 4239
      java.lang.RuntimeException: Unable to start activity ComponentInfo{com.tamrefrank.www.listviewandroidstudio/com.tamrefrank.www.listviewandroidstudio.MainActivity}: java.lang.NullPointerException: Attempt to invoke virtual method 'java.lang.String org.json.JSONArray.toString()' on a null object reference
              at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2298)
              at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2360)
              at android.app.ActivityThread.access$800(ActivityThread.java:144)
              at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1278)
              at android.os.Handler.dispatchMessage(Handler.java:102)
              at android.os.Looper.loop(Looper.java:135)
              at android.app.ActivityThread.main(ActivityThread.java:5221)
              at java.lang.reflect.Method.invoke(Native Method)
              at java.lang.reflect.Method.invoke(Method.java:372)
              at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:899)
              at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:694)
       Caused by: java.lang.NullPointerException: Attempt to invoke virtual method 'java.lang.String org.json.JSONArray.toString()' on a null object reference
              at com.tamrefrank.www.listviewandroidstudio.MainActivity.onCreate(MainActivity.java:38)
              at android.app.Activity.performCreate(Activity.java:5933)
              at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1105)
              at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2251)
              at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2360)
              at android.app.ActivityThread.access$800(ActivityThread.java:144)
              at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1278)
              at android.os.Handler.dispatchMessage(Handler.java:102)
              at android.os.Looper.loop(Looper.java:135)
              at android.app.ActivityThread.main(ActivityThread.java:5221)
              at java.lang.reflect.Method.invoke(Native Method)
              at java.lang.reflect.Method.invoke(Method.java:372)
              at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:899)
              at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:694)
  02-23 22:48:09.332    4239-4254/com.tamrefrank.www.listviewandroidstudio I/log_tag﹕ [{"Name":"Cabinet","Location":"In Storage","Latitude":"40.83990100","Longitude":"14.25185000","pk":19587,"image_id":"2006AJ6728"},{"Name":"Panel","Location":"Medieval and Renaissance, room 8, case WS EXP","Latitude":"48.87287900","Longitude":"4.63710000","pk":11371,"image_id":"2006AP3163"},{"Name":"Wallpaper","Location":"British Galleries, room 122f, case 1","Latitude":"53.47962200","Longitude":"-2.24881000","pk":19492,"image_id":"2006AU6265"},{"Name":"Portrait miniature","Location":"British Galleries, room 58c, case 2","Latitude":"52.88328900","Longitude":"-1.97685000","pk":9491,"image_id":"2006AH0271"},{"Name":"Caricature","Location":"In Storage","Latitude":"53.02513900","Longitude":"-2.18676000","pk":29979,"image_id":"2006AE9142"},{"Name":"Card game","Location":"In Storage","Latitude":"52.88328900","Longitude":"-1.97685000","pk":26483,"image_id":"2006AU5916"},{"Name":"Tile","Location":"Islamic Middle East, room 42, case WW9","Latitude":"39.76586200","Longitude":"64.42234000","pk":30220,"image_id":"2006AY5617"},{"Name":"Sculpture","Location":"Sculpture, room 22, case 2","Latitude":"52.88328900","Longitude":"-1.97685000","pk":36026,"image_id":"2006AM7780"},{"Name":"Oil painting","Location":"Prints &amp; Drawings Study Room, room 315, case 24, shelf R","Latitude":"52.88328900","Longitude":"-1.97685000","pk":6905,"image_id":"2006AU6480"},{"Name":"Snuff bottle","Location":"In Storage","Latitude":"36.89445100","Longitude":"104.16564900","pk":10895,"image_id":"2006AU8783"},{"Name":"Snuff bottle","Location":"In Storage","Latitude":"36.89445100","Longitude":"104.16564900","pk":10902,"image_id":"2006AU9234"}]
  02-23 22:48:09.332    4239-4254/com.tamrefrank.www.listviewandroidstudio I/log_tag﹕ [{"Name":"Cabinet","Location":"In Storage","Latitude":"40.83990100","Longitude":"14.25185000","pk":19587,"image_id":"2006AJ6728"},{"Name":"Panel","Location":"Medieval and Renaissance, room 8, case WS EXP","Latitude":"48.87287900","Longitude":"4.63710000","pk":11371,"image_id":"2006AP3163"},{"Name":"Wallpaper","Location":"British Galleries, room 122f, case 1","Latitude":"53.47962200","Longitude":"-2.24881000","pk":19492,"image_id":"2006AU6265"},{"Name":"Portrait miniature","Location":"British Galleries, room 58c, case 2","Latitude":"52.88328900","Longitude":"-1.97685000","pk":9491,"image_id":"2006AH0271"},{"Name":"Caricature","Location":"In Storage","Latitude":"53.02513900","Longitude":"-2.18676000","pk":29979,"image_id":"2006AE9142"},{"Name":"Card game","Location":"In Storage","Latitude":"52.88328900","Longitude":"-1.97685000","pk":26483,"image_id":"2006AU5916"},{"Name":"Tile","Location":"Islamic Middle East, room 42, case WW9","Latitude":"39.76586200","Longitude":"64.42234000","pk":30220,"image_id":"2006AY5617"},{"Name":"Sculpture","Location":"Sculpture, room 22, case 2","Latitude":"52.88328900","Longitude":"-1.97685000","pk":36026,"image_id":"2006AM7780"},{"Name":"Oil painting","Location":"Prints &amp; Drawings Study Room, room 315, case 24, shelf R","Latitude":"52.88328900","Longitude":"-1.97685000","pk":6905,"image_id":"2006AU6480"},{"Name":"Snuff bottle","Location":"In Storage","Latitude":"36.89445100","Longitude":"104.16564900","pk":10895,"image_id":"2006AU8783"},{"Name":"Snuff bottle","Location":"In Storage","Latitude":"36.89445100","Longitude":"104.16564900","pk":10902,"image_id":"2006AU9234"}]
  02-23 22:48:32.712    4239-4239/com.tamrefrank.www.listviewandroidstudio I/Process﹕ Sending signal. PID: 4239 SIG: 9
  </code></pre>
  
  <p>Code:</p>
  
  <pre><code>package com.tamrefrank.www.listviewandroidstudio;
  //All the imports happen when you auto complete. Often you may have erros when you copy paste things directly because libraries may not get imported
  import android.os.AsyncTask;
  import android.os.StrictMode;
  import android.support.v7.app.ActionBarActivity;
  import android.os.Bundle;
  import android.util.Log;
  import android.view.Menu;
  import android.view.MenuItem;
  import android.widget.ArrayAdapter;
  import android.widget.ListView;
  
  import org.apache.http.HttpEntity;
  import org.apache.http.HttpResponse;
  import org.apache.http.client.ClientProtocolException;
  import org.apache.http.client.HttpClient;
  import org.apache.http.client.methods.HttpGet;
  import org.apache.http.impl.client.DefaultHttpClient;
  import org.json.JSONArray;
  import org.json.JSONException;
  import org.json.JSONObject;
  
  import java.io.IOException;
  import java.io.InputStream;
  
  
  public class MainActivity extends ActionBarActivity {
      private String [] drinks;
      JSONArray jsonObject;
      @Override
      protected void onCreate(Bundle savedInstanceState) {
          super.onCreate(savedInstanceState);
          //set the content view to activity_main.xml
          setContentView(R.layout.activity_main);
  
          JSONArray object = new JSONArray();
          object = getData();
          Log.i("log_tag", jsonObject.toString());
  
  //        System.out.print("success: " + object.toString());
  
  
          drinks = new String[3];
          drinks[0] = "hi";
          drinks[1] = "5";
          drinks[2] = "3";
   /**
    * Lists require adapters-Adapters are the place that we store the various data items we want
    to appear in the Lists. This will be handled in an adapter.
    */
  
          ArrayAdapter&lt;String&gt; adapter;
  
  //We will create the array adapter and reference it to our individual List item from the ListView and then to the array we just created- Drinks.
          adapter = new ArrayAdapter&lt;String&gt;(this, android.R.layout.simple_list_item_1,drinks);
  
  //We finally will connect the adapter to the List View
          ListView drinkLists = (ListView) findViewById(R.id.listView);
  
          //Set the drinks array to the adapter below
          drinkLists.setAdapter(adapter);
      }
  
      public JSONArray getData(){
          new Thread(new Runnable() {
                  public void run() {
  
                      HttpGet httpGet = new HttpGet("https://stampwatch.herokuapp.com/");
                      HttpClient client = new DefaultHttpClient();
                      HttpResponse response;
                      StringBuilder stringBuilder = new StringBuilder();
  
                      try {
                          response = client.execute(httpGet);
                          HttpEntity entity = response.getEntity();
                          InputStream stream = entity.getContent();
                          int b;
                          while ((b = stream.read()) != -1) {
                              stringBuilder.append((char) b);
                          }
                      } catch (ClientProtocolException e) {
                      } catch (IOException e) {
                          System.out.println(e);
                      }
  
                      try {
                          jsonObject = new JSONArray(stringBuilder.toString());
                          Log.i("log_tag", jsonObject.toString());
  ;
                      } catch (JSONException e) {
                          e.printStackTrace();
                      }
                      Log.i("log_tag", jsonObject.toString());
                      }
  
              }).start();
              return jsonObject;
          }
  
  
      @Override
      public boolean onCreateOptionsMenu(Menu menu) {
          // Inflate the menu; this adds items to the action bar if it is present.
          getMenuInflater().inflate(R.menu.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();
  
          //noinspection SimplifiableIfStatement
          if (id == R.id.action_settings) {
              return true;
          }
           return super.onOptionsItemSelected(item);
      }
  }
  </code></pre>