Async Task An error occured while executing doInBackground()

Question

From my previous question

I was getting NullPointor exception. So i have done some changes in my code and now progress bar is showing up but getting the below errors.

11-17 23:39:51.373: ERROR/AndroidRuntime(495): Uncaught handler: thread AsyncTask #1 exiting due to uncaught exception
11-17 23:39:51.373: ERROR/AndroidRuntime(495): java.lang.RuntimeException: An error occured while executing doInBackground()
11-17 23:39:51.373: ERROR/AndroidRuntime(495):     at android.os.AsyncTask$3.done(AsyncTask.java:200)
11-17 23:39:51.373: ERROR/AndroidRuntime(495):     at java.util.concurrent.FutureTask$Sync.innerSetException(FutureTask.java:273)
11-17 23:39:51.373: ERROR/AndroidRuntime(495):     at java.util.concurrent.FutureTask.setException(FutureTask.java:124)
11-17 23:39:51.373: ERROR/AndroidRuntime(495):     at java.util.concurrent.FutureTask$Sync.innerRun(FutureTask.java:307)
11-17 23:39:51.373: ERROR/AndroidRuntime(495):     at java.util.concurrent.FutureTask.run(FutureTask.java:137)
11-17 23:39:51.373: ERROR/AndroidRuntime(495):     at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1068)
11-17 23:39:51.373: ERROR/AndroidRuntime(495):     at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:561)
11-17 23:39:51.373: ERROR/AndroidRuntime(495):     at java.lang.Thread.run(Thread.java:1096)
11-17 23:39:51.373: ERROR/AndroidRuntime(495): Caused by: java.lang.RuntimeException: Can't create handler inside thread that has not called Looper.prepare()

Code is...

 public class JsonExampleActivity extends ListActivity {
/** Called when the activity is first created. */
ProgressDialog mDialog;

final String TAG="a.c.b";
JSONFunction JSONfunction;

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

    setContentView(R.layout.listplaceholder);

   new JSONPasingShowList().execute();
}

public void updateWithNewLocation(Location location2) {
    if(location2!=null) {
          double geoLat = location2.getLatitude();

            double geoLng = location2.getLongitude();

    }

}

class JSONPasingShowList extends AsyncTask<String, Integer,ArrayList<HashMap<String,String>>>
{


  @Override
    protected void onPreExecute() {
        super.onPreExecute();
        mDialog = new ProgressDialog(JsonExampleActivity.this);
        mDialog.setCancelable(true);
        mDialog.setMessage("Loading...");
        mDialog.setProgressStyle(ProgressDialog.STYLE_SPINNER);
        mDialog.setProgress(0);
        mDialog.show();
    }


@Override
protected ArrayList<HashMap<String,String>> doInBackground(String... params) {

    double latitude[]=new double[20];
    double longitude[]=new double[20];
    String reference[]=new String[20];
    double distance[]=new double[20];
    LocationManager locationManager;
    String context=Context.LOCATION_SERVICE;
    locationManager=(LocationManager)getSystemService(context);
    Criteria criteria = new Criteria();
    criteria.setAccuracy(Criteria.ACCURACY_FINE);
    criteria.setAltitudeRequired(false);
    criteria.setBearingRequired(false);
    criteria.setCostAllowed(true);
    criteria.setPowerRequirement(Criteria.POWER_LOW);
    String provider = locationManager.getBestProvider(criteria, true);
    Location location = locationManager.getLastKnownLocation(provider);

    final LocationListener locationListener = new LocationListener() {
        public void onLocationChanged(Location location) {
        updateWithNewLocation(location);
        }
        public void onProviderDisabled(String provider){
        updateWithNewLocation(null);
        }
        public void onProviderEnabled(String provider){ }
        public void onStatusChanged(String provider, int status,
        Bundle extras){ }
        };

    updateWithNewLocation(location);
    locationManager.requestLocationUpdates(provider, 2000, 10,
            locationListener);


    double geoLat = location.getLatitude();
    Log.v(TAG, "hiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiii"+geoLat);
    double geoLng = location.getLongitude();
    Log.v(TAG, "hiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiii"+geoLng);
    ArrayList<HashMap<String, String>> mylist = new ArrayList<HashMap<String, String>>();


    JSONObject  json=JSONFunction.getJSONfromURL("https://maps.googleapis.com/maps/api/place/search/json?location=37.422006,-122.084095&radius=1000&types=doctor&sensor=true&key=xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx");

    try{
        JSONArray  JArray = json.getJSONArray("results");
           Log.v(TAG, "getting results");
        for(int i=0;i<JArray.length();i++){                     
            HashMap<String, String> map = new HashMap<String, String>();    
            JSONObject e = JArray.getJSONObject(i);
            JSONObject location1=e.getJSONObject("geometry").getJSONObject("location");
            latitude[i]=location1.getDouble("lat");
            longitude[i]=location1.getDouble("lng");
            reference[i]=e.getString("reference");
            Log.v(TAG, reference[i]);
            distance[i]=GetLatAndLng.gps2m(geoLat, geoLng,latitude[i] ,longitude[i]); 

            map.put("id",  String.valueOf(i));
            map.put("name", "" + e.getString("name"));
            map.put("vicinity", "Address " +  e.getString("vicinity")+" "+"Disance:"+distance[i]);

            mylist.add(map);                        
        }   }catch(JSONException e)        {
             Log.e("log_tag", "Error parsing data "+e.toString());
        }
        final Intent intent=new Intent(JsonExampleActivity.this ,GetLatAndLng.class);
        Bundle b=new Bundle();
        b.putStringArray("key", reference);
        intent.putExtras(b);   
    return mylist;
}

 @Override
    protected void onProgressUpdate(Integer... values) {
        super.onProgressUpdate(values);
    }

protected void onPostExecute(ArrayList<HashMap<String, String>> result) {
    mDialog.dismiss();
     ListAdapter adapter = new SimpleAdapter(JsonExampleActivity.this, result , R.layout.listview, 
             new String[] { "name", "vicinity", }, 
             new int[] { R.id.item_title, R.id.item_subtitle });

 setListAdapter(adapter);
 mDialog.dismiss();
 final ListView lv = getListView();
 lv.setTextFilterEnabled(true); 
 lv.setOnItemClickListener(new OnItemClickListener() {
public void onItemClick(AdapterView<?> parent, View view, int position, long id) {          
    @SuppressWarnings("unchecked")
        HashMap<String, String> o = (HashMap<String, String>) lv.getItemAtPosition(position);                   
   Toast.makeText(JsonExampleActivity.this, "ID '" + o.get("id") + "' was clicked.", Toast.LENGTH_SHORT).show();
  final Intent intent=new Intent(JsonExampleActivity.this ,GetLatAndLng.class);
   intent.putExtra("clickedid",position);
    startActivity(intent);
    }
});
}
public class MySimpleAdapter extends SimpleAdapter {
     public MySimpleAdapter(Context context, List<? extends Map<String, ?>> data, int resource, String[] from, int[] to) {
        super(context, data, resource, from, to);
        // TODO Auto-generated constructor stub
}
}
}
}

What is going wrong? Thanks in Advance!!!

Answer 1

Can't create handler inside thread that has not called Looper.prepare()

You are accessing something on the UI thread from inside doInBackground. And that's not allowed.

*edit: I've seen everything. To me, what looks mostly unusual are those lines:

updateWithNewLocation(location); // What does this do? Could you tell me?
locationManager.requestLocationUpdates(provider, 2000, 10,
        locationListener); // I don't think this is it

Try to move all those location update stuff into the onProgressUpdate. I'm blind here since I can't see your code, but I'm guessing it does something with the UI. Try this:

@Override
protected void onProgressUpdate(Location... locations) {
    super.onProgressUpdate(values);
    updateWithNewLocation(location);
}

But as I said, I'm not sure since I can't know what updateWithNewLocation does unless you post that code here.

Answer 2

This is exactly why it's valuable to start understanding some basics around threading instead of just saying "AsyncTask" for everything that seems remotely threading-related in Android. Multi-threading can be tricky and you have to think things through.

I suspect this is what's happening: You have an AsyncTask which among other things gets the location... asynchronously. That means you start on the main thread, you execute doInBackground in another thread implicitly (the AsyncTask's thread), then you call off to whatever thread is doing your location acquisition. Then your AsyncTask thread continues on, finishing off all that JSON-related work in doInBackground, probably finishing. The AsyncTask thread likely finishes. Then you are getting your location lock, and the listener that you provided is called back, except that now the AsyncTask has already finished, and its thread is no longer valid.

Just based on a look at your code I suspect that you want to make that Google Maps API call after you get your location, right? If so, call your "get location" code synchronously. In the callback to that, you can put the code to kick off your AsyncTask which now only does the Google Maps API call and processing.

Answer 3

You're doing a bunch of stuff in your doInBackground() that you don't need to do in there. Only do the stuff in your doInBackground() method that would cause the stuttering on the UI thread. In other words, all the code that doesn't directly deal with your network communication needs to be moved out of your doInBackground() method.