java.lang.nullpointerexception attempt to invoke method 'int java.util.List.size()'

Question

Main Activity

trying to add google map please help as soon as u can

import java.util.ArrayList;
import java.util.HashMap;
import java.util.List;

import org.json.JSONObject;

import android.app.ActionBar;
import android.content.Intent;
import android.graphics.Color;
import android.os.AsyncTask;
import android.os.Bundle;
import android.support.v4.app.FragmentActivity;
import android.util.Log;
import android.view.Menu;
import android.view.MenuItem;

import com.google.android.gms.maps.CameraUpdateFactory;
import com.google.android.gms.maps.GoogleMap;
import com.google.android.gms.maps.SupportMapFragment;
import com.google.android.gms.maps.model.LatLng;
import com.google.android.gms.maps.model.MarkerOptions;
import com.google.android.gms.maps.model.PolylineOptions;
import com.parse.ParseAnalytics;
import com.parse.ParseUser;

public class OnscreenActivity extends FragmentActivity {

    private static final LatLng sydney = new LatLng(30.8894669, 75.8246729);
    private static final LatLng connct = new LatLng(30.8914863, 75.874398);
    GoogleMap googleMap;
    final String TAG1 = "PathGoogleMapActivity";

    public static final String TAG = OnscreenActivity.class.getSimpleName();

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_map);
        SupportMapFragment fm = (SupportMapFragment) getSupportFragmentManager()
                .findFragmentById(R.id.fragment1);
        googleMap = fm.getMap();
        ParseAnalytics.trackAppOpened(getIntent());
        ParseUser currentUser = ParseUser.getCurrentUser();
        if (currentUser == null) {
            navigateToLogin();
        } else {
            Log.i(TAG, currentUser.getUsername());
        }
        ActionBar actionbar = getActionBar();
        actionbar.show();
        MarkerOptions options = new MarkerOptions();
        options.position(sydney);
        options.position(connct);
        googleMap.addMarker(options);
        String url = getMapsApiDirectionsUrl();
        ReadTask downloadTask = new ReadTask();
        downloadTask.execute(url);

        googleMap.moveCamera(CameraUpdateFactory.newLatLngZoom(connct, 16));
        addMarkers();

    }

    private void addMarkers() {
        // TODO Auto-generated method stub
        if (googleMap != null) {
            googleMap.addMarker(new MarkerOptions().position(sydney).title(
                    "First Point"));
            googleMap.addMarker(new MarkerOptions().position(connct).title(
                    "Second Point"));

        }

    }

    private String getMapsApiDirectionsUrl() {
        String waypoints = "waypoints=optimize:true|" + sydney.latitude + ","
                + sydney.longitude + "|" + "|" + connct.latitude + ","
                + connct.longitude;

        String sensor = "sensor=false";
        String params = waypoints + "&" + sensor;
        String output = "json";
        String url = "https://maps.googleapis.com/maps/api/directions/"
                + output + "?" + params;
        return url;

    }

    private class ReadTask extends AsyncTask<String, Void, String> {
        @Override
        protected String doInBackground(String... url) {
            String data = "";
            try {
                HttpConnection http = new HttpConnection();
                data = http.readUrl(url[0]);
            } catch (Exception e) {
                Log.d("Background Task", e.toString());
            }
            return data;
        }

        @Override
        protected void onPostExecute(String result) {
            super.onPostExecute(result);
            new ParserTask().execute(result);
        }
    }

    private class ParserTask extends
            AsyncTask<String, Integer, List<List<HashMap<String, String>>>> {

        @Override
        protected List<List<HashMap<String, String>>> doInBackground(
                String... jsonData) {

            JSONObject jObject;
            List<List<HashMap<String, String>>> routes = null;

            try {
                jObject = new JSONObject(jsonData[0]);
                PathJsonParser parser = new PathJsonParser();
                routes = parser.parse(jObject);
            } catch (Exception e) {
                e.printStackTrace();
            }
            return routes;
        }

        @Override
        protected void onPostExecute(List<List<HashMap<String, String>>> routes) {
            ArrayList<LatLng> points = null;
            PolylineOptions polyLineOptions = null;

            // traversing through routes
            for (int i = 0; i < routes.size(); i++) {
                points = new ArrayList<LatLng>();
                polyLineOptions = new PolylineOptions();
                List<HashMap<String, String>> path = routes.get(i);

                for (int j = 0; j < path.size(); j++) {
                    HashMap<String, String> point = path.get(j);

                    double lat = Double.parseDouble(point.get("lat"));
                    double lng = Double.parseDouble(point.get("lng"));
                    LatLng position = new LatLng(lat, lng);

                    points.add(position);
                }

                polyLineOptions.addAll(points);
                polyLineOptions.width(2);
                polyLineOptions.color(Color.BLUE);
            }

            googleMap.addPolyline(polyLineOptions);
        }
    }

    private void navigateToLogin() {
        Intent intent = new Intent(this, Login.class);
        intent.addFlags(Intent.FLAG_ACTIVITY_NEW_TASK);
        intent.addFlags(Intent.FLAG_ACTIVITY_CLEAR_TASK);
        startActivity(intent);
    }

    public boolean onCreateOptionsMenu(Menu menu) {
        // Inflate the menu; this adds items to the action bar if it is present.
        getMenuInflater().inflate(R.menu.map, menu);
        return true;
    }

    public boolean onOptionsItemSelected(MenuItem item) {
        int itemId = item.getItemId();
        if (itemId == R.id.action_logout) {
            ParseUser.logOut();
            navigateToLogin();

        }
        if (itemId == R.id.options) {
            Intent intent = new Intent(this, UserOptions.class);
            intent.addFlags(Intent.FLAG_ACTIVITY_NEW_TASK);
            intent.addFlags(Intent.FLAG_ACTIVITY_CLEAR_TASK);
            startActivity(intent);
        }
        return super.onOptionsItemSelected(null);

    }

}

help with what exactly? on which variable/method call is this exception thrown? — Stultuske, Jul 14 '15 at 11:21
You've got List>> routes = null; and then attempt to get the size of this List object which has been set to null. — smoggers, Jul 14 '15 at 11:27
always add logcat n point out line of code where error occurs — Prachi, Jul 14 '15 at 11:31
Well, I suggest you start learning the basics of Java first. — Manu, Jul 14 '15 at 11:33
java.lang.NullPointerException: Attempt to invoke interface method 'int java.util.List.size()' on a null object reference at com.example.testmap12.OnscreenActivity$ParserTask.onPostExecute(OnscreenActivity.java:138) at com.example.testmap12.OnscreenActivity$ParserTask.onPostExecute(OnscreenActivity.java:1) at android.os.AsyncTask.finish(AsyncTask.java:632) at android.os.AsyncTask.access$600(AsyncTask.java:177) at android.os.AsyncTask$InternalHandler.handleMessage(AsyncTask.java:645) — Heman Parbhakar, Jul 14 '15 at 11:35
You have a List which is null. That means it does not exist. You cannot ask the size of something that does not exist, that would result in a NullPointer, as you can see. Make sure it is not null. — Manu, Jul 14 '15 at 11:42
@HemanParbhakar: stop with collections, and start learning the basics. — Stultuske, Jul 14 '15 at 11:44

score 0 · Answer 1 · answered Jul 14 '15 at 11:56

It is impossible for us to tell you exactly why the routes List is null in your onPostExecute in the ParserTask, but it is.

If it is intended that your doInBackground in ParserTask can return null, you should at least check if the routes variable is null before you attempt to do anything with it. This will not fix the error and might result in your app not doing what it should, but as I mentioned previously, it's impossible to tell you any more without the full log.

if (routes == null) return; will suppress the error, but only solve your problem if you read multiple json files and some of them actually parse.

java.lang.nullpointerexception attempt to invoke method 'int java.util.List.size()'

1 Answers1