GPS Tracker FATAL EXCEPTION

Question

I have got a small problem withe my code , am try to get the latitude and longitude for my location , to get weather information data json from wunderground api useing volley .

my MainActivity class :

package imo.meteoiraq;

import android.app.AlarmManager;
import android.app.PendingIntent;
import android.app.ProgressDialog;
import android.content.Intent;
import android.icu.text.DateFormat;
import android.icu.text.SimpleDateFormat;
import android.icu.util.Calendar;
import android.os.Build;
import android.os.Bundle;
import android.os.Handler;
import android.support.annotation.RequiresApi;
import android.support.v7.app.AppCompatActivity;
import android.widget.TextView;
import android.widget.Toast;

import com.android.volley.Request;
import com.android.volley.RequestQueue;
import com.android.volley.Response;
import com.android.volley.VolleyError;
import com.android.volley.toolbox.JsonObjectRequest;
import com.android.volley.toolbox.Volley;

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

import java.util.Date;

public class MainActivity extends AppCompatActivity {
    RequestQueue rq;
    TextView timeDesc,windspeedDesc;
    String wind;
    GPSTracker gps;
     double latitude = gps.getLatitude();
     double longitude = gps.getLongitude();

    String url = "http://api.wunderground.com/api/xxxxxxx/conditions/hourly/forecast10day/geolookup/q/"+latitude+","+longitude+".json";
    @RequiresApi(api = Build.VERSION_CODES.N)
    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        gps = new GPSTracker(MainActivity.this);

        // check if GPS enabled
        if(gps.canGetLocation()){

            double latitude = gps.getLatitude();
            double longitude = gps.getLongitude();

            // \n is for new line
            Toast.makeText(getApplicationContext(), "Your Location is - \nLat: " + latitude + "\nLong: " + longitude, Toast.LENGTH_LONG).show();
        }else{
            // can't get location
            // GPS or Network is not enabled
            // Ask user to enable GPS/network in settings
            gps.showSettingsAlert();
        }
        rq = Volley.newRequestQueue(this);

        windspeedDesc = (TextView) findViewById(R.id.timeupdateDesc);


        sendjsonrequest();



    }
    public void sendjsonrequest() {
        JsonObjectRequest jsonObjectRequest = new JsonObjectRequest(Request.Method.GET, url, null, new Response.Listener<JSONObject>() {
            @RequiresApi(api = Build.VERSION_CODES.N)
            @Override
            public void onResponse(JSONObject response) {
                try {

                    JSONObject stationsJO = response.getJSONObject("response");
                    JSONArray array = stationsJO.optJSONArray("days");

                    wind= stationsJO.getString("version");
                    windspeedDesc.setText(wind);



                } catch (JSONException e) {
                    e.printStackTrace();
                }
            }
        }, new Response.ErrorListener() {
            @Override
            public void onErrorResponse(VolleyError error) {
            }
        });
        rq.add(jsonObjectRequest);

    }


}

GPSTracker class :

package imo.meteoiraq;

import android.Manifest;
import android.app.AlertDialog;
import android.app.Service;
import android.content.Context;
import android.content.DialogInterface;
import android.content.Intent;
import android.content.pm.PackageManager;
import android.location.Location;
import android.location.LocationListener;
import android.location.LocationManager;
import android.os.Bundle;
import android.os.IBinder;
import android.provider.Settings;
import android.support.v4.app.ActivityCompat;
import android.util.Log;

public class GPSTracker extends Service implements LocationListener {

    private final Context mContext;

    // flag for GPS status
    boolean isGPSEnabled = false;

    // flag for network status
    boolean isNetworkEnabled = false;

    // flag for GPS status
    boolean canGetLocation = false;

    Location location; // location
    double latitude; // latitude
    double longitude; // longitude

    // The minimum distance to change Updates in meters
    private static final long MIN_DISTANCE_CHANGE_FOR_UPDATES = 10; // 10 meters

    // The minimum time between updates in milliseconds
    private static final long MIN_TIME_BW_UPDATES = 1000 * 60 * 1; // 1 minute

    // Declaring a Location Manager
    protected LocationManager locationManager;

    public GPSTracker(Context context) {
        this.mContext = context;
        getLocation();
    }

    public Location getLocation() {
        try {
            locationManager = (LocationManager) mContext
                    .getSystemService(LOCATION_SERVICE);

            // getting GPS status
            isGPSEnabled = locationManager
                    .isProviderEnabled(LocationManager.GPS_PROVIDER);

            // getting network status
            isNetworkEnabled = locationManager
                    .isProviderEnabled(LocationManager.NETWORK_PROVIDER);

            if (!isGPSEnabled && !isNetworkEnabled) {
                // no network provider is enabled
            } else {
                this.canGetLocation = true;
                // First get location from Network Provider
                if (isNetworkEnabled) {
                    if (ActivityCompat.checkSelfPermission(this, Manifest.permission.ACCESS_FINE_LOCATION) != PackageManager.PERMISSION_GRANTED && ActivityCompat.checkSelfPermission(this, Manifest.permission.ACCESS_COARSE_LOCATION) != PackageManager.PERMISSION_GRANTED) {
                        // TODO: Consider calling
                        //    ActivityCompat#requestPermissions
                        // here to request the missing permissions, and then overriding
                        //   public void onRequestPermissionsResult(int requestCode, String[] permissions,
                        //                                          int[] grantResults)
                        // to handle the case where the user grants the permission. See the documentation
                        // for ActivityCompat#requestPermissions for more details.
                        return location;
                    }
                    locationManager.requestLocationUpdates(
                            LocationManager.NETWORK_PROVIDER,
                            MIN_TIME_BW_UPDATES,
                            MIN_DISTANCE_CHANGE_FOR_UPDATES, this);
                    Log.d("Network", "Network");
                    if (locationManager != null) {
                        location = locationManager
                                .getLastKnownLocation(LocationManager.NETWORK_PROVIDER);
                        if (location != null) {
                            latitude = location.getLatitude();
                            longitude = location.getLongitude();
                        }
                    }
                }
                // if GPS Enabled get lat/long using GPS Services
                if (isGPSEnabled) {
                    if (location == null) {
                        locationManager.requestLocationUpdates(
                                LocationManager.GPS_PROVIDER,
                                MIN_TIME_BW_UPDATES,
                                MIN_DISTANCE_CHANGE_FOR_UPDATES, this);
                        Log.d("GPS Enabled", "GPS Enabled");
                        if (locationManager != null) {
                            location = locationManager
                                    .getLastKnownLocation(LocationManager.GPS_PROVIDER);
                            if (location != null) {
                                latitude = location.getLatitude();
                                longitude = location.getLongitude();
                            }
                        }
                    }
                }
            }

        } catch (Exception e) {
            e.printStackTrace();
        }

        return location;
    }

    /**
     * Stop using GPS listener
     * Calling this function will stop using GPS in your app
     * */
    public void stopUsingGPS(){
        if(locationManager != null){
            locationManager.removeUpdates(GPSTracker.this);
        }
    }

    /**
     * Function to get latitude
     * */
    public double getLatitude(){
        if(location != null){
            latitude = location.getLatitude();
        }

        // return latitude
        return latitude;
    }

    /**
     * Function to get longitude
     * */
    public double getLongitude(){
        if(location != null){
            longitude = location.getLongitude();
        }

        // return longitude
        return longitude;
    }

    /**
     * Function to check GPS/wifi enabled
     * @return boolean
     * */
    public boolean canGetLocation() {
        return this.canGetLocation;
    }

    /**
     * Function to show settings alert dialog
     * On pressing Settings button will lauch Settings Options
     * */
    public void showSettingsAlert(){
        AlertDialog.Builder alertDialog = new AlertDialog.Builder(mContext);

        // Setting Dialog Title
        alertDialog.setTitle("GPS is settings");

        // Setting Dialog Message
        alertDialog.setMessage("GPS is not enabled. Do you want to go to settings menu?");

        // On pressing Settings button
        alertDialog.setPositiveButton("Settings", new DialogInterface.OnClickListener() {
            public void onClick(DialogInterface dialog,int which) {
                Intent intent = new Intent(Settings.ACTION_LOCATION_SOURCE_SETTINGS);
                mContext.startActivity(intent);
            }
        });

        // on pressing cancel button
        alertDialog.setNegativeButton("Cancel", new DialogInterface.OnClickListener() {
            public void onClick(DialogInterface dialog, int which) {
                dialog.cancel();
            }
        });

        // Showing Alert Message
        alertDialog.show();
    }

    @Override
    public void onLocationChanged(Location location) {
    }

    @Override
    public void onProviderDisabled(String provider) {
    }

    @Override
    public void onProviderEnabled(String provider) {
    }

    @Override
    public void onStatusChanged(String provider, int status, Bundle extras) {
    }

    @Override
    public IBinder onBind(Intent arg0) {
        return null;
    }

}

when i run app for test i get " app his Stop working "

FATAL EXCEPTION

09-12 23:44:07.803 27113-27113/imo.meteoiraq E/AndroidRuntime: FATAL EXCEPTION: main
                                                               Process: imo.meteoiraq, PID: 27113
                                                               java.lang.RuntimeException: Unable to instantiate activity ComponentInfo{imo.meteoiraq/imo.meteoiraq.MainActivity}: java.lang.NullPointerException: Attempt to invoke virtual method 'double imo.meteoiraq.GPSTracker.getLatitude()' on a null object reference
                                                                   at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2849)
                                                                   at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:3045)
                                                                   at android.app.ActivityThread.-wrap14(ActivityThread.java)
                                                                   at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1642)
                                                                   at android.os.Handler.dispatchMessage(Handler.java:102)
                                                                   at android.os.Looper.loop(Looper.java:154)
                                                                   at android.app.ActivityThread.main(ActivityThread.java:6776)
                                                                   at java.lang.reflect.Method.invoke(Native Method)
                                                                   at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:1496)
                                                                   at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:1386)
                                                                Caused by: java.lang.NullPointerException: Attempt to invoke virtual method 'double imo.meteoiraq.GPSTracker.getLatitude()' on a null object reference
                                                                   at imo.meteoiraq.MainActivity.<init>(MainActivity.java:36)
                                                                   at java.lang.Class.newInstance(Native Method)
                                                                   at android.app.Instrumentation.newActivity(Instrumentation.java:1086)
                                                                   at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2839)
                                                                   at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:3045) 
                                                                   at android.app.ActivityThread.-wrap14(ActivityThread.java) 
                                                                   at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1642) 
                                                                   at android.os.Handler.dispatchMessage(Handler.java:102) 
                                                                   at android.os.Looper.loop(Looper.java:154) 
                                                                   at android.app.ActivityThread.main(ActivityThread.java:6776) 
                                                                   at java.lang.reflect.Method.invoke(Native Method) 
                                                                   at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:1496) 
                                                                   at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:1386)

if i delete the code of GPSTRACKER , app working fine

Someboy care to help?

Possible duplicate of [What is a NullPointerException, and how do I fix it?](https://stackoverflow.com/questions/218384/what-is-a-nullpointerexception-and-how-do-i-fix-it) — Juan Cruz Soler, Sep 12 '17 at 21:30
Please minimize the amount of code and format it for better readability. — Quality Catalyst, Sep 13 '17 at 07:34

Juan Cruz Soler · Answer 1 · 2017-09-13T13:16:11.793

0

You are trying to call getLatitude before creating a GPSTracker object.
Remove these 3 class members:

double latitude = gps.getLatitude();
double longitude = gps.getLongitude();
String url = "http://api.wunderground.com/api/xxxxxxx/conditions/hourly/forecast10day/geolookup/q/"+latitude+","+longitude+".json";

And then in your onCreate you could do:

@Override
protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_main);

    windspeedDesc = (TextView) findViewById(R.id.timeupdateDesc);
    gps = new GPSTracker(MainActivity.this);

    if(gps.canGetLocation()){
        double latitude = gps.getLatitude();
        double longitude = gps.getLongitude();
        String url = "http://api.wunderground.com/api/xxxxxxx/conditions/hourly/forecast10day/geolookup/q/"+latitude+","+longitude+".json";

        Toast.makeText(getApplicationContext(), "Your Location is - \nLat: " + latitude + "\nLong: " + longitude, Toast.LENGTH_LONG).show();

        rq = Volley.newRequestQueue(this);
        sendjsonrequest(url); 
    } else {
        gps.showSettingsAlert();
    }
}

public void sendjsonrequest(String url) {
    //......
}

edited Sep 13 '17 at 13:16

answered Sep 12 '17 at 21:10

Juan Cruz Soler

8,172
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44

thanks for reply , what about the latitude and longitude in url ? i want get this things in url to get my location – aligassan Sep 12 '17 at 21:15
if i keep latitude and longitude just in onCreate , i get error red in ulr , check link https://b.top4top.net/p_620afe4x1.png – aligassan Sep 12 '17 at 21:21
same error ` Caused by: java.lang.NullPointerException: Attempt to invoke virtual method 'double imo.meteoiraq.GPSTracker.getLatitude()' on a null object reference` – aligassan Sep 12 '17 at 21:29
Unfortunately not helpful , check https://a.top4top.net/p_620waf3g1.png – aligassan Sep 12 '17 at 21:35
Add the url as a parameter: `sendjsonrequest(String url)`. You should read the IDE errors.. – Juan Cruz Soler Sep 13 '17 at 01:37
your code is working fine , but i get error location , Latitude and Longitude value 0,0 – aligassan Sep 13 '17 at 15:57
You should set the latitude when `onLocationChanged` is called, try to debug your code – Juan Cruz Soler Sep 13 '17 at 16:01
`09-13 18:33:46.798 11091-11236/? I/LocationFilter: Forcing stable location. Original location:Location[fused 33.236843,44.339216 acc=52 {Bundle[{wifiScan=[B@9e43969, noGPSLocation=Location[fused 33.236843,44.339216 acc=52 et=+11d21h19m28s131ms {Bundle[mParcelledData.dataSize=172]}], locationType=3}]}] because connected WiFi network is the same,` – aligassan Sep 13 '17 at 16:06

GPS Tracker FATAL EXCEPTION

1 Answers1