Cannot get location from async task

Question

I used async task for upload image in the background thread to show a progress dialog. But while getting a location from async task, it throws the following error:

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

Although it is work without an async task. I want that process of getting location done in a background thread so that main thread can work without disturbance.

I got error in GPSlocater.java at locationmanager.requestLocationUpdates() while calling from async task.

So what should I do?

This is onLocate function which calls from mainActivity.java

public void onLocate(View view) {

    asyncG asyncG1 = new asyncG(this);
    asyncG1.execute();
}

This is a sub class which created in mainActivity.java

class asyncG extends AsyncTask
{
    Context context;
    ProgressDialog progressDialog;

    public asyncG(MainActivity mainActivity) {
        this.context = mainActivity;
    }

    @Override
    protected Object doInBackground(Object[] objects) {



        GPSlocater gpSlocater = new GPSlocater(context);
        gpSlocater.getLocation();

        lat = gpSlocater.getLatitude();
        longi = gpSlocater.getLongitude();




        return null;
    }



    @Override
    protected void onPreExecute() {
        super.onPreExecute();

        progressDialog = new ProgressDialog(context);
        progressDialog.setMessage("Finding Location");
        progressDialog.show();

    }

    @Override
    protected void onPostExecute(Object o) {
        super.onPostExecute(o);

        progressDialog.dismiss();
        Geocoder geocoder = new Geocoder(context, Locale.getDefault());
        try {
            List<Address> arr;
            arr = geocoder.getFromLocation(lat,longi,1);
            String pincode = arr.get(0).getPostalCode();
            String stat = arr.get(0).getAdminArea();
            String city1 = arr.get(0).getLocality();
            String city2 = arr.get(0).getSubAdminArea();
            String area1 = arr.get(0).getSubLocality();
            String area2 = arr.get(0).getLocality();

            if(pincode!=null && stat!=null)
            {
                state.setText(stat);
                pin.setText(pincode);
            }

            if(city1!=null)
            {
                city.setText(city1);
            }
            else if(city2!=null)
            {
                city.setText(city2);
            }

            if(area1!=null)
            {
                area.setText(area1);
            }
            else if(area2!=null)
            {
                area.setText(area2);
            }


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



    }
}

This is GPSlocater class which called from doInBackground

    package com.example.samarth.serviceprovider1;
import android.app.AlertDialog;
import android.app.ProgressDialog;
import android.app.Service;
import android.content.Context;
import android.content.DialogInterface;
import android.content.Intent;
import android.location.Location;
import android.location.LocationListener;
import android.location.LocationManager;
import android.os.AsyncTask;
import android.os.Bundle;
import android.os.IBinder;
import android.provider.Settings;
import android.util.Log;

public class GPSlocater 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 GPSlocater(Context context) {
        this.mContext = context;


    }

    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
                showSettingsAlert();
            } else {
                this.canGetLocation = true;
                // First get location from Network Provider
                if (isNetworkEnabled) {
                    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(GPSlocater.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;
    }

}

Answer 1

you need to create a handler to access UI elements from a thread. https://developer.android.com/training/multiple-threads/communicate-ui.html This tutorial should get you going, good luck (: