Question

Hello StackOverflow 🙂

I have created some code inside my onStart(); method to ensure that the user has GPS enabled so i can figure out in which country is he right now. If GPS is disabled, it should show an alert dialog prompting the user to enable GPS before using the app.

For some reason, it seems like that whole chunk of code isn’t working. I have disabled GPS and nothing is happening, no dialog and nothing like that. Why is this happening?

Here is my code:

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

    LocationManager locationManager =
            (LocationManager) getSystemService(Context.LOCATION_SERVICE);
    final boolean gpsEnabled = locationManager.isProviderEnabled(LocationManager.GPS_PROVIDER);

    Location loc = locationManager.getLastKnownLocation(LocationManager.GPS_PROVIDER);
    Geocoder code = new Geocoder(TipCalculatorActivity.this);
    try {
        Address adr = (Address) code.getFromLocation(loc.getLatitude(), loc.getLongitude(), 1);
        CountryName = adr.getCountryCode();
    } catch (IOException e) {
        // TODO Auto-generated catch block
        e.printStackTrace();
    }

    if (!gpsEnabled) {
        AlertDialog.Builder builder = new AlertDialog.Builder(this);
        builder.setMessage("This application requires GPS connectivity to determine your current country, and deliver you accurate tip ratings. Do you wish to turn GPS on?")
               .setCancelable(false)
               .setPositiveButton("Yes", new DialogInterface.OnClickListener() {
                   public void onClick(DialogInterface dialog, int id) {
                        TipCalculatorActivity.this.enableLocationSettings();
                   }
               })
               .setNegativeButton("No", new DialogInterface.OnClickListener() {
                   public void onClick(DialogInterface dialog, int id) {
                        dialog.cancel();
                        TipCalculatorActivity.this.finish();
                        System.exit(1);
                   }
               });
        AlertDialog alert = builder.create();
        alert.show();
    }
}

private void enableLocationSettings() {
    Intent settingsIntent = new Intent(Settings.ACTION_LOCATION_SOURCE_SETTINGS);
    startActivity(settingsIntent);
}

Thanks a lot for any help 🙂

Answer 1

Location loc = locationManager
.getLastKnownLocation(LocationManager.GPS_PROVIDER);

Is may be returning null in your case since your mobile has no cached locations.

So change your code to

if (loc != null) {
    Geocoder code = new Geocoder(AbcActivity.this);
    try {
        Address adr = (Address) code.getFromLocation(loc.getLatitude(), loc.getLongitude(), 1);
        // CountryName = adr.getCountryCode();
    } catch (IOException e) {
        // TODO Auto-generated catch block
        e.printStackTrace();
    }
}

If you need to query current Location.Then you need to have active Data connection or GPS turned on.
Following Snippet will help you

import android.app.Activity;
import android.content.Context;
import android.location.Criteria;
import android.location.Location;
import android.location.LocationListener;
import android.location.LocationManager;
import android.os.Bundle;
import android.widget.TextView;
import android.widget.Toast;

public class ShowLocationActivity extends Activity implements LocationListener {
    private TextView latituteField;
    private TextView longitudeField;
    private LocationManager locationManager;
    private String provider;


/** Called when the activity is first created. */

    @Override
    public void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.main);
        latituteField = (TextView) findViewById(R.id.TextView02);
        longitudeField = (TextView) findViewById(R.id.TextView04);

        // Get the location manager
        locationManager = (LocationManager) getSystemService(Context.LOCATION_SERVICE);
        // Define the criteria how to select the locatioin provider -> use
        // default
        Criteria criteria = new Criteria();
        provider = locationManager.getBestProvider(criteria, false);
        Location location = locationManager.getLastKnownLocation(provider);

        // Initialize the location fields
        if (location != null) {
            System.out.println("Provider " + provider + " has been selected.");
            int lat = (int) (location.getLatitude());
            int lng = (int) (location.getLongitude());
            latituteField.setText(String.valueOf(lat));
            longitudeField.setText(String.valueOf(lng));
        } else {
            latituteField.setText("Provider not available");
            longitudeField.setText("Provider not available");
        }
    }

    /* Request updates at startup */
    @Override
    protected void onResume() {
        super.onResume();
        locationManager.requestLocationUpdates(provider, 400, 1, this);
    }

    /* Remove the locationlistener updates when Activity is paused */
    @Override
    protected void onPause() {
        super.onPause();
        locationManager.removeUpdates(this);
    }

    @Override
    public void onLocationChanged(Location location) {
        int lat = (int) (location.getLatitude());
        int lng = (int) (location.getLongitude());
        latituteField.setText(String.valueOf(lat));
        longitudeField.setText(String.valueOf(lng));
    }

    @Override
    public void onStatusChanged(String provider, int status, Bundle extras) {
        // TODO Auto-generated method stub

    }

    @Override
    public void onProviderEnabled(String provider) {
        Toast.makeText(this, "Enabled new provider " + provider,
                Toast.LENGTH_SHORT).show();

    }

    @Override
    public void onProviderDisabled(String provider) {
        Toast.makeText(this, "Disabled provider " + provider,
                Toast.LENGTH_SHORT).show();
    }
}

Finally make sure you have added following permissions.

< uses - permission android: name = "android.permission.ACCESS_FINE_LOCATION" / > 
< uses - permission android: name = "android.permission.ACCESS_COARSE_LOCATION" / >