Question

I’m having problems properly displaying an alert in my Android app. The goal is to send GPS coordinates to a database, but first check to see if the user is in a defined area. If the user is outside of the area, I want to display the alert. I keep getting problems on the line AlertDialog.Builder alert = new AlertDialog.Builder(this); with the error The constructor AlertDialog.Builder(new LocationListener(){}) is undefined I asked a similar question previously, but the solutions did not work and I think it’s because I failed to include enough code. I’d appreciate any suggestions!

        import java.io.BufferedReader;

        public class FindLocation  {

        protected static final Context SendLocation = null;
        private LocationManager locManager;
        private LocationListener locListener;


        private class SendLocation extends AsyncTask<String, Void, String> {

            protected String doInBackground(String... params) {

                String lat = params[0];
                String lon = params[1];
                String usr_id2 = params[2];

                HttpClient httpclient = new DefaultHttpClient();
                HttpPost httppost = new HttpPost("http://example.com/example.php");

                try {
                       List<NameValuePair> nameValuePairs = new ArrayList<NameValuePair>(2);
                       nameValuePairs.add(new BasicNameValuePair("lat", lat)); 
                       nameValuePairs.add(new BasicNameValuePair("lon", lon));
                       nameValuePairs.add(new BasicNameValuePair("id", usr_id2));
                       httppost.setEntity(new UrlEncodedFormEntity(nameValuePairs));
                       httpclient.execute(httppost);
                 } 
                 catch (ClientProtocolException e) {
                     // TODO Auto-generated catch block
                 } 
                 catch (IOException e) {
                     // TODO Auto-generated catch block
                 }
                return lon; 
            }
        }
        public void startLocation(Context context, String usr_id2) { //changed context to final when AlertDialog was added

            final String usr = usr_id2;

            //get a reference to the LocationManager
            locManager = (LocationManager) context.getSystemService(Context.LOCATION_SERVICE);


            //checked to receive updates from the position
            locListener = new LocationListener() {
                public void onLocationChanged(Location loc) {

                    String lat = String.valueOf(loc.getLatitude()); 
                    String lon = String.valueOf(loc.getLongitude());

                    Double latitude = loc.getLatitude();
                    Double longitude = loc.getLongitude();

                    if (latitude >= 39.15296 && longitude >= -86.547546 && latitude <= 39.184901 && longitude <= -86.504288) {
                            Log.i("Test", "Yes");                           
                            CityActivity check = new CityActivity();
                            check.checkDataBase(usr);

                            SendLocation task = new SendLocation();
                            task.execute(lat, lon, usr);
                    }
                    else {
                        Log.i("Test", "No");
                        AlertDialog.Builder alert = new AlertDialog.Builder(this); //****error here*****
                        alert.setTitle("Warning");
                        alert.setMessage("Sorry");
                        alert.setPositiveButton("OK", new DialogInterface.OnClickListener() {
                           public void onClick(DialogInterface dialog, int which) {
                              // here you can add functions
                           }
                        });
                        alert.show();
                    }

                }
                public void onProviderDisabled(String provider){
                }
                public void onProviderEnabled(String provider){ 
                }
                public void onStatusChanged(String provider, int status, Bundle extras){
                    }
                };
                locManager.requestLocationUpdates(LocationManager.GPS_PROVIDER, 1000, 0, locListener);
            }

Answer 1

You are declaring your AlertDialog in the anonymous listener LocationListener. If you are trying to get a reference to the Context in the constructor by using this you’ll actually reference the LocationListener and not the Context of the Activity. Use your Activity name + this like ActivityName.this(if you are in an activity) or get a real reference to a Context.

EDIT:

In your FindLocation class make a constructor that takes a Context as a parameter like this:

//private field in your FindLocation class
Context ctx;

public FindLocation(Context ctx) {
     this.ctx = ctx;
}

Then in the Activity where you instantiate the FindLocation class just pass this(or ActivityName.this)

FindLocation obj = new FindLocation(this);

Then you could use the field ctx to pass in the constructor of the AlertDialog.