Android Google Map how to check if the gps location is inside the circle

Question

I'm trying to detect if a user is in the radius of a Marker , using the users gps location. I have the marker's coordinates, but I don't know how to calculate whether the user is in the area. I've tried to use the following, but even when the current location is inside the circle I keep getting the "outside" message.

public class MapaEscola extends FragmentActivity {

    private GoogleMap googleMap;
    private Serializable escolas;
    private ProgressDialog dialog;
    private Circle mCircle;
    private Marker mMarker;



    @TargetApi(Build.VERSION_CODES.ICE_CREAM_SANDWICH)
    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);

        getActionBar().setDisplayHomeAsUpEnabled(true);
        getActionBar().setHomeButtonEnabled(true);

        setContentView(R.layout.maps);

        // Loading map
        initilizeMap();

        // Changing map type
        googleMap.setMapType(GoogleMap.MAP_TYPE_NORMAL);

        // Showing / hiding your current location
        googleMap.setMyLocationEnabled(true);

        // Enable / Disable zooming controls
        googleMap.getUiSettings().setZoomControlsEnabled(true);

        // Enable / Disable my location button
        googleMap.getUiSettings().setMyLocationButtonEnabled(true);

        // Enable / Disable Compass icon
        googleMap.getUiSettings().setCompassEnabled(true);

        // Enable / Disable Rotate gesture
        googleMap.getUiSettings().setRotateGesturesEnabled(true);

        // Enable / Disable zooming functionality
        googleMap.getUiSettings().setZoomGesturesEnabled(true);

        Bundle extra = getIntent().getBundleExtra("extra");
        ArrayList<Escolas> objects = (ArrayList<Escolas>) extra.getSerializable("array");


        try {

            for(int i = 0; i < objects.size(); i ++) {
                System.out.println(" escolas " + objects.get(i).getLatitude() + " " + objects.get(i).getLongitude());

                float latitude = objects.get(i).getLatitude();
                float longitude = objects.get(i).getLongitude();

                googleMap.moveCamera(CameraUpdateFactory.newLatLngZoom(new LatLng(-23.316281, -51.155528), 15));

                MarkerOptions options = new MarkerOptions();

                // Setting the position of the marker

                options.position(new LatLng(latitude, longitude));

                googleMap = ((MapFragment) getFragmentManager().findFragmentById(R.id.map)).getMap();

                LatLng latLng = new LatLng(latitude, longitude);
                drawMarkerWithCircle(latLng);


                googleMap.setOnMyLocationChangeListener(new GoogleMap.OnMyLocationChangeListener() {
                    @Override
                    public void onMyLocationChange(Location location) {
                        float[] distance = new float[2];

                        Location.distanceBetween( mMarker.getPosition().latitude, mMarker.getPosition().longitude,
                                mCircle.getCenter().latitude, mCircle.getCenter().longitude, distance);

                        if( distance[0] > (mCircle.getRadius() / 2)  ){
                            Toast.makeText(getBaseContext(), "Outside", Toast.LENGTH_LONG).show();
                        } else {
                            Toast.makeText(getBaseContext(), "Inside", Toast.LENGTH_LONG).show();
                        }

                    }
                });




            }



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


    private void drawMarkerWithCircle(LatLng position){
        double radiusInMeters = 500.0;
        int strokeColor = 0xffff0000; //red outline
        int shadeColor = 0x44ff0000; //opaque red fill

        CircleOptions circleOptions = new CircleOptions().center(position).radius(radiusInMeters).fillColor(shadeColor).strokeColor(strokeColor).strokeWidth(8);
        mCircle = googleMap.addCircle(circleOptions);

        MarkerOptions markerOptions = new MarkerOptions().position(position);
        mMarker = googleMap.addMarker(markerOptions);
    }



    private void initilizeMap() {

        if (googleMap == null) {
            googleMap = ((MapFragment) getFragmentManager().findFragmentById(
                    R.id.map)).getMap();

            // check if map is created successfully or not
            if (googleMap == null) {
                Toast.makeText(getApplicationContext(),
                        "Não foi possível carregar o mapa", Toast.LENGTH_SHORT)
                        .show();
            }
        }
    }

    @TargetApi(Build.VERSION_CODES.HONEYCOMB)
    @Override
    public void onBackPressed() {

        super.onBackPressed();
        finish();

    }

    @Override
    public boolean onCreateOptionsMenu(Menu menu) {
        // TODO Auto-generated method stub
        MenuInflater inflater = getMenuInflater();
        inflater.inflate(R.menu.menu_main, menu);

        return super.onCreateOptionsMenu(menu);
    }

    @TargetApi(Build.VERSION_CODES.HONEYCOMB)
    public boolean onOptionsItemSelected(MenuItem item) {


        switch (item.getItemId()) {

            case android.R.id.home:
                super.onBackPressed();
                finish();

                return true;


        }

        return true;

    }

    @Override
    protected void onResume() {
        super.onResume();
        initilizeMap();
    }


}

Answer 1

@Daniel Nugent: imho getRadius() will return the radius and not the diameter so the "/2" is wrong

@WARpoluido: I cant see that the mMarker variable is updated when the location changes. Why dont you use the value given to onMyLocationChange()?

Location.distanceBetween( mCircle.getCenter().latitude, mCircle.getCenter().longitude, location.getLatitude(), location.getLongitude(), distance);
if( distance[0] > mCircle.getRadius() ){
...

Answer 2

I just ran the updated code and figured out what the main problem is.

You should be using the Location passed into the onMyLocationChange() callback, so that it uses your current location to tell if the device is within the circle or not:

googleMap.setOnMyLocationChangeListener(new GoogleMap.OnMyLocationChangeListener() {
                @Override
                public void onMyLocationChange(Location location) {
                    float[] distance = new float[2];

                    /*
                    Location.distanceBetween( mMarker.getPosition().latitude, mMarker.getPosition().longitude,
                            mCircle.getCenter().latitude, mCircle.getCenter().longitude, distance);
                            */

                    Location.distanceBetween( location.getLatitude(), location.getLongitude(),
                            mCircle.getCenter().latitude, mCircle.getCenter().longitude, distance);

                    if( distance[0] > mCircle.getRadius() ){
                        Toast.makeText(getBaseContext(), "Outside, distance from center: " + distance[0] + " radius: " + mCircle.getRadius(), Toast.LENGTH_LONG).show();
                    } else {
                        Toast.makeText(getBaseContext(), "Inside, distance from center: " + distance[0] + " radius: " + mCircle.getRadius() , Toast.LENGTH_LONG).show();
                    }

                }
            });

Here is the full working example that I ran, it's a pared down version of your original code:

public class MainActivity extends ActionBarActivity {

    private GoogleMap googleMap;
    private Serializable escolas;
    private ProgressDialog dialog;
    private Circle mCircle;
    private Marker mMarker;



    @TargetApi(Build.VERSION_CODES.ICE_CREAM_SANDWICH)
    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);

        getSupportActionBar().setDisplayHomeAsUpEnabled(true);
        getSupportActionBar().setHomeButtonEnabled(true);

        setContentView(R.layout.activity_main);

        // Loading map
        initilizeMap();

        // Changing map type
        googleMap.setMapType(GoogleMap.MAP_TYPE_NORMAL);

        // Showing / hiding your current location
        googleMap.setMyLocationEnabled(true);

        // Enable / Disable zooming controls
        googleMap.getUiSettings().setZoomControlsEnabled(true);

        // Enable / Disable my location button
        googleMap.getUiSettings().setMyLocationButtonEnabled(true);

        // Enable / Disable Compass icon
        googleMap.getUiSettings().setCompassEnabled(true);

        // Enable / Disable Rotate gesture
        googleMap.getUiSettings().setRotateGesturesEnabled(true);

        // Enable / Disable zooming functionality
        googleMap.getUiSettings().setZoomGesturesEnabled(true);

       // Bundle extra = getIntent().getBundleExtra("extra");
        //ArrayList<Escolas> objects = (ArrayList<Escolas>) extra.getSerializable("array");


        try {
               //test outside
               double mLatitude = 37.77657;
               double mLongitude = -122.417506;


                //test inside
                //double mLatitude = 37.7795516;
                //double mLongitude = -122.39292;


                googleMap.moveCamera(CameraUpdateFactory.newLatLngZoom(new LatLng(mLatitude, mLongitude), 15));

                MarkerOptions options = new MarkerOptions();

                // Setting the position of the marker

                options.position(new LatLng(mLatitude, mLongitude));

                //googleMap = ((SupportMapFragment) getSupportFragmentManager().findFragmentById(R.id.map)).getMap();

                LatLng latLng = new LatLng(mLatitude, mLongitude);
                drawMarkerWithCircle(latLng);


                googleMap.setOnMyLocationChangeListener(new GoogleMap.OnMyLocationChangeListener() {
                    @Override
                    public void onMyLocationChange(Location location) {
                        float[] distance = new float[2];

                        /*
                        Location.distanceBetween( mMarker.getPosition().latitude, mMarker.getPosition().longitude,
                                mCircle.getCenter().latitude, mCircle.getCenter().longitude, distance);
                                */

                        Location.distanceBetween( location.getLatitude(), location.getLongitude(),
                                mCircle.getCenter().latitude, mCircle.getCenter().longitude, distance);

                        if( distance[0] > mCircle.getRadius()  ){
                            Toast.makeText(getBaseContext(), "Outside, distance from center: " + distance[0] + " radius: " + mCircle.getRadius(), Toast.LENGTH_LONG).show();
                        } else {
                            Toast.makeText(getBaseContext(), "Inside, distance from center: " + distance[0] + " radius: " + mCircle.getRadius() , Toast.LENGTH_LONG).show();
                        }

                    }
                });




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


    private void drawMarkerWithCircle(LatLng position){
        double radiusInMeters = 500.0;
        int strokeColor = 0xffff0000; //red outline
        int shadeColor = 0x44ff0000; //opaque red fill

        CircleOptions circleOptions = new CircleOptions().center(position).radius(radiusInMeters).fillColor(shadeColor).strokeColor(strokeColor).strokeWidth(8);
        mCircle = googleMap.addCircle(circleOptions);

        MarkerOptions markerOptions = new MarkerOptions().position(position);
        mMarker = googleMap.addMarker(markerOptions);
    }



    private void initilizeMap() {

        if (googleMap == null) {
            googleMap = ((SupportMapFragment) getSupportFragmentManager().findFragmentById(
                    R.id.map)).getMap();

            // check if map is created successfully or not
            if (googleMap == null) {
                Toast.makeText(getApplicationContext(),
                        "Não foi possível carregar o mapa", Toast.LENGTH_SHORT)
                        .show();
            }
        }
    }

    @TargetApi(Build.VERSION_CODES.HONEYCOMB)
    @Override
    public void onBackPressed() {

        super.onBackPressed();
        finish();

    }

    @Override
    public boolean onCreateOptionsMenu(Menu menu) {
        // TODO Auto-generated method stub
        MenuInflater inflater = getMenuInflater();
        inflater.inflate(R.menu.menu_main, menu);

        return super.onCreateOptionsMenu(menu);
    }

    @TargetApi(Build.VERSION_CODES.HONEYCOMB)
    public boolean onOptionsItemSelected(MenuItem item) {


        switch (item.getItemId()) {

            case android.R.id.home:
                super.onBackPressed();
                finish();

                return true;


        }

        return true;

    }

    @Override
    protected void onResume() {
        super.onResume();
        initilizeMap();
    }


}

Results of Inside the circle:

Results of outside the circle: