multiple markers on user location Android

Question

i want to delete a marker that it keeps multiplying because of the location Changed i've tried map.clear() but it also erases the polyline that i drew and marker.remove but it stops showing, i also want to implement another marker that shows me a GPS location and get the distance between those markers, does anyone know how i can do that? Thank you!

This is my code

package com.example.alejandro.integradora2;

import android.Manifest;
import android.content.pm.PackageManager;
import android.graphics.Color;
import android.location.Location;
import android.os.Bundle;
import android.support.v4.app.ActivityCompat;
import android.support.v7.app.AppCompatActivity;

import com.google.android.gms.maps.CameraUpdateFactory;
import com.google.android.gms.maps.GoogleMap;
import com.google.android.gms.maps.OnMapReadyCallback;
import com.google.android.gms.maps.SupportMapFragment;
import com.google.android.gms.maps.model.BitmapDescriptorFactory;
import com.google.android.gms.maps.model.LatLng;
import com.google.android.gms.maps.model.Marker;
import com.google.android.gms.maps.model.MarkerOptions;
import com.google.android.gms.maps.model.Polyline;
import com.google.android.gms.maps.model.PolylineOptions;

public class Route extends AppCompatActivity implements OnMapReadyCallback {

    public GoogleMap mMap;
    Marker marker;
    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_maps);

        SupportMapFragment mapFragment = (SupportMapFragment) getSupportFragmentManager()
                .findFragmentById(R.id.map);
        mapFragment.getMapAsync(this);
        setUpMapIfNeeded();

    }
//here is the marker that keeps multiplying
    private void setUpMapIfNeeded() {
        // Do a null check to confirm that we have not already instantiated the map.
        if (mMap == null) {
            // Try to obtain the map from the SupportMapFragment.
            mMap = ((SupportMapFragment) getSupportFragmentManager().findFragmentById(R.id.map))
                    .getMap();
            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;
            }
            mMap.setMyLocationEnabled(true);

            // Check if we were successful in obtaining the map.
            if (mMap != null) {


                mMap.setOnMyLocationChangeListener(new GoogleMap.OnMyLocationChangeListener() {

                    @Override
                    public void onMyLocationChange(Location arg0) {
                        // TODO Auto-generated method stub

                     marker= mMap.addMarker(new MarkerOptions().position(new LatLng(arg0.getLatitude(), arg0.getLongitude())).title("Tu Ubicacion Actual"));

                    }
                });

            }
        }
    }

    public void onMapReady(GoogleMap map) {
        map=mMap;

        // Add a marker in Sydney and move the camera
        LatLng inicio = new LatLng(23.979804, -104.641936);
        LatLng fin = new LatLng(24.024227, -104.664647);
        mMap.addMarker(new MarkerOptions().position(inicio).title("Inicio Ruta").icon(BitmapDescriptorFactory.defaultMarker(BitmapDescriptorFactory.HUE_BLUE)));
        mMap.addMarker(new MarkerOptions().position(fin).title("Fin Ruta"));
        //mMap.animateCamera(CameraUpdateFactory.zoomTo(10));

        mMap.moveCamera(CameraUpdateFactory.newLatLngZoom(new LatLng(23.979804, -104.641936), 12));

        PolylineOptions RutaIda = new PolylineOptions()
                .add(new LatLng(23.979804, -104.641936),new LatLng(23.986028, -104.663826),new LatLng(23.986337, -104.664357),new LatLng(23.996928, -104.662372),new LatLng(23.997051, -104.662469),
                        new LatLng(23.998414, -104.662179),new LatLng(24.007054, -104.662335),new LatLng(24.008568, -104.662292),new LatLng(24.015409, -104.663338),new LatLng(24.017710, -104.663729),
                        new LatLng(24.019288, -104.664051),new LatLng(24.023110, -104.663981),new LatLng(24.024296, -104.664153),new LatLng(24.024227, -104.664647)
                        )
                .width(5)
                .color(Color.RED);
        Polyline polyline = mMap.addPolyline(RutaIda);

        PolylineOptions RutaVuelta = new PolylineOptions()
                .add(new LatLng(24.024227, -104.664647),new LatLng(24.023497, -104.669067),new LatLng(24.021361, -104.668826),new LatLng(24.021430, -104.668161),new LatLng(24.019950, -104.667893),
                        new LatLng(24.019666, -104.665200),new LatLng(24.019490, -104.664937),new LatLng(24.019431, -104.664524),new LatLng(24.018319, -104.664030),new LatLng(24.016864, -104.664062),
                        new LatLng(24.015170, -104.663458),new LatLng(24.008048, -104.662445),new LatLng(23.998369, -104.662447),new LatLng(23.993684, -104.663177),new LatLng(23.986396, -104.664572),
                        new LatLng(23.986318, -104.664277),new LatLng(23.986053, -104.663848),new LatLng(23.979804, -104.641936))
                .width(8)
                .color(Color.parseColor("#802E2EFE"));
        //.color(Color.BLUE);





        Polyline polylinevenida = mMap.addPolyline(RutaVuelta);

    }





}

Answer 1

For preventing the current location Marker from being duplicated, just call remove() on the Marker reference if it's not null each time a new Location comes in:

@Override
public void onMyLocationChange(Location arg0) {
        //Add this:
        if (marker != null) {
            marker.remove();
        }

        marker= mMap.addMarker(new MarkerOptions().position(new LatLng(arg0.getLatitude(), arg0.getLongitude())).title("Tu Ubicacion Actual"));

}

Please note though that using the GoogleMap location listener is deprecated, so you should switch to using the FusedLocationProviderAPI, see here for a complete example.

As for getting the distance between two markers, you can use the Location.distanceBetween() method.

If you have two Markers:

Marker marker1;
Marker marker2;

Here is how you can get the distance between them:

LatLng latLng1 = marker1.getPosition();
LatLng latLng2 = marker2.getPosition();

float[] distance = new float[2];

Location.distanceBetween( latLng1.latitude, latLng1.longitude,
        latLng2.latitude, latLng2.longitude, distance);

if( distance[0] < 100 ){
    // do something if distance between
    // is less than 100 meters
}