Store Android user location in Firebase database and display it on map using Geofire

Question

I have created an Android app that has a user login and registration linked to my Firebase database.

I am trying to use Geofire to store and display the users that are logged in on a map, I have used the SF vehicle example and if I'm honest I don't understand it that much. I have used the exact same code to test and see if it worked and I get the error in the image provided.

I am looking for help with writing a function to detect the logged in user's location and display it on the map in real-time, updating as the user moves, I am stuck on this weeks now and have tried all there is out there (which is not a lot).

Some help would be greatly appreciated, any further information needed just ask.

This is the code from the SF Vehicle example that I am using, the original is connected to the San Fransisco bus department and displaying them, so i need the code to write the location to my database and display them in the same way.

package nixer.nixer;

import android.app.AlertDialog;
import android.app.Fragment;
import android.content.Intent;
import android.graphics.Color;
import android.os.Bundle;
import android.os.Handler;
import android.os.SystemClock;
import android.support.v4.app.FragmentActivity;
import android.support.v7.app.AppCompatActivity;
import android.support.v7.widget.Toolbar;
import android.view.Menu;
import android.view.MenuItem;
import android.view.animation.AccelerateDecelerateInterpolator;
import android.view.animation.Interpolator;
import com.firebase.client.Firebase;
import com.firebase.client.FirebaseError;
import com.firebase.geofire.GeoFire;
import com.firebase.geofire.GeoLocation;
import com.firebase.geofire.GeoQuery;
import com.firebase.geofire.GeoQueryEventListener;
import com.firebase.geofire.LocationCallback;
import com.google.android.gms.maps.CameraUpdateFactory;
import com.google.android.gms.maps.GoogleMap;
import com.google.android.gms.maps.SupportMapFragment;
import com.google.android.gms.maps.model.*;
import java.util.HashMap;
import java.util.Map;


public class MapActivity extends AppCompatActivity implements   GeoQueryEventListener, GoogleMap.OnCameraChangeListener {

private Firebase mRef;
private String mUserId;
private String itemsUrl;
private static final GeoLocation INITIAL_CENTER = new GeoLocation(53.349805,  -6.260309 );
private static final int INITIAL_ZOOM_LEVEL = 14;
private static final String GEO_FIRE_REF = "https://nixer.firebaseio.com/";
private GoogleMap map;
private Circle searchCircle;
private GeoFire geoFire;
private GeoQuery geoQuery;

private Map<String,Marker> markers;

@Override
protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_map);
    Toolbar toolbar = (Toolbar) findViewById(R.id.toolbar);
    setSupportActionBar(toolbar);

    // setup map and camera position
    SupportMapFragment mapFragment =  (SupportMapFragment)getSupportFragmentManager().findFragmentById(R.id.map);
    this.map = mapFragment.getMap();
    LatLng latLngCenter = new LatLng(INITIAL_CENTER.latitude,  INITIAL_CENTER.longitude);
    this.searchCircle = this.map.addCircle(new CircleOptions().center(latLngCenter).radius(1000));
    this.searchCircle.setFillColor(Color.argb(66, 255, 0, 255));
    this.searchCircle.setStrokeColor(Color.argb(66, 0, 0, 0));
     this.map.moveCamera(CameraUpdateFactory.newLatLngZoom(latLngCenter,   INITIAL_ZOOM_LEVEL));
    this.map.setOnCameraChangeListener(this);

    Firebase.setAndroidContext(this);

    // setup GeoFire
    this.geoFire = new GeoFire(new Firebase(GEO_FIRE_REF));
    // radius in km
    this.geoQuery = this.geoFire.queryAtLocation(INITIAL_CENTER, 1);

    // setup markers
    this.markers = new HashMap<String, Marker>();       




    // Check Authentication
    mRef = new Firebase(Constants.FIREBASE_URL);
    if (mRef.getAuth() == null) {
        loadLoginView();
    }


    try {
        mUserId = mRef.getAuth().getUid();
    } catch (Exception e) {
        loadLoginView();
    }

}




@Override
protected void onStop() {
    super.onStop();
    // remove all event listeners to stop updating in the background
    this.geoQuery.removeAllListeners();
    for (Marker marker: this.markers.values()) {
        marker.remove();
    }
    this.markers.clear();
}

@Override
protected void onStart() {
    super.onStart();
    // add an event listener to start updating locations again
    this.geoQuery.addGeoQueryEventListener(this);
}

@Override
public void onKeyEntered(String key, GeoLocation location) {
    // Add a new marker to the map
    Marker marker = this.map.addMarker(new MarkerOptions().position(new   LatLng(location.latitude, location.longitude)));
    this.markers.put(key, marker);
}

@Override
public void onKeyExited(String key) {
    // Remove any old marker
    Marker marker = this.markers.get(key);
    if (marker != null) {
        marker.remove();
        this.markers.remove(key);
    }
}

@Override
public void onKeyMoved(String key, GeoLocation location) {
    // Move the marker
    Marker marker = this.markers.get(key);
    if (marker != null) {
        this.animateMarkerTo(marker, location.latitude, location.longitude);
    }
}

@Override
public void onGeoQueryReady() {
}

@Override
public void onGeoQueryError(FirebaseError error) {
    new AlertDialog.Builder(this)
            .setTitle("Error")
            .setMessage("There was an unexpected error querying GeoFire: " + error.getMessage())
            .setPositiveButton(android.R.string.ok, null)
            .setIcon(android.R.drawable.ic_dialog_alert)
            .show();
}

// Animation handler for old APIs without animation support
private void animateMarkerTo(final Marker marker, final double lat, final double lng) {
    final Handler handler = new Handler();
    final long start = SystemClock.uptimeMillis();
    final long DURATION_MS = 3000;
    final Interpolator interpolator = new AccelerateDecelerateInterpolator();
    final LatLng startPosition = marker.getPosition();
    handler.post(new Runnable() {
        @Override
        public void run() {
            float elapsed = SystemClock.uptimeMillis() - start;
            float t = elapsed/DURATION_MS;
            float v = interpolator.getInterpolation(t);

            double currentLat = (lat - startPosition.latitude) * v +   startPosition.latitude;
            double currentLng = (lng - startPosition.longitude) * v +   startPosition.longitude;
            marker.setPosition(new LatLng(currentLat, currentLng));

            // if animation is not finished yet, repeat
            if (t < 1) {
                handler.postDelayed(this, 16);
            }
        }
    });
}

private double zoomLevelToRadius(double zoomLevel) {
    // Approximation to fit circle into view
    return 16384000/Math.pow(2, zoomLevel);
}

@Override
public void onCameraChange(CameraPosition cameraPosition) {
    // Update the search criteria for this geoQuery and the circle on the map
    LatLng center = cameraPosition.target;
    double radius = zoomLevelToRadius(cameraPosition.zoom);
    this.searchCircle.setCenter(center);
    this.searchCircle.setRadius(radius);
    this.geoQuery.setCenter(new GeoLocation(center.latitude,  center.longitude));
    // radius in km
    this.geoQuery.setRadius(radius/1000);
}

Update:

Firebase rules :

{
"rules": {
  "users": {
    "$uid": {
      ".read": "auth != null && auth.uid == $uid",
      ".write": "auth != null && auth.uid == $uid",
      "items": {
        "$item_id": {
          "title": {
            ".validate": "newData.isString() && newData.val().length > 0"
            }
        }
      }
    }
  }

  }
}

Answer 1

{
    "rules": {
        "users": {
            "$uid": {
                ".read": true,
                ".write": true,
                "items": {
                    "$item_id": {
                        "title": {
                            ".validate": "newData.isString() && newData.val().length > 0"
                        }
                    }
                }
            }
        }
    }
}