Draw accuracy circle using MyLocationOverlay

Question

I am working on an Android application that shows a map with the user's location, and so far I am able to show the map online and offline. Now I want to know how I can draw an accuracy circle that appears with the marker in osmdroid using MylocationOverlay?

Here is my code:

public class AhmedActivity extends Activity 
{
    /** Called when the activity is first created. */
    private MapView mapView;
    private MapController mapController;
    private ScaleBarOverlay mScaleBarOverlay; 
    MyLocationOverlay myLocationOverlay = null;
    private LocationManager locationManager;

    @Override
    public void onCreate(Bundle savedInstanceState) 
    {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.main);

        // Initialize the location:
        locationManager = (LocationManager) this.getSystemService(Context.LOCATION_SERVICE);

        initializemap();

        /* My location overlay */
        /* Create a static Overlay showing a the current location and a compass */                  
        myLocationOverlay = new MyLocationOverlay(this, mapView);
        mapView.getOverlays().add(myLocationOverlay);
        myLocationOverlay.runOnFirstFix( new Runnable() {
            public void run() {
                mapController.animateTo( myLocationOverlay
                                 .getMyLocation());
            }
        });

        //Add Scale Bar
        mScaleBarOverlay = new ScaleBarOverlay(this);                           
        ScaleBarOverlay myScaleBarOverlay = new ScaleBarOverlay(this);
        mScaleBarOverlay.setLineWidth(50); 
        mapView.getOverlays().add(myScaleBarOverlay);
    }

    /** (re-)enable location and compass updates */      
    @Override
    public void onResume() {
        super.onResume();
        myLocationOverlay.enableCompass();
        myLocationOverlay.enableMyLocation();
        //myLocationOverlay.followLocation(true);
        //myLocationOverlay.setDrawAccuracyEnabled(true);
        //myLocationOverlay.isDrawAccuracyEnabled();
    }  

    /** disable compass and location updates */        
    @Override      
    public void onPause() {
        super.onPause();
        myLocationOverlay.disableMyLocation();
        myLocationOverlay.disableCompass();
    }

    public void initializemap()
    {
        mapView = (MapView) this.findViewById(R.id.mapView); 
        mapView.setTileSource(TileSourceFactory.MAPNIK); 
        mapView.setBuiltInZoomControls(true); 
        mapView.setMultiTouchControls(true); 
        mapController = this.mapView.getController();     
        mapController.setZoom(12);
        mapController.setCenter(new GeoPoint(15.610762,32.540345));
    }
}

Answer 1

Abo 7med,

You need to extend Overlay for example

public class AccuracyCircleOverlay extends Overlay {
    public AccuracyCircleOverlay() {}
    public void draw(Canvas canvas, MapView mapv, boolean shadow){
       super.draw(canvas, mapv, shadow);
       // your drawing code here
    }
}

You can add the overlay to your view as such:

mapView.getOverlays().add(new AccuracyCircleOverlay());

Answer 2

A fully worked example to draw an accuracy circle at your location (this does not include a marker for your location). This is based on the OSMDroid class DirectedLocationOverlay for showing your location with directional arrow (which I didn't need and removed).

import android.graphics.Canvas;
import android.graphics.Color;
import android.graphics.Paint;
import android.graphics.Point;

import org.osmdroid.util.GeoPoint;
import org.osmdroid.views.MapView;
import org.osmdroid.views.Projection;
import org.osmdroid.views.overlay.Overlay;

public class AccuracyOverlay extends Overlay {

    private Paint paint = new Paint();
    private Paint accuracyPaint = new Paint();
    private GeoPoint location;
    private final Point screenCoords = new Point();
    private float accuracy = 0;

    public AccuracyOverlay(GeoPoint location, float accuracyInMeters) {
        super();

        this.location = location;
        this.accuracy = accuracyInMeters;
        this.accuracyPaint.setStrokeWidth(2);
        this.accuracyPaint.setColor(Color.BLUE);
        this.accuracyPaint.setAntiAlias(true);
    }

    @Override
    public void onDetach(MapView view){
        paint = null;
        accuracyPaint = null;
    }

    @Override
    public void draw(final Canvas c, final MapView map, final boolean shadow) {

        if (shadow) {
            return;
        }

        if (location != null) {
            final Projection pj = map.getProjection();
            pj.toPixels(location, screenCoords);

            if (accuracy > 0) {  //Set this to a minimum pixel size to hide if accuracy high enough
                final float accuracyRadius = pj.metersToEquatorPixels(accuracy);

                /* Draw the inner shadow. */
                accuracyPaint.setAntiAlias(false);
                accuracyPaint.setAlpha(30);
                accuracyPaint.setStyle(Paint.Style.FILL);
                c.drawCircle(screenCoords.x, screenCoords.y, accuracyRadius, accuracyPaint);

                /* Draw the edge. */
                accuracyPaint.setAntiAlias(true);
                accuracyPaint.setAlpha(150);
                accuracyPaint.setStyle(Paint.Style.STROKE);
                c.drawCircle(screenCoords.x, screenCoords.y, accuracyRadius, accuracyPaint);
            }
        }
    }
}

Then in your activity:

@Override
public void onLocationChanged(Location location) {
    if (accuracyOverlay != null) {
        map.getOverlays().remove(accuracyOverlay);
        map.invalidate();
    }

    accuracyOverlay = new AccuracyOverlay(new GeoPoint(location), location.getAccuracy());
    map.getOverlays().add(accuracyOverlay);
}