Question

I want to draw a circle on MapView, i.e. radius. I do it like this:

Overlay to draw circle:

public class RadiusOverlay extends Overlay {

    private Context context;
    private double latitude;
    private double longitude;
    private float radius;

    public RadiusOverlay(Context context, double latitude, double longitude, float radius){
     /*.....................*/
    }

    public void draw(Canvas canvas, MapView mapView, boolean shadow){
        super.draw(canvas, mapView, shadow); 

        Point point = new Point();
        GeoPoint geoPoint = new GeoPoint((int) (latitude *1e6), (int)(longitude * 1e6));

        Projection projection = mapView.getProjection();
        projection.toPixels(geoPoint, point);
        radius = projection.metersToEquatorPixels(radius);

        Paint paint = new Paint();
        paint.setStyle(Paint.Style.FILL);
        paint.setARGB(100, 100, 100, 100);

        canvas.drawCircle((float)point.x, (float)point.y, radius, paint);
    }

}

In MapActivity:

List<Overlay> mapOverlays = mapView.getOverlays();
RadiusOverlay radiusOverlay = new RadiusOverlay(this, latitude, longitude, radius);
mapOverlays.add(radiusOverlay);

I see circle when MapActivity starts, and it’s the size I intended, but then it grows to the size of the screen and disappears. How do I fix this?
Will appreciate any help.

Answer 1

It looks like you are re-calculating the radius using metersToEquatorPixels every time you draw it. You should move that calculation to the constructor and see if that fixes your problem.

EDIT:

As Olgas pointed out, the Projection can change. Therefore what you want to do is store the original `radius value as you are, then in your draw method do:

    float projectedRadius = projection.metersToEquatorPixels(radius);

and use this value later in draw as well:

    canvas.drawCircle((float)point.x, (float)point.y, projectedRadius, paint);