OSMDroid offset polygon

Question

I draw polygon on my map using a code similar to this :

    GeoPoint pt1=new GeoPoint(13002798,77580000);
    GeoPoint pt2= new GeoPoint(pt1.getLatitudeE6()+diff, pt1.getLongitudeE6());
    GeoPoint pt3= new GeoPoint(pt1.getLatitudeE6()+diff, pt1.getLongitudeE6()+diff);
    GeoPoint pt4= new GeoPoint(pt1.getLatitudeE6(), pt1.getLongitudeE6()+diff);
    GeoPoint pt5= new GeoPoint(pt1);


    PathOverlay myOverlay= new PathOverlay(Color.RED, this);
    myOverlay.getPaint().setStyle(Paint.Style.FILL);

    myOverlay.addPoint(pt1);
    myOverlay.addPoint(pt2);
    myOverlay.addPoint(pt3);
    myOverlay.addPoint(pt4);
    myOverlay.addPoint(pt5);

    map.getOverlays().add(myOverlay);

Now I want to offset my overlay polygon exactly 10px up, independent of zoom or other parameters. How can I do that? I need this to draw line above my POI marker arrows.

Answer 1

Something like that:

Projection pj = mapView.getProjection();
Point pix = pj.toPixels(p);
pix.y -= 10; //10 pixels up
GeoPoint p2 = pj.fromPixels(pix2.x, pix2.y);
double offset = p2.getLatitude() - p.getLatitude();

Then you can offset latitude of all points by adding offset.

However, this solution is a little bit strange. Instead, you could also display your polygon "under" your POI markers. osmdroid displays overlays following their order: first at the bottom, latest on top.

Latest point: never use PathOverlay for filled polygons, you will get weird behaviours in some cases (when a part of polygon is inside the view, a part is outside). You can use OSMBonusPack Polygon instead.