Question

Recently I have drew a custom polygon around my country by creating a overlay class and drew it using path.
I have many sector of a map, each sector is divided and filled with color with a overlay class. However when I use the ontap function, only the last overlay item ontap function get called.

I believe is because I did not set a boundary for the overlay? The following is my overlay code

public class SectorOverlay  extends  Overlay{

CustomPolygon customPolygon =null;
Context context;

public SectorOverlay(Context context, CustomPolygon customPolygon) {
    this.context=context;
    this.customPolygon =customPolygon;
}
@Override
public void draw(Canvas canvas, MapView mapView, boolean shadow) 
{
    shadow=false;

    Paint paint = new Paint();
    paint = new Paint(Paint.ANTI_ALIAS_FLAG);
    paint.setStrokeWidth(2);
    paint.setColor(0x10000000);     
    paint.setStyle(Paint.Style.FILL_AND_STROKE);
    paint.setAntiAlias(true);
    Point point1_draw = new Point();        

    if(customPolygon!=null)
    {

            Path path = new Path();
            path.setFillType(Path.FillType.EVEN_ODD);
            for(int n=0;n<customPolygon.getCorrdinateList().size();n++)
            {

                GeoPoint sector1 = new GeoPoint((int)(customPolygon.getCorrdinateList().get(n).getLatitude()*1e6), (int)((customPolygon.getCorrdinateList().get(n).getLongitude())*1e6));
                if(n==0){
                    mapView.getProjection().toPixels(sector1, point1_draw);
                    path.moveTo(point1_draw.x,point1_draw.y);
                }else
                {
                    mapView.getProjection().toPixels(sector1, point1_draw);
                    path.lineTo(point1_draw.x,point1_draw.y);
                }
            }

            path.close();
            canvas.drawPath(path, paint);



    }

}
@Override
public boolean onTap(GeoPoint p, MapView mapView) {


    new CommonOpearation().showToast(context, customPolygon.getName());


return  true;
}
}

Answer 1

It is being called for the “last” Overlay, because it is the topmost. MapView draws its overlays from 0..end, but when there is an event, the last drawn is on top, so it gets the event first, and since you return true in Overlay.onTap (same applies to Overlay.onTouchEvent, and practically a lot of Android events) you’re saying that the event is handled, therefore it doesn’t bother calling the overlays down the line. So the event handlers are called in end..0 order.

I did not use onTap, but according to CommonsWare at Android – Map overlay onTouchEvent / onTap howto? if you use ItemizedOverlay you should get onTap only for your bounded/drawn area.
It is surely possible that common onTap and onTouchEvents are called for any touch point on screen. In this case you can find the GeoPoint with getProjection from MapView applying it reversly to (x,y) getting (lon,lat). Or using onTap (again, I haven’t heard about this before).

If you need to do a hit-test with the drawn polygon of the overlay, here’s one which helps zou determine whether the point is in the (not necessarily convex) polygon:
http://verkkoopetus.cs.utu.fi/vhanke/trakla/PointInPolygon.html

• for 2. LStart.x = minXOfPolygon, LEnd.x = maxXOfPolygon, LStart.y = LEnd.y = 0
  (you may need extend the line by 1 unit at LStart.x and LEnd.x just to be safe.)
• for 4. use findIntersection from http://workshop.evolutionzone.com/2007/09/10/code-2d-line-intersection/