How to change the marker for the overlay on tap for android?

i have made an application in which i need to change the drawable of an overlayitem when a user clicks on it. i am using the following code to achieve this effect:

        protected boolean onTap(int index) {
        OverlayItem item = mOverlays.get(index);
        if(item.getTitle().equals("true")){
            if(item.getMarker(OverlayItem.ITEM_STATE_FOCUSED_MASK).equals(greenMarker)){
                item.setMarker(orangeMarker);
                view1ComplainPoleList.add(item.getSnippet());
                Log.i("adding",item.getSnippet());
                map.invalidate();
            }
            else{
                item.setMarker(greenMarker);
                view1ComplainPoleList.remove(item.getSnippet());
                Log.i("removing",item.getSnippet());
                map.invalidate();
            }
        }
        return true;
    }

But this does not seem to be working. whenever i click on an overlayitem it disappears from view. what is going wrong?

UPDATE:

could you also tell me how to load new views when the map is scrolled...?

thank you in advance.