I want to disable clicking/tapping on map markers. I know you can disable default behavior by setting up an empty map.setOnMarkerClickListener
        
Apply OnMarkerClickListenerto your map. Implement onMarkerClick()method and returnfalse
googleMap.setOnMarkerClickListener(new OnMarkerClickListener() {
    public boolean onMarkerClick(Marker marker) {
        return true;
    }
});
map.setOnMarkerClickListener(null); try this
It is not necessary to implement OnMarkerClickListner. Just try to remove this statement
map.setOnMarkerClickListner(this)
from your code and I hope it will solve your problem.
class MyInfoWindowAdapter implements GoogleMap.InfoWindowAdapter
{
     @Override
     public View getInfoContents(Marker mar)
     {
         return null;
     }
     @Override
     public View getInfoWindow(Marker mar)
     {
         return null;
     }
}
gmap.setInfoWindowAdapter(new MyInfoWindowAdapter);
Try this code above. This will set your infowindow to null.
i have two suggestions:
if i understood right, you want to offer the functionality to place a marker on the map, right?! If you cannot remove the setOnMarkerClickListener, did you tried to draw at the map and "convert" your drawing to a Marker in the end. (get 'LatLng' from drawing and create a Marker). 
actually the second suggestion isn't really a good one (depending if you can zoom/move your map). I had a similar task and we used an transparent overlay over the map, which handled all user input and delegates it. but we didn`t had the functionality of zoom and move, which would be pain in the ass...
Just override the onclick event:
map.setOnMarkerClickListener(new OnMarkerClickListener() {
    public boolean onMarkerClick(Marker arg0) {
        return true;
    }
});