从Firebase获取经度和纬度值

Question

 private void setMarker(DataSnapshot dataSnapshot) {

            String key = dataSnapshot.getKey();
            HashMap<String, Object> value = (HashMap<String, Object>) dataSnapshot.getValue();
            double lat = Double.parseDouble(value.get("latitude").toString());
            double lng = Double.parseDouble(value.get("longitude").toString());
            LatLng location = new LatLng(lat, lng);
            if (!mMarkers.containsKey(key)) {
                mMarkers.put(key, mMap.addMarker(new MarkerOptions().title(key).position(location)));
            } else {
                mMarkers.get(key).setPosition(location);
            }
            LatLngBounds.Builder builder = new LatLngBounds.Builder();
            for (Marker marker : mMarkers.values()) {
                builder.include(marker.getPosition());
            }

        }

我遇到错误
HashMap<String, Object> value = (HashMap<String, Object>) dataSnapshot.getValue(); .......请帮助

logcat中的错误是

  

java.lang.Double无法转换为java.util.HashMap

Database hierarchy