question: public void showCrosshairsForCentroid ( ) { if ( selectedWays == null ) { return ; } synchronized ( selectedWays ) { float centroid [ ] = centroidXY ( map . getWidth ( ) , map . getHeight ( ) , viewBox , selectedWays . get ( 0 ) ) ; if ( centroid == null ) { return ; } centroidX = centroid [ 0 ] ; centroidY = centroid [ 1 ] ; showCrosshairs ( centroidX , centroidY ) ; } }
target:  Calculates the coordinates for the center of the screen and displays a crosshair there. 