question: protected MapTile findCovering ( int zoom , long i , long j ) { while ( zoom > 0 ) { zoom -- ; i = i / 2 ; j = j / 2 ; MapTile candidate = findTile ( zoom , i , j ) ; if ( ( candidate != null ) && ( ! candidate . loading ( ) ) ) { return candidate ; } } return null ; }
target:  Find the "nearest" lower-zoom tile that covers a specific tile. This is used to find out what tile we have to show while a new tile is still loading