private void cleanDirtyRegion(float eventX,float eventY){
  dirtyRect.left=Math.min(lastTouchX,eventX);
  dirtyRect.right=Math.max(lastTouchX,eventX);
  dirtyRect.top=Math.min(lastTouchY,eventY);
  dirtyRect.bottom=Math.max(lastTouchY,eventY);
}

private void cleanDirtyRegion ( float eventX , float eventY ) { dirtyRect . left = Math . min ( lastTouchX , eventX ) ; dirtyRect . right = Math . max ( lastTouchX , eventX ) ; dirtyRect . top = Math . min ( lastTouchY , eventY ) ; dirtyRect . bottom = Math . max ( lastTouchY , eventY ) ; }
retrieve the region needing to be redrawn
