public synchronized void updateOneStep() { if (initFlag) { loc.update(); int[] tXY = loc.getCurrentTruePosition(); int[] sXY = loc.getCurrentReading(); if (sXY != null) updateViewer(tXY[0], tXY[1], sXY[0], sXY[1]); else updateViewer(tXY[0], tXY[1], -1, -1); } }