android自己写的类似刻度尺的东西(9)

        private float result = 0; 
        /**
         * @param direction 方向，-1向左，1向右，0不动
         */ 
        public void draw(int direction){ 
            //获取画布 
            canvas = mSurfaceHolder.lockCanvas(); 
            if (mSurfaceHolder == null || canvas == null) {   
                return;   
            } 
            canvas.drawColor(Color.WHITE); 
             
            paint.setAntiAlias(true);   
            paint.setColor(Color.GRAY); 
             
            canvas.drawBitmap(background, new Matrix(), paint); 
             
            if(isInit){ 
                result = initValue; 
            }else{ 
                switch(direction){ 
                    case 1: 
                        result = Arithmetic.add(result, interval); 
                        break; 
                    case -1: 
                        result = Arithmetic.sub(result, interval); 
                        if(result < 0){