https://www.kancloud.cn/apachecn/programiz-zh/1951767
val num = 1.34567
var o = list.get(i).ori_price.toDouble()
var p = list.get(i).price.toDouble()
val o1 = BigDecimal(Double.toString(o))
val p1 = BigDecimal(Double.toString(p))
//减法 保留两位
val liangwei = o1.subtract(p1).setScale(2)
打印结果为:1.35