flutter shadow drawing

      Container(
              width: 300,
              height: 100,
              margin: EdgeInsets.all(10),
              decoration: new BoxDecoration(
                  border: new Border.all(width: 0, color: Colors.red),
                  color: Colors.blue,
                  boxShadow: [
                    BoxShadow(
                        color: Colors.yellow,
                        offset: Offset(0, 1), //阴影y轴偏移量
                        blurRadius: 20, //阴影模糊程度
                        spreadRadius: 10 //阴影扩散程度
                    ),
                    BoxShadow(
                        color: Colors.yellow,
                        offset: Offset(-1, 0), //阴影y轴偏移量
                        blurRadius: 2, //阴影模糊程度
                        spreadRadius: 0 //阴影扩散程度
                    ),
                  ]),
            ),