PhysicalModel将帮助你给它立面阴影。

 Container(
        alignment: Alignment.center,
        child: Column(
          children: <Widget>[
            SizedBox(
              height: 60,
            ),
            Container(
              child: PhysicalModel(
                borderRadius: BorderRadius.circular(20),
                color: Colors.blue,
                elevation: 18,
                shadowColor: Colors.red,
                child: Container(
                  height: 100,
                  width: 100,
                ),
              ),
            ),
            SizedBox(
              height: 60,
            ),
            Container(
              child: PhysicalShape(
                color: Colors.blue,
                shadowColor: Colors.red,
                elevation: 18,
                clipper: ShapeBorderClipper(shape: CircleBorder()),
                child: Container(
                  height: 150,
                  width: 150,
                ),
              ),
            )
          ],
        ),
      )

PhysicalModel将帮助你给它立面阴影。

 Container(
        alignment: Alignment.center,
        child: Column(
          children: <Widget>[
            SizedBox(
              height: 60,
            ),
            Container(
              child: PhysicalModel(
                borderRadius: BorderRadius.circular(20),
                color: Colors.blue,
                elevation: 18,
                shadowColor: Colors.red,
                child: Container(
                  height: 100,
                  width: 100,
                ),
              ),
            ),
            SizedBox(
              height: 60,
            ),
            Container(
              child: PhysicalShape(
                color: Colors.blue,
                shadowColor: Colors.red,
                elevation: 18,
                clipper: ShapeBorderClipper(shape: CircleBorder()),
                child: Container(
                  height: 150,
                  width: 150,
                ),
              ),
            )
          ],
        ),
      )

检查BoxShadow和BoxDecoration

Container可以带一个BoxDecoration(脱离你最初发布的代码)，它带一个boxShadow

return Container(
  margin: EdgeInsets.only(left: 30, top: 100, right: 30, bottom: 50),
  height: double.infinity,
  width: double.infinity,
  decoration: BoxDecoration(
    color: Colors.white,
    borderRadius: BorderRadius.only(
      topLeft: Radius.circular(10),
        topRight: Radius.circular(10),
        bottomLeft: Radius.circular(10),
        bottomRight: Radius.circular(10)
    ),
    boxShadow: [
      BoxShadow(
        color: Colors.grey.withOpacity(0.5),
        spreadRadius: 5,
        blurRadius: 7,
        offset: Offset(0, 3), // changes position of shadow
      ),
    ],
  ),
)

class ShadowContainer extends StatelessWidget {
  ShadowContainer({
    Key key,
    this.margin = const EdgeInsets.fromLTRB(0, 10, 0, 8),
    this.padding = const EdgeInsets.symmetric(horizontal: 8),
    this.circular = 4,
    this.shadowColor = const Color.fromARGB(
        128, 158, 158, 158), //Colors.grey.withOpacity(0.5),
    this.backgroundColor = Colors.white,
    this.spreadRadius = 1,
    this.blurRadius = 3,
    this.offset = const Offset(0, 1),
    @required this.child,
  }) : super(key: key);

  final Widget child;
  final EdgeInsetsGeometry margin;
  final EdgeInsetsGeometry padding;
  final double circular;
  final Color shadowColor;
  final double spreadRadius;
  final double blurRadius;
  final Offset offset;
  final Color backgroundColor;

  @override
  Widget build(BuildContext context) {
    return Container(
      margin: margin,
      padding: padding,
      decoration: BoxDecoration(
        color: backgroundColor,
        borderRadius: BorderRadius.circular(circular),
        boxShadow: [
          BoxShadow(
            color: shadowColor,
            spreadRadius: spreadRadius,
            blurRadius: blurRadius,
            offset: offset,
          ),
        ],
      ),
      child: child,
    );
  }
}

The given answers do the trick for outer shadow i.e. around the widget. I wanted a shadow on the widget which is inside the boundaries and according to the github issue there is no inset attribute in ShadowBox yet. My workaround was to add a layer of widget with a gradient using the stack widget so that it looks like the widget itself has the shadows. You must use the mediaQuery for dimensions otherwise the layout will be messed up on different devices. Here's a sample of code for better understanding:

Stack(
            children: <Widget>[
              Container(
                decoration: BoxDecoration(
                  image: DecorationImage(
                    fit: BoxFit.cover,
                    image: AssetImage("assets/sampleFaces/makeup.jpeg"),
                    // fit: BoxFit.cover,
                  ),
                ),
                height: 350.0,
              ),
              Container(
                decoration: BoxDecoration(
                  gradient: LinearGradient(
                    begin: FractionalOffset.topCenter,
                    end: FractionalOffset.bottomCenter,
                    colors: [
                      Colors.black.withOpacity(0.0),
                      Colors.black54,
                    ],
                    stops: [0.95, 5.0],
                  ),
                ),
              )
            ],
          ),

我就是这么做的

    Container(
  decoration: new BoxDecoration(
    boxShadow: [
      BoxShadow(
        color: Colors.grey[200],
        blurRadius: 2.0, // has the effect of softening the shadow
        spreadRadius: 2.0, // has the effect of extending the shadow
        offset: Offset(
          5.0, // horizontal, move right 10
          5.0, // vertical, move down 10
        ),
      )
    ],
  ),
  child: Container( 
       color: Colors.white, //in your example it's blue, pink etc..
       child: //your content
  )