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],
                  ),
                ),
              )
            ],
          ),

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

decoration: BoxDecoration(
    borderRadius: BorderRadius.circular(10),
    boxShadow: [
        BoxShadow(
            color: Colors.grey.withOpacity(0.5),
            spreadRadius: 5,
            blurRadius: 7,
            offset: Offset(0, 3), // changes position of shadow
        ),
    ],
),

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
      ),
    ],
  ),
)

使用BoxDecoration和BoxShadow。

下面是一个操作以下选项的可视化演示:

不透明度 x抵消 y抵消 模糊半径 扩散半径

动图在色彩方面做得不太好。你可以自己在设备上试试。

以下是演示的完整代码:

import 'package:flutter/material.dart';

void main() => runApp(MyApp());

class MyApp extends StatelessWidget {
  @override
  Widget build(BuildContext context) {
    return MaterialApp(
      home: Scaffold(
        body: ShadowDemo(),
      ),
    );
  }
}

class ShadowDemo extends StatefulWidget {
  @override
  _ShadowDemoState createState() => _ShadowDemoState();
}

class _ShadowDemoState extends State<ShadowDemo> {
  var _image = NetworkImage('https://placebear.com/300/300');

  var _opacity = 1.0;
  var _xOffset = 0.0;
  var _yOffset = 0.0;
  var _blurRadius = 0.0;
  var _spreadRadius = 0.0;

  @override
  Widget build(BuildContext context) {
    return Stack(
      children: <Widget>[
        Center(
          child:
          Container(
            decoration: BoxDecoration(
              color: Color(0xFF0099EE),
              boxShadow: [
                BoxShadow(
                  color: Color.fromRGBO(0, 0, 0, _opacity),
                  offset: Offset(_xOffset, _yOffset),
                  blurRadius: _blurRadius,
                  spreadRadius: _spreadRadius,
                )
              ],
            ),
            child: Image(image:_image, width: 100, height: 100,),
          ),
        ),
        Align(
          alignment: Alignment.bottomCenter,
          child: Padding(
            padding: const EdgeInsets.only(bottom: 80.0),
            child: Column(
              children: <Widget>[
                Spacer(),
                Slider(
                  value: _opacity,
                  min: 0.0,
                  max: 1.0,
                  onChanged: (newValue) =>
                  {
                    setState(() => _opacity = newValue)
                  },
                ),
                Slider(
                  value: _xOffset,
                  min: -100,
                  max: 100,
                  onChanged: (newValue) =>
                  {
                    setState(() => _xOffset = newValue)
                  },
                ),
                Slider(
                  value: _yOffset,
                  min: -100,
                  max: 100,
                  onChanged: (newValue) =>
                  {
                    setState(() => _yOffset = newValue)
                  },
                ),
                Slider(
                  value: _blurRadius,
                  min: 0,
                  max: 100,
                  onChanged: (newValue) =>
                  {
                    setState(() => _blurRadius = newValue)
                  },
                ),
                Slider(
                  value: _spreadRadius,
                  min: 0,
                  max: 100,
                  onChanged: (newValue) =>
                  {
                    setState(() => _spreadRadius = newValue)
                  },
                ),
              ],
            ),
          ),
        )
      ],
    );
  }
}

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,
                ),
              ),
            )
          ],
        ),
      )

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,
    );
  }
}