颤振：未显示VerticalDivider

我有这个小部件树：

Scaffold
  AppBar
  Column
    Center
    SingleChildScrollView
    FutureBuilder
       Container
       Flex
          direction: Axis.vertical,
          children: <Widget>[
              Row(
                          mainAxisAlignment: MainAxisAlignment.spaceEvenly,
                          children: <Widget>[
                            FlatButton(
                              color: Colors.red,
                              onPressed: () => {},
                              padding: EdgeInsets.all(10.0),
                              child: Row(
                                children: <Widget>[
                                  Icon(
                                    Icons.star,
                                    color: Colors.red,
                                  ),
                                  Text(
                                    "4.5",
                                    style: TextStyle(
                                        color: Colors.blue,
                                        fontWeight: FontWeight.bold),
                                  )
                                ],
                              ),
                            ),
                            VerticalDivider(
                              width: 1,
                              color: Colors.black,
                              thickness: 1,
                              indent: 2,
                              endIndent: 2,
                            ),
                            FlatButton() //like above
                            VerticalDivider()//like above
                            FlatButton()//like above

The codes make this image:

我想知道为什么没有显示VerticalDivider？

I am using flutter_linux_1.17.0-stable flutter sdk