flutter how to give height to the childrens of GridView.Builder

I am tring to give height to the childrens of gridview.builder but it's not accepting. I tried by using container but its not working... please help

GridView.builder(
              gridDelegate: SliverGridDelegateWithFixedCrossAxisCount(
                crossAxisCount: 2,
              ),
              itemCount: snapshot.data.length,
              itemBuilder: (BuildContext context, int index) {
                return Container(
                  height: 280.0,
                  child: Column(
                    children: <Widget>[
                      Padding(
                        padding:
                            EdgeInsets.fromLTRB(10.0, 10.0, 10.0, 10.0),
                      ),
                      Padding(
                        padding: const EdgeInsets.all(8.0),
                        child: Container(
                          height: 208.5,
                          width: 138.75,
                          decoration: BoxDecoration(
                              borderRadius: BorderRadius.circular(10.0),
                              image: DecorationImage(
                                  image: NetworkImage(
                                      "${snapshot.data[index].url}"),
                                  fit: BoxFit.fill)),
                        ),
                      ),
                      Text(
                        snapshot.data[index].title,
                        style: TextStyle(fontSize: 17.0),
                      ),
                    ],
                  ),
                );
              },
            ),`

You want to use the childAspectRatio property of the SliverGridDelegate preferably with MediaQuery:

class HomePage extends StatelessWidget {
  final List<String> items = <String>[
    "Item 1",
    "Item 2",
    "Item 3",
    "Item 4",
    "Item 5",
    "Item 6",
  ];

  @override
  Widget build(BuildContext context) {
    return Scaffold(
      appBar: AppBar(title: Text('Home')),
      body: GridView.builder(
        gridDelegate: SliverGridDelegateWithFixedCrossAxisCount(
          crossAxisCount: 2,
          childAspectRatio: MediaQuery.of(context).size.width /
              (MediaQuery.of(context).size.height / 4),
        ),
        itemCount: items.length,
        itemBuilder: (context, index) {
          return GridTile(child: Text(items[index]));
        },
      ),
    );
  }
}

You can use mainAxisExtent instead of childAspectRatio

    GridView.builder(
            physics: BouncingScrollPhysics(),
            itemCount: resumes.length,
            gridDelegate: SliverGridDelegateWithFixedCrossAxisCount(
              crossAxisCount: 2,
              mainAxisExtent: 256,
            ),
            itemBuilder: (_, index) => Container(),
          ),