Flutter Staggered Grid View 无法传递变量 - 未定义名称“viewModel”

Question

我在尝试构建交错网格视图并将变量传递给 Material 类时出现错误

Undefined name 'viewModel'

：

  Material Items(String heading) {
    return Material(
        child: InkWell(
          onTap: () {
            if (heading ==
                ('Text')) {
                  showMainDialog(context, viewModel); <- The error is here: Undefined name 'viewModel'
            }
          },
        ));
  }

  @override
  Widget build(BuildContext context) {
     body: SingleChildScrollView(child: loadMainPage(viewModel)),
  }

  Widget loadMainPage(ViewModel viewModel) {
    return StaggeredGridView.count(
        children: <Widget>[
          Items(
              ('Text')
            ),
        ],
        staggeredTiles: [
          StaggeredTile.extent(1, 150.0),
        ],
      );
  }

  showMainDialog(BuildContext context, ViewModel viewModel) {

    Dialog simpleDialog = Dialog(
        ...
    showDialog(
        context: context, builder: (BuildContext context) => simpleDialog);
  }
}