Show a SnackBar Above Modal Bottom Sheet

Just wrap your child widget with Scaffold

await showModalBottomSheet(   context: context,   builder: (builder) => Scaffold(      body: YourModalContentWidget()   ));

You will need to use GlobalKey<ScaffoldState> to show the Snackbar in desired Scaffold, for that you can added Scaffold in your showModalBottomSheet like below snip;

Define you GlobalKey in your Statefull or Stateless widget class

final GlobalKey<ScaffoldState> _modelScaffoldKey = GlobalKey<ScaffoldState>();

And on button press you can have;

                showModalBottomSheet(                  context: context,                  builder: (_) => Scaffold(                      extendBody: false,                      key: _modelScaffoldKey,                      resizeToAvoidBottomInset: true,                      body: FlatButton(                        child: Text("Snackbar"),                        onPressed: () {                          _modelScaffoldKey.currentState.showSnackBar(SnackBar(                            content: Text("Snackbar"),                          ));                        },                      )),                );

DartPad

Thanks @alexey i solve mine this way

showMaterialModalBottomSheet(  context: context,  enableDrag: false,  isDismissible: false,  expand: false,  builder: (context) => Container(  //padding: EdgeInsets.only(bottom: 20),  height: MediaQuery.of(context).size.height * 0.9, //bottom sheet height  color: Colors.black.withOpacity(0.0),  child: Scaffold(  body: NewTripPopupDialog(kInitialPosition: kInitialPosition))),);