Check out example codes for "how to create a toast in flutter". It will help you in understanding the concepts better.

Code Example 1

# add this line to your dependencies
fluttertoast: ^7.1.1

Fluttertoast.showToast(
        msg: "This is Center Short Toast",
        toastLength: Toast.LENGTH_SHORT,
        gravity: ToastGravity.CENTER,
        timeInSecForIosWeb: 1,
        backgroundColor: Colors.red,
        textColor: Colors.white,
        fontSize: 16.0
    );

Code Example 2

You can show material design snackbars using the following code:

Scaffold.of(context).showSnackBar(SnackBar(
      content: Text("New Notification"),
    ));
   
In some cases, this will throw an error and it can be resolved using a workaround:

//Declare a GlobalKey
GlobalKey<ScaffoldState> _scaffoldKey = GlobalKey<ScaffoldState>();

//Assing this key to the scaffold
Scaffold(
  key: _scaffoldKey,
  body: ...
)

//finally in the topmost code use this key in the following way
_scaffoldKey.showSnackBar(SnackBar(
      content: Text("New Notification"),
    ));

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