Check out example codes for "flutter snackbar showing error". It will help you in understanding the concepts better.

Code Example 1

You can show material design snackbars using the following code:

      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
  key: _scaffoldKey,
  body: ...

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

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