flutter Scaffold.of() called with a context that does not contain a Scaffold
This exception happens because you are using the context of the widget that
instantiated Scaffold.
Not the context of a child of Scaffold.
You can solve this by just using a different context :
Scaffold(
appBar: AppBar(
title: Text('SnackBar Playground'),
),
body: Builder(
builder: (context) =>
Center(
child: RaisedButton(
color: Colors.pink,
textColor: Colors.white,
onPressed: () => _displaySnackBar(context),
child: Text('Display SnackBar'),
),
),
),
);