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'),
            ),
        ),
    ),
);

Note that while we're using Builder here, this is not the only way to obtain a different BuildContext.

It is also possible to extract the subtree into a different Widget (usually using extract widget refactor)

You can use a GlobalKey. The only downside is that using GlobalKey might not be the most efficient way of doing this.

A good thing about this is that you can also pass this key to other custom widgets class that do not contain any scaffold. See(here)

class HomePage extends StatelessWidget {
  final _scaffoldKey = GlobalKey<ScaffoldState>(); \\ new line
  @override
  Widget build(BuildContext context) {
    return Scaffold(
      key: _scaffoldKey,                           \\ new line
      appBar: AppBar(
        title: Text('SnackBar Playground'),
      ),
      body: Center(
        child: RaisedButton(
          color: Colors.pink,
          textColor: Colors.white,
          onPressed: _displaySnackBar(context),
          child: Text('Display SnackBar'),
        ),
      ),
    );
  }
  _displaySnackBar(BuildContext context) {
    final snackBar = SnackBar(content: Text('Are you talkin\' to me?'));
    _scaffoldKey.currentState.showSnackBar(snackBar);   \\ edited line
  }
}