title: Change position of a Flutter Snackbar
body: <p>I want to display a simple disappearing error message <strong>above</strong> a button when certain conditions aren't met. It seems as if Flutter's Snackbar is well suited to this purpose. </p>
  
  <p>However, I'm having difficulty changing the position of the Snackbar to be anything other than at the very bottom of the screen. Is this possible? If not, is there a Widget better suited for this purpose?</p>
  
  <p>My current snackbar code:</p>
  
  <pre><code>class ContinueButton extends StatelessWidget {
    @override
    Widget build(BuildContext context) {
      return Container(
        margin: const EdgeInsets.only(
            bottom: 24.0, top: 24.0),
        child: Align(
          alignment: FractionalOffset.bottomCenter,
          child: MaterialButton(
            onPressed: () {
              final snackBar = SnackBar(
                content: Text('Yay! A SnackBar!'),
              );
              Scaffold.of(context).showSnackBar(snackBar);
            },
  
            child: Text('Continue'),
            height: 40.0,
            minWidth: 300.0,
            color: Colors.greenAccent,
          ),
        ),
      );
    }
  }
  </code></pre>