SnackBar Örneği-Builder Widgetı.dart

import 'package:flutter/material.dart';

void main() => runApp(MyApp());

class MyApp extends StatelessWidget {
  @override
  Widget build(BuildContext context) {
    return MaterialApp(
      debugShowCheckedModeBanner: false,
      title: 'Projem',
      theme: ThemeData(
        primarySwatch: Colors.green,
      ),
      home: Mesaj(),
    );
  }
}

class Mesaj extends StatelessWidget {
  @override
  Widget build(BuildContext context) {
    return Scaffold(
        appBar: AppBar(),
        body: Builder(builder: (BuildContext context) {
          return RaisedButton(
            onPressed: () {
              Scaffold.of(context).showSnackBar(SnackBar(
                  content: Text(
                "Merhaba",
                style: TextStyle(color: Colors.red),
              )));
            },
            child: Text("Mesaj At"),
          );
        }));
  }
}