main.dart

//main.dart
import 'package:flutter/material.dart'; 
void main() { 
runApp(App()); 
} 
class App extends StatelessWidget { 
 @override 
 Widget build(BuildContext context) { 
 return MaterialApp( 
title: 'Demo for swatch', 
 theme: ThemeData(   
 primarySwatch: Colors.black, //here is where the error resides 
 ), 
 home: YourFirstPage(), 
 ); 
 } 
}