main.dart

import 'dart:io';
import 'package:flutter/material.dart';


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

class MyApp extends StatelessWidget {

    final textController = new TextEditingController();
    final globalKey = GlobalKey<ScaffoldState>();
    final String fileName = 'textPadNote.txt';

     Future<void> _exportToFile(BuildContext context) async {
       final File file = File('${Directory.current.absolute.path}/${fileName}');
       final snackBar = SnackBar(content: Text('Saved to: ${file.path}'));
       
       await file.writeAsString(textController.text);
       globalKey.currentState.showSnackBar(snackBar);
    }
  @override
  Widget build(BuildContext context) {
  
    return MaterialApp(
      title: 'TextPad',
      theme: ThemeData(
                brightness: Brightness.dark,
           ),
      home: Scaffold(
        key: globalKey,
        appBar: AppBar(
          title: Text('TextPad'),
          actions: <Widget>[
              IconButton(
                    icon: const Icon(Icons.save),
                    tooltip: 'Export to ${fileName}',
                    onPressed: () {_exportToFile(context);}
                  )]
        ),
        body: Center(
          child: TextField(
                controller: textController,
                maxLines: null,
                keyboardType: TextInputType.multiline,
                expands: true,
                  decoration: InputDecoration(
    hintText: 'Play with your notes here...',
    contentPadding: EdgeInsets.all(12.0)
  ),
          ),
        ),
      ),
    );
  }
}