how can i run this code? every time i try i get error saying cannot be run without async?

Question

I am unsure how I can use this code- every time i try to run it i get many errors.

var databasesPath = await getDatabasesPath();
var path = join(databasesPath, "demo_always_copy_asset_example.db");

// delete existing if any
await deleteDatabase(path);

// Make sure the parent directory exists
try {
  await Directory(dirname(path)).create(recursive: true);
} catch (_) {}

// Copy from asset
ByteData data = await rootBundle.load(join("assets", "example.db"));
List<int> bytes = data.buffer.asUint8List(data.offsetInBytes, data.lengthInBytes);
await new File(path).writeAsBytes(bytes, flush: true);

// open the database
var db = await openDatabase(path, readOnly: true);

Answer 1

You can copy paste run full code below
Step 1: You can create a DatabaseHelper class and put your code in initDb()

class DatabaseHelper {
  static final DatabaseHelper _instance = new DatabaseHelper.internal();
  factory DatabaseHelper() => _instance;

  static Database _db;

  Future<Database> get db async {
    if (_db != null) {
      return _db;
    }
    _db = await initDb();
    return _db;
  }

  DatabaseHelper.internal();

  initDb() async {

Step 2: The first time you call dbHelper.db, it will copy example.db from assets

var dbHelper = DatabaseHelper();
var dbClient = await dbHelper.db;

working demo

full code

import 'package:flutter/material.dart';
import 'dart:io';
import 'dart:typed_data';
import 'package:flutter/services.dart';
import 'package:path/path.dart';
import 'dart:async';
import 'package:path_provider/path_provider.dart';
import 'package:sqflite/sqflite.dart';

class DatabaseHelper {
  static final DatabaseHelper _instance = new DatabaseHelper.internal();
  factory DatabaseHelper() => _instance;

  static Database _db;

  Future<Database> get db async {
    if (_db != null) {
      return _db;
    }
    _db = await initDb();
    return _db;
  }

  DatabaseHelper.internal();

  initDb() async {
    var databasesPath = await getDatabasesPath();
    var path = join(databasesPath, "demo_always_copy_asset_example.db");
    print(path);
    // delete existing if any
    await deleteDatabase(path);

    // Make sure the parent directory exists
    try {
      await Directory(dirname(path)).create(recursive: true);
    } catch (_) {}

    // Copy from asset
    ByteData data = await rootBundle.load(join("assets", "example.db"));
    List<int> bytes =
        data.buffer.asUint8List(data.offsetInBytes, data.lengthInBytes);
    await new File(path).writeAsBytes(bytes, flush: true);

   // open the database
    var db = await openDatabase(path, readOnly: true);
    return db;
  }
}

void main() {
  runApp(MyApp());
}

class MyApp extends StatelessWidget {
  @override
  Widget build(BuildContext context) {
    return MaterialApp(
      title: 'Flutter Demo',
      theme: ThemeData(
        primarySwatch: Colors.blue,
        visualDensity: VisualDensity.adaptivePlatformDensity,
      ),
      home: MyHomePage(title: 'Flutter Demo Home Page'),
    );
  }
}

class MyHomePage extends StatefulWidget {
  MyHomePage({Key key, this.title}) : super(key: key);

  final String title;

  @override
  _MyHomePageState createState() => _MyHomePageState();
}

class _MyHomePageState extends State<MyHomePage> {
  int _counter = 0;

  void _incrementCounter() async{
    var dbHelper = DatabaseHelper();
    var dbClient = await dbHelper.db;

    setState(() {
      _counter++;
    });
  }

  @override
  Widget build(BuildContext context) {
    return Scaffold(
      appBar: AppBar(
        title: Text(widget.title),
      ),
      body: Center(
        child: Column(
          mainAxisAlignment: MainAxisAlignment.center,
          children: <Widget>[
            Text(
              'You have pushed the button this many times:',
            ),
            Text(
              '$_counter',
              style: Theme.of(context).textTheme.headline4,
            ),
          ],
        ),
      ),
      floatingActionButton: FloatingActionButton(
        onPressed: _incrementCounter,
        tooltip: 'Increment',
        child: Icon(Icons.add),
      ),
    );
  }
}