在flutter中使用sqlite数据库中的数据填充下拉菜单

dependencies:
  sqflite: ^1.3.2
  path: ^1.8.0

import 'dart:async';
import 'dart:io';
import 'package:path/path.dart';
import 'package:sqflite/sqflite.dart';
import 'package:path_provider/path_provider.dart';

class DatabaseHelper {
  static final DatabaseHelper _instance = 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();

  Future<Database> initDb() async {
    Directory documentDirectory = await getApplicationDocumentsDirectory();
    String path = join(documentDirectory.path, "mydatabase.db");
    var ourDb = await openDatabase(path, version: 1, onCreate: _onCreate);
    return ourDb;
  }

  void _onCreate(Database db, int version) async {
    await db.execute(
        "CREATE TABLE mytable(id INTEGER PRIMARY KEY, name TEXT)");
  }

  Future<int> saveItem(String name) async {
    var dbClient = await db;
    int res = await dbClient!.insert("mytable", {"name": name});
    return res;
  }

  Future<List<Map<String, dynamic>>> getItems() async {
    var dbClient = await db;
    var res = await dbClient!.query("mytable");
    return res;
  }
}

import 'package:flutter/material.dart';

class MyDropdown extends StatefulWidget {
  @override
  _MyDropdownState createState() => _MyDropdownState();
}

class _MyDropdownState extends State<MyDropdown> {
  List<String> items = [];
  String selectedValue = "";

  @override
  void initState() {
    super.initState();
    loadItems();
  }

  void loadItems() async {
    var dbHelper = DatabaseHelper();
    var data = await dbHelper.getItems();
    List<String> tempList = [];
    for (var item in data) {
      tempList.add(item['name']);
    }
    setState(() {
      items = tempList;
    });
  }

  @override
  Widget build(BuildContext context) {
    return DropdownButton<String>(
      value: selectedValue,
      onChanged: (String? newValue) {
        setState(() {
          selectedValue = newValue!;
        });
      },
      items: items.map<DropdownMenuItem<String>>((String value) {
        return DropdownMenuItem<String>(
          value: value,
          child: Text(value),
        );
      }).toList(),
    );
  }
}

import 'package:flutter/material.dart';

class MyPage extends StatelessWidget {
  @override
  Widget build(BuildContext context) {
    return Scaffold(
      appBar: AppBar(title: Text("My Page")),
      body: Center(child: MyDropdown()),
    );
  }
}