Question

我想从资产访问数据库，但出现此错误

NoSuchMethodError（NoSuchMethodError：方法“ rawQuery”在null上调用。接收者：null 尝试致电：rawQuery("SELECT * FROM productss")）


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


class DatabaseHelper2{
  static final DatabaseHelper2 _instance = DatabaseHelper2.internal();
  factory DatabaseHelper2() =>_instance;
  var oneSecond = Duration(seconds: 5);
  static Database _db;

  Future<Database> get db async{
    if(_db != null){
      print("database does");
      return _db;
    }
    _db = await initDbs();
    print("database doesnt");
    return _db;
  }

  DatabaseHelper2.internal();



  initDbs() async{
   // Construct a file path to copy database to
      var databasesPath = await getDatabasesPath();
      var path = join(databasesPath, "productss.db");

      // Check if the database exists
      var exists = await databaseExists(path);

      if (!exists) {
        // Should happen only the first time you launch your application
        print("Creating new copy from asset");

        // 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", "productss.db"));
        List<int> bytes =
        data.buffer.asUint8List(data.offsetInBytes, data.lengthInBytes);

        // Write and flush the bytes written
        await File(path).writeAsBytes(bytes, flush: true);

      } else {
        print("Opening existing database");

      }
      // open the database
      _db = await openDatabase(path);


    } 
    void productDb2(Database database, int version)async{
    await database.execute("""
    CREATE TABLE productss
    (
      id INTEGER PRIMARY KEY,
      name TEXT,
      price INTEGER,
      size INTEGER,
      fat100 INTEGER,
      carbs100 INTEGER,
      protein100 INTEGER,
      dateCreated String
    )
    """);
  }


  Future<List> getProductsdb()async{

        var dbClient = await db;
        var result = await dbClient.rawQuery("SELECT * FROM productss");
        return result.toList();
      }


}

我不知道为什么会这样。数据库不为空。我检查了。

Answer 1

您正在尝试await db，但是类属性被命名为_db。 IDE是否没有捕获到此错误？

颤振sqflite数据库资产

1 个答案: