如何将现有的 sqlite 数据库添加到 Flutter 并打印为卡片列表？

Question

我一直在寻找解决我问题的方法。 许多人写过一些关于将现有的 SQLite 数据库添加到 Flutter 的文章，但其中没有一个是准确的。

所以我的问题是如何在我的 Flutter 应用程序中添加现有的 SQLite 数据库（名为products.db ）。 我已经创建了产品的 model class 并添加了一个包含products.db文件的资产文件夹，当然我已经用 assets.db 编辑了pubspec.yaml 这是我的products.dart 。dart model class：

class Products {

int _pid;
int _cid;
int _tid;
String _model;
String _description;
String _pictureURI;
double _price;

// Construktor
  Products(this._pid, this._cid, this._tid , this._model, this._description, this._pictureURI, 
  this._price);

// getters
int get id => _pid;
int get cid => _cid;
int get tid => _tid;
String get model => _model;
String get description => _description;
String get pictureURI => _pictureURI;
double get price => _price;

// setters dont needed

// Extract a Product Object from a Map Oject
Products.fromMapOject(Map <String,dynamic> map) {

this._pid = map['pid'];
this._cid = map ['cid'];
this._tid = map ['tid'];
this._model = map ['model'];
this._description = map ['description'];
this._pictureURI = map ['pictureURI'];
this._price = map ['price'];

 }

}

Answer 1

@Soner624，假设您按照这些说明操作并且您有一个 products.db 实例，

• 创建数据库函数来获取您的产品（我没有您的数据库信息，所以下面只是一个示例，让您了解一下。PRODUCTS_TABLE_NAME = 您的表名，COLUMN_PRODUCT_ID = 您的产品 id 列名），

// Get product based on id
Future<Products> getProduct(Database assetDB, int id) async {
    final db = assetDB;
    var res = await db.query(PRODUCTS_TABLE_NAME, where: COLUMN_PRODUCT_ID + " = ?", whereArgs: [id]);
    Products product = res.isNotEmpty ? Products.fromMap(res.first) : null;
    return product;
}

// Get all products
Future<List<Products>> getAllProducts(Database assetDB) async {
    final db = assetDB;
    var res = await db.query(PRODUCTS_TABLE_NAME);
    List<Products> list =
    res.isNotEmpty ? res.map((c) => Products.fromMap(c)).toList() : [];
    return list;
}

• 在您的应用程序中使用它（假设assetDB是您的 products.db 实例）以使用 Card 小部件显示产品列表，

  @override
  Widget build(BuildContext context) {
    return FutureBuilder(
        future: getAllProducts(assetDB),
        builder: (context, snapshot) {
          if (snapshot.hasData) {
            return Column(
              children: List.generate(snapshot.data.length, (itemIndex) {
                Products product = snapshot.data[itemIndex];
                return Card(
                  child: ListTile(
                    leading: SizedBox(height: 50.0, width: 50.0, child: NetworkImage(product._pictureURI)),
                    title: Text(product._model),
                    subtitle: Text(product._description + ', ' + product._price),
                ));
              }),
            );
          } else {
            return Center(child: CircularProgressIndicator());
          }
        });
  }

希望这可以帮助。 祝你好运！

Answer 2

这是我的 database_helper.dart 文件

import 'package:eecalc/models/products.dart';
import 'package:sqflite/sqflite.dart';
import 'dart:async';
import 'dart:io';
import 'package:path/path.dart';
import 'dart:typed_data';
import 'package:flutter/services.dart';


class DatabaseHelper {


 static Database _db;
 String dbName = "products.db";

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

initDb() async {
  var databasesPath = await getDatabasesPath();
  var path = join(databasesPath, dbName);
  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',dbName));
      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");
   }
   return await openDatabase(path);
 }


  // Fetch Operation: Get all Product Objects from Database
  Future<List<Map<String, dynamic>>> getProductsMapList () async {



     Database db = await this.db;

    var result = await db.rawQuery('SELECT * FROM Products WHERE CategoryID = 1');





     // if to check it contains something
     if(result.length != 0){


     return result;


   }

     print('Database Fetch empty');

    return result;
  }

  // Get the 'Map List' [List<Map>] and convert it to 'Product List' [List<Products>]
  Future<List<Products>> getProductsList() async{

     // Get 'Map List' from Database
    // Count the number of map entries in db table
   var productsMapList = await getProductsMapList();
    int count = productsMapList.length;

    // Create empty list for Products
    List<Products> productList = List<Products>();

    // For loop to create a ProductList from a MapList
   for (int i = 0; i < count; i++) {
    productList.add(Products.fromMapOject(productsMapList[i]));

   }


   return productList;



  }

}