Dart Flatter中的Sqlite，数据库assets如何工作

首先，您需要从CSV构造一个sqlite数据库.这可以通过以下方式完成:

1. 创建所需的表(users.sql)

   CREATE TABLE users(
      firstname TEXT NOT NULL,
      lastname TEXT NOT NULL,
      dob TEXT NOT NULL
   );
   

2. 创建sqlite数据库

   sqlite3 database.db < users.sql
   

3. 插入CSV数据

   sqlite3 database.db
   .mode csv
   .import data.csv users
   

4. 放入数据库.将db添加到您的assets资源 中，并将其添加到pubspec中.亚马尔.

   flutter:
     # ...
     assets:
       - assets/database.db
   

5. 在你的应用程序中，你必须将assets资源 文件复制到"文档"中.这有点复杂.

   // Construct a file path to copy database to
   Directory documentsDirectory = await getApplicationDocumentsDirectory();
   String path = join(documentsDirectory.path, "asset_database.db");
   
   // Only copy if the database doesn't exist
   if (FileSystemEntity.typeSync(path) == FileSystemEntityType.notFound){
     // Load database from asset and copy
     ByteData data = await rootBundle.load(join('assets', 'database.db'));
     List<int> bytes = data.buffer.asUint8List(data.offsetInBytes, data.lengthInBytes);
   
     // Save copied asset to documents
     await new File(path).writeAsBytes(bytes);
   }
   

6. 最后，您可以像这样访问数据库.

   Directory appDocDir = await getApplicationDocumentsDirectory();
   String databasePath = join(appDocDir.path, 'asset_database.db');
   this.db = await openDatabase(databasePath);
   initialized = true;
   

7. 示例查询(此._initialize()为步骤6)

   Future<List<Page>> search(String word, int parentId) async {
       if (!initialized) await this._initialize();
       String query = '''
         SELECT * FROM users
         LIMIT 25''';
       return await this.db.rawQuery(query);
   }