Flutter数据库的使用方法

dependencies:
  sqflite: ^1.3.0
  path:版本号

import 'dart:async';

import 'package:path/path.dart';
import 'package:sqflite/sqflite.dart';

var db = await openDatabase('my_db.db');

await db.close();

var databasesPath = await getDatabasesPath();
String path = join(databasesPath, 'demo.db');

Database database = await openDatabase(path, version: 1,
    onCreate: (Database db, int version) async {
  // 创建数据库时创建表
  await db.execute(
      'CREATE TABLE Test (id INTEGER PRIMARY KEY, name TEXT, value INTEGER, num REAL)');
});

await database.transaction((txn) async {
  int id1 = await txn.rawInsert(
      'INSERT INTO Test(name, value, num) VALUES("some name", 1234, 456.789)');
  print('inserted1: $id1');
  int id2 = await txn.rawInsert(
      'INSERT INTO Test(name, value, num) VALUES(?, ?, ?)',
      ['another name', 12345678, 3.1416]);
  print('inserted2: $id2');
});

count = await database
    .rawDelete('DELETE FROM Test WHERE name = ?', ['another name']);

int count = await database.rawUpdate('UPDATE Test SET name = ?, value = ? WHERE name = ?',
    ['updated name', '9876', 'some name']);
print('updated: $count');

// Get the records
List<Map> list = await database.rawQuery('SELECT * FROM Test');
List<Map> expectedList = [
  {'name': 'updated name', 'id': 1, 'value': 9876, 'num': 456.789},
  {'name': 'another name', 'id': 2, 'value': 12345678, 'num': 3.1416}
];
print(list);
print(expectedList);

count = Sqflite.firstIntValue(await database.rawQuery('SELECT COUNT(*) FROM Test'));

await database.close();

await deleteDatabase(path);

//字段
final String tableTodo = 'todo';
final String columnId = '_id';
final String columnTitle = 'title';
final String columnDone = 'done';

//对应类
class Todo {
  int id;
  String title;
  bool done;

  //把当前类中转换成Map，以供外部使用
  Map<String, Object?> toMap() {
    var map = <String, Object?>{
      columnTitle: title,
      columnDone: done == true ? 1 : 0
    };
    if (id != null) {
      map[columnId] = id;
    }
    return map;
  }
  //无参构造
  Todo();
  
  //把map类型的数据转换成当前类对象的构造函数。
  Todo.fromMap(Map<String, Object?> map) {
    id = map[columnId];
    title = map[columnTitle];
    done = map[columnDone] == 1;
  }
}

class TodoProvider {
  Database db;

  Future open(String path) async {
    db = await openDatabase(path, version: 1,
        onCreate: (Database db, int version) async {
      await db.execute('''
  create table $tableTodo ( 
  $columnId integer primary key autoincrement, 
  $columnTitle text not null,
  $columnDone integer not null)
                        ''');
    });
  }

  //向表中插入一条数据，如果已经插入过了，则替换之前的。
  Future<Todo> insert(Todo todo) async {
    todo.id = await db.insert(tableTodo, todo.toMap()，conflictAlgorithm: ConflictAlgorithm.replace,);
    return todo;
  }

  Future<Todo> getTodo(int id) async {
    List<Map> maps = await db.query(tableTodo,
        columns: [columnId, columnDone, columnTitle],
        where: '$columnId = ?',
        whereArgs: [id]);
    if (maps.length > 0) {
      return Todo.fromMap(maps.first);
    }
    return null;
  }

  Future<int> delete(int id) async {
    return await db.delete(tableTodo, where: '$columnId = ?', whereArgs: [id]);
  }

  Future<int> update(Todo todo) async {
    return await db.update(tableTodo, todo.toMap(),
        where: '$columnId = ?', whereArgs: [todo.id]);
  }

  Future close() async => db.close();
}

List<Map<String, Object?>> records = await db.query('my_table');

Map<String, Object?> mapRead = records.first;

mapRead['my_column'] = 1;
// Crash... `mapRead` is read-only

// 根据上面的map创建一个map副本
Map<String, Object?> map = Map<String, Object?>.from(mapRead);
// 在内存中修改此副本中存储的字段值
map['my_column'] = 1;

// Convert the List<Map<String, dynamic> into a List<Todo>.
  return List.generate(maps.length, (i) {
    return Todo(
      id: maps[i][columnId],
      title: maps[i][columnTitle],
      done: maps[i][columnDown],
    );
  });

batch = db.batch();
batch.insert('Test', {'name': 'item'});
batch.update('Test', {'name': 'new_item'}, where: 'name = ?', whereArgs: ['item']);
batch.delete('Test', where: 'name = ?', whereArgs: ['item']);
results = await batch.commit();

await batch.commit(noResult: true);

await database.transaction((txn) async {
  var batch = txn.batch();
  
  // ...
  
  // commit but the actual commit will happen when the transaction is committed
  // however the data is available in this transaction
  await batch.commit();
  
  //  ...
});

await batch.commit(continueOnError: true);