Flutter中SQLite数据库的使用

同时支持android和ios

支持事务和批量操作
支持插入/查询/更新/删除操作
在iOS和Android上的后台线程中执行数据库操作

1.添加依赖

dependencies:
  ...
  sqflite: any

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2.导入依赖

import 'package:sqflite/sqflite.dart';

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3.支持SQL查询

// 获取本地SQLite数据库
var databasesPath = await getDatabasesPath();
String path = join(databasesPath, "demo.db");

// 删除数据库
await deleteDatabase(path);

// 打开数据库
Database database = await openDatabase(path, version: 1,
    onCreate: (Database db, int version) async {
  // 当打开数据库的时候创建一张表
  await db.execute(
      "CREATE TABLE Test (id INTEGER PRIMARY KEY, name TEXT, value INTEGER, num REAL)");
});

// 开启事务，增加两条记录
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");
});

// 更新一条记录
int count = await database.rawUpdate(
    'UPDATE Test SET name = ?, VALUE = ? WHERE name = ?',
    ["updated name", "9876", "some name"]);
print("updated: $count");

// 获取Test表的数据
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);
assert(const DeepCollectionEquality().equals(list, expectedList));

// 获取记录的数量
count = Sqflite
    .firstIntValue(await database.rawQuery("SELECT COUNT(*) FROM Test"));
assert(count == 2);

// 删除一条记录
count = await database
    .rawDelete('DELETE FROM Test WHERE name = ?', ['another name']);
assert(count == 1);

// 关闭数据库
await database.close();

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4.用法示例

final String tableTodo = "todo";
final String columnId = "_id";
final String columnTitle = "title";
final String columnDone = "done";

class Todo {
  int id;
  String title;
  bool done;

  Map<String, dynamic> toMap() {
    var map = <String, dynamic>{
      columnTitle: title,
      columnDone: done == true ? 1 : 0
    };
    if (id != null) {
      map[columnId] = id;
    }
    return map;
  }

  Todo();

  Todo.fromMap(Map<String, dynamic> 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)
''');
    });
  }

  Future<Todo> insert(Todo todo) async {
    todo.id = await db.insert(tableTodo, todo.toMap());
    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 new 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();
}

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注意事项

1.Transaction(事务)

当使用transaction对象访问数据时，不能再使用database对象访问数据库

await database.transaction((txn) async {
  // 完全Ok
  await txn.execute("CREATE TABLE Test1 (id INTEGER PRIMARY KEY)");

  // 不能在transaction对象里面使用database对象，这会发生死锁
  // await database.execute("CREATE TABLE Test2 (id INTEGER PRIMARY KEY)");
});

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2.支持批量操作

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();

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这些操作返回结果，都会有一些开销；如果你不考虑结果，可以使用：

await batch.commit(noResult: true);

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事务期间，直到事务被提交，批量操作才能提交

await database.transaction((txn) async {
  var batch = txn.batch();
  //...
  // 实际提交将在事务启动时发生
  await batch.commit();
});

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3.表和列的名字

通常避免使用SQLite的关键字作为表名或者列名，例如以下其中之一：

"add","all","alter","and","as","autoincrement","between","case","check","collate","commit","constraint","create","default","deferrable","delete","distinct","drop","else","escape","except","exists","foreign","from","group","having","if","in","index","insert","intersect","into","is","isnull","join","limit","not","notnull","null","on","or","order","primary","references","select","set","table","then","to","transaction","union","unique","update","using","values","when","where"

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否则要使用双引号转义，例如：

db.rawQuery('SELECT * FROM "table"');
db.query("table", columns: ["group"], where: '"group" = ?', whereArgs: ["my_group"]);

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4.支持的列类型

INTEGER   相当于dart类型中int
 REAL     相当于dart类型中num
 TEXT     相当于dart类型中String
 BLOB     相当于dart类型中Uint8List