Flutter本地存储插件local_shared的使用

local_shared 是一个用于JSON文件存储的SharedPreferences封装库，提供了对本地存储的安全CRUD操作支持。本文将介绍如何在Flutter项目中使用该插件，并提供完整的示例代码。

安装

首先，在你的 pubspec.yaml 文件中添加以下依赖：

dependencies:
  local_shared: ^1.0.5

然后运行 flutter pub get 来安装这个包。

初始化

在你的 main 函数中初始化 LocalShared 实例：

import 'package:flutter/material.dart';
import 'package:local_shared/local_shared.dart';

void main() async {
  WidgetsFlutterBinding.ensureInitialized();
  await LocalShared('db').initialize();

  runApp(MyApp());
}

你还可以为方便起见创建自定义类型定义：

typedef DB = LocalShared;

集合操作 (Collection)

创建集合

final result = await Shared.col('myCollection').create();
print(result); // SharedMany(success: true, message: '...', data: <JSON>[])

读取集合

final response = await Shared.col('myCollection').read();
print(response); // SharedMany(success: true, message: '...', data: <JSON>[])

更新集合

final response = await Shared.col('myCollection').update('myNewCollection');
print(response); // SharedMany(success: true, message: '...', data: <JSON>[])

删除集合

final response = await Shared.col('myNewCollection').delete();
print(response); // SharedNone(success: true, message: '....')

文档操作 (Document)

创建文档

final result = await Shared.col('myCollection').doc('documentId').create({'key': 'value'});
print(result); // SharedOne(success: true, message: '...', data: JSON)

读取文档

final response = await Shared.col('myCollection').doc('documentId').read();
print(response); // SharedOne(success: true, message: '...', data: JSON)

更新文档

final response = await Shared.col('myCollection').doc('documentId').update({'newKey': 'newValue'});
print(response); // SharedOne(success: true, message: '...', data: JSON)

删除文档

final response = await Shared.col('myCollection').doc('documentId').delete();
print(response); // SharedNone(success: true, message: '...')

多文档操作 (Many Document)

创建多文档

final result = await Shared.col('myCollection').docs(['docId1', 'docId2']).create((index) => {'key': 'value'});
print(result); // SharedMany(success: true, message: '...', data: <JSON>[])

读取多文档

final response = await Shared.col('myCollection').docs(['docId1', 'docId2']).read();
print(response); // SharedMany(success: true, message: '...', data: <JSON>[])

更新多文档

final response = await Shared.col('myCollection').docs(['docId1', 'docId2']).update((index) => {'newKey': 'newValue'});
print(response); // SharedMany(success: true, message: '...', data: <JSON>[])

删除多文档

final response = await Shared.col('myCollection').docs(['docId1', 'docId2']).delete();
print(response); // SharedNone(success: true, message: '...')

数据流监听 (Stream)

LocalShared 提供了JSON数据流来监听集合的变化：

LocalShared.stream.listen(print);

await Shared.col('myCollection').docs(['A','B']).create((index) => {'desc': 'test'});

结果输出：

{id: myCollection,
documents: [
{id: A, data: {desc: test}},
{id: B, data: {desc: test}}
]}

自定义数据流监听

如果你想只监听特定集合的变化，可以这样做：

final controller = StreamController<JSON>.broadcast();
final collection = SharedCollection('myCertainCollection', controller: controller);

controller.stream.listen(print);

await collection.docs(['A','B']).create((index) => {'desc': 'test'});

结果输出：

{id: myCertainCollection,
documents: [
{id: A, data: {desc: test}},
{id: B, data: {desc: test}}
]}

示例应用

下面是一个简单的Flutter应用示例，展示了如何使用 local_shared 进行CRUD操作：

import 'package:flutter/material.dart';
import 'package:local_shared/local_shared.dart';

void main() async {
  WidgetsFlutterBinding.ensureInitialized();
  await LocalShared('MY_DB').initialize();

  runApp(const MaterialApp(
    title: 'Local Shared CRUD',
    home: MyApp(),
  ));
}

class MyApp extends StatelessWidget {
  const MyApp({super.key});

  [@override](/user/override)
  Widget build(BuildContext context) {
    return Scaffold(
      appBar: AppBar(title: const Text('Local Shared CRUD')),
      body: Column(
        mainAxisAlignment: MainAxisAlignment.center,
        children: [
          ElevatedButton(
            onPressed: () async {
              final result = await Shared.col('example').create();
              print('Create Collection: $result');
            },
            child: const Text('Create Collection'),
          ),
          ElevatedButton(
            onPressed: () async {
              final result = await Shared.col('example').doc('doc1').create({'key': 'value'});
              print('Create Document: $result');
            },
            child: const Text('Create Document'),
          ),
        ],
      ),
    );
  }
}