Flutter二进制地图文件处理插件binary_map_file的使用

Flutter二进制地图文件处理插件binary_map_file的使用

BinaryMapFile 是一个用于在纯Dart中通过文件系统进行高效键值存储的库，并且提供了安全支持。

开始使用

要开始使用该库，只需导入 binary_map_file 包：

import "dart:io";
import 'package:binary_map_file/binary_map_file.dart';

final file = File(path);
final binaryMapFile = BinaryMapFile(file, secured: false); 
await binaryMapFile.ensureInitialized();
// 如果你需要安全的序列化，可以将标志 secured 设置为 `true`

获取值

获取键 firstRun 对应的布尔值。如果该键未设置或为 null，则将其重置为默认值 true 并返回获取到的值。

final firstRun = binaryMapFile.getDefaultValue<bool>('firstRun', true); // 返回布尔值或默认值
// 或者
final value = binaryMapFile.getValue<bool>('firstRun'); // 返回布尔值或 null

设置值

将键 firstRun 的值设置为 false：

binaryMapFile.setValue<bool>('firstRun', false);

检查包含键

检查是否存在键 firstRun：

final existed = binaryMapFile.containsKey('firstRun');

序列化

将当前映射保存到文件：

await binaryMapFile.serialize();

支持的数据类型

该库支持所有由 Flutter 标准二进制编码使用的 MessageCodec 所支持的数据类型。支持的消息包括以下无环值：

• null
• bool 布尔值
• num 数值
• String 字符串
• Uint8List, Int32List, Int64List, Float64List 数组
• List 列表
• Map 映射

示例代码

以下是完整的示例代码，展示了如何使用 BinaryMapFile 插件来管理应用中的计数器数据：

import 'dart:io';

import 'package:binary_map_file/binary_map_file.dart';
import 'package:flutter/material.dart';
import 'package:path_provider/path_provider.dart';
import 'package:path/path.dart' as path;

void main() {
  runApp(const MyApp());
}

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

  [@override](/user/override)
  Widget build(BuildContext context) {
    return MaterialApp(
      title: 'Flutter Demo',
      theme: ThemeData(
        colorScheme: ColorScheme.fromSeed(seedColor: Colors.deepPurple),
        useMaterial3: true,
      ),
      home: const MyHomePage(title: 'Count will be saved into map file'),
    );
  }
}

class MyHomePage extends StatefulWidget {
  const MyHomePage({super.key, required this.title});

  final String title;

  [@override](/user/override)
  State<MyHomePage> createState() => _MyHomePageState();
}

class _MyHomePageState extends State<MyHomePage> {
  static const String key = 'count';
  late final BinaryMapFile binaryMapFile;
  late final ValueNotifier<bool> initNotifier;
  late final ValueNotifier<int> countNotifier;
  int _counter = 0;

  [@override](/user/override)
  void initState() {
    super.initState();

    initNotifier = ValueNotifier<bool>(false);

    WidgetsBinding.instance.addPostFrameCallback((_) async => initialize());
  }

  Future<void> initialize() async {
    final Directory appDocumentsDir = await getApplicationDocumentsDirectory();
    final filePath = path.join(appDocumentsDir.path, 'file.dat');

    binaryMapFile = BinaryMapFile(path: filePath);
    await binaryMapFile.ensureInitialized();
    initNotifier.value = true;

    final count = binaryMapFile.getDefaultValue<int>(key, 0) ?? 0;
    countNotifier = ValueNotifier<int>(count);
  }

  Future<void> _incrementCounter() async {
    var count = binaryMapFile.getValue<int>(key) ?? 0;
    ++count;

    binaryMapFile.setValue<int>(key, count);
    await binaryMapFile.serialize();
    countNotifier.value = count;

    setState(() {
      ++_counter;
    });
  }

  [@override](/user/override)
  Widget build(BuildContext context) {
    return Scaffold(
      appBar: AppBar(
        backgroundColor: Theme.of(context).colorScheme.inversePrimary,
        title: Text(widget.title),
      ),
      body: Center(
        child: ValueListenableBuilder(
          valueListenable: initNotifier,
          builder: (context, init, _) {
            if (!init) {
              return const Center(child: CircularProgressIndicator());
            }

            return Column(
              mainAxisAlignment: MainAxisAlignment.center,
              children: [
                const Text(
                  'Increase value and hot start the app to check saved value:',
                ),
                ValueListenableBuilder(
                    valueListenable: countNotifier,
                    builder: (context, count, _) {
                      return Text(
                        '$count',
                        style: Theme.of(context).textTheme.headlineMedium,
                      );
                    }),
                const Text(
                  'This is normal counter:',
                ),
                Text(
                  '$_counter',
                  style: Theme.of(context).textTheme.headlineMedium,
                ),
              ],
            );
          },
        ),
      ),
      floatingActionButton: ValueListenableBuilder(
          valueListenable: initNotifier,
          builder: (context, init, _) {
            if (!init) {
              return const SizedBox();
            }

            return FloatingActionButton(
              onPressed: _incrementCounter,
              tooltip: 'Increment',
              child: const Icon(Icons.add),
            );
          }),
    );
  }
}