Flutter网络连接检测插件ac_connectivity的使用

Flutter网络连接检测插件ac_connectivity的使用

标题

Flutter网络连接检测插件ac_connectivity的使用

内容

• connectivity_plus extended with Internet Connectivity

  • 这个包扩展了connectivity_plus插件：
    • 带有互联网连接状态（可按需访问或通过变更流访问），
    • 解决了Android应用从后台恢复时刷新连接的问题，
    • 具有两种状态：connectivity_plus和互联网连接状态（有一些限制，见下文重要说明）。

• Usage

  • Access to the original connectivity_plus members

    • checkConnectivity

      final ConnectivityPlusState state = await Connectivity().checkConnectivityPlusState();
      
      print(state); // ConnectivityPlusState.none, .mobile, .ethernet, etc.
      

    • onConnectivityChanged stream

      Connectivity().getConnectivityPlusStream().listen((state) {
        // It is guaranteed that two successive events have different values.
        print(result);
      });
      

  • Internet connectivity

    • 对于互联网连接，此包使用ac_inet_connectivity_checker并推荐配置根域名服务器的IPv4和IPv6地址。

      final state = Connectivity().lastInetConnectivityState;
      
      if (state == InetConnectivityState.disconnected) {
        // disconnected (same as ConnectivityResult.none)
      } else if (state == InetConnectivityState.connected) {
        // connected to a network without Internet access.
      } else if (state == InetConnectivityState.internet) {
        // connected to Internet.
      }
      

  • On-demand fresh value

    • 相对于网络连接测试，互联网连接测试允许定义超时。如果自己处理超时，则可以使用可取消的操作。注意，如果没有指定超时，可能会使用默认操作系统超时，通常是120秒。

      final cancelableOperation = Connectivity().checkInetConnectivityState(
        timeout: const Duration(seconds: 3),
      );
      
      final state = await cancelableOperation.value;
      

  • Stream

    • Important note on Internet Connectivity Stream

      • 检测互联网连接变化需要持续背景测试，以确保当应用程序重新上线时能够快速通知。
      • 如果设备更改网络配置（例如，从4G网络切换到Wi-Fi网络），互联网检测几乎会立即发生。
      • 而如果设备连接到具有无互联网访问的路由器的Wi-Fi网络，则可能需要指定backgroundChecksInterval配置中的时间（默认为0秒）来检测丢失连接。
      • 当Connectivity().lastInetConnectivityState == InetConnectivityState.internet时，该包选择不进行常量背景互联网检查。相反，它提供了一个notifyChange方法，您必须在HTTP请求错误时调用。即使不确定也可以调用它。

      import 'package:http/http.dart' as http;
      
      try {
        var response = await http.get(Uri.https('google.com'));
      } on SocketException {
        Connectivity().notifyChange();
      
        rethrow;
      } catch(error) {
        print(error);
      }
      

      • 如果真的想实现常量背景互联网检查，可以参考以下示例：

    CancelableTimer? connectivityChecker;

    Connectivity().listen((state) { if (state == InetConnectivityState.internet) { connectivityChecker = CancelableTimer.periodic( const Duration(seconds: 60), (_) => Connectivity().checkInetConnectivityState(), wait: true, ); } else { connectivityChecker?.cancel(); connectivityChecker = null; } })

示例代码

// SPDX-FileCopyrightText: © 223 - 2024 Anthony Champagne <dev@anthonychampagne.fr>
//
// SPDX-License-Identifier: BSD-3-Clause

import 'dart:async';

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

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

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

  [@override](/user/override)
  Widget build(BuildContext context) {
    return const MaterialApp(
      title: 'Flutter Demo',
      home: MyHomePage(),
    );
  }
}

class MyHomePage extends StatefulWidget {
  const MyHomePage({super.key});

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

class _MyHomePageState extends State<MyHomePage> {
  ConnectivityPlusState? _lastConnectivityPlusState;
  InetConnectivityState? _lastInetConnectivityState;
  StreamSubscription? _inetConnectivityStreamSubscription;
  StreamSubscription? _connectivityPlusStreamSubscription;

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

    _lastConnectivityPlusState = Connectivity().lastConnectivityPlusState;
    _lastInetConnectivityState = Connectivity().lastInetConnectivityState;

    _connectivityPlusStreamSubscription =
        Connectivity().getConnectivityPlusStream().listen((state) {
      setState(() {
        _lastConnectivityPlusState = state;
      });
    });

    _inetConnectivityStreamSubscription = Connectivity().listen((state) {
      setState(() {
        _lastInetConnectivityState = state;
      });
    });
  }

  [@override](/user/override)
  void dispose() {
    _inetConnectivityStreamSubscription?.cancel();
    _connectivityPlusStreamSubscription?.cancel();

    super.dispose();
  }

  void _notifyConnectivityChange() {
    Connectivity().notifyChange();
  }

  [@override](/user/override)
  Widget build(BuildContext context) {
    return Scaffold(
      body: Center(
        child: Column(
          mainAxisAlignment: MainAxisAlignment.center,
          children: <Widget>[
            const Text('Last connectivity_plus state:'),
            Text(
              '$_lastConnectivityPlusState',
              style: Theme.of(context).textTheme.headlineMedium,
            ),
            const SizedBox(height: 20),
            const Text('Last Internet connectivity state:'),
            Text(
              '$_lastInetConnectivityState',
              style: Theme.of(context).textTheme.headlineMedium,
            ),
          ],
        ),
      ),
      floatingActionButton: FloatingActionButton(
        onPressed: _notifyConnectivityChange,
        tooltip: 'Notify connectivity change',
        child: const Icon(Icons.refresh),
      ),
    );
  }
}