只是试图简化代码使用连接包颤振。

import 'package:connectivity/connectivity.dart';

var connectivityResult = await (Connectivity().checkConnectivity());
if (connectivityResult == ConnectivityResult.mobile) {
  // I am connected to a mobile network.
} else if (connectivityResult == ConnectivityResult.wifi) {
  // I am connected to a wifi network.
} else {
  // I am not connected to the internet
}

Null安全代码:

One time check: Create this method: Future<bool> hasNetwork() async { try { final result = await InternetAddress.lookup('example.com'); return result.isNotEmpty && result[0].rawAddress.isNotEmpty; } on SocketException catch (_) { return false; } } Usage: bool isOnline = await hasNetwork(); Setting up a listener: Add the following dependency to your pubspec.yaml file. connectivity_plus: ^2.0.2 Full code: void main() => runApp(MaterialApp(home: HomePage())); class HomePage extends StatefulWidget { @override _HomePageState createState() => _HomePageState(); } class _HomePageState extends State<HomePage> { Map _source = {ConnectivityResult.none: false}; final MyConnectivity _connectivity = MyConnectivity.instance; @override void initState() { super.initState(); _connectivity.initialise(); _connectivity.myStream.listen((source) { setState(() => _source = source); }); } @override Widget build(BuildContext context) { String string; switch (_source.keys.toList()[0]) { case ConnectivityResult.mobile: string = 'Mobile: Online'; break; case ConnectivityResult.wifi: string = 'WiFi: Online'; break; case ConnectivityResult.none: default: string = 'Offline'; } return Scaffold( body: Center(child: Text(string)), ); } @override void dispose() { _connectivity.disposeStream(); super.dispose(); } } class MyConnectivity { MyConnectivity._(); static final _instance = MyConnectivity._(); static MyConnectivity get instance => _instance; final _connectivity = Connectivity(); final _controller = StreamController.broadcast(); Stream get myStream => _controller.stream; void initialise() async { ConnectivityResult result = await _connectivity.checkConnectivity(); _checkStatus(result); _connectivity.onConnectivityChanged.listen((result) { _checkStatus(result); }); } void _checkStatus(ConnectivityResult result) async { bool isOnline = false; try { final result = await InternetAddress.lookup('example.com'); isOnline = result.isNotEmpty && result[0].rawAddress.isNotEmpty; } on SocketException catch (_) { isOnline = false; } _controller.sink.add({result: isOnline}); } void disposeStream() => _controller.close(); }

截图:

来源:connectivity_plus和Günter Zöchbauer

我几乎读了所有的帖子，@dennmat的帖子对我最有用。虽然它对我没用，而且也过时了。我有更新颤振更新连接包(I。E connectivity_plus)和data_connection_checker(检查移动和wifi是否有实际的互联网连接)。 在这篇文章之后，你将能够连续监听互联网连接。

1. 添加依赖关系 A)连通性:^1.0.6 B) data_connection_checker: ^0.3.4

2. 处理所有连接的自定义类。

import 'dart:async';
import 'package:connectivity_plus/connectivity_plus.dart';
import 'package:data_connection_checker/data_connection_checker.dart'; 

class ConnectionUtil {
  //This creates the single instance by calling the `_internal` constructor specified below
  static final ConnectionUtil _singleton = new ConnectionUtil._internal();
  ConnectionUtil._internal();
  //This is what's used to retrieve the instance through the app
  static ConnectionUtil getInstance() => _singleton;
  //This tracks the current connection status
  bool hasConnection = false;
  //This is how we'll allow subscribing to connection changes
  StreamController connectionChangeController = StreamController();
  //flutter_connectivity
  final Connectivity _connectivity = Connectivity();
  void initialize() {
    _connectivity.onConnectivityChanged.listen(_connectionChange);
  }
  //flutter_connectivity's listener
  void _connectionChange(ConnectivityResult result) {
    hasInternetInternetConnection();
  }
  Stream get connectionChange => connectionChangeController.stream;
  Future<bool> hasInternetInternetConnection() async {
    bool previousConnection = hasConnection;
    var connectivityResult = await (Connectivity().checkConnectivity());
    //Check if device is just connect with mobile network or wifi
    if (connectivityResult == ConnectivityResult.mobile ||
        connectivityResult == ConnectivityResult.wifi) {
      //Check there is actual internet connection with a mobile network or wifi
      if (await DataConnectionChecker().hasConnection) {
        // Network data detected & internet connection confirmed.
        hasConnection = true;
      } else {
        // Network data detected but no internet connection found.
        hasConnection = false;
      }
    }
    // device has no mobile network and wifi connection at all
    else {
      hasConnection = false;
    }
    // The connection status changed send out an update to all listeners
    if (previousConnection != hasConnection) {
      connectionChangeController.add(hasConnection);
    }
    return hasConnection;
  }
}

检查任何地方的连接并倾听变化。

@override
  initState() {
    print('called');
    //Create instance
    ConnectionUtil connectionStatus = ConnectionUtil.getInstance();
    //Initialize
    connectionStatus.initialize();
    //Listen for connection change
    _connectionChangeStream = connectionStatus.connectionChange.listen((event) {
      print(event);
    });

    super.initState();
  }

切换飞行模式时检查日志。你应该得到有true和false值的日志。

注意:这将无法在flutter web工作，如果你想让它工作，请使用dio或http插件而不是data_connection_checker。

项目示例可以在这里找到。谢谢

import 'dart:async';
import 'dart:io';
import 'package:flutter/material.dart';
import 'package:app_settings/app_settings.dart';
import 'package:connectivity/connectivity.dart';

class InternetConnect extends StatefulWidget {
  @override
  InternetConnectState createState() => InternetConnectState();
}

class InternetConnectState extends State<InternetConnect> {
  ConnectivityResult previous;
  bool dialogshown = false;
  StreamSubscription connectivitySubscription;

  Future<bool> checkinternet() async {
    try {
      final result = await InternetAddress.lookup('google.com');
      if (result.isNotEmpty && result[0].rawAddress.isNotEmpty) {
        return Future.value(true);
      }
    } on SocketException catch (_) {
      return Future.value(false);
    }
  }

  void checkInternetConnect(BuildContext context) {
    connectivitySubscription = Connectivity()
        .onConnectivityChanged
        .listen((ConnectivityResult connresult) {
      if (connresult == ConnectivityResult.none) {
        dialogshown = true;
        showDialog(
            context: context, barrierDismissible: false, child: alertDialog());
      } else if (previous == ConnectivityResult.none) {
        checkinternet().then((result) {
          if (result == true) {
            if (dialogshown == true) {
              dialogshown = false;
              Navigator.pop(context);
            }
          }
        });
      }

      previous = connresult;
    });
  }

  AlertDialog alertDialog() {
    return AlertDialog(
      title: Text('ERROR'),
      content: Text("No Internet Detected."),
      actions: <Widget>[
        FlatButton(
          // method to exit application programitacally

          onPressed: () {
            AppSettings.openWIFISettings();
          },
          child: Text("Settings"),
        ),
      ],
    );
  }

  @override
  Widget build(BuildContext context) {
    return Container();
  }
}

    and you can use this method in init of any class

@override
void initState() {
  // TODO: implement initState
  InternetConnectState().checkInternetConnect(context);
  super.initState();
}

我有一个问题与提出的解决方案，使用查找并不总是返回预期的值。

这是由于DNS缓存，调用的值被缓存，而不是在下一次尝试时进行正确的调用，它会返回缓存的值。当然，这是一个问题，因为这意味着如果你失去了连接和调用查找，它仍然可以返回缓存的值，就像你有互联网一样，相反，如果你重新连接你的互联网后，查找返回null，它仍然会在缓存的持续时间内返回null，这可能是几分钟，即使你现在有互联网。

查找返回一些东西并不一定意味着你有网络，它不返回任何东西并不一定意味着你没有网络。它不可靠。

我从data_connection_checker插件中获得灵感，实现了以下解决方案:

 /// If any of the pings returns true then you have internet (for sure). If none do, you probably don't.
  Future<bool> _checkInternetAccess() {
    /// We use a mix of IPV4 and IPV6 here in case some networks only accept one of the types.
    /// Only tested with an IPV4 only network so far (I don't have access to an IPV6 network).
    final List<InternetAddress> dnss = [
      InternetAddress('8.8.8.8', type: InternetAddressType.IPv4), // Google
      InternetAddress('2001:4860:4860::8888', type: InternetAddressType.IPv6), // Google
      InternetAddress('1.1.1.1', type: InternetAddressType.IPv4), // CloudFlare
      InternetAddress('2606:4700:4700::1111', type: InternetAddressType.IPv6), // CloudFlare
      InternetAddress('208.67.222.222', type: InternetAddressType.IPv4), // OpenDNS
      InternetAddress('2620:0:ccc::2', type: InternetAddressType.IPv6), // OpenDNS
      InternetAddress('180.76.76.76', type: InternetAddressType.IPv4), // Baidu
      InternetAddress('2400:da00::6666', type: InternetAddressType.IPv6), // Baidu
    ];

    final Completer<bool> completer = Completer<bool>();

    int callsReturned = 0;
    void onCallReturned(bool isAlive) {
      if (completer.isCompleted) return;

      if (isAlive) {
        completer.complete(true);
      } else {
        callsReturned++;
        if (callsReturned >= dnss.length) {
          completer.complete(false);
        }
      }
    }

    dnss.forEach((dns) => _pingDns(dns).then(onCallReturned));

    return completer.future;
  }

  Future<bool> _pingDns(InternetAddress dnsAddress) async {
    const int dnsPort = 53;
    const Duration timeout = Duration(seconds: 3);

    Socket socket;
    try {
      socket = await Socket.connect(dnsAddress, dnsPort, timeout: timeout);
      socket?.destroy();
      return true;
    } on SocketException {
      socket?.destroy();
    }
    return false;
  }

对_checkInternetAccess的调用最多需要一个超时时间才能完成(这里是3秒)，如果我们可以到达任何一个DNS，它将在到达第一个DNS时立即完成，而不需要等待其他DNS(因为到达一个DNS就足以知道您有internet)。所有对_pingDns的调用都是并行完成的。

它似乎在IPV4网络上工作得很好，当我不能在IPV6网络上测试它时(我没有访问IPV6网络)，我认为它仍然可以工作。它也适用于发布模式构建，但我还必须将我的应用提交给苹果，看看他们是否发现了这个解决方案的任何问题。

它也应该在大多数国家(包括中国)工作，如果它不能在一个工作，你可以添加一个DNS到列表中，可以从你的目标国家访问。

连接插件在其文档中声明，它只在有网络连接的情况下提供信息，但不包括网络连接到Internet的情况

请注意，在Android上，这并不保证连接到互联网。例如，应用程序可能有wifi接入，但它可能是一个VPN或酒店wifi，没有接入。

你可以使用

import 'dart:io';
...
try {
  final result = await InternetAddress.lookup('example.com');
  if (result.isNotEmpty && result[0].rawAddress.isNotEmpty) {
    print('connected');
  }
} on SocketException catch (_) {
  print('not connected');
}

更新

不建议使用连接包。请使用官方的Flutter Community connectivity_plus包。