前言

在Android中會(huì)在基礎(chǔ)類中監(jiān)聽手機(jī)的網(wǎng)絡(luò)狀態(tài)结执，并作出相應(yīng)的提示谴麦，在Flutter 中也提供了相應(yīng)的package,但是略有不同宇挫；

1.依賴

dependencies:
  connectivity: ^0.3.2

2.導(dǎo)入

import 'package:flutter_cache_manager/flutter_cache_manager.dart';

3.簡單使用

檢查當(dāng)前網(wǎng)絡(luò)狀態(tài)

注意：在Android上荧止，這并不保證連接到Internet稼跳。例如盟庞，該應(yīng)用程序可能有WiFi接入，但可能是VPN或沒有接入的酒店WiFi汤善。也就是說網(wǎng)絡(luò)狀態(tài)是'wifi',也不代表你的手機(jī)能進(jìn)行網(wǎng)絡(luò)訪問什猖。

import 'package:connectivity/connectivity.dart';

var connectivityResult = await (new 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.
}

監(jiān)聽網(wǎng)絡(luò)狀態(tài)

請(qǐng)注意，不應(yīng)該使用當(dāng)前的網(wǎng)絡(luò)狀態(tài)來決定是否可以可靠地進(jìn)行網(wǎng)絡(luò)連接红淡。
網(wǎng)絡(luò)層可能會(huì)出現(xiàn)超時(shí)和錯(cuò)誤不狮，需要在應(yīng)用程序代碼中做好異常處理；

import 'package:connectivity/connectivity.dart';

initState() {
  subscription = new Connectivity().onConnectivityChanged.listen((ConnectivityResult result) {
    // Got a new connectivity status!
  })
}

// Be sure to cancel subscription after you are done
dispose() {
  subscription.cancel();
}

4.例子

import 'dart:async';

import 'package:flutter/material.dart';
import 'package:flutter/services.dart';
import 'package:connectivity/connectivity.dart';

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

class MyApp extends StatelessWidget {
  // This widget is the root of your application.
  @override
  Widget build(BuildContext context) {
    return MaterialApp(
      title: 'Flutter Demo',
      theme: ThemeData(
        primarySwatch: Colors.blue,
      ),
      home: MyHomePage(title: 'Flutter Demo Home Page'),
    );
  }
}

class MyHomePage extends StatefulWidget {
  MyHomePage({Key key, this.title}) : super(key: key);

  final String title;

  @override
  _MyHomePageState createState() => _MyHomePageState();
}

class _MyHomePageState extends State<MyHomePage> {
  String _connectionStatus = 'Unknown';
  final Connectivity _connectivity = Connectivity();
  StreamSubscription<ConnectivityResult> _connectivitySubscription;

  @override
  void initState() {
    super.initState();
    initConnectivity();
    _connectivitySubscription =
        _connectivity.onConnectivityChanged.listen((ConnectivityResult result) {
      setState(() => _connectionStatus = result.toString());
    });
  }

  @override
  void dispose() {
    _connectivitySubscription.cancel();
    super.dispose();
  }

   //平臺(tái)消息是異步的在旱，所以我們用異步方法初始化荤傲。
  Future<Null> initConnectivity() async {
    String connectionStatus;
    //平臺(tái)消息可能會(huì)失敗冀值，因此我們使用Try/Catch PlatformException猎贴。
    try {
      connectionStatus = (await _connectivity.checkConnectivity()).toString();
    } on PlatformException catch (e) {
      print(e.toString());
      connectionStatus = 'Failed to get connectivity.';
    }

    // 如果在異步平臺(tái)消息運(yùn)行時(shí)從樹中刪除了該小部件，
    // 那么我們希望放棄回復(fù)安接，而不是調(diào)用setstate來更新我們不存在的外觀俊嗽。
    if (!mounted) {
      return;
    }

    setState(() {
      _connectionStatus = connectionStatus;
    });
  }

  @override
  Widget build(BuildContext context) {
    return Scaffold(
      appBar: AppBar(
        title: const Text('Plugin example app'),
      ),
      body: Center(child: Text('Connection Status: $_connectionStatus\n')),
    );
  }
}

5.tips

當(dāng) wifi 和 移動(dòng)網(wǎng)絡(luò) 同時(shí)存在時(shí)雾家，監(jiān)聽中提示當(dāng)前網(wǎng)絡(luò)wifi;并且此時(shí)斷開或者連接移動(dòng)網(wǎng)絡(luò)無回調(diào)

6.資料參考

https://pub.dartlang.org/packages/connectivity

• 這個(gè)網(wǎng)址提供了很多兼容Android 和 IOS 的 package；