我有一个网络调用要执行。但在此之前，我需要检查设备是否有互联网连接。
这是我目前为止所做的:
var connectivityResult = new Connectivity().checkConnectivity();// User defined class
if (connectivityResult == ConnectivityResult.mobile ||
connectivityResult == ConnectivityResult.wifi) {*/
this.getData();
} else {
neverSatisfied();
}
上述方法行不通。
当前回答
这是我的解决方案，它检查互联网连接以及数据连接，我希望你喜欢它。
First of all add dependencies in your pubsec.yamldependencies:
data_connection_checker:
import 'dart:async';
import 'package:data_connection_checker/data_connection_checker.dart';
import 'package:flutter/material.dart';
void main() => runApp(MyApp());
class MyApp extends StatelessWidget {
@override
Widget build(BuildContext context) {
return MaterialApp(
title: "Data Connection Checker",
home: HomePage(),
);
}
}
class HomePage extends StatefulWidget {
@override
_HomePageState createState() => _HomePageState();
}
class _HomePageState extends State<HomePage> {
StreamSubscription<DataConnectionStatus> listener;
var Internetstatus = "Unknown";
@override
void initState() {
// TODO: implement initState
super.initState();
// _updateConnectionStatus();
CheckInternet();
}
@override
void dispose() {
// TODO: implement dispose
listener.cancel();
super.dispose();
}
CheckInternet() async {
// Simple check to see if we have internet
print("The statement 'this machine is connected to the Internet' is: ");
print(await DataConnectionChecker().hasConnection);
// returns a bool
// We can also get an enum instead of a bool
print("Current status: ${await DataConnectionChecker().connectionStatus}");
// prints either DataConnectionStatus.connected
// or DataConnectionStatus.disconnected
// This returns the last results from the last call
// to either hasConnection or connectionStatus
print("Last results: ${DataConnectionChecker().lastTryResults}");
// actively listen for status updates
listener = DataConnectionChecker().onStatusChange.listen((status) {
switch (status) {
case DataConnectionStatus.connected:
Internetstatus="Connectd TO THe Internet";
print('Data connection is available.');
setState(() {
});
break;
case DataConnectionStatus.disconnected:
Internetstatus="No Data Connection";
print('You are disconnected from the internet.');
setState(() {
});
break;
}
});
// close listener after 30 seconds, so the program doesn't run forever
// await Future.delayed(Duration(seconds: 30));
// await listener.cancel();
return await await DataConnectionChecker().connectionStatus;
}
@override
Widget build(BuildContext context) {
return Scaffold(
appBar: AppBar(
title: Text("Data Connection Checker"),
),
body: Container(
child: Center(
child: Text("$Internetstatus"),
),
),
);
}
}
其他回答
我使用data_connection_checker包来检查互联网访问，即使连接可用的wifi或手机，它工作得很好: 下面是检查连接的代码:
bool result = await DataConnectionChecker().hasConnection;
if(result == true) {
print('YAY! Free cute dog pics!');
} else {
print('No internet :( Reason:');
print(DataConnectionChecker().lastTryResults);
}
如果你想了解更多信息，请抬头看看包装。 数据连接检查包
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
在@dennmatt的回答之后，我注意到InternetAddress。查找可能会返回成功的结果，即使互联网连接断开-我测试它从我的模拟器连接到我的家庭WiFi，然后断开我的路由器的电缆。我认为原因是路由器缓存了域查找结果，所以它不必在每个查找请求时查询DNS服务器。
不管怎样，如果你像我一样使用Firestore，你可以用一个空事务替换try-SocketException-catch块并捕获TimeoutExceptions:
try {
await Firestore.instance.runTransaction((Transaction tx) {}).timeout(Duration(seconds: 5));
hasConnection = true;
} on PlatformException catch(_) { // May be thrown on Airplane mode
hasConnection = false;
} on TimeoutException catch(_) {
hasConnection = false;
}
另外，请注意，previousConnection是在async internet -check之前设置的，因此理论上，如果checkConnection()在短时间内被调用多次，那么在一行中可能有多个hasConnection=true或多个hasConnection=false。 我不确定@dennmatt是否故意这样做，但在我们的用例中没有副作用(setState只被调用两次，具有相同的值)。
使用
dependencies:
connectivity: ^0.4.2
我们从资源处得到的是
import 'package:connectivity/connectivity.dart';
Future<bool> check() async {
var connectivityResult = await (Connectivity().checkConnectivity());
if (connectivityResult == ConnectivityResult.mobile) {
return true;
} else if (connectivityResult == ConnectivityResult.wifi) {
return true;
}
return false;
}
未来对我来说没什么问题，我们必须每次都实现它，比如:
check().then((intenet) {
if (intenet != null && intenet) {
// Internet Present Case
}
// No-Internet Case
});
所以为了解决这个问题，我创建了一个类，它接受一个布尔isNetworkPresent参数的函数，就像这样
methodName(bool isNetworkPresent){}
实用工具类是
import 'package:connectivity/connectivity.dart'; class NetworkCheck { Future<bool> check() async { var connectivityResult = await (Connectivity().checkConnectivity()); if (connectivityResult == ConnectivityResult.mobile) { return true; } else if (connectivityResult == ConnectivityResult.wifi) { return true; } return false; } dynamic checkInternet(Function func) { check().then((intenet) { if (intenet != null && intenet) { func(true); } else{ func(false); } }); } }
并使用连接检查实用程序
fetchPrefrence(bool isNetworkPresent) {
if(isNetworkPresent){
}else{
}
}
我将使用这种语法
NetworkCheck networkCheck = new NetworkCheck();
networkCheck.checkInternet(fetchPrefrence)
对我来说，我只是在Firebase中创建一个数据，并使用未来构建器来等待数据。在这里，就像这样，你可以检查连接是否太慢，所以数据将被加载:
FutureBuilder(
future: _getImage(context),
builder: (context, snapshot) {
switch (snapshot.connectionState) {
case ConnectionState.none:
return Text('Press button to start.');
case ConnectionState.active:
case ConnectionState.waiting:
return Container(
height:
MediaQuery.of(context).size.height / 1.25,
width:
MediaQuery.of(context).size.width / 1.25,
child: Loading());
case ConnectionState.done:
if (snapshot.hasData) {
return snapshot.data;
} else {
return FlatButton(
onPressed: () {
Navigator.push(
context,
MaterialPageRoute(
builder: (context) =>
ProfilePage()));
},
child: Icon(
Icons.add_a_photo,
size: 50,
),
);
}
// You can reach your snapshot.data['url'] in here
}
return null;
},
),
