E/EventChannel#plugins.flutter.io/connectivity_status(28677)：无法关闭现有的事件流

Question

我已经开始在颤振中进行开发。在一种情况下，我必须检查用户是否已连接到互联网。我结合使用连接 0.4.9+5和data_connection_checker 0.3.4来检查用户是否有活动连接。

我创建了一个文件 internet_connectivity_service.dart 来执行与之相关的所有任务。

class InternetConnectivityService {
  StreamSubscription<ConnectivityResult> _subscription;

  /*
    * This function check if the device has internet connectivity.
    * With the help of DataConnectionChecker it checks for actual internet connectivity. 
  */
  Future<bool> _checkConnectivity() async {
    if (await DataConnectionChecker().hasConnection) {
      return true;
    } else {
      return false;
    }
  }

  /*
    * This function is invoked to on each connection change request.
    * Using Connectivity package it will check for connectivity and connection type.
    * This function has return type of Future<bool> which perform async request to check connectivity.
    * After checking connection type it check for divice has internet accesssible or not.
  */
  Future<bool> _hasInternet() async {
    var connectivityResult = await (Connectivity().checkConnectivity());
    if (connectivityResult == ConnectivityResult.mobile) {
      return _checkConnectivity();
    } else if (connectivityResult == ConnectivityResult.wifi) {
      return _checkConnectivity();
    } else {
      return false;
    }
  }

  StreamSubscription<ConnectivityResult> initInterNetConnectivitySubscription(
      BuildContext context) {
    // * Subscribe to connectivity changes
    _subscription = Connectivity().onConnectivityChanged.listen(
      (ConnectivityResult result) {
        _hasInternet().then(
          (result) {
            // * When internet is disconnected
            Size size = MediaQuery.of(context).size;
            if (!result) {
              Scaffold.of(context).showSnackBar(
                snackBarBuilder(
                    color: kErrorColor,
                    text: 'Connection Lost',
                    context: context),
              );
            } else {
              Scaffold.of(context).showSnackBar(
                snackBarBuilder(
                    color: kSuccessColor, text: 'Connected', context: context),
              );
            }
          },
        );
      },
    );
    return _subscription;
  }

  disposeSubscription() {
    _subscription.cancel();
  }
}

函数initInterNetConnectivitySubscription和disposeSubscription用于订阅和取消订阅特定事件。我正在从需要此功能的组件中调用这些方法。

例如：

     InternetConnectivityService internetConnectivityService =
      InternetConnectivityService();

  @override
  initState() {
    internetConnectivityService.initInterNetConnectivitySubscription(context);
    super.initState();
  }

  @override
  dispose() {
    internetConnectivityService.disposeSubscription();
    super.dispose();
  }

通过这样做，功能有时会起作用，但有时我会遇到错误说明 E/EventChannel#plugins.flutter.io/connectivity_status(28677): Failed to close existing event stream。

完整的堆栈跟踪。

   Restarted application in 5,259ms.
E/EventChannel#plugins.flutter.io/connectivity_status(28677): Failed to close existing event stream
E/EventChannel#plugins.flutter.io/connectivity_status(28677): java.lang.IllegalArgumentException: NetworkCallback was not registered
E/EventChannel#plugins.flutter.io/connectivity_status(28677):   at com.android.internal.util.Preconditions.checkArgument(Preconditions.java:50)
E/EventChannel#plugins.flutter.io/connectivity_status(28677):   at android.net.ConnectivityManager.unregisterNetworkCallback(ConnectivityManager.java:4009)
E/EventChannel#plugins.flutter.io/connectivity_status(28677):   at io.flutter.plugins.connectivity.ConnectivityBroadcastReceiver.onCancel(ConnectivityBroadcastReceiver.java:53)
E/EventChannel#plugins.flutter.io/connectivity_status(28677):   at io.flutter.plugin.common.EventChannel$IncomingStreamRequestHandler.onListen(EventChannel.java:182)
E/EventChannel#plugins.flutter.io/connectivity_status(28677):   at io.flutter.plugin.common.EventChannel$IncomingStreamRequestHandler.onMessage(EventChannel.java:167)
E/EventChannel#plugins.flutter.io/connectivity_status(28677):   at io.flutter.embedding.engine.dart.DartMessenger.handleMessageFromDart(DartMessenger.java:85)
E/EventChannel#plugins.flutter.io/connectivity_status(28677):   at io.flutter.embedding.engine.FlutterJNI.handlePlatformMessage(FlutterJNI.java:692)
E/EventChannel#plugins.flutter.io/connectivity_status(28677):   at android.os.MessageQueue.nativePollOnce(Native Method)
E/EventChannel#plugins.flutter.io/connectivity_status(28677):   at android.os.MessageQueue.next(MessageQueue.java:336)
E/EventChannel#plugins.flutter.io/connectivity_status(28677):   at android.os.Looper.loop(Looper.java:174)
E/EventChannel#plugins.flutter.io/connectivity_status(28677):   at android.app.ActivityThread.main(ActivityThread.java:7356)
E/EventChannel#plugins.flutter.io/connectivity_status(28677):   at java.lang.reflect.Method.invoke(Native Method)
E/EventChannel#plugins.flutter.io/connectivity_status(28677):   at com.android.internal.os.RuntimeInit$MethodAndArgsCaller.run(RuntimeInit.java:492)
E/EventChannel#plugins.flutter.io/connectivity_status(28677):   at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:930)**strong text**

由于此错误，我的应用程序没有崩溃，但有时功能无法正常工作。如果我犯了一些错误，或者他们是否有更好的方法，请告诉我。我只是不想拥有这样的功能：当用户没有连接时，应用程序会显示您没有连接到互联网。

Answer 1

我假设你已经解决了这个问题，所以如果将来来的人仍然有这个问题。

我通过升级到他们解决问题的最新版本来修复它：

connectivity: ^2.0.2