connectivityResult returns null in flutter app's startup?

Question

I am using connectivity: ^0.4.6 plugin for checking the connectivity in the flutter app. My code is as below:

Future<void> main() async {

  StreamSubscription connectivitySubscription;

  ConnectivityResult _previousResult;

  connectivitySubscription = Connectivity()
    .onConnectivityChanged
    .listen((ConnectivityResult connectivityResult) {
      if (connectivityResult == ConnectivityResult.none) {
        nav.currentState.push(CupertinoPageRoute(
          builder: (BuildContext _) => NoConnectivityView()));
      } else if (_previousResult == ConnectivityResult.none) {
        nav.currentState.push(CupertinoPageRoute(
          builder: (BuildContext _) =>  LoginScreen()));
      }

      _previousResult = connectivityResult;
    });

  Future.delayed(Duration(seconds: 3));
  runApp(MyApp());
}

It's working perfectly when the connection changes after the app starts. But if there is no connection in initial state its not working. connectivityResult is null this time.

How can I solve this?

So if you were to print the value of `connectivityResult` aka the variable from the callback, it would be null? — Benjamin, Dec 17 '19 at 12:11

score 0 · Answer 1 · answered Dec 17 '19 at 12:39

0

Since you're listening to the connectivity of the device, this callback will fire multiple times so at one moment it might be null but at another moment it won't be null.

I have added a null case for you:

Future<void> main() async {

  StreamSubscription connectivitySubscription;

  ConnectivityResult _previousResult;

  connectivitySubscription = Connectivity()
    .onConnectivityChanged
    .listen((ConnectivityResult connectivityResult) {
      if (connectivityResult == null || connectivityResult == ConnectivityResult.none) {
        nav.currentState.push(CupertinoPageRoute(
          builder: (BuildContext _) => NoConnectivityView()));
      } else if (_previousResult == ConnectivityResult.none) {
        nav.currentState.push(CupertinoPageRoute(
          builder: (BuildContext _) =>  LoginScreen()));
      }

      _previousResult = connectivityResult;
    });

  Future.delayed(Duration(seconds: 3));
  runApp(MyApp());
}

answered Dec 17 '19 at 12:39

Benjamin

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Its not firing when the app in startup and the connection is off.. But after changing the connection its working perfectly.. What I have to do is to navigate to NoConnectivityView() in startup itself if the connection is not there.. – afsal.an Dec 17 '19 at 12:47
Maybe it's because you're doing it before the app even starts... – Benjamin Dec 17 '19 at 12:48
This code should be after the app gets initialized aka after `MyApp` gets loaded. – Benjamin Dec 17 '19 at 12:50
added it in initstate of MyApp.. but in startup its not working – afsal.an Dec 17 '19 at 12:54
Remove it entirely from the `main` function, it's not supposed to be there. – Benjamin Dec 17 '19 at 12:59
Then where should be added? – afsal.an Dec 17 '19 at 13:01
Its already there in initstate of MyApp.. working perfectly everything except the startup issue – afsal.an Dec 17 '19 at 13:04
Did you remove it from `main`? – Benjamin Dec 17 '19 at 13:06
For future readers, you can directly check the initial state of the app using `await Connectivity().checkConnectivity()` and then listen to the changes. – Mohit Shetty Apr 12 '21 at 13:58

connectivityResult returns null in flutter app's startup?

1 Answers1