Flutter: Unhandled Exception: Looking up a deactivated widget's ancestor is unsafe

Question

I am trying to navigate to a page after a specific duration. However, whenever i run the app, i receive an error saying: At this point the state of the widget's element tree is no longer stable. To safely refer to a widget's ancestor in its dispose() method, save a reference to the ancestor by calling inheritFromWidgetOfExactType() in the widget's didChangeDependencies() method.

My code looks like this:

@override
void initState() {
  super.initState();
  googleSignIn.signInSilently(suppressErrors: false)
    .then((account) async {
      if (account != null) {
        List<Post> posts = await initTimelinePosts(account.id);
        List<String> followingList = await configureTimelineForNoPost(
          account.id
        );
        currentUser =
          User.fromDocument(await usersRef.document(account.id).get());
        Navigator.pushReplacement(
          context,
          MaterialPageRoute(
            builder: (context) => Home(
              posts: posts,
              followingList: followingList,
              savedState: widget.savedState
            )
          )
        );
      } else {
        Navigator.pushReplacement(
          context,
          MaterialPageRoute(
            settings: RouteSettings(name: Auth.route),
            builder: (context) => Auth(savedState: widget.savedState)
          )
        );
      }
    }).catchError((_) async {
      final SharedPreferences prefs = await SharedPreferences.getInstance();
      String userId = prefs.getString('userId');
      if (userId != null && userId.isNotEmpty) {
        DocumentSnapshot doc = await usersRef.document(userId).get();
        currentUser = User.fromDocument(doc);
        List<Post> posts = await initTimelinePosts(userId);
        List<String> followingList = await configureTimelineForNoPost(userId);
        Navigator.pushReplacement(
          context,
          MaterialPageRoute(
            builder: (context) => Home(
              posts: posts,
              followingList: followingList,
              savedState: widget.savedState,
            )
          )
        );
      } else {
        _timer = new Timer(
          Duration(milliseconds: 3000),
          () {
            Navigator.pushReplacement( // the error message points to this line
              context,
              MaterialPageRoute(
                settings: RouteSettings(name: Auth.route),
                builder: (context) => Auth(savedState: widget.savedState)
              )
            );
          }
        );
      }
    });
}

I expect the app to run without errors but it doesn't. How do I solve this?

Note: I seriously don't know what to write anymore and SO keeps complaining that i need to add some more details. I believe i've provided enough explanation with the description, the title, and the code.

Answer 1

I think the problem is that you are trying to navigate to a new page and replace this page in your initState(). Because the widget tree is not built when you run initState() method, it might cause an error.

Have a look at this answer for detailed explanation and this for a similar issue.