Firebase auto login via google id asserts debug error-CodePudding

I'm still new and in progress of understanding flutter, so please somebody tell me which is wrong. My code for auto login is as following :

class _login_pageState extends State<login_page> {
  void initState() {
    super.initState();
    final auth = FirebaseAuth.instance;
    print(auth.currentUser);
    if (auth.currentUser !=null)
    {
      Navigator.of(context).push(MaterialPageRoute(builder: (context) =>main_bone()));
    }
    // Enable virtual display.
  }

  @override
  Widget build(BuildContext context) {
...

My intention is to automatically login when auth.currentUser exists, and navigate to main_bone() class. By print code I confirmed the auth correctly gets login-ed user info.

The error message I got is this.

 Exception caught by widgets library =======================================================
The following assertion was thrown building Builder:
setState() or markNeedsBuild() called during build.

...


'package:flutter/src/widgets/navigator.dart': Failed assertion: line 5127 pos 12: '!_debugLocked': is not true.

I saw these error message several times but still not completely understanding why this appears. Please tell me what I did wrong and why these error occurs.

CodePudding user response：

Try using the StreamBuilder and userChanges provided by Firebase to listen to authentication events. Try in your main function

home: StreamBuilder(
          stream: FirebaseAuth.instance.userChanges(),
          builder: (context, snapshot) {
            if (snapshot.connectionState == ConnectionState.active) {
              if (snapshot.hasData) {
                return main_bone();
              } else if (snapshot.hasError) {
                return Center(
                  child: Text('${snapshot.error}'),
                );
              }
            }
            if (snapshot.connectionState == ConnectionState.waiting) {
              return Center(
                child: CircularProgressIndicator(),
              );
            }
            return const LoginPage();
          },
        ),