Login and go to other page after

[Mattias Månsson]

I have a small problem I'm thinking of how to best solve it in flutter. I could probably solve it myself with some hack, but I'm sure there is a more beautiful flutter way, so here goes...

I have a button in my UI where if clicked I want to tell the user that to go to this page, he should first login. Right now I show a dialog telling this with yes/no and yes redirects the user to the login page. But after logging it, it will go back to the main page and the button has to be clicked again. Is there a nicer way to do this in flutter so I can get the flow main page->dialog->login->next page?

[Sócrates Díaz Severino]

One of the ways to solve this problem is using the Navigation object provided by Flutter. You can pop a widget with a return value and await for it in the widget that pushed it. That way you could achieve the navigation flow that you described.

You can find more info here: https://api.flutter.dev/flutter/widgets/Navigator-class.html (specifically in the section "Routes can return a value")

[Mattias Månsson]

Tried what you're saying but there is something with the state of the app and async calls I don't get right. Basically when the user presses the button that requires login, I call a method like this (removed the uninteresting code):

Future<void> _openSignInDialog() {
  return showDialog<void>(
    context: context,
    builder: (BuildContext context) {
      return AlertDialog(
        title: Text('Please sign in'),
        content: const Text(
            '...'),
        actions: <Widget>[
          FlatButton.icon(
            icon: Icon(Icons.check_circle, color: Colors.green),
            label: Text('Yes'),
            onPressed: () {
              // Replace this dialog with the login page
              Navigator.pushReplacementNamed(context, '/login').then((_) {
                Navigator.of(context).pushNamed('/otherpage');
              });
            },
          ),
          FlatButton.icon(
            icon: Icon(Icons.cancel, color: Colors.red),
            label: Text('No'),
            onPressed: () {
              Navigator.pop(context);
            },
          ),
        ],
      );
    },
  );
}

But if I run this, it will crash after returning from the login page with this exception:

E/flutter (27459): [ERROR:flutter/lib/ui/ui_dart_state.cc(148)] Unhandled Exception: Looking up a deactivated widget's ancestor is unsafe.

E/flutter (27459): 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.

I guess it is too many levels of async magic, but not 100% sure on how to fix it.

[Mattias Månsson]

Think I figured it out, I can't use pushReplacementNamed on the dialog as it would then be gone when I come back. If I change it to the following it works better:

Navigator.pushNamed(context, '/login').then((_) {
  Navigator.of(context).pushReplacementNamed('/otherpage');
});

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[Peter Kretschmer]

Did you Try

Navigator.popAndPushNamed(context, /route);

I hade a simular problem and this was the solution. So you basically go one step back first and then Push on Top. If you then push either the return button or try to go back by Navigator.pop it will nither crash nor go back to anything. But my loginflow was slightly different

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