Navigation within Nested FutureBuilder

[Esen]

Hi,

This is the SoF link: Click Here

This is my Boot Screen and I want to create conditional Navigations but as I understand FutureBuilder does not have logic for Navigation.

This is my Boot Screen build method:

@override

Widget build(BuildContext context) {
  return Material(
    child: ScopedModelDescendant<MainModel>(
      builder: (BuildContext context, Widget child, MainModel model) {
        return FutureBuilder(
          future: model.bootUp(),
          builder: (context, bootSnapshot) {
            print('====${bootSnapshot.data} is SNAPSHOT DATA====');
            return !bootSnapshot.hasData
                ? _buildSplash(context)
                : bootSnapshot.data
                    ? FutureBuilder(
                        future: model.fetchAll(model.tempUser),
                        builder: (context, dataSnapshot) {
                          return !dataSnapshot.hasData
                              ? _buildSplash(context)
                              : Navigator.of(context).pushReplacement(
                                  MaterialPageRoute(
                                      builder: (context) => HomePage()),
                                );
                        })
                    : Navigator.of(context).pushReplacement(
                        MaterialPageRoute(
                          builder: (context) => FirstScreen(),
                        ),
                      );
          },
        );
      },
    ),
  );
}

As you see in the code, first I check up is user login before or not with an async method, then if he is logined before, then I'm fetching the data related to him, once the fetching completed I want to navigate into the User Home page.

The error log:

I/flutter (24348): ══╡ EXCEPTION CAUGHT BY WIDGETS LIBRARY ╞═══════════════════════════════════════════════════════════
I/flutter (24348): The following assertion was thrown building FutureBuilder<String>(dirty, state:
I/flutter (24348): _FutureBuilderState<String>#e0594):
I/flutter (24348): setState() or markNeedsBuild() called during build.
I/flutter (24348): This Overlay widget cannot be marked as needing to build because the framework is already in the
I/flutter (24348): process of building widgets. A widget can be marked as needing to be built during the build phase
I/flutter (24348): only if one of its ancestors is currently building. This exception is allowed because the framework
I/flutter (24348): builds parent widgets before children, which means a dirty descendant will always be built.
I/flutter (24348): Otherwise, the framework might not visit this widget during this build phase.
I/flutter (24348): The widget on which setState() or markNeedsBuild() was called was:
I/flutter (24348):   Overlay-[LabeledGlobalKey<OverlayState>#c7eb6](state: OverlayState#953bd(entries:
I/flutter (24348):   [OverlayEntry#b9486(opaque: false; maintainState: false), OverlayEntry#af059(opaque: false;
I/flutter (24348):   maintainState: true), OverlayEntry#81d00(opaque: false; maintainState: false),
I/flutter (24348):   OverlayEntry#be7c4(opaque: false; maintainState: true)]))
I/flutter (24348): The widget which was currently being built when the offending call was made was:
I/flutter (24348):   FutureBuilder<String>(dirty, state: _FutureBuilderState<String>#e0594)
I/flutter (24348):
I/flutter (24348): When the exception was thrown, this was the stack:
I/flutter (24348): #0      Element.markNeedsBuild.<anonymous closure> (package:flutter/src/widgets/framework.dart:3485:11)
I/flutter (24348): #1      Element.markNeedsBuild (package:flutter/src/widgets/framework.dart:3511:6)
I/flutter (24348): #2      State.setState (package:flutter/src/widgets/framework.dart:1146:14)
I/flutter (24348): #3      OverlayState.insertAll (package:flutter/src/widgets/overlay.dart:301:5)
I/flutter (24348): #4      OverlayRoute.install (package:flutter/src/widgets/routes.dart:43:24)
I/flutter (24348): #5      TransitionRoute.install (package:flutter/src/widgets/routes.dart:185:11)
I/flutter (24348): #6      ModalRoute.install (package:flutter/src/widgets/routes.dart:861:11)
I/flutter (24348): #7      NavigatorState.pushReplacement (package:flutter/src/widgets/navigator.dart:1618:14)
I/flutter (24348): #8      BootScreen.build.<anonymous closure>.<anonymous closure>.<anonymous closure> (package:mostadam/pages/boot_screen.dart:49:49)
I/flutter (24348): #9      _FutureBuilderState.build (package:flutter/src/widgets/async.dart)
I/flutter (24348): #10     StatefulElement.build (package:flutter/src/widgets/framework.dart:3809:27)
I/flutter (24348): #11     ComponentElement.performRebuild (package:flutter/src/widgets/framework.dart:3721:15)
I/flutter (24348): #12     Element.rebuild (package:flutter/src/widgets/framework.dart:3547:5)
I/flutter (24348): #13     BuildOwner.buildScope (package:flutter/src/widgets/framework.dart:2286:33)
I/flutter (24348): #14     _WidgetsFlutterBinding&BindingBase&GestureBinding&ServicesBinding&SchedulerBinding&PaintingBinding&SemanticsBinding&RendererBinding&WidgetsBinding.drawFrame (package:flutter/src/widgets/binding.dart:676:20)
I/flutter (24348): #15     _WidgetsFlutterBinding&BindingBase&GestureBinding&ServicesBinding&SchedulerBinding&PaintingBinding&SemanticsBinding&RendererBinding._handlePersistentFrameCallback (package:flutter/src/rendering/binding.dart:219:5)
I/flutter (24348): #16     _WidgetsFlutterBinding&BindingBase&GestureBinding&ServicesBinding&SchedulerBinding._invokeFrameCallback (package:flutter/src/scheduler/binding.dart:990:15)
I/flutter (24348): #17     _WidgetsFlutterBinding&BindingBase&GestureBinding&ServicesBinding&SchedulerBinding.handleDrawFrame (package:flutter/src/scheduler/binding.dart:930:9)
I/flutter (24348): #18     _WidgetsFlutterBinding&BindingBase&GestureBinding&ServicesBinding&SchedulerBinding._handleDrawFrame (package:flutter/src/scheduler/binding.dart:842:5)
I/flutter (24348): #19     _invoke (dart:ui/hooks.dart:154:13)
I/flutter (24348): #20     _drawFrame (dart:ui/hooks.dart:143:3)

[Andrew Brogdon]

It looks like you're trying to return the result of Navigator.pushNamed() in your build method as if it were a widget, which is not the way it's meant to be used.

A simple solution would be to just return the widget you're trying to navigate to (either FirstScreen() or HomePage()). That way you're just building and returning widgets, rather than interacting with the inherited Navigator.

-Andrew

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[Esen]

Such an easy solution :) Thank you. I think I need a vacation :))

[Tanuj Pandey]

Really thanks for the solution. 

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