Unhandled Exception: setState() or markNeedsBuild() called during build. inside BlocListener

Question

I'm new to flutter and trying to implement bloc in the application. I want to change the value of the flag through the event and refresh the state after the boolean value of the flag changes. I tried to setState() inside the blog listener but returning the following exception.

[ERROR:flutter/lib/ui/ui_dart_state.cc(166)] Unhandled Exception: setState() or markNeedsBuild() called during build.
E/flutter ( 2570): This Overlay widget cannot be marked as needing to build because the framework is already in the process of building widgets.  A widget can be marked as needing to be built during the build phase only if one of its ancestors is currently building. This exception is allowed because the framework builds parent widgets before children, which means a dirty descendant will always be built. Otherwise, the framework might not visit this widget during this build phase.
E/flutter ( 2570): The widget on which setState() or markNeedsBuild() was called was:
E/flutter ( 2570):   Overlay-[LabeledGlobalKey<OverlayState>#94b3b]
E/flutter ( 2570): The widget which was currently being built when the offending call was made was:
E/flutter ( 2570):   ActivitySignUpWidget
E/flutter ( 2570): #0      Element.markNeedsBuild.<anonymous closure> (package:flutter/src/widgets/framework.dart:4211:11)
E/flutter ( 2570): #1      Element.markNeedsBuild (package:flutter/src/widgets/framework.dart:4226:6)
E/flutter ( 2570): #2      State.setState (package:flutter/src/widgets/framework.dart:1260:14)
E/flutter ( 2570): #3      OverlayState.insert (package:flutter/src/widgets/overlay.dart:326:5)
E/flutter ( 2570): #4      ToastView.createView (package:toast/toast.dart:67:18)
E/flutter ( 2570): #5      Toast.show (package:toast/toast.dart:19:15)
E/flutter ( 2570): #6      _ActivitySignUpState._selectCountrCode (package:crm_application_devops/signup/ActivitySignUp.dart:471:11)
E/flutter ( 2570): #7      _ActivitySignUpState._createForm (package:crm_application_devops/signup/ActivitySignUp.dart:219:53)
E/flutter ( 2570): #8      _ActivitySignUpState.build (package:crm_application_devops/signup/ActivitySignUp.dart:115:42)
E/flutter ( 2570): #9      StatefulElement.build (package:flutter/src/widgets/framework.dart:4663:28)
E/flutter ( 2570): #10     ComponentElement.performRebuild (package:flutter/src/widgets/framework.dart:4546:15)
E/flutter ( 2570): #11     StatefulElement.performRebuild (package:flutter/src/widgets/framework.dart:4719:11)
E/flutter ( 2570): #12     Element.rebuild (package:flutter/src/widgets/framework.dart:4262:5)
E/flutter ( 2570): #13     BuildOwner.buildScope (package:flutter/src/widgets/framework.dart:2667:33)
E/flutter ( 2570): #14     WidgetsBinding.drawFrame (package:flutter/src/widgets/binding.dart:866:20)
E/flutter ( 2570): #15     RendererBinding._handlePersistentFrameCallback (package:flutter/src/rendering/binding.dart:286:5)
E/flutter ( 2570): #16     SchedulerBinding._invokeFrameCallback (package:flutter/src/scheduler/binding.dart:1117:15)
E/flutter ( 2570): #17     SchedulerBinding.handleDrawFrame (package:flutter/src/scheduler/binding.dart:1056:9)
E/flutter ( 2570): #18     SchedulerBinding._handleDrawFrame (package:flutter/src/scheduler/binding.dart:972:5)
E/flutter ( 2570): #19     _rootRun (dart:async/zone.dart:1190:13)
E/flutter ( 2570): #20     _CustomZone.run (dart:async/zone.dart:1093:19)
E/flutter ( 2570): #21     _CustomZone.runGuarded (dart:async/zone.dart:997:7)
E/flutter ( 2570): #22     _invoke (dart:ui/hooks.dart:253:10)
E/flutter ( 2570): #23     _drawFrame (dart:ui/hooks.dart:211:3)
E/flutter ( 2570): 

Below is my code. help me to solve this. Thanks in advance.

@override
  Widget build(BuildContext context) {
    signupBloc = BlocProvider.of<SignUpBloc>(context);
    return Scaffold(
      body: Container(
        color: Colors.white,
        child: SafeArea(
          child: Column(children: [
            Column(
              children: [
                BlocListener<SignUpBloc, SignUpState>(
                  listener: (context, state) {
                    if(state is ContryCodeChangeState){
                      print("State called");
                      setState(() {
                        valueOfInput = state.getContryCodeValue;
                      });
                    }
                  },
                  child: Container(
                    child: Column(
                      children: [
                        _signUpHeader(),
                        Padding(
                          padding: const EdgeInsets.only(top: 30.0),
                          child: jsonStringValues != null
                              ? Text(
                                  jsonStringValues[
                                      "Sign_up_to_become_a_member"],
                                  style: TextStyle(
                                      color: Colors.purpleAccent,
                                      fontSize: 16.0,
                                      fontWeight: FontWeight.bold),
                                )
                              : null,
                        ),
                        _createAccount(),
                        Center(
                            child: Padding(
                                padding: EdgeInsets.only(right: 30, left: 30),
                                child: Visibility(
                                  visible: true,
                                  child: _createForm(),
                                ))),
                        Padding(
                          padding: const EdgeInsets.only(top: 16),
                          child: Align(
                            alignment: FractionalOffset.bottomCenter,
                            child: Text(
                              "By sign up you are agreeing to th T&C",
                              style:
                                  TextStyle(color: Colors.black, fontSize: 11),
                            ),
                          ),
                        ),
                      ],
                    ),
                  ),
                ),
              ],
            ),
          ]),
        ),
      ),
    );
  }

Answer 1

if(mounted){
 //call set state here
}