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我是新来的颤振并试图在应用程序中实现 bloc 。我想通过事件改变flag的值，在flag的布尔值改变后刷新状态。我尝试在博客侦听器中设置状态（），但返回以下异常。

[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):

下面是我的代码。帮我解决这个问题。提前致谢。

@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),
                            ),
                          ),
                        ),
                      ],
                    ),
                  ),
                ),
              ],
            ),
          ]),
        ),
      ),
    );
  }
4

1 回答 1

0 
if(mounted){
 //call set state here
}
于 2020-10-10T08:00:34.907 回答