构建期间调用的 setState() 或 markNeedsBuild() - Flutter

Question

我遇到了这个错误。 Link 调试控制台中可能发生错误的包的 Link 是 ResponsiveSafeArea class 的构建函数，如下所示

══╡ EXCEPTION CAUGHT BY WIDGETS LIBRARY ╞═══════════════════════════════════════════════════════════
The following assertion was thrown building LayoutBuilder:
setState() or markNeedsBuild() called during build.
This _ModalScope<dynamic> 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.
The widget on which setState() or markNeedsBuild() was called was:
  _ModalScope<dynamic>-[LabeledGlobalKey<_ModalScopeState<dynamic>>#e51b7]
The widget which was currently being built when the offending call was made was:
  LayoutBuilder

下面是class导致错误

class CustSigninView extends StatefulWidget {
  @override
  _CustSigninViewState createState() => _CustSigninViewState();
}

class _CustSigninViewState extends State<CustSigninView> {
  final TextEditingController _phNoController = TextEditingController();
  @override
  Widget build(BuildContext context) {
    final deviceSize = MediaQuery.of(context).size;

    bool tempBool = true;             <------------ TEMP "BOOL" JUST FOR TESTING
    
   return BaseView<CustSignInViewModel>(
      builder: (context, model, child) => ResponsiveSafeArea(
        builder: (context, widgetSize) => Scaffold(
          body: Material(
            type: MaterialType.card,
            child: Stack(
              children: <Widget>[

             ListView(  //ListView
                
                // --------  I'M GETTING  E R R O R  IN BELOW LINE.
                tempBool
                    ? UIHelper().showErrorButtomSheet(context, "errorText"))
                    : Container(),
              ],
            ),
          ),
        ),
      ),
    );
  }
}

如果我在 tempBool 条件中用 Container() 替换 UIHelper().showErrorButtomSheet(context, "errorText"))，它工作正常。 UIHelper().showErrorButtomSheet(context, "errorText")).

有问题

下面是UIHelperclass

中的showErrorButtomSheet函数

  /// Returns a Error Dialog
  Future showErrorButtomSheet(BuildContext context, String errorText) {
    Size deviceSize = MediaQuery.of(context).size;
    return showModalBottomSheet(
      context: context,
      builder: (context) => Container(
        child: StatefulBuilder(
          builder: (BuildContext context, StateSetter stateSetter) {
            return Row(
              children: <Widget>[
                Icon(...),
                Text(...),
                ),
              ],
            );
          },
        ),
      ),
    );
  }

ResponsiveSafeArea class 看起来像这样。单击 Debug Console

中的错误包 link 后重定向到构建器函数

typedef Responsive_Builder = Widget Function(
  BuildContext context,
  Size,
);

class ResponsiveSafeArea extends StatelessWidget {
  final Responsive_Builder responsiveBuilder;

  const ResponsiveSafeArea({
    Key key,
    @required Responsive_Builder builder,
  })  : responsiveBuilder = builder,
        super(key: key);

  @override
  Widget build(BuildContext context) {
    return SafeArea(
      child: LayoutBuilder(
        builder: (context, constraints) {
          return responsiveBuilder(
            context,
            constraints.biggest,
          );
        },
      ),
    );
  }
}

Answer 1

Faizan Kamal 您正在尝试显示 showModalBottomSheet，但无法像其他小部件那样显示。我建议您使用自定义小部件来显示下面的 errorText：

Widget showErrorWidget(BuildContext context, String errorText) {
    return Row(
      children: <Widget>[
        Icon(Icons.error),
        Text(errorText),
      ],
    );
  }

并像这样使用它：

...
   tempBool
        ? UIHelper(). showErrorWidget(context, "errorText"))
        : Container(),
   ...

要显示对话框，您必须处理一个事件来实现此目的，例如在布局事件之后：

if(!tempBool)
     Container(), // We display this container when tempBool is false, else we display the dialog

最后添加afterLayout事件：

@override
  void initState() {
    WidgetsBinding.instance.addPostFrameCallback((_) => _afterLayout(context));
    super.initState();
...
}

_afterLayout(BuildContext context) async {
    if(tempBool)
        await UIHelper().showErrorButtomSheet(context, "errorText");
}

构建期间调用的 setState() 或 markNeedsBuild() - Flutter

setState() or markNeedsBuild() called during build - Flutter

state

builder

dart

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