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

Posted 2023-04-14

【中文标题】在构建期间调用 setState() 或 markNeedsBuild() - Flutter

【英文标题】：setState() or markNeedsBuild() called during build - Flutter

【发布时间】：2020-12-12 02:33:55

【问题描述】：

我收到此错误。 调试控制台中可能发生错误的包的链接是ResponsiveSafeArea类的构建器函数，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

下面是导致错误的类

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 条件下将 UIHelper().showErrorButtomSheet(context, "errorText")) 替换为 Container()，它可以正常工作。 UIHelper().showErrorButtomSheet(context, "errorText")) 存在问题。

下面是UIHelper类中的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 类看起来像这样。点击Debug Console中的错误包链接后重定向到builder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,
          );
        ,
      ),
    );
  

【参考方案1】：

Faizan Kamal 您正在尝试显示showModalBottomSheet，它无法像其他小部件一样显示。我建议您使用自定义小部件在下面显示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这一点，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");