flutter - 如何在不单击按钮的情况下在 flutter 中显示警报对话框

Question

当接收到特定的错误状态并且列表数据不为空时，我找不到在列内显示对话框警报的方法。警报对话框不涉及任何按钮点击，所有在线示例都包含一个按钮 onTap。

我想在列表数据不为空且设置了错误标志时显示警报。

下面是我的代码:

  @override
  Widget build(BuildContext context) {
    return Scaffold(
      key: scaffoldKey,
      appBar: _myAppBar(),
      body: RefreshIndicator(
        key: _refreshIndicatorKey,
        onRefresh: handleRefresh,
        child: isListError && ordersListData.isEmpty
            ? _mainErrorWidget()
            : Column(
                children: <Widget>[
                  Expanded(
                    child: NotificationListener<ScrollNotification>(
                      onNotification: (ScrollNotification scrollInfo) {
                        if (hasMoreToLoad &&
                            !isListLoading &&
                            !isListError &&
                            scrollInfo.metrics.pixels ==
                                scrollInfo.metrics.maxScrollExtent) {
                          handleLoadMore();
                        }
                      },
                      child: ListView.builder(
                          itemCount: ordersListData.length,
                          itemBuilder: (BuildContext context, int index) {
                            return Card(
                              child: InkWell(
                                onTap: () {
                                  Navigator.push(
                                    context,
                                    MaterialPageRoute(
                                      builder: (context) => OrderDetailsPage(
                                        baseurl: widget.baseurl,
                                        username: widget.username,
                                        password: widget.password,
                                        id: ordersListData[index]["id"],
                                      ),
                                    ),
                                  );
                                },
                                child: Row(
                                    mainAxisAlignment: MainAxisAlignment.start,
                                    mainAxisSize: MainAxisSize.max,
                                    crossAxisAlignment:
                                        CrossAxisAlignment.center,
                                    children: <Widget>[
                                      Expanded(
                                        child: Padding(
                                          padding: const EdgeInsets.all(10.0),
                                          child: Column(
                                              mainAxisAlignment:
                                                  MainAxisAlignment.start,
                                              mainAxisSize: MainAxisSize.min,
                                              crossAxisAlignment:
                                                  CrossAxisAlignment.start,
                                              children: <Widget>[
                                                _orderDate(
                                                    ordersListData[index]),
                                                _orderIdAndBillingName(
                                                    ordersListData[index]),
                                                _orderStatus(
                                                    ordersListData[index]),
                                                _orderTotal(
                                                    ordersListData[index])
                                              ]),
                                        ),
                                      )
                                    ]),
                              ),
                            );
                          }),
                    ),
                  ),
                  if (isListLoading)
                    Container(
                      height: 60,
                      child: Center(
                          child: SpinKitPulse(
                        color: Colors.purple,
                        size: 50,
                      )),
                    ),
                    _showErrorAlert(),
                ],
              ),
      ),
    );
  }

void _showErrorAlert() {
    if (isListError && ordersListData.isNotEmpty) {
      showDialog<void>(
          context: context,
          barrierDismissible: false,
          builder: (BuildContext context) {
            return AlertDialog(
              title: Text("Retry"),
              titlePadding: EdgeInsets.fromLTRB(15, 20, 15, 0),
              content: Column(
                children: <Widget>[
                  listError ?? Text(listError),
                  Text(
                    "Do you want to retry?",
                    style: Theme.of(context).textTheme.body1,
                  ),
                ],
              ),
              contentPadding: EdgeInsets.fromLTRB(15, 10, 15, 0),
              actions: <Widget>[
                FlatButton(
                  child: Text("No"),
                  onPressed: () {
                    Navigator.of(context).pop();
                  },
                ),
                FlatButton(
                  child: Text("Yes"),
                  onPressed: () {
                    Navigator.of(context).pop();
                    fetchOrdersList();
                  },
                )
              ],
            );
          });
    }
  }

我收到以下异常:

I/flutter (15007): ══╡ EXCEPTION CAUGHT BY WIDGETS LIBRARY ╞═══════════════════════════════════════════════════════════
I/flutter (15007): The following assertion was thrown building OrdersListPage(dirty, dependencies:
I/flutter (15007): [_LocalizationsScope-[GlobalKey#a6289], _InheritedTheme], state: _OrdersListPageState#ed7e3):
I/flutter (15007): setState() or markNeedsBuild() called during build.
I/flutter (15007): This Overlay widget cannot be marked as needing to build because the framework is already in the
I/flutter (15007): process of building widgets.  A widget can be marked as needing to be built during the build phase       
I/flutter (15007): only if one of its ancestors is currently building. This exception is allowed because the framework      
I/flutter (15007): builds parent widgets before children, which means a dirty descendant will always be built.
I/flutter (15007): Otherwise, the framework might not visit this widget during this build phase.
I/flutter (15007): The widget on which setState() or markNeedsBuild() was called was:
I/flutter (15007):   Overlay-[LabeledGlobalKey<OverlayState>#d7fb9]
I/flutter (15007): The widget which was currently being built when the offending call was made was:
I/flutter (15007):   OrdersListPage
I/flutter (15007):
I/flutter (15007): The relevant error-causing widget was:
I/flutter (15007):   OrdersListPage file:///C:/Users/itsga/Desktop/flutter/woocommerceadmin/lib/main.dart:121:13
I/flutter (15007):
I/flutter (15007): When the exception was thrown, this was the stack:
I/flutter (15007): #0      Element.markNeedsBuild.<anonymous closure> (package:flutter/src/widgets/framework.dart:3896:11)  
I/flutter (15007): #1      Element.markNeedsBuild (package:flutter/src/widgets/framework.dart:3911:6)
I/flutter (15007): #2      State.setState (package:flutter/src/widgets/framework.dart:1168:14)
I/flutter (15007): #3      OverlayState.insertAll (package:flutter/src/widgets/overlay.dart:344:5)
I/flutter (15007): #4      OverlayRoute.install (package:flutter/src/widgets/routes.dart:44:24)
I/flutter (15007): #5      TransitionRoute.install (package:flutter/src/widgets/routes.dart:181:11)
I/flutter (15007): #6      ModalRoute.install (package:flutter/src/widgets/routes.dart:959:11)
I/flutter (15007): #7      NavigatorState.push (package:flutter/src/widgets/navigator.dart:1791:11)
I/flutter (15007): #8      showGeneralDialog (package:flutter/src/widgets/routes.dart:1634:65)
I/flutter (15007): #9      showDialog (package:flutter/src/material/dialog.dart:711:10)
I/flutter (15007): #10     _OrdersListPageState._showErrorAlert (package:woocommerceadmin/src/orders/widgets/OrdersListPage.dart:408:7)
I/flutter (15007): #11     _OrdersListPageState.build (package:woocommerceadmin/src/orders/widgets/OrdersListPage.dart:143:21)
I/flutter (15007): #12     StatefulElement.build (package:flutter/src/widgets/framework.dart:4334:27)
I/flutter (15007): #13     ComponentElement.performRebuild (package:flutter/src/widgets/framework.dart:4223:15)
I/flutter (15007): #14     Element.rebuild (package:flutter/src/widgets/framework.dart:3947:5)
I/flutter (15007): #15     BuildOwner.buildScope (package:flutter/src/widgets/framework.dart:2432:33)
I/flutter (15007): #16     WidgetsBinding.drawFrame (package:flutter/src/widgets/binding.dart:773:20)
I/flutter (15007): #17     RendererBinding._handlePersistentFrameCallback (package:flutter/src/rendering/binding.dart:283:5)I/flutter (15007): #18     SchedulerBinding._invokeFrameCallback (package:flutter/src/scheduler/binding.dart:1102:15)       
I/flutter (15007): #19     SchedulerBinding.handleDrawFrame (package:flutter/src/scheduler/binding.dart:1041:9)
I/flutter (15007): #20     SchedulerBinding._handleDrawFrame (package:flutter/src/scheduler/binding.dart:957:5)
I/flutter (15007): #24     _invoke (dart:ui/hooks.dart:259:10)
I/flutter (15007): #25     _drawFrame (dart:ui/hooks.dart:217:3)
I/flutter (15007): (elided 3 frames from package dart:async)
I/flutter (15007): 
I/flutter (15007): ════════════════════════════════════════════════════════════════════════════════════════════════════     

Answer 1

问题是 showDialog 不返回任何 Widget，因此您不能将它用作 child。

你可以做的是，

@override
void initState() {
  super.initState();

  SchedulerBinding.instance.addPostFrameCallback((_) { 
    _showErrorAlert();
  });
}