Question

我不知所措。因此，我知道要显示小吃店，您必须能够访问其祖先是脚手架的构建环境。为了解决这个问题，我通常只在支架中制作一个单独的小部件，即可在其中调用新的构建上下文。但是，当我使用警报对话框时，似乎无法正常工作。

我在脚手架下制作的“孩子”小部件如下所示：

class DeleteButton extends StatelessWidget {
  DeleteButton({@required this.vm, @required this.popCallback});

  final AddJobVM vm;
  final Function popCallback;

  @override
  Widget build(BuildContext context) {
    final continueCallBack = () async {
      print("deleting ${vm.jobName}");
      ToasterBundle toast;
      toast = await vm.deleteJob();
      print(toast.success);
      Scaffold.of(context).showSnackBar(generateSnackBar(toast));
      await Future.delayed(
        Duration(seconds: 2),
      );
      if (toast.success) {
        popCallback();
      }
    };
    return Padding(
      padding: EdgeInsets.only(right: kStandardPadding),
      child: GestureDetector(
        onTap: () {
          showDialog(
              context: context,
              builder: (context) {
                return AlertDialogueBlurredBG(
                  title: 'Delete Job',
                  content: 'Are you sure you want to delete this job?',
                  continueCallBack: continueCallBack,
                );
              });
        },
        child: Icon(
          Icons.delete_outline,
          color: kColorWhite,
          size: 28,
        ),
      ),
    );
  }
}

但是当我调用“ continueCallBack”时出现错误：

[VERBOSE-2:ui_dart_state.cc(157)] Unhandled Exception: Looking up a deactivated widget's ancestor is unsafe.
At this point the state of the widget's element tree is no longer stable.
To safely refer to a widget's ancestor in its dispose() method, save a reference to the ancestor by calling dependOnInheritedWidgetOfExactType() in the widget's didChangeDependencies() method.
#0      Element._debugCheckStateIsActiveForAncestorLookup.<anonymous closure> (package:flutter/src/widgets/framework.dart:3781:9)
#1      Element._debugCheckStateIsActiveForAncestorLookup (package:flutter/src/widgets/framework.dart:3795:6)
#2      Element.findAncestorStateOfType (package:flutter/src/widgets/framework.dart:3914:12)
#3      Scaffold.of (package:flutter/src/material/scaffold.dart:1453:42)
#4      DeleteButton.build.<anonymous closure> (package:upworkv2/screens/jobs/add_edit_job_screen.dart:615:16)
<asynchronous suspension>
#5      DeleteButton.build.<anonymous closure> (package:upworkv2/screens/jobs/add_edit_job_scree<…>

我会认为，使用在警报对话框之外引用构建上下文的回调会奏效，但没有成功。关于我在哪里出错的任何想法吗？

Answer 1

Builder窗口小部件在这种情况下会有所帮助，请参阅我如何使用和实现它，

body: Builder(
        builder: (BuildContext innerContext) {
          return RaisedButton(
            onPressed: () {
              showDialog(
                context: context,
                builder: (context) => AlertDialog(
                  title: Text('Are you sure?'),
                  content: Text('Do you want to go to background?'),
                  actions: <Widget>[
                    FlatButton(
                        onPressed: () => Navigator.of(context).pop(),
                        child: Text('NO')),
                    FlatButton(
                        onPressed: () {
                          Scaffold.of(innerContext).showSnackBar(SnackBar(
                            content: Text('Added added into cart'),
                            duration: Duration(seconds: 2),
                            action:
                                SnackBarAction(label: 'UNDO', onPressed: () {}),
                          ));
                        },
                        child: Text('YES'))
                  ],
                ),
              );
            },
          );
        },
      ),

发生此异常是因为您正在使用实例化Scaffold的窗口小部件的上下文。不是脚手架的孩子的上下文。

输出：

从警报对话框显示小吃栏

1 个答案: