android - NoSuchMethodError : The method 'ancestorStateOfType' was called on null with await and async method

Question

我想创建一个加载器数据，最后加载数据屏幕将自动更改屏幕(使用导航器)。

但我有一些问题。

Unhandled Exception: NoSuchMethodError: The method 'ancestorStateOfType' was called on null.

在“getDataOfUser()”方法结束时，“print(a)”执行得很好，但是当它试图改变屏幕时它崩溃了，我有这个错误:

E/flutter (32148): [ERROR:flutter/lib/ui/ui_dart_state.cc(148)] Unhandled Exception: NoSuchMethodError: The method 'ancestorStateOfType' was called on null.
E/flutter (32148): Receiver: null
E/flutter (32148): Tried calling: ancestorStateOfType(Instance of 'TypeMatcher<NavigatorState>')
E/flutter (32148): #0      Object.noSuchMethod (dart:core-patch/object_patch.dart:50:5)
E/flutter (32148): #1      Navigator.of (package:flutter/src/widgets/navigator.dart:1446:19)
E/flutter (32148): #2      LoginScreenPresenter.initState.<anonymous closure> (package:test_app/login_presenter.dart:35:17)

class loginPresenter extends StatefulWidget {
  Vendeur v;
  loginPresenter({Key key, this.v}) : super(key: key);

  @override
  LoginScreenPresenter createState() => new LoginScreenPresenter();
}

class LoginScreenPresenter extends State<loginPresenter> {
  RestDatasource api = new RestDatasource();

  BuildContext context;

  bool finish = false;

  @override
  void initState() {
    getDataOfUser(widget.v).then((a) {
      print(a)
      Navigator.of(context).pushReplacement(new MaterialPageRoute(
          builder: (BuildContext context) => HomePage(
                v: widget.v,
              )));
    });

    super.initState();
  }

  Future<bool> getDataOfUser(Vendeur user) async {

    await api.getRegionsFromUser(user.idV).then((list) async {
      if (list != null) {
        for (var i = 0; i < list.length; ++i) {
          await DBProvider.db.newRegion(list[i], 1);
        }
      }
    });

    await api.getClientsFromUser(user.idV).then((list) async {
      if (list != null) {
        for (var i = 0; i < list.length; ++i) {
          await DBProvider.db.newClient(list[i], 1);
        }
      }
    });

    await api.getInterlocuteursFromUser(user.idV).then((list) async {
      if (list != null) {
        for (var i = 0; i < list.length; ++i) {
          await DBProvider.db.newInterlocuteurs(list[i], 1);
        }
      }
    });

    await api.getVisitesFromUser(user.idV).then((list) async {
      if (list != null) {
        for (var i = 0; i < list.length; ++i) {
          await DBProvider.db.newVisite(list[i], 1);
        }
      }
    });

    await api.getAvoirsFromUser(user.idV).then((list) async {
      if (list != null) {
        for (var i = 0; i < list.length; ++i) {
          if (list[i].deleted == 0) {
            await DBProvider.db.newAvoir(list[i], 1);
          }
        }
      }
    });

    await api.getRapportsFromUser(user.idV).then((list) async {
      if (list != null) {
        for (var i = 0; i < list.length; ++i) {
          await DBProvider.db.newRapport(list[i], user);
        }
      }
    });

    return true;
  }

  @override
  Widget build(context) {
    return RaisedButton(
      onPressed: () {
        Navigator.push(
            context,
            SlideRightRoute(
                widget: HomePage(
              v: widget.v,
            )));
      },
      child: Text('go'),
    );

  }

}

Answer 1

我遇到了这个问题，我检查了 mounted ，现在它工作正常。

{...
  if(!mounted) return;
  Navigator.of(context).pop();
...}