Question

我正在尝试通过Flutter中的页面控制器使用Bloc模式及其抛出的“'_positions.isNotEmpty'：ScrollController未附加到任何滚动视图”来更改活动页面索引。

这是我的代码：

WelcomeWizardScreen：

import 'package:flutter/widgets.dart';
import 'package:flutter_bloc/flutter_bloc.dart';
import 'package:fluttertest/blocs/wizard/bloc/bloc.dart';
import 'package:fluttertest/screens/wizardsteps/joincongregation.dart';
import 'package:fluttertest/screens/wizardsteps/welcometomapman.dart';

class WelcomeWizardScreen extends StatefulWidget {
  @override
  _WelcomeWizardScreenState createState() => _WelcomeWizardScreenState();
}

class _WelcomeWizardScreenState extends State<WelcomeWizardScreen> {
  final WizardBloc wizardBloc = WizardBloc();

  @override
  Widget build(BuildContext context) {
    // TODO: implement build
    return BlocProvider(
      builder: (BuildContext context) => WizardBloc(),
      child: PageView(
        children: <Widget>[WelcomeToMapMan(), JoinCongregation()],
        controller: wizardBloc.pageController,

      ),
    );
  }
}

WizardBloc：

import 'package:bloc/bloc.dart';
import 'package:flutter/widgets.dart';
import 'wizard_state.dart';

import 'wizard_event.dart';

class WizardBloc extends Bloc<WizardEvent, WizardState> {
  int activeStep = 0;
  final PageController pageController = PageController(initialPage: 0, keepPage: false, viewportFraction: 0.4);
  @override
  WizardState get initialState => WelcomeToMapManState();


  @override
  Stream<WizardState> mapEventToState(
    WizardEvent event,
  ) async* {

    if (event is ChangePage)
    {

   pageController.jumpToPage(event.pageIndex);


    }
    // TODO: Add Logic
  }


  Stream<WizardState> _mapJoinCongregationToState() async* {


  }
}

PageView中的屏幕之一：

class JoinCongregation extends StatelessWidget {
  @override
  Widget build(BuildContext context) {
    final WizardBloc _wizardBloc = BlocProvider.of<WizardBloc>(context);
    // TODO: implement build
    return Column(
      children: <Widget>[
        Center(
          child: Text("this is step 2"),
        ),
        RaisedButton(
          child: Text("back to step 1"),
          onPressed: () => {_wizardBloc.dispatch(ChangePage(0))},
        )
      ],
    );
  }
}

当它被调用来更改页面时，PageViewController似乎没有“附加”到PageView，但是它正确地初始化了（在正确的页面索引上）。

我该如何解决？我是新来的人。

Answer 1

您不应在整体中创建PageController，因为整体不应与UI耦合（从理论上讲，您应该能够在Flutter和AngularDart之间重用您的整体）。请参阅https://github.com/felangel/bloc/issues/18，以获取有关如何完成此操作的示例。

PageView抛出'_positions.isNotEmpty'：ScrollController未附加到任何滚动视图

1 个答案: