Flutter - cubit - 改变cubit内的布尔值

Posted 2023-02-23

【中文标题】Flutter - cubit - 改变cubit内的布尔值

【英文标题】：Flutter - cubit - changing boolean value inside cubit

【发布时间】：2022-01-09 17:23:55

【问题描述】：

我想从cubit更改bool值，但我不知道该怎么做。

我想要实现的是，例如：if (boolean value stored in cubit is true) "show widget A" : "show widget B"

我的代码：

class ChangeBoolCubit extends Cubit<bool> 
  ChangeBoolCubit() : super(false);

  bool one = false;
  bool two = true;

  void changeValue(bool booleanToChange) 
    booleanToChange = !state;
    emit(booleanToChange);
  

查看：

class BoolView extends StatelessWidget 
  @override
  Widget build(BuildContext context) 
    return Scaffold(
      appBar: AppBar(title: const Text('Changing Bool')),
      body: Column(
        mainAxisAlignment: MainAxisAlignment.center,
        crossAxisAlignment: CrossAxisAlignment.center,
        children: [
          Center(
            child: BlocBuilder<ChangeBoolCubit, bool>(
              builder: (context, state) 
                return (ChangeBoolCubit().one)
                    ? Text('TRUE: $ChangeBoolCubit().one')
                    : Text('FALSE: $ChangeBoolCubit().one;');
              ,
            ),
          ),
          Center(
            child: BlocBuilder<ChangeBoolCubit, bool>(
              builder: (context, state) 
                return (ChangeBoolCubit().two)
                    ? Text('TRUE: $ChangeBoolCubit().two')
                    : Text('FALSE: $ChangeBoolCubit().two;');
              ,
            ),
          ),
      ],),
      floatingActionButton: Column(
        mainAxisAlignment: MainAxisAlignment.end,
        crossAxisAlignment: CrossAxisAlignment.end,
        children: <Widget>[
          FloatingActionButton(
            child: const Icon(Icons.add),
            onPressed: () => context.read<ChangeBoolCubit>().changeValue(ChangeBoolCubit().one),
          ),
          const SizedBox(height: 8),
          FloatingActionButton(
            child: const Icon(Icons.remove),
            onPressed: () => context.read<ChangeBoolCubit>().changeValue(ChangeBoolCubit().two),
          ),
        ],
      ),
    );
  

对于这个微不足道的问题，我很抱歉，但我是 Cubit/Bloc 的新手。

【参考方案1】：

您应该使用 BlocBuilder 中的状态。

例如：

BlocBuilder<ChangeBoolCubit, bool>(
          builder: (context, state) 
            return state
                ? Text('TRUE: $ChangeBoolCubit().one')
                : Text('FALSE: $ChangeBoolCubit().one;');
          ,
        )

但是，我认为这就是你想要的：

class ChangeBoolState 
    final bool one;
    final bool two;
    ChangeBoolState(this.one = false, this.two = true);
    ChangeBoolState copyWith(
        bool? one,
        bool? two,
    )
        return RegisterState(
            one: one != null ? one : this.one,
            two: two != null ? two : this.two
        );
    


class ChangeBoolCubit extends Cubit<ChangeBoolState> 
    void changeOne() 
        emit(state.copyWith(
            one: !state.one,
        ));
    

然后像这样使用它：

BlocBuilder<ChangeBoolCubit, bool>(
          builder: (context, state) 
            return state.one
                ? Text('TRUE: $state.one')
                : Text('FALSE: $state.two;');
          ,
        )