Flutter bloc：第一次陈述状态时，BlocBuilder不会重新调用构建器方法

Question

我正在尝试使用bloc更改flutter应用程序的主题。 但是自从状态改变后第二次出现问题。

状态仍处于更新状态，但用户界面未更改，builder方法未再次运行

我的日志：

Performing hot restart...
Syncing files to device iPhone 11...
Restarted application in 1,386ms.
flutter: builder ThemeState
flutter: builder ThemeState
flutter: build
flutter: _ChangeThemeScreenState AppTheme.BlueDark
flutter: ThemeBloc AppTheme.BlueDark
flutter: ThemeBloc isThemeChange
flutter: builder ThemeState
flutter: _ChangeThemeScreenState AppTheme.BlueLight
flutter: ThemeBloc AppTheme.BlueLight
flutter: ThemeBloc isThemeChange
flutter: _ChangeThemeScreenState AppTheme.GreenDark
flutter: ThemeBloc AppTheme.GreenDark
flutter: ThemeBloc isThemeChange

我的代码：

class ThemeBloc extends Bloc<ThemeEvent, ThemeState> {
  ThemeBloc() : super(ThemeState(themeData: appThemeData[AppTheme.GreenLight]));

  @override
  Stream<ThemeState> mapEventToState(
    ThemeEvent event,
  ) async* {
    print("ThemeBloc " + (event as ThemeChanged).theme.toString());
    if (event is ThemeChanged) {
      print("ThemeBloc " +'isThemeChange');
      yield ThemeState(themeData: appThemeData[event.theme]);
    }
  }
}

class _MyAppState extends State<MyApp> {
  @override
  Widget build(BuildContext context) {
    return BlocProvider(
      create: (context) => ThemeBloc(),
      child: BlocBuilder<ThemeBloc, ThemeState>(
        builder: (context, state) {
          print("builder " + state.toString());
          return MaterialApp(
              debugShowCheckedModeBanner: false,
              title: 'Bitradez',
              routes: routes,
              theme: state.themeData);
        }
      ),
    );
  }
}

当标签页按钮

onTap: () {
                print("_ChangeThemeScreenState " + itemAppTheme.toString());
                BlocProvider.of<ThemeBloc>(context)
                    .add(ThemeChanged(theme: itemAppTheme));
              },

Answer 1

在您的ThemeState类中，尝试将您的themeData属性传递给道具，我很确定我遇到了和您前一段时间相同的问题。据我了解，您为props设置的值是bloc在决定是否重建窗口小部件时实际查看的内容。

我认为类似的方法应该起作用：

List<Object> get props => [themeData]

您显然仍然需要正确产生此状态。