我正在使用 flutter_bloc图书馆。我的屏幕小部件代码看起来像这样:
class RegisterScreen extends StatefulWidget {
RegisterScreen();
@override
_RegisterScreenState createState() => _RegisterScreenState();
}
class _RegisterScreenState extends State<RegisterScreen> {
@override
Widget build(BuildContext context) {
return BlocProvider<RegisterBloc>(
create: (BuildContext context) {
// RegisterBloc.get(context).add(RegisterGetCitiesEvent());<=== This gives me error `BlocProvider.of() called with a context that does not contain a Cubit of type RegisterBloc. \n No ancestor could be found starting from the context that was passed to BlocProvider.of<RegisterBloc>().`
return RegisterBloc();
},
child: BlocConsumer<RegisterBloc, RegisterState>(
listener: (BuildContext context, RegisterState state) {},
builder: (BuildContext context, RegisterState state) {
// RegisterBloc.get(context).add(RegisterGetCitiesEvent());<=== This line is executed infinite times
return Scaffold(
floatingActionButton: FloatingActionButton(
onPressed: () {
RegisterBloc.get(context).add(RegisterGetCitiesEvent());
},
child: new Icon(Icons.refresh),
),
body: Conteiner(
child: Text(RegisterBloc.get(context).cities==null?'':RegisterBloc.get(context).cities,)
),
);
},
),
);
}
}
和 bloc
文件是这样的:class RegisterBloc extends Bloc<RegisterEvent, RegisterState> {
static RegisterBloc get(BuildContext context) => BlocProvider.of(context);
RegisterBloc() : super(RegisterInitial());
String cities = '';
@override
Stream<RegisterState> mapEventToState(
RegisterEvent event,
) async* {
if (event is RegisterGetCitiesEvent) {
yield* getCities();
}
}
Stream<RegisterGetCitiesState> getCities() async* {
yield await (CustomerServer.getCities()).then((res) {
cities = res;
return RegisterGetCitiesState();
});
}
}
在我的代码中,我必须点击 FAB
调用 RegisterGetCitiesEvent
块事件。我怎样才能立即调用该事件 RegisterBloc.get(context).add(RegisterGetCitiesEvent())
不需要用户点击任何按钮?我试过的:
我试图在
BlocConsumer
中添加该行builder 函数,但该函数执行了无限次。我试图在
BlocProvider
中添加该行创建函数,但它给了我一个错误 BlocProvider.of() called with a context that does not contain a Cubit of type RegisterBloc.
我应该把这条线放在哪里RegisterBloc.get(context).add(RegisterGetCitiesEvent())
调用RegisterGetCitiesEvent
屏幕显示时自动事件(无需单击任何按钮)?
最佳答案
我建议你阅读 BLoC文件完整。但这里是这个问题的快速答案:你应该在 BlocProvider
中做到这一点。的创建功能。像这样:
class RegisterScreen extends StatefulWidget {
RegisterScreen();
@override
_RegisterScreenState createState() => _RegisterScreenState();
}
class _RegisterScreenState extends State<RegisterScreen> {
@override
Widget build(BuildContext context) {
return BlocProvider<RegisterBloc>(
create: (context) => RegisterBloc()..add(RegisterGetCitiesEvent())
);
}
}
关于flutter - 如何在屏幕加载时只调用一次 bloc 事件,我们在Stack Overflow上找到一个类似的问题: https://stackoverflow.com/questions/63525376/