小部件不与 RaisedButton 的 onPressed 事件一起显示

Question

I am trying to show CircularProgressIndicator while calling API with dio & BLoC pattern.

Here is the code :

class UserWidget extends StatefulWidget {
  @override
  State<StatefulWidget> createState() {
    return _UserWidgetState();
  }
}

class _UserWidgetState extends State<UserWidget> {
  @override
  void initState() {
    super.initState();
  }

  @override
  Widget build(BuildContext context) {
    return Scaffold(
      body: Container(
        margin: EdgeInsets.only(top: 200),
        child: RaisedButton(
          child: Text("Click"),
          onPressed: () {
            bloc.getUser();
            StreamBuilder<MemberLogin>(
              stream: bloc.subject.stream,
              builder: (context, AsyncSnapshot<MemberLogin> snapshot) {
                if (snapshot.hasData) {
                  return _buildUserWidget(snapshot.data);
                } else if (snapshot.hasError) {
                  return _buildErrorWidget(snapshot.error);
                } else {
                  return _buildLoadingWidget();
                }
              },
            );
          },
        ),
      ),
    );
  }

 Widget _buildLoadingWidget() {
    return Center(
      child: CircularProgressIndicator(),
    );
  }

  Widget _buildErrorWidget(String error) {
    return Center(
        child: Column(
      mainAxisAlignment: MainAxisAlignment.center,
      children: [
        Text("Error occured: $error"),
      ],
    ));
  }

  Widget _buildUserWidget(MemberLogin data) {
    return Center(
        child: Column(
      mainAxisAlignment: MainAxisAlignment.center,
      children: [
        Text("User widget"),
      ],
    ));
  }

When i click on button it hits the url and get the data but it is not showing CircularProgressIndicator . But if i write bloc.getUser(); in initState() then it show the loading. But i want to get the loading after click on button.

BLoC class :

class UserBloc {
  final UserRepository _repository = UserRepository();
  final BehaviorSubject<MemberLogin> _subject = BehaviorSubject<MemberLogin>();

  getUser() async {
    MemberLogin response = await _repository.getUser();
    _subject.sink.add(response);
  }

  dispose() {
    _subject.close();
  }

  BehaviorSubject<MemberLogin> get subject => _subject;
}

final bloc = UserBloc();


class UserRepository{
  MemberApiProvider _apiProvider = MemberApiProvider();

  Future<MemberLogin> getUser(){
    return _apiProvider.getUser();
  }
}

I am getting data from API but only problem is for showing loading progress.

Answer 1

Your RaisedButton onPress() will never open a widget.

Because, onPress() is a method used to handle or your data processing, events and functions.

onPress() is not expecting or looking for a Widget to render on the screen. onPress() is a function not a Structure or Widget.

In your case, bloc.getUser(); is okay as it is a function. But you have already written a StreamBuilder Widget inside a function. Which should not be added inside the function.

Place it inside your build method and you will be able to view/render it on your screen.