Question

如何使用团体操作来更改列表项中的窗口小部件。我应该在整个ListView.builder上还是仅对单个项目使用BlockBuilder或侦听器。如果您分享一个示例或教程，那将是很好的。例如，如果我有一个复选框，则需要在单击它时更改其状态。这些是我的Bloc课程集团

const String SERVER_FAILURE_MESSAGE = 'Server Failure';
const String CACHE_FAILURE_MESSAGE = 'Cache Failure';
class MarkAttendanceBloc extends Bloc<MarkAttendanceEvent, MarkAttendanceState> {

  final MarkStudentPresent markStudentPresent;
  final MarkStudentAbsent markStudentAbsent;

  MarkAttendanceBloc({@required this.markStudentPresent,@required this.markStudentAbsent});

  @override
  MarkAttendanceState get initialState => MarkedInitial();

  @override
  Stream<MarkAttendanceState> mapEventToState(MarkAttendanceEvent event) async* {
    yield MarkedLoading();
    if(event is MarkAbsentEvent){
      final remotelyReceived = await markStudentAbsent(MarkStudentParams(classId: event.classId, courseId: event.courseId,studentId: event.studentId));
      yield* _eitherLoadedOrErrorState(remotelyReceived);
    }
    else if(event is MarkPresentEvent){
      final remotelyReceived = await markStudentPresent(MarkStudentParams(classId: event.classId, courseId: event.courseId,studentId: event.studentId));
      yield* _eitherLoadedOrErrorState(remotelyReceived);
    }
  }
  Stream<MarkAttendanceState> _eitherLoadedOrErrorState(
    Either<StudentDetailsFacultyFailure,int> failureOrClasses,
    ) async* {
    yield failureOrClasses.fold(
        (failure) => MarkedError(_mapFailureToMessage(failure)),
        (studentId) => Marked(studentId),
    );
  }
  String _mapFailureToMessage(StudentDetailsFacultyFailure failure) {
    switch (failure.runtimeType) {
      case ServerError:
        return SERVER_FAILURE_MESSAGE;
      default:
        return 'No internet';
    }
  }

}

州

abstract class MarkAttendanceState extends Equatable{
  const MarkAttendanceState();
}

class MarkedInitial extends MarkAttendanceState{
  const MarkedInitial();
  @override
  List<Object> get props => [];

}

class MarkedLoading extends MarkAttendanceState{
  const MarkedLoading();
  @override
  List<Object> get props => [];

}

class Marked extends MarkAttendanceState{
  final int studentId;

  Marked(this.studentId);

  @override
  List<Object> get props => [studentId];

}

class MarkedError extends MarkAttendanceState{
  final String errorMessage;
  MarkedError(this.errorMessage);
  @override
  List<Object> get props => [errorMessage];
}

事件

import 'package:equatable/equatable.dart';

abstract class MarkAttendanceEvent extends Equatable {
  const MarkAttendanceEvent();
}
class MarkPresentEvent extends MarkAttendanceEvent {
  final int studentId;
  final int courseId;
  final int classId;

  MarkPresentEvent(this.studentId, this.courseId, this.classId);

  @override
  List<Object> get props =>[studentId,courseId,classId];

}

class MarkAbsentEvent extends MarkAttendanceEvent {
  final int studentId;
  final int courseId;
  final int classId;

  MarkAbsentEvent(this.studentId, this.courseId, this.classId);

  @override
  List<Object> get props =>[studentId,courseId,classId];

}

Answer 1

也许现在您已经找到了解决方案，但这就是我设法使用颤振肘实现相同功能的方法。这段代码是手写的，没有经过测试，但它应该能指导你实现你的目标

1 声明类对象

    class ClassItem{
      int? price;
      bool isChecked;
    
      ClassItem({
        this.price,
        this.isChecked=false,
      });
}
    class ClassOverall{
      List<ClassItem> items;
      double? total;
      ClassOverall(this.items,this.total);
    }

声明肘类

  class OverallCubit extends Cubit<ClassOverall> {
  OverallCubit(ClassOverallinitialState) : super(initialState);

  void checkUncheckCart(int index) {
  if (!state.items
      .elementAt(index).isChecked) {
    state.items
            .elementAt(index).isChecked =
        !state.items
            .elementAt(index).isChecked;
    var t_total = double.tryParse(state.items
            .elementAt(index).price!)! * 1;
    emit(OverallCubit (state.items,state.total));
  } else {
    state.items.elementAt(index).isChecked =
        !state.items
            .elementAt(index).isChecked;
    emit(OverallCubit (state.items,state.total));
  }
  calculateTotal();
}
void calculateTotal() {
  var tot = 0.0;
    for (var tick in state.items) {
      if (tick.isChecked) {
        tot = (tick.t_total! + tot);

  }

  }
emit(OverallCubit (state.items,tot));
 }
 }

声明顶级小部件来保存状态

class TopState extends StatelessWidget {
      @override
      Widget build(BuildContext context) {
        return BlocProvider(
          create: (_) => OverallCubit(ClassOverall(items,0)),//fetch items from your source 
          child: Home(),
        );
      }
    }

声明有状态小部件并添加块构建器

 class Home extends StatefulWidget {
        @override
   _HomePageState createState() => _HomePageState();
 }

 class _HomePageState extends State<Home> {
   @override
   Widget build(BuildContext context) {
     return  BlocBuilder<OverallCubit, ClassOverall>(
                               builder: (ctx, state) {
 return Column(children:[ 
 ListView.builder(
 padding: EdgeInsets.all(0.0),
                                       shrinkWrap: true,
                                       itemCount: state.items.length,
                                       itemBuilder: (context, index) {
                                         return ListTile(
 onTap: () {
             ctx
                 .read<OverallCubit>()
                 .checkUncheckCart(index);
           },
 tileColor: state.elementAt(index).isChecked ? Colors.red : Colors.white
 title: Text(state.items.elementAt(index).price!),
 );
 }),
 Text(state.total.toString),
 ]);
                                  });
 }

 }

如何使用群体抖动来更改单个列表项的状态？

1 个答案: