已编辑

Question

我有两个列表视图构建器，如下图所示：

尝试获取特定项目列表时出错，这是以下错误：

RangeError (index): Invalid value: Valid value range is empty: 4

When the exception was thrown, this was the stack: 
#0      List.[] (dart:core-patch/growable_array.dart:254:60)
#1      AppCubit.changeCategoryModelState (package:ipet/shared/cubit/cubit.dart:116:35)
#2      CategoriesScreen.buildPetsCategoryItem.<anonymous closure>.<anonymous closure> (package:ipet/modules/categories/categories_screen.dart:97:43)
#3      GestureRecognizer.invokeCallback (package:flutter/src/gestures/recognizer.dart:182:24)
#4      TapGestureRecognizer.handleTapUp (package:flutter/src/gestures/tap.dart:607:11)
...
Handler: "onTap"
Recognizer: TapGestureRecognizer#0916b
  debugOwner: GestureDetector
  state: ready
  won arena
  finalPosition: Offset(272.1, 219.8)
  finalLocalPosition: Offset(51.1, 42.8)
  button: 1
  sent tap down

所以我想在点击 buildPetsCategoryItem() 中的项目时只需更改 buildCategoriesListView()

那么最好的方法是什么...

这是下面的代码：

        return SingleChildScrollView(
          controller: cubit.scrollController,
          physics: BouncingScrollPhysics(),
          child: Column(
            children: [
              SizedBox(
                height: 30,
              ),
              Padding(
                padding: const EdgeInsets.only(left: 20.0),
                child: CustomText(
                  text: "Categories",
                ),
              ),
              SizedBox(
                height: 30,
              ),
              // buildCategoryItem(context),
              buildPetsCategoryItem(context),
              buildCategoriesListView(cubit)
            ],
          ),
        );

更清楚地说，我在下面的类别构建器中有这个：

 Widget buildPetsCategoryItem(context) {
    return Container(
      height: 120,
      child: ListView.builder(
        physics: BouncingScrollPhysics(),
        scrollDirection: Axis.horizontal,
        itemCount: AppCubit.get(context).petsCategories.length,
        itemBuilder: (context, index) {
          return Container(
            padding: EdgeInsets.only(top: 20),
            child: Column(
              crossAxisAlignment: CrossAxisAlignment.center,
              children: [
                GestureDetector(
                  onTap: () {
                    AppCubit.get(context).changePetsCategoryBorder(index);
                    AppCubit.get(context).changeCategoryModelState(index);
                  },
                  child: Container(
                    width: 60,
                    height: 60,
                    margin: EdgeInsets.symmetric(horizontal: 18),
                    padding: EdgeInsets.all(12),
                    decoration: BoxDecoration(
                      color: Colors.white,
                      boxShadow: customShadow,
                      border:
                          AppCubit.get(context).selectedPetsCategory == index
                              ? Border.all(
                                  color: secondaryGreen,
                                  width: 2,
                                )
                              : null,
                      borderRadius: BorderRadius.circular(20),
                    ),
                    child: Image.network(
                      AppCubit.get(context).petsCategories[index].image,
                      scale: 1.8,
                    ),
                  ),
                ),
                SizedBox(
                  height: 6,
                ),
                Text(
                  AppCubit.get(context).petsCategories[index].name,
                  style: TextStyle(fontSize: 12, color: Colors.grey),
                ),
              ],
            ),
          );
        },
      ),
    );
  }

这是 CategoriesListView：

  ListView buildCategoriesListView(AppCubit cubit) {
    return ListView.builder(
      shrinkWrap: true,
      physics: BouncingScrollPhysics(),
      // scrollDirection: Axis.horizontal,
      itemCount: cubit.currentCategoryPets.length,
      itemBuilder: (context, index) {
        return GestureDetector(
          onTap: () {
            navigateTo(
              context,
              DetailsScreen(
                pets: cubit.currentCategoryPets[index],
              ),
            );
          },
          child: Container(
            margin: EdgeInsets.symmetric(vertical: 5),
            child: PetCard(
              petId: cubit.currentCategoryPets[index].id,
              petName: cubit.currentCategoryPets[index].name,
              age: cubit.currentCategoryPets[index].age,
              breed: cubit.currentCategoryPets[index].petType,
              gender: cubit.currentCategoryPets[index].gender,
              distance: cubit.currentCategoryPets[index].distance,
              imagePath: cubit.currentCategoryPets[index].image,
            ),
          ),
        );
      },
    );
  }

因为我有两种获取每个类别的 PetsModel 数据的方法，一个获取所有宠物，另一个获取 Cats：

  List<PetsModel> pets = [];
  List<PetsModel> cats = [];
  void getPetsData() {
    FirebaseFirestore.instance.collection('pets').get().then((value) {
      value.docs.forEach((element) {
        pets.add(PetsModel.fromJson(element.data()));
      });
      emit(AppGetPetsSuccessState());
    }).catchError((error) {
      emit(AppGetPetsErrorState(error.toString()));
    });
  }

  void getCatsData() {
    FirebaseFirestore.instance.collection('pets').where('type', isEqualTo: 'cat').get().then((value) {
      value.docs.forEach((element) {
        cats.add(PetsModel.fromJson(element.data()));
      });
      emit(AppGetPetsSuccessState());
    }).catchError((error) {
      emit(AppGetPetsErrorState(error.toString()));
    });
  }

我尝试创建一种将 Category Model State 更改为以下内容的方法：

  PetsModel petModel;
  List<PetsModel> currentCategoryModel = [];

  void changeCategoryModelState(int position) {
    petModel = currentCategoryPets[position];
    if (position == 4) getPetsData();
    if (position == 5) getCatsData();
    emit(AppChangeCategoryModelState());
  }

这是包含 BlocProvider 的主类：

return BlocProvider(
      create: (BuildContext context) => AppCubit()
        ..getUserData()
        ..getCategoriesData()
        ..getPetsData()
        ..getCatsData()
        ..handleScroll(),
      child: BlocConsumer<AppCubit, AppStates>(...),);

有关更多信息，这是宠物卡小部件：

@override
  Widget build(BuildContext context) {
    final size = MediaQuery.of(context).size;
    // final randomColor = colors[_random.nextInt(colors.length)];
    return Container(
      margin: EdgeInsets.symmetric(horizontal: 20),
      height: 240,
      child: Stack(
        children: [
          Container(
            // height: 200,
            margin: EdgeInsets.only(
              top: 70,
              bottom: 20,
            ),
            child: Row(
              children: [
                Container(
                  width: size.width * 0.48,
                ),
                Expanded(
                  child: Container(
                    margin: EdgeInsets.symmetric(horizontal: 10, vertical: 20),
                    child: Column(
                      crossAxisAlignment: CrossAxisAlignment.start,
                      mainAxisAlignment: MainAxisAlignment.spaceBetween,
                      children: [
                        Row(
                          mainAxisAlignment: MainAxisAlignment.spaceBetween,
                          children: [
                            CustomText(
                              text: petName,
                              fontSize: 20,
                              fontWeight: FontWeight.bold,
                              maxLine: 1,
                              overflow: TextOverflow.ellipsis,
                            ),
                            Icon(
                              gender == 'female'
                                  ? FontAwesomeIcons.venus
                                  : FontAwesomeIcons.mars,
                              size: 18,
                              color: Colors.black54,
                            )
                          ],
                        ),
                        Text(
                          breed,
                          style: TextStyle(
                            fontSize: 12,
                            color: fadedBlack,
                            fontWeight: FontWeight.bold,
                          ),
                        ),
                        CustomText(
                          text: age + ' years',
                          fontSize: 12,
                          color: fadedBlack,
                        ),
                        Row(
                          children: [
                            Icon(
                              Icons.location_pin,
                              size: 16,
                              color: primaryGreen,
                            ),
                            SizedBox(
                              width: 5,
                            ),
                            CustomText(
                              text: 'Distance: ' + distance + ' Km',
                              fontSize: 12,
                              color: fadedBlack,
                            ),
                          ],
                        )
                      ],
                    ),
                  ),
                )
              ],
            ),
            decoration: BoxDecoration(
              color: Colors.white,
              boxShadow: customShadow,
              borderRadius: BorderRadius.only(
                topRight: Radius.circular(20),
                bottomRight: Radius.circular(20),
              ),
            ),
          ),
          Container(
            width: size.width * 0.48,
            child: Stack(
              children: [
                Container(
                  decoration: BoxDecoration(
                    color: Theme.of(context).scaffoldBackgroundColor,
                    boxShadow: customShadow,
                    borderRadius: BorderRadius.circular(22),
                  ),
                  margin: EdgeInsets.only(top: 50),
                ),
                Align(
                  child: Hero(
                    tag: petId,
                    child: Image.network(
                      imagePath,
                      loadingBuilder: loadingNetworkImage,
                    ),
                  ),
                ),
              ],
            ),
          )
        ],
      ),
    );
  }

以下方法与 selectedPetsCategories() 相关：

  int selectedPetsCategory = 0;

  void changePetsCategoryBorder(int index) {
    selectedPetsCategory = index;
    emit(AppChangePetsCategoryBorderState());
  }

我该如何解决这个错误？

已编辑

所以对于之前的错误，因为我必须在 init 中添加 changeCategoryModelState() 方法，同时在 blocProvider 中启动应用程序，所以我将 int position 参数设为可选参数并尝试添加方法 { {1}} 如下代码：

addAll

并像下面的代码一样在 main 中调用它：

  void changeCategoryModelState({int position}) {
    petModel = currentCategoryPets[position];
    if (position == 4) getPetsData();
    if (position == 5) getCatsData();
    currentCategoryPets.addAll(pets);
    emit(AppChangeCategoryModelState());
  }

我发现以下错误：

return BlocProvider(
      create: (BuildContext context) => AppCubit()
        ..getUserData()
        ..getCategoriesData()
        ..getPetsData()
        ..getCatsData()
        ..changeCategoryModelState()
        ..handleScroll(),
      child: BlocConsumer<AppCubit, AppStates>(...),);

Answer 1

这是正确的答案，然后只需删除参数并将changeCategoryModelState 方法更新为：

  void changeCategoryModelState() {
    if (selectedPetsCategory == 5) {
      currentCategoryPets.clear();
      currentCategoryPets.addAll(cats);
      print(selectedPetsCategory.toString());
    }
    else if (selectedPetsCategory == 4) {
      currentCategoryPets.clear();
      currentCategoryPets.addAll(pets);
      print(selectedPetsCategory.toString());
    }
    emit(AppChangeCategoryModelState());
  }

失败的断言：第 4191 行 pos 14：'owner!._debugCurrentBuildTarget == this'：不是真的

已编辑

1 个答案: