发生异常。 _TypeError（对空值使用空检查运算符）

Question

我有一个应用程序，我构建了一个帖子页面，当我打开并去添加帖子页面并写入时，一切都运行良好，也可以，当我单击帖子按钮时发生此错误。我使用 Appwrite 来保存数据，并且帖子未保存在 appwrite 数据库中

所以当我单击按钮时出现此错误，他将我带到 post_controller.dart 错误：

 Exception has occurred.
_TypeError (Null check operator used on a null value)

错误所在的代码：

    void _shareTextPost({
    required List<File> images,
    required String text,
    required BuildContext context,
  }) async {
    state = true;
    final hashtags = _getHashtagsFromText(text);
    String link = _getLinkFromText(text);
    final user = _ref.read(currentUserDetailsProvider).value!;
    //
    Post post = Post(
      text: text,
      hashtags: hashtags,
      link: link,
      imageLinks: [],
      uid: user.uid,
      postType: PostType.text,
      postedAt: DateTime.now(),
      likes: [],
      commentIds: [],
      id: '',
      reshareCount: 0,
      repostedBy: '',
      repliedTo: '',
    );
    final res = await _postAPI.sharePost(post);
    state = false;
    res.fold((l) => showSnackBar(context, l.message), (r) => null);
  }

帖子页面中的代码：

class CreatePostScreen extends ConsumerStatefulWidget {
  static route() => MaterialPageRoute(
        builder: (context) => const CreatePostScreen(),
      );
  const CreatePostScreen({super.key});

  @override
  ConsumerState<ConsumerStatefulWidget> createState() =>
      _CreatePostScreenState();
}

class _CreatePostScreenState extends ConsumerState<CreatePostScreen> {
  final postTextController = TextEditingController();
  List<File> images = [];
  @override
  void dispose() {
    super.dispose();
    postTextController.dispose();
  }

  void sharePost() {
    ref.read(postControllerProvider.notifier).sharePost(
          images: images,
          text: postTextController.text,
          context: context,
        );
  }

  void onPickImages() async {
    images = await pickImages();
    setState(() {});
  }

  @override
  Widget build(BuildContext context) {
    final isLoading = ref.watch(postControllerProvider);
    //final currentUser = ref.watch(currentUserDetailsProvider).value;
    //
    return Scaffold(
      appBar: AppBar(
        leading: IconButton(
          onPressed: () {
            Navigator.pop(context);
          },
          icon: Icon(
            Icons.close,
            size: 30,
            color: Colors.black,
          ),
        ),
        actions: [
          Padding(
            padding: const EdgeInsets.only(
                right: 16.0), // Adjust the padding as needed
            child: RoundedSmallButton(
              onTap: sharePost,
              label: 'Post',
              backgroundColor: Pallete.pinkColor,
              TextColor: Pallete.whiteColor,
            ),
          ),
        ],
      ),
      // ignore: unnecessary_null_comparison
      body: isLoading == null
          //|| currentUser == null
          ? const Loader()
          : SafeArea(
              child: SingleChildScrollView(
                  child: Column(
                children: [
                  Row(
                    children: [
                      //  Padding(
                      //       padding: const EdgeInsets.all(
                      //         10.0), // Adjust the padding as needed
                      //   child: CircleAvatar(
                      //   backgroundImage: NetworkImage(currentUser.profilePic),
                      //   radius: 30,
                      //  ),
                      //  ),
                      const SizedBox(width: 2),
                      Expanded(
                          child: TextField(
                        controller: postTextController,
                        style: const TextStyle(
                          fontSize: 18,
                          color: Colors.black,
                          // fontWeight: FontWeight.bold,
                        ),
                        decoration: const InputDecoration(
                          hintText: "Got study tips to share?",
                          hintStyle: TextStyle(
                            color: Pallete.greyColor,
                            fontSize: 18,
                            fontWeight: FontWeight.w600,
                          ),
                          border: InputBorder.none,
                          // focusedBorder: UnderlineInputBorder(
                          //  borderSide: BorderSide(color: Pallete.pinkColor),
                          //  ),
                        ),
                        maxLines: null,
                        cursorColor: Pallete.pinkColor,
                      )),
                    ],
                  ),
                  if (images.isNotEmpty)
                    CarouselSlider(
                      items: images.map(
                        (file) {
                          return Container(
                              width: MediaQuery.of(context).size.width,
                              margin: const EdgeInsets.symmetric(
                                horizontal: 5,
                              ),
                              child: Image.file(file));
                        },
                      ).toList(),
                      options: CarouselOptions(
                        height: 400,
                        enableInfiniteScroll: false,
                      ),
                    ),
                ],
              )),
            ),
      bottomNavigationBar: Container(
        padding: const EdgeInsets.only(bottom: 10),
        decoration: const BoxDecoration(
          border: Border(
              top: BorderSide(
            color: Pallete.greyColor,
            width: 0.3,
          )),
        ),
        child: Row(
          children: [
            Padding(
              padding: const EdgeInsets.all(10.0).copyWith(
                left: 15,
                right: 15,
              ),
              child: GestureDetector(
                  onTap: onPickImages,
                  child: SvgPicture.asset(AssetsConstants.galleryIcon)),
            ),
            Padding(
              padding: const EdgeInsets.all(10.0).copyWith(
                left: 15,
                right: 15,
              ),
              child: SvgPicture.asset(AssetsConstants.gifIcon),
            ),
            Padding(
              padding: const EdgeInsets.all(10.0).copyWith(
                left: 15,
                right: 15,
              ),
              child: SvgPicture.asset(AssetsConstants.emojiIcon),
            ),
          ],
        ),
      ),
    );
  }
}

 

我是颤振新手，请帮忙??

Answer 1

当您尝试对

!

值使用

null

运算符时，会发生此异常。在你的情况下，在行中

final user = _ref.read(currentUserDetailsProvider).value!;

您尝试检查

user

的值是否不为空。可能当您初始化提供者

currentUserDetailsProvider

时，它会使用

null

的内在值进行构建。因此，您要么接受

user

可以是

null

，而是使用

?

运算符，要么修复提供程序，以便构建时的值不是

null

。