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

Question

I have an app I built a post page everything worked good in app when I opened and go to add a post page and wrote is also okay this error happened when I clicked on the post button.. I use Appwrite to save data and the posts do not saved in appwrite database

so this error when I click on button he take me to post_controller.dart the error :

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

the code where the error is :

    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);
  }

the code in the post page :

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),
            ),
          ],
        ),
      ),
    );
  }
}

 

I am new at flutter please help ??

Answer 1

This exception occurs when you try to use the ! operator on a value that is null. In your case, in the line

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

you try to check if the value of user is not null. Probably when you initialize the provider currentUserDetailsProvider it builds with an intrinsic value of null. So you either accept that the user can be null, using the ? operator instead, or fix the provider so that the value on build is not null.