RangeError index invalid value only valid value is empty 0 see also in Flutter

Question

I'm in a Flutter project using Getx. Every time I enter the screen that lists the records I get an error message as you can see below;

I don't know where I'm going wrong, but I'll leave the main parts of the code. I need to find where I'm going wrong.

Class Repository

 Future<List<Post>> getAlbum({

        bool isFavoritedPage = false,
        bool isNewEdition = false,
      }) async {
          dio.options.headers['Cookie'] = 'ASP.NET_SessionId=${user.sessionID}';

    final response = await dio.get(
      isFavoritedPage ? AppConstants.apiFavoritedsPost : AppConstants.apiPosts,
      queryParameters: {
        'sessionId': user.sessionID,
        'CodUserProfile': '${user.codUser!}',
        'CodUserLogged': '${user.codUser!}',
        'Page': '${page}',
        'pagesize': '10',
        'myPostOnly': isFavoritedPage ? 'true' : 'false',
      },
    );

    final body = response.data['ListPosts'] as List;
    return body.map((post) => Post.fromJson(post)).toList();
  }

Class Controller

var lstPost = List<Post>.empty(growable: true).obs;
  var page = 1;
  var isDataProcessing = false.obs;

  // For Pagination
  ScrollController scrollController = ScrollController();
  var isMoreDataAvailable = true.obs;


  @override
  void onInit() async {
    super.onInit();
    // Fetch Data
    getPost(page);
    //For Pagination
    paginateTask();

  }

  void getPost(var page) {
    try {
      isMoreDataAvailable(false);
      isDataProcessing(true);
      getAlbum(page).then((resp) {
        isDataProcessing(false);
        lstPost.addAll(resp);
      }, onError: (err) {
        isDataProcessing(false);
        showSnackBar("Error", err.toString(), Colors.red);
      });
    } catch (exception) {
      isDataProcessing(false);
      showSnackBar("Exception", exception.toString(), Colors.red);
    }
  }


  showSnackBar(String title, String message, Color backgroundColor) {
    Get.snackbar(title, message,
        snackPosition: SnackPosition.BOTTOM,
        backgroundColor: backgroundColor,
        colorText: Colors.white);
  }

  void paginateTask() {
    scrollController.addListener(() {
      if (scrollController.position.pixels ==
          scrollController.position.maxScrollExtent) {
        print("reached end");
        page++;
        getMoreTask(page);
      }
    });
  }

  void getMoreTask(var page) {
    try {
      getAlbum(page).then((resp) {
        if (resp.length > 0) {
          isMoreDataAvailable(true);
        } else {
          isMoreDataAvailable(false);
          showSnackBar("Message", "Não existem registro", Colors.lightBlueAccent);
        }
        lstPost.addAll(resp);
      }, onError: (err) {
        isMoreDataAvailable(false);
        showSnackBar("Error", err.toString(), Colors.red);
      });
    } catch (exception) {
      isMoreDataAvailable(false);
      showSnackBar("Exception", exception.toString(), Colors.red);
    }
  }


  @override
  void onClose() {
    searchDrawerEC.dispose();
    super.onClose();
  }

  Future<List<Post>> getAlbum(pagina,[bool isFavoritedPage = false]) async {
    final response =
        await repository.getAlbum(isFavoritedPage: isFavoritedPage);
    return response;
  }

Class Page

Expanded(
         child: ListView.builder(
             itemBuilder: (BuildContext context, int index) {
               if (index == controller.lstPost.length - 1 &&
                   controller.isMoreDataAvailable.value == true) {
                 return Center(child: CircularProgressIndicator());
               }
               return PostWidget(post: controller.lstPost[index]);
             }
         ),
      ),

I'm basing myself on this github project.

https://github.com/RipplesCode/FlutterGetXTodoAppWithLaravel/tree/master/lib/app/modules/home

Jon Mountjoy · Accepted Answer · 2022-04-25 15:17:29Z

2

I don't use getx, but I see something odd in your Listview.builder. It feels as if you're abusing it a little, to also show the "no data" case, and there's also no count. I think it should have a count, so something like this:

if (lstPost.isEmpty) {
  return Center(child: CircularProgressIndicator());
} else {
return ListView.builder(
 itemCount: lstPost.length,
 itemBuilder: (BuildContext context, int index) {
    return PostWidget(...);
 }
 );
}

answered Apr 25, 2022 at 15:17

Jon Mountjoy

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