I am trying to create notebook with sqlite database in flutter 3.1.0 . I have problem with initialing my NoteEntityData with late and initState().

import 'package:flutter/material.dart';
import 'package:get/get.dart';
import 'package:intl/intl.dart';
import 'package:samsung_note/Database/database.dart';
import 'package:samsung_note/Screens/edit_screen.dart';
import 'package:samsung_note/app_style.dart';

class DetailsScreen extends StatefulWidget {
  final int id;

  const DetailsScreen({Key? key, required this.id}) : super(key: key);

  @override
  State<DetailsScreen> createState() => _DetailsScreenState();
}

class _DetailsScreenState extends State<DetailsScreen> {
  late Database _database;
  late NoteEntityData _noteData;

  @override
  void initState() {
    super.initState();
    _database = Database();
    getSingleNote();
  }

  @override
  void dispose() {
    _database.close();
    super.dispose();
  }

  @override
  Widget build(BuildContext context) {
    final time = DateFormat.Hm().format(_noteData.createdTime);
    final dateTime = DateFormat.yMMMd().format(_noteData.createdTime);
    return Scaffold(
      appBar: AppBar(
          elevation: 1,
          leading: IconButton(
              onPressed: () => Get.back(),
              icon: const Icon(Icons.arrow_back_ios)),
          actions: [
            IconButton(
                onPressed: () => Get.to(() => const EditScreen()),
                icon: const Icon(Icons.edit)),
            const SizedBox(width: 10),
            _noteData.isImportant
                ? const Icon(Icons.star, color: Colors.orange)
                : const Icon(Icons.star_border),
            const SizedBox(width: 10),
            IconButton(onPressed: () {}, icon: const Icon(Icons.delete)),
          ]),
      body: Padding(
        padding: const EdgeInsets.symmetric(vertical: 32, horizontal: 16),
        child: Column(
          mainAxisAlignment: MainAxisAlignment.start,
          crossAxisAlignment: CrossAxisAlignment.stretch,
          children: [
            Text(
              _noteData.title,
              style: AppStyle.titleTextStyle,
            ),
            const SizedBox(height: 25),
            Text(_noteData.description, style: AppStyle.descriptionTextStyle),
            const SizedBox(height: 50),
            Text(
              "Created time: $time",
              style: AppStyle.smallTextStyle
                  .copyWith(fontSize: 16, color: Colors.grey.shade500),
              textAlign: TextAlign.end,
            ),
            const SizedBox(height: 10),
            Text(
              "Created Datetime: $dateTime",
              style: AppStyle.smallTextStyle
                  .copyWith(fontSize: 16, color: Colors.grey.shade500),
              textAlign: TextAlign.end,
            ),
          ],
        ),
      ),
    );
  }
  getSingleNote() async {
    _noteData = await _database.getSingleNote(widget.id);
  }
}

I know that we can't use async in initState() , so I create a Future method to initial my noteData . but when I run my code , compiler can't understand initialing noteData and I got this error :

======== Exception caught by widgets library =======================================================
The following LateError was thrown building DetailsScreen(dirty, state: _DetailsScreenState#e1c83):
LateInitializationError: Field '_noteData@861302000' has not been initialized.

The relevant error-causing widget was: 
  DetailsScreen DetailsScreen:file:///C:/Users/Hp/AndroidStudioProjects/samsung_note/lib/Screens/home_screen.dart:72:51
When the exception was thrown, this was the stack: 
#0      _DetailsScreenState._noteData (package:samsung_note/Screens/details_screen.dart)
#1      _DetailsScreenState.build (package:samsung_note/Screens/details_screen.dart:36:41)
#2      StatefulElement.build (package:flutter/src/widgets/framework.dart:4919:27)
#3      ComponentElement.performRebuild (package:flutter/src/widgets/framework.dart:4806:15)
#4      StatefulElement.performRebuild (package:flutter/src/widgets/framework.dart:4977:11)
#5      Element.rebuild (package:flutter/src/widgets/framework.dart:4529:5)
#6      ComponentElement._firstBuild (package:flutter/src/widgets/framework.dart:4787:5)
#7      StatefulElement._firstBuild (package:flutter/src/widgets/framework.dart:4968:11)
#8      ComponentElement.mount (package:flutter/src/widgets/framework.dart:4781:5)
...     Normal element mounting (275 frames)
===================================================================================================

here is where I got one note id in HomeScreen :

Scaffold(
      backgroundColor: Colors.grey.shade200,
      drawer: const Drawer(),
      appBar: AppBar(
        elevation: 0,
        backgroundColor: Colors.grey.shade200,
        title: Text(
          "All notes",
          style: AppStyle.normalTextStyle.copyWith(fontWeight: FontWeight.w600),
        ),
        actions: [
          IconButton(onPressed: () {}, icon: const Icon(Icons.search)),
          IconButton(
              onPressed: () {}, icon: const Icon(Icons.more_vert_outlined))
        ],
      ),
      body: FutureBuilder<List<NoteEntityData>>(
        future: _database.getAllNotes(),
        builder: (context, snapshot) {
          final List<NoteEntityData>? notes = snapshot.data;
          if (snapshot.connectionState != ConnectionState.done) {
            return Center(
              child: LoadingAnimationWidget.inkDrop(
                  color: Colors.deepOrange, size: 200),
            );
          } else if (snapshot.hasError) {
            return Center(
              child: Text(snapshot.error.toString()),
            );
          } else if (notes!.isNotEmpty) {
            return Padding(
                padding: const EdgeInsets.symmetric(vertical: 16),
                child: GridView.builder(
                  gridDelegate: const SliverGridDelegateWithFixedCrossAxisCount(
                      crossAxisCount: 2),
                  itemCount: notes.length,
                  itemBuilder: (context, index) {
                    final note = notes[index];
                    return GestureDetector(
                        onTap: () => Get.to(() => DetailsScreen(id: note.id)),
                        child: BaseContainer(note: note));
                  },
                ));
          }

and I have to mention ALL THIS CODE is for some course and it's Same as teacher Code.. That code it's work just fine but mine has this ERROR .

CodePudding user response：

Try to add setState((){}) to your getSingleNote method

like this :

  getSingleNote() async {
    setState((){
      _noteData = await _database.getSingleNote(widget.id);
    });
  }

CodePudding user response：

that because getSingleNote is an async function and when Flutter framwork call build function of your class _noteData is not initialized.

I think you can use a FutureBuilder in build function for initialize _noteData before use it