Flutter + Hive 检查 Future Builder 的框中是否存在值

Question

我正在制作一个新应用程序并将 REST API 调用的响应保存到 Hive 框，这是成功的（据我所知）。我在 main.dart 中尝试做的是检查令牌的值是否在 Hive 中设置，以及它是否加载登录视图以外的替代视图。

我的main.dart

import 'package:flutter/material.dart';
import 'package:hive_flutter/hive_flutter.dart';
import 'package:path_provider/path_provider.dart' as path_provider;
import 'package:myapp/model/user_model.dart';
import 'package:myapp/views/login_view.dart';
import 'package:myapp/views/project_view.dart';

void main() async {
  WidgetsFlutterBinding.ensureInitialized();
  final appDocsDir = await path_provider.getApplicationDocumentsDirectory();
  Hive.init(appDocsDir.path);
  Hive.registerAdapter(UserModelAdapter());
  runApp(MyApp());
}

class MyApp extends StatefulWidget {
  @override
  State<PocketPolarix> createState() => _PocketPolarixState();
}

class _MyAppState extends State<MyApp> {
  @override
  Widget build(BuildContext context) {
    final user = Hive.box('user');
    return MaterialApp(
      title: 'Startup Name Generator',
      theme: ThemeData(
        appBarTheme: const AppBarTheme(
          backgroundColor: Color(0xFF2036B8),
          foregroundColor: Colors.white,
        ),
      ),
      home: FutureBuilder(
        future: Hive.openBox('user'),
        builder: (BuildContext context, AsyncSnapshot snapshot) {
          if (snapshot.connectionState == ConnectionState.done) {
            if (snapshot.hasError) {
              return Text(snapshot.error.toString());
            } else {

              Hive.openBox('user');
              if (user.get('token') != null) {
                return const ProjectView();
              } else {
                return const LoginView();
              }

            }
          } else {
            return Scaffold();
          }
        },
      ),
    );
  }

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

代码在第二个 if 语句处失败，我在其中检查是否 Hive.box('user').get('token') != null 我一直得到的是以下错误。

throw HiveError('Box not found. Did you forget to call Hive.openBox()?');不过你可以从代码中看到，我正在打开盒子。

我是 Dart、Flutter 和 Hive 的新手，所以如果能帮上忙就太好了，谢谢！

Answer 1

问题出在您的 build 函数中的第一行代码。您正在尝试从 Hive 获取 user 框而不先打开它。您可以改为执行以下操作：

@override
Widget build(BuildContext context) {
  return MaterialApp(
    title: 'Startup Name Generator',
    theme: ThemeData(
      appBarTheme: const AppBarTheme(
        backgroundColor: Color(0xFF2036B8),
        foregroundColor: Colors.white,
      ),
    ),
    home: FutureBuilder<Box>(
      future: Hive.openBox('user'),
      builder: (BuildContext context, snapshot) {
        if (snapshot.connectionState == ConnectionState.done) {
          if (snapshot.hasError) {
            return Text(snapshot.error.toString());
          } else {
            if (snapshot.data?.get('token') != null) {
              return const ProjectView();
            } else {
              return const LoginView();
            }
          }
        } else {
          return Scaffold();
        }
      },
    ),
  );
}

Answer 2

问题的第 1 部分是您在打开之前尝试访问用户。其次，我相信您需要在进行任何操作之前检查 snapshot.hasData 是否

  @override
  Widget build(BuildContext context) {
    return MaterialApp(
      title: 'Startup Name Generator',
      theme: ThemeData(
        appBarTheme: const AppBarTheme(
          backgroundColor: Color(0xFF2036B8),
          foregroundColor: Colors.white,
        ),
      ),
      home: FutureBuilder(
        future: Hive.openBox<YourUserModelBox>('user'),
        builder: (BuildContext context, AsyncSnapshot snapshot) {
          if (snapshot.connectionState == ConnectionState.done) {
            if (snapshot.hasError) {
              return Text(snapshot.error.toString());
            } else if (snapshot.hasData) {
              if (snapshot.data is YourUserModelBox) {
                final user = snapshot.data as YourUserModelBox;
                if (user.get('token') != null) {
                  return const ProjectView();
                } else {
                  return const LoginView();
                }
              } else {
                Scaffold();
              }
            }
          } else {
            return Scaffold();
          }
        },
      ),
    );
  }

Flutter + Hive 检查 Future Builder 的框中是否存在值

Flutter + Hive Check if value is present in box in Future Builder

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