SQLite 无法插入通过 json_serializable 生成的 json

Question

我想了解为什么在数据库插入时会出现以下异常以及如何正确执行此操作。

错误：flutter/lib/ui/ui_dart_state.cc(157)] 未处理的异常：DatabaseException（java.util.HashMap 无法转换为 java.lang.Integer）sql 'INSERT OR REPLACE INTO homes (id, name, color, pets) VALUES (?, ?, ?, ?)' args [ 1，史密斯，格林，[{姓名：麦基，身份证：1，品种：罗威纳犬，年龄：8}，{姓名：坦纳，身份证：2，品种：獒犬，年龄：8}]]}

其中哪一部分被解释为导致转换错误的整数？

通过其他 posts 和建议，我已经将 json_serializable 添加到我的项目中，并且我项目中的两个模型 classes 都被注释了，导致 toJson 和 fromJson 方法被在构建过程中创建。

插入简单的 Dog 对象效果很好插入包含列表作为其字段之一的 House 对象失败。

我正在使用从可序列化生成的 toJson 函数插入到我的数据库中。

打印每个对象的输出结果如下：

一只狗： {id: 1, breed: Rottweiler, name: Mackie, age: 8}

A House: {id: 1, name: Smith, color: Green, pets: [{id: 1, breed: Rottweiler, name: Mackie, age: 8 }, {id: 2, breed: Mastiff, name: Tanner, age: 8}]}

房子 json 有什么问题阻止插入成功并导致我在 post 开头提到的转换异常？

我的代码

狗Class

import 'package:json_annotation/json_annotation.dart';

part 'dog.g.dart';

@JsonSerializable()
class Dog {
  final int id;
  final String breed;
  final String name;
  final int age;

  Dog({this.id, this.breed, this.name, this.age});

  factory Dog.fromJson(Map<String, dynamic> json) => _$DogFromJson(json);
  Map<String, dynamic> toJson() => _$DogToJson(this);
}

狗部分

// GENERATED CODE - DO NOT MODIFY BY HAND

part of 'dog.dart';

// **************************************************************************
// JsonSerializableGenerator
// **************************************************************************

Dog _$DogFromJson(Map<String, dynamic> json) {
  return Dog(
    id: json['id'] as int,
    breed: json['breed'] as String,
    name: json['name'] as String,
    age: json['age'] as int,
  );
}

Map<String, dynamic> _$DogToJson(Dog instance) => <String, dynamic>{
      'id': instance.id,
      'breed': instance.breed,
      'name': instance.name,
      'age': instance.age,
    };

房子class

import 'dog.dart';
import 'package:json_annotation/json_annotation.dart';

part 'house.g.dart';

@JsonSerializable(explicitToJson: true)
class House{
  final int id;
  final String name;
  final String color;
  final List<Dog> pets;

  House({this.id, this.name, this.color, this.pets});

  factory House.fromJson(Map<String, dynamic> json) => _$HouseFromJson(json);
  Map<String, dynamic> toJson() => _$HouseToJson(this);
}

房子部分

// GENERATED CODE - DO NOT MODIFY BY HAND

part of 'house.dart';

// **************************************************************************
// JsonSerializableGenerator
// **************************************************************************

House _$HouseFromJson(Map<String, dynamic> json) {
  return House(
    id: json['id'] as int,
    name: json['name'] as String,
    color: json['color'] as String,
    pets: (json['pets'] as List)
        ?.map((e) => e == null ? null : Dog.fromJson(e as Map<String, dynamic>))
        ?.toList(),
  );
}

Map<String, dynamic> _$HouseToJson(House instance) => <String, dynamic>{
      'id': instance.id,
      'name': instance.name,
      'color': instance.color,
      'pets': instance.pets?.map((e) => e?.toJson())?.toList(),
    };

如果能帮助我理解我在这里遗漏的部分，我们将不胜感激。

当所讨论的对象不仅仅是一个由基本类型组成的简单 PODO 时，在将数据提交到我的数据库插入方法之前，我还需要按照 toJson 函数做一些额外的事情吗？

完全错误

E/flutter ( 2822): [ERROR:flutter/lib/ui/ui_dart_state.cc(157)] Unhandled Exception: DatabaseException(java.util.HashMap cannot be cast to java.lang.Integer) sql 'INSERT OR REPLACE  INTO homes (id, name, color, pets) VALUES (?, ?, ?, ?)' args [1, Smith, Green, [{name: Mackie, id: 1, breed: Rottweiler, age: 8}, {name: Tanner, id: 2, breed: Mastiff, age: 8}]]}
E/flutter ( 2822): #0      wrapDatabaseException (package:sqflite/src/exception_impl.dart:12:7)
E/flutter ( 2822): <asynchronous suspension>
E/flutter ( 2822): #1      SqfliteDatabaseFactoryImpl.wrapDatabaseException (package:sqflite/src/factory_impl.dart:25:7)
E/flutter ( 2822): #2      SqfliteDatabaseMixin.safeInvokeMethod (package:sqflite/src/database_mixin.dart:188:15)
E/flutter ( 2822): #3      SqfliteDatabaseMixin.txnRawInsert.<anonymous closure> (package:sqflite/src/database_mixin.dart:363:14)
E/flutter ( 2822): #4      SqfliteDatabaseMixin.txnSynchronized.<anonymous closure> (package:sqflite/src/database_mixin.dart:307:22)
E/flutter ( 2822): #5      BasicLock.synchronized (package:synchronized/src/basic_lock.dart:32:26)
E/flutter ( 2822): #6      SqfliteDatabaseMixin.txnSynchronized (package:sqflite/src/database_mixin.dart:303:43)
E/flutter ( 2822): #7      SqfliteDatabaseMixin.txnWriteSynchronized (package:sqflite/src/database_mixin.dart:325:7)
E/flutter ( 2822): #8      SqfliteDatabaseMixin.txnRawInsert (package:sqflite/src/database_mixin.dart:362:12)
E/flutter ( 2822): #9      SqfliteDatabaseExecutorMixin.rawInsert (package:sqflite/src/database_mixin.dart:49:15)
E/flutter ( 2822): #10     SqfliteDatabaseExecutorMixin.insert (package:sqflite/src/database_mixin.dart:59:12)
E/flutter ( 2822): #11     Homes.addNewHome (package:search_list_view/providers/homes.dart:20:31)
E/flutter ( 2822): <asynchronous suspension>
E/flutter ( 2822): #12     _MyAppState.build.<anonymous closure> (package:search_list_view/main.dart:104:26)
E/flutter ( 2822): #13     _InkResponseState._handleTap (package:flutter/src/material/ink_well.dart:706:14)
E/flutter ( 2822): #14     _InkResponseState.build.<anonymous closure> (package:flutter/src/material/ink_well.dart:789:36)
E/flutter ( 2822): #15     GestureRecognizer.invokeCallback (package:flutter/src/gestures/recognizer.dart:182:24)
E/flutter ( 2822): #16     TapGestureRecognizer.handleTapUp (package:flutter/src/gestures/tap.dart:486:11)
E/flutter ( 2822): #17     BaseTapGestureRecognizer._checkUp (package:flutter/src/gestures/tap.dart:264:5)
E/flutter ( 2822): #18     BaseTapGestureRecognizer.handlePrimaryPointer (package:flutter/src/gestures/tap.dart:199:7)
E/flutter ( 2822): #19     PrimaryPointerGestureRecognizer.handleEvent (package:flutter/src/gestures/recognizer.dart:467:9)
E/flutter ( 2822): #20     PointerRouter._dispatch (package:flutter/src/gestures/pointer_router.dart:76:12)
E/flutter ( 2822): #21     PointerRouter._dispatchEventToRoutes.<anonymous closure> (package:flutter/src/gestures/pointer_router.dart:117:9)
E/flutter ( 2822): #22     _LinkedHashMapMixin.forEach (dart:collection-patch/compact_hash.dart:379:8)
E/flutter ( 2822): #23     PointerRouter._dispatchEventToRoutes (package:flutter/src/gestures/pointer_router.dart:115:18)
E/flutter ( 2822): #24     PointerRouter.route (package:flutter/src/gestures/pointer_router.dart:101:7)
E/flutter ( 2822): #25     GestureBinding.handleEvent (package:flutter/src/gestures/binding.dart:218:19)
E/flutter ( 2822): #26     GestureBinding.dispatchEvent (package:flutter/src/gestures/binding.dart:198:22)
E/flutter ( 2822): #27     GestureBinding._handlePointerEvent (package:flutter/src/gestures/binding.dart:156:7)
E/flutter ( 2822): #28     GestureBinding._flushPointerEventQueue (package:flutter/src/gestures/binding.dart:102:7)
E/flutter ( 2822): #29     GestureBinding._handlePointerDataPacket (package:flutter/src/gestures/binding.dart:86:7)
E/flutter ( 2822): #30     _rootRunUnary (dart:async/zone.dart:1138:13)
E/flutter ( 2822): #31     _CustomZone.runUnary (dart:async/zone.dart:1031:19)
E/flutter ( 2822): #32     _CustomZone.runUnaryGuarded (dart:async/zone.dart:933:7)
E/flutter ( 2822): #33     _invoke1 (dart:ui/hooks.dart:273:10)
E/flutter ( 2822): #34     _dispatchPointerDataPacket (dart:ui/hooks.dart:182:5)
E/flutter ( 2822):

谢谢，鲍勃

Answer 1

您可以复制粘贴运行下面的完整代码
将 Pet 作为 json 字符串存储在 TEXT 字段中并将 json 转换回 class Pet

工作演示

完整代码

import 'package:flutter/material.dart';
import 'dart:io';
import 'package:path/path.dart';
import 'package:path_provider/path_provider.dart';
import 'package:sqflite/sqflite.dart';
import 'package:dio/dio.dart';
import 'dart:convert';

void main() => runApp(MyApp());

class MyApp extends StatelessWidget {
  @override
  Widget build(BuildContext context) {
    return MaterialApp(
      title: 'Flutter Demo',
      theme: ThemeData(
        primarySwatch: Colors.blue,
      ),
      home: HomePage(),
    );
  }
}

class HomePage extends StatefulWidget {
  const HomePage({Key key}) : super(key: key);

  @override
  _HomePageState createState() => _HomePageState();
}

class _HomePageState extends State<HomePage> {
  var isLoading = false;

  @override
  Widget build(BuildContext context) {
    return Scaffold(
      appBar: AppBar(
        title: Text('Api to sqlite'),
        centerTitle: true,
        actions: <Widget>[
          Container(
            padding: EdgeInsets.only(right: 10.0),
            child: IconButton(
              icon: Icon(Icons.settings_input_antenna),
              onPressed: () async {
                await _loadFromApi();
              },
            ),
          ),
          Container(
            padding: EdgeInsets.only(right: 10.0),
            child: IconButton(
              icon: Icon(Icons.delete),
              onPressed: () async {
                await _deleteData();
              },
            ),
          ),
        ],
      ),
      body: isLoading
          ? Center(
              child: CircularProgressIndicator(),
            )
          : _buildHouseListView(),
    );
  }

  _loadFromApi() async {
    setState(() {
      isLoading = true;
    });

    var apiProvider = HouseApiProvider();
    await apiProvider.getAllHouses();

    // wait for 2 seconds to simulate loading of data
    await Future.delayed(const Duration(seconds: 2));

    setState(() {
      isLoading = false;
    });
  }

  _deleteData() async {
    setState(() {
      isLoading = true;
    });

    await DBProvider.db.deleteAllHouses();

    // wait for 1 second to simulate loading of data
    await Future.delayed(const Duration(seconds: 1));

    setState(() {
      isLoading = false;
    });

    print('All Houses deleted');
  }

  _buildHouseListView() {
    return FutureBuilder(
      future: DBProvider.db.getAllHouses(),
      builder: (BuildContext context, AsyncSnapshot snapshot) {
        if (!snapshot.hasData) {
          return Center(
            child: CircularProgressIndicator(),
          );
        } else {
          return ListView.separated(
            separatorBuilder: (context, index) => Divider(
              color: Colors.black12,
            ),
            itemCount: snapshot.data.length,
            itemBuilder: (BuildContext context, int index) {
              List<Pet> pets = snapshot.data[index].pets;

              return ListTile(
                leading: Text(
                  "${index + 1}",
                  style: TextStyle(fontSize: 20.0),
                ),
                title: Text(
                    "Name: ${snapshot.data[index].id} ${snapshot.data[index].name} "),
                subtitle: Text('pets: ${pets[0].name}  ${pets[1].name}'),
              );
            },
          );
        }
      },
    );
  }
}

class DBProvider {
  static Database _database;
  static final DBProvider db = DBProvider._();

  DBProvider._();

  Future<Database> get database async {
    // If database exists, return database
    if (_database != null) return _database;

    // If database don't exists, create one
    _database = await initDB();

    return _database;
  }

  // Create the database and the House table
  initDB() async {
    Directory documentsDirectory = await getApplicationDocumentsDirectory();
    final path = join(documentsDirectory.path, 'House2.db');

    return await openDatabase(path, version: 1, onOpen: (db) {},
        onCreate: (Database db, int version) async {
      await db.execute('CREATE TABLE House('
          'id INTEGER PRIMARY KEY,'
          'name TEXT,'
          'color TEXT,'
          'pets TEXT'
          ')');
    });
  }

  // Insert House on database
  createHouse(House newHouse) async {
    await deleteAllHouses();
    final db = await database;
    //final res = await db.insert('House', newHouse.toJson());

    String petsString = petToJson(newHouse.pets);
    var raw = await db.rawInsert(
        "INSERT Into House (id,name,color,pets)"
        " VALUES (?,?,?,?)",
        [newHouse.id, newHouse.name, newHouse.color, petsString]);

    print('createHouse ${raw}');
    return raw;
  }

  // Delete all Houses
  Future<int> deleteAllHouses() async {
    final db = await database;
    final res = await db.rawDelete('DELETE FROM House');

    return res;
  }

  Future<List<House>> getAllHouses() async {
    final db = await database;
    final res = await db.rawQuery("SELECT * FROM House");
    print('getAllHouses $res');
    List<House> list = [];

    if (res != null) {
      res.forEach((row) {
        print(row["name"]);
        print(row["pets"]);
        var petsString = row["pets"];
        var pets = petFromJson(petsString);
        var house = House(
            id: row["id"],
            name: row["name"],
            color: row["color"],
            pets: pets);
        list.add(house);
      });
    }
    print('list  ${list.toString()} ');
    return list;
  }
}

class HouseApiProvider {
  Future<List<House>> getAllHouses() async {
    /* var url = "http://demo8161595.mockable.io/House";
    Response response = await Dio().get(url);

    return (response.data as List).map((House) {
      print('Inserting $House');
      DBProvider.db.createHouse(House.fromJson(House));
    }).toList();*/

    String response = '''
   [{"id": 1, "name": "Smith", "color": "Green", "pets": 
[{"id": 1, "breed": "Rottweiler", "name": "Mackie", "age": 8}, {"id": 2, "breed": "Mastiff", "name": "Tanner", "age": 8}]}]
   ''';

    List<House> houseList = houseFromJson(response);
    houseList.forEach((house) {
      DBProvider.db.createHouse(house);
    });

    print('houseList ${houseList.toString()}');
    return houseList;
  }
}

List<House> houseFromJson(String str) =>
    List<House>.from(json.decode(str).map((x) => House.fromJson(x)));

String houseToJson(List<House> data) =>
    json.encode(List<dynamic>.from(data.map((x) => x.toJson())));

List<Pet> petFromJson(String str) =>
    List<Pet>.from(json.decode(str).map((x) => Pet.fromJson(x)));

String petToJson(List<Pet> data) =>
    json.encode(List<dynamic>.from(data.map((x) => x.toJson())));

class House {
  int id;
  String name;
  String color;
  List<Pet> pets;

  House({
    this.id,
    this.name,
    this.color,
    this.pets,
  });

  factory House.fromJson(Map<String, dynamic> json) => House(
        id: json["id"],
        name: json["name"],
        color: json["color"],
        pets: List<Pet>.from(json["pets"].map((x) => Pet.fromJson(x))),
      );

  Map<String, dynamic> toJson() => {
        "id": id,
        "name": name,
        "color": color,
        "pets": List<dynamic>.from(pets.map((x) => x.toJson())),
      };
}

class Pet {
  int id;
  String breed;
  String name;
  int age;

  Pet({
    this.id,
    this.breed,
    this.name,
    this.age,
  });

  factory Pet.fromJson(Map<String, dynamic> json) => Pet(
        id: json["id"],
        breed: json["breed"],
        name: json["name"],
        age: json["age"],
      );

  Map<String, dynamic> toJson() => {
        "id": id,
        "breed": breed,
        "name": name,
        "age": age,
      };
}

SQLite 无法插入通过 json_serializable 生成的 json

SQLite fails for insert for json generated via json_serializable

dart

flutter

sqflite