Flutter Hive store color

Question

I need to store colour in my Hive database to retrieve in my eCommerce Application, it gave me the error below saying that I need to make an adapter, can anyone tell me how to make a colour adapter?

part 'items_model.g.dart';

@HiveType(typeId: 0)
class Item {
  @HiveField(0)
  final String name;
  @HiveField(1)
  final double price;
  @HiveField(2)
  final String? description;
  @HiveField(3)
  var image;
  @HiveField(4)
  final String id;
  @HiveField(5)
  final String shopName;
  @HiveField(6)
  final List<Category> category;
  @HiveField(7)
  Color? color;
  @HiveField(8)
  int? quantity;
  Item({
    required this.category,
    required this.image,
    required this.name,
    required this.price,
    this.description,
    required this.id,
    required this.shopName,
    this.color,
    required this.quantity,
  });



}

does anyone know how to generate or create Color Adapter? as I don't know-how

E/flutter ( 4621): [ERROR:flutter/lib/ui/ui_dart_state.cc(209)] Unhandled Exception: HiveError: Cannot write, unknown type: MaterialColor. Did you forget to register an adapter?

score 6 · Accepted Answer · answered Mar 21 '22 at 15:03

I think the easiest thing to do here would be to store the int value of the color.

Here's an example.

final colorValue = Colors.blue.value; // colorValue is an integer here

So your Hive color could be stored like this

@HiveField(7)
int? colorValue;

Then, in your app when you're creating a color from storage it would look like this.

final item = Item(...however you initialize your Item);

final color = Color(item.colorValue);

score 3 · Answer 2 · answered Aug 06 '22 at 06:59

Base on previous answers by @Cryptozord and @Loren.A one can simply just write specific adapter for color

import 'package:flutter/cupertino.dart';
import 'package:hive/hive.dart';

class ColorAdapter extends TypeAdapter<Color> {
  @override
  final typeId = 221;

  @override
  Color read(BinaryReader reader) => Color(reader.readUint32());

  @override
  void write(BinaryWriter writer, Color obj) => writer.writeUint32(obj.value);
}

and remember to register your adapter with

Hive.registerAdapter(ColorAdapter());

make sure your typeId is not taken by other models

now you can use

@HiveField(7)
Color? colorValue;

score 0 · Answer 3 · answered Jul 06 '22 at 15:39

I was confused about this for a whole day and I figured out how to do it. You should instead create your adapter manually like so:

  class ItemAdapter extends TypeAdapter<Item> {
  @override
  final typeId = 0;

  @override
  ThemeState read(BinaryReader reader) {
    return Item(
       color: Color(reader.readUint32()),
       //the rest of the fields here
     );
    }

  @override
  void write(BinaryWriter writer, ThemeState obj) {
    writer.writeUint32(obj.color.value);
    writer.writeString(obj.name);
    //the rest of the fields here
  }
}

Color needs to saved and written as a Uint32 value because the Int32 value only has a range of -2147483648 to 2147483647 and an unsigned integer is 0 to 4294967295. The integer values of Color() can go past 2147483647. If Uint32 is not used then your values will not be stored correctly and weird colors will be saved instead.

Flutter Hive store color

3 Answers3