Type Adapter for Offset in hive flutter

I have this class called DrawLine and I have generated the adapter class

import 'dart:ui';
import 'package:hive/hive.dart';

part 'draw_line.g.dart';

@HiveType(typeId: 0)
class DrawnLine extends HiveObject{
  @HiveField(0)
  final List<Offset> path;

  @HiveField(1)
  final Color color;

  @HiveField(2)
  final double width;

  @HiveField(3)
  final bool isEraser;
  DrawnLine(this.path, this.color, this.width, this.isEraser);
}

When I try to save list of DrawLine objects, there is an error which indicates hive does not recognize the type Offset in the object.

Which means that I have to in turn make an adapter for Offset too but I don't know how to go about it. Any help will be much appreciated.

Offset is not supported in Hive. Hive only supports List, Map, DateTime and Uint8List.

To support other objects you have to register a TypeAdapter which converts the object from and to binary form.

In your case, to support a Offset you have to create its own adapter and register it in the main method.

void main() async {
  await Hive.initFlutter();
  Hive.registerAdapter(OffsetAdapter());
  await Hive.openBox<Offset>('offsetBox');
}

Check the Offset Adapter code:

import 'package:flutter/material.dart';
import 'package:hive_flutter/hive_flutter.dart';

class OffsetAdapter extends TypeAdapter<Offset> {
  @override
  final typeId = 0;

  @override
  Offset read(BinaryReader reader) {
    final value = reader.readMap();
    final dx = value['dx'] as double;
    final dy = value['dy'] as double;

    return Offset(dx, dy);
  }

  @override
  void write(BinaryWriter writer, Offset obj) {
    writer.writeMap({
      'dx': obj.dx,
      'dy': obj.dy,
    });
  }
}

To open offsetBox:

final box = Hive.box<Offset>('offsetBox');