trackoffical_app/lib/service/compass.dart

import 'dart:async';
import 'dart:math';
import 'package:get/get.dart';
import 'package:sensor/sensor.dart';
import '../logger.dart';
import 'package:simple_kalman/simple_kalman.dart';


class Compass extends GetxController with GetSingleTickerProviderStateMixin {
  @override
  void onClose() {
    super.onClose();
    compassListener?.cancel();
  }
  final _tmp = <double>[];
  double? _lastAngle;
  var _angle = 0.0;
  final kalman = SimpleKalman(errorMeasure: 256, errorEstimate: 150, q: 0.9);

  Compass() {
    compassListener = Sensor.orientationStream.listen((event) {
      final direction = event.z;
      var nowAngle = -direction * 180 / pi;
      var lastAngle = _lastAngle;


      if(lastAngle != null){
        _lastAngle = nowAngle;
        if(nowAngle - lastAngle >180){
          lastAngle += 360;
        }
        if(nowAngle - lastAngle < -180){
          lastAngle -=360;
        }

        var da = nowAngle - lastAngle;

        _angle += da;


        _tmp.add(_angle);
        if(_tmp.length>50){
          _tmp.removeAt(0);
        }

        angle.value = kalman.filtered(_angle) ;
      }else{
        for(var i = 0; i< 9; i++){
          kalman.filtered(nowAngle);
        }
        _angle = kalman.filtered(nowAngle);
        _lastAngle = _angle;
      }


    });

    info('指南针初始化成功');
  }

  final angle = 0.0.obs;
  StreamSubscription<Orientation>? compassListener;
}