Flutter Shake Detection Attempt (algorithm doesn't filter events well)

shake_utils.dart

import 'dart:async';

import 'package:rxdart/rxdart.dart';
import 'package:sensors/sensors.dart';

Stream<bool> isShaking() {
  final timeout = Duration(milliseconds: 300);
  final accelerationThreshold = 3;
  final sampleInterval = Duration(milliseconds: 50);
  final moveCountThreshold = 5;

  Stream<bool> extractShake(Stream<UserAccelerometerEvent> stream) async* {
    int moveCount = 0;

    var lastSampleAt = DateTime.now();

    double lastX = 0;
    double lastY = 0;
    double lastZ = 0;

    bool _isReverted(num now, num rev) {
      return now * rev <= 0;
    }

    bool _isMoving(num now) {
      return now.abs() >= accelerationThreshold;
    }

    await for (final e in stream) {
      final now = DateTime.now();
      final sinceLast = now.difference(lastSampleAt);

      if (sinceLast < sampleInterval) continue;

      if (sinceLast > timeout) {
        moveCount = 0;
      }
      lastSampleAt = now;

      if (!_isMoving(e.x) && !_isMoving(e.y) && !_isMoving(e.z)) continue;

      final bool isShaking = (_isMoving(e.x) && _isReverted(e.x, lastX)) ||
          (_isMoving(e.y) && _isReverted(e.y, lastY)) ||
          (_isMoving(e.z) && _isReverted(e.z, lastZ));

      lastX = e.x;
      lastY = e.y;
      lastZ = e.z;

      if (isShaking) moveCount++;

      if (moveCount >= moveCountThreshold) yield true;
    }
  }

  final Stream<bool> shake = userAccelerometerEvents
      .transform(StreamTransformer.fromBind((stream) => extractShake(stream)));
  return shake
      .switchMap((e) => TimerStream(false, timeout).startWith(e))
      .startWith(false);
}