Sensor

• Coordinate system used by rotation vector sensor (device front is at Z)

Shake

class ShakeDetector(private val onShake: () -> Unit) : SensorEventListener {
    private var lastUpdate: Long = 0L
    private val shakeThreshold = 5f
    private var lastShake: Long = 0L

    override fun onAccuracyChanged(p0: Sensor?, p1: Int) {}

    override fun onSensorChanged(event: SensorEvent) {
        if (event.sensor.type == Sensor.TYPE_ACCELEROMETER) {
            val currentTime = System.currentTimeMillis()
            if ((currentTime - lastUpdate) > 100) {
                val x = event.values[0]
                val y = event.values[1]
                val z = event.values[2]

//                Log.i("Accelerometer","X: $x, Y: $y, Z: $z")

                val accelerometer =
                    abs(sqrt(x * x + y * y + z * z) - SensorManager.GRAVITY_EARTH) // 3D畢氏定理計算總重力後去掉地心引力

                if (accelerometer > shakeThreshold) {
                    if (currentTime - lastShake > 500) {
                        lastShake = currentTime
                        onShake()
                    }
                }
                lastUpdate = currentTime
            }
        }
    }
}

Composable:

val context = LocalContext.current

DisposableEffect(Unit) {
    val sensorManager = context.getSystemService(SensorManager::class.java)
    val accelerometer = sensorManager.getDefaultSensor(Sensor.TYPE_ACCELEROMETER)

    val detector = ShakeDetector {
        // fun when shake
    }

    sensorManager.registerListener(detector, accelerometer, SensorManager.SENSOR_DELAY_UI)

    onDispose {
        sensorManager.unregisterListener(detector)
    }
}

Roll & Pitch

$\text{Roll} = \operatorname{atan2}(x, z) \times \frac{180}{\pi}$

$\text{Pitch} = \operatorname{atan2}(-y, \sqrt{x^2 + z^2}) \times \frac{180}{\pi}$

• Math.toDegrees() convert radius to degrees

val context = LocalContext.current
var rollAngle by remember { mutableFloatStateOf(0f) }

DisposableEffect(Unit) {
    val manager = context.getSystemService(SensorManager::class.java)
    val sensor = manager.getDefaultSensor(Sensor.TYPE_ROTATION_VECTOR)
    val rotationMatrix = FloatArray(9)
    val orientation = FloatArray(3)
    val listener = object : SensorEventListener {
        override fun onAccuracyChanged(p0: Sensor, p1: Int) {}

        override fun onSensorChanged(sensor: SensorEvent) {
            SensorManager.getRotationMatrixFromVector(rotationMatrix, sensor.values)
            SensorManager.getOrientation(rotationMatrix, orientation)
            rollAngle = Math.toDegrees(orientation[2].toDouble()).toFloat()
          }
        }

        manager.registerListener(listener, sensor, SensorManager.SENSOR_DELAY_UI)

    onDispose {
        manager.unregisterListener(listener)
    }
}