Step counter example

MainActivity.kt

package com.josiassena.simplepedometer

import android.content.Context
import android.content.pm.PackageManager
import android.hardware.Sensor
import android.hardware.SensorEvent
import android.hardware.SensorEventListener
import android.hardware.SensorManager
import android.os.Bundle
import android.support.v7.app.AppCompatActivity
import kotlinx.android.synthetic.main.activity_main.*

class MainActivity : AppCompatActivity(), SensorEventListener {

    private val sensorManager by lazy { getSystemService(Context.SENSOR_SERVICE) as SensorManager }

    private var stepCounterSensor: Sensor? = null
    private var hasStepCounter: Boolean = false
    private var stepOffset: Float = 0f

    companion object {
        private const val TAG = "MainActivity"
    }

    override fun onCreate(savedInstanceState: Bundle?) {
        super.onCreate(savedInstanceState)
        setContentView(R.layout.activity_main)

        hasStepCounter = packageManager.hasSystemFeature(PackageManager.FEATURE_SENSOR_STEP_COUNTER)

        if (hasStepCounter) {
            stepCounterSensor = sensorManager.getDefaultSensor(Sensor.TYPE_STEP_COUNTER)
        }

    }

    override fun onStart() {
        super.onStart()
        sensorManager.registerListener(this, stepCounterSensor, SensorManager.SENSOR_DELAY_NORMAL)
    }

    override fun onStop() {
        super.onStop()
        sensorManager.unregisterListener(this)
    }

    override fun onAccuracyChanged(sensor: Sensor?, accuracy: Int) {
    }

    override fun onSensorChanged(event: SensorEvent?) {
        val values = event?.values
        val overallStepsTaken = values?.get(0)

        if (stepOffset == 0f) {
            stepOffset = overallStepsTaken as Float
        }

        if (event?.sensor?.type == Sensor.TYPE_STEP_COUNTER) {
            val newStepsTaken = overallStepsTaken?.minus(stepOffset)

            tvStepsTaken.text = newStepsTaken?.toString()
        }
    }
}