Use Sensor Manager to measure steps from a mobile device

Use Sensor Manager to populate steps data in a mobile app, as described in this guide. For more information about how to design and manage an exercise app UI, refer to Build a basic fitness app.

Getting started

To get started with measuring the steps of your basic step counter from your mobile device, you will need to add the dependencies to your app module build.gradle file. Ensure that you use the latest versions of dependencies. Also, when you extend your app's support to other form factors, such as Wear OS, add the dependencies that these form factors require.

Below are a few examples of some of the UI dependencies. For a complete list, refer to this UI Elements guide.

implementation(platform("androidx.compose:compose-bom:2023.10.01"))
implementation("androidx.activity:activity-compose")
implementation("androidx.compose.foundation:foundation")
implementation("androidx.compose.material:material")

Obtain the step counter sensor

After the user has granted the necessary activity recognition permission, you can access the step counter sensor:

  1. Obtain the SensorManager object from getSystemService().
  2. Acquire the step counter sensor from the SensorManager:
private val sensorManager by lazy {
        getSystemService(Context.SENSOR_SERVICE) as SensorManager }
private val sensor: Sensor? by lazy {
        sensorManager.getDefaultSensor(Sensor.TYPE_STEP_COUNTER) }

Some devices don't have the step counter sensor. You should check for the sensor and show an error message if the device doesn't have one:

if (sensor == null) {
    Text(text = "Step counter sensor is not present on this device")
}

Create your foreground service

In a basic fitness app, you might have a button to receive start and stop events from the user for tracking steps.

Keep in mind sensor best practices. In particular, the step counter sensor should only count steps while the sensor listener is registered. By associating sensor registration with a foreground service, the sensor is registered as long as it's needed, and the sensor can remain registered when the app is not in the foreground.

Use the following snippet to unregister the sensor in the onPause() method of your foreground service:

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

Analyze data for events

To access the sensor data, implement the SensorEventListener interface. Note that you should associate sensor registration with your foreground service's lifecycle, unregistering the sensor when the service is paused or ended. The following snippet shows how to implement the SensorEventListener interface for Sensor.TYPE_STEP_COUNTER:

private const val TAG = "STEP_COUNT_LISTENER"

context(Context)
class StepCounter {
    private val sensorManager = getSystemService(Context.SENSOR_SERVICE) as SensorManager
    private val sensor: Sensor? = sensorManager.getDefaultSensor(Sensor.TYPE_STEP_COUNTER)

    suspend fun steps() = suspendCancellableCoroutine { continuation ->
        Log.d(TAG, "Registering sensor listener... ")

        val listener: SensorEventListener by lazy {
            object : SensorEventListener {
                override fun onSensorChanged(event: SensorEvent?) {
                    if (event == null) return

                    val stepsSinceLastReboot = event.values[0].toLong()
                    Log.d(TAG, "Steps since last reboot: $stepsSinceLastReboot")

                    if (continuation.isActive) {
                        continuation.resume(stepsSinceLastReboot)
                    }
                }

                override fun onAccuracyChanged(sensor: Sensor?, accuracy: Int) {
                      Log.d(TAG, "Accuracy changed to: $accuracy")
                }
            }
       }

        val supportedAndEnabled = sensorManager.registerListener(listener,
                sensor, SensorManager.SENSOR_DELAY_UI)
        Log.d(TAG, "Sensor listener registered: $supportedAndEnabled")
    }
}

Create a database for the sensor events

Your app might show a screen where the user can view their steps over time. To provide this capability in your app, use the Room persistence library.

The following snippet creates a table that contains a set of step count measurements, along with the time when your app accessed each measurement:

@Entity(tableName = "steps")
data class StepCount(
  @ColumnInfo(name = "steps") val steps: Long,
  @ColumnInfo(name = "created_at") val createdAt: String,
)

Create a data access object (DAO) to read and write the data:

@Dao
interface StepsDao {
    @Query("SELECT * FROM steps")
    suspend fun getAll(): List<StepCount>

    @Query("SELECT * FROM steps WHERE created_at >= date(:startDateTime) " +
            "AND created_at < date(:startDateTime, '+1 day')")
    suspend fun loadAllStepsFromToday(startDateTime: String): Array<StepCount>

    @Insert
    suspend fun insertAll(vararg steps: StepCount)

    @Delete
    suspend fun delete(steps: StepCount)
}

To instantiate the DAO, create a RoomDatabase object:

@Database(entities = [StepCount::class], version = 1)
abstract class AppDatabase : RoomDatabase() {
    abstract fun stepsDao(): StepsDao
}

Store the sensor data into the database

The ViewModel uses the new StepCounter class, so you can store the steps as soon as you read them:

viewModelScope.launch {
    val stepsFromLastBoot = stepCounter.steps()
    repository.storeSteps(stepsFromLastBoot)
}

The repository class would look like this:

class Repository(
    private val stepsDao: StepsDao,
) {

    suspend fun storeSteps(stepsSinceLastReboot: Long) = withContext(Dispatchers.IO) {
        val stepCount = StepCount(
            steps = stepsSinceLastReboot,
            createdAt = Instant.now().toString()
        )
        Log.d(TAG, "Storing steps: $stepCount")
        stepsDao.insertAll(stepCount)
    }

    suspend fun loadTodaySteps(): Long = withContext(Dispatchers.IO) {
        printTheWholeStepsTable() // DEBUG

        val todayAtMidnight = (LocalDateTime.of(LocalDate.now(), LocalTime.MIDNIGHT).toString())
        val todayDataPoints = stepsDao.loadAllStepsFromToday(startDateTime = todayAtMidnight)
        when {
            todayDataPoints.isEmpty() -> 0
            else -> {
                val firstDataPointOfTheDay = todayDataPoints.first()
                val latestDataPointSoFar = todayDataPoints.last()

                val todaySteps = latestDataPointSoFar.steps - firstDataPointOfTheDay.steps
                Log.d(TAG, "Today Steps: $todaySteps")
                todaySteps
            }
        }
    }
}

Periodically retrieving sensor data

If you use a foreground service, you don't need to configure WorkManager because, during the time when your app is actively tracking the user's steps, the updated total step count should appear in your app.

If you want to batch your steps records, however, you can use WorkManager to measure steps at a specific interval, such as once every 15 minutes. WorkManager is the component that performs the background work for guaranteed execution. Learn more in the WorkManager codelab.

To configure the Worker object to retrieve the data, override the doWork() method, as shown in the following code snippet:

private const val TAG = " StepCounterWorker"

@HiltWorker
class StepCounterWorker @AssistedInject constructor(
    @Assisted appContext: Context,
    @Assisted workerParams: WorkerParameters,
    val repository: Repository,
    val stepCounter: StepCounter
) : CoroutineWorker(appContext, workerParams) {

    override suspend fun doWork(): Result {
        Log.d(TAG, "Starting worker...")

        val stepsSinceLastReboot = stepCounter.steps().first()
        if (stepsSinceLastReboot == 0L) return Result.success()

        Log.d(TAG, "Received steps from step sensor: $stepsSinceLastReboot")
        repository.storeSteps(stepsSinceLastReboot)

        Log.d(TAG, "Stopping worker...")
        return Result.success()
    }
}

To set up WorkManager to store the current step count every 15 minutes, do the following:

  1. Extend the Application class to implement the Configuration.Provider interface.
  2. In the onCreate() method, enqueue a PeriodicWorkRequestBuilder.

This process appears in the following code snippet:

@HiltAndroidApp
@RequiresApi(Build.VERSION_CODES.S)
internal class PulseApplication : Application(), Configuration.Provider {

    @Inject
    lateinit var workerFactory: HiltWorkerFactory

    override fun onCreate() {
        super.onCreate()

        val myWork = PeriodicWorkRequestBuilder<StepCounterWorker>(
                15, TimeUnit.MINUTES).build()

        WorkManager.getInstance(this)
            .enqueueUniquePeriodicWork("MyUniqueWorkName",
                    ExistingPeriodicWorkPolicy.UPDATE, myWork)
    }

    override val workManagerConfiguration: Configuration
        get() = Configuration.Builder()
            .setWorkerFactory(workerFactory)
            .setMinimumLoggingLevel(android.util.Log.DEBUG)
            .build()
}

To initialize the content provider that controls access to your app's step counter database immediately upon app startup, add the following element to your app's manifest file:

<provider
    android:name="androidx.startup.InitializationProvider"
    android:authorities="${applicationId}.androidx-startup"
    tools:node="remove" />