| **Note:** This guide uses `SensorManager` for retrieving steps data. We recommend using the [Recording API on mobile](https://developer.android.com/health-and-fitness/guides/recording-api) for recording steps in a power-efficient way.

This guide walks you through building a basic mobile step counter app, which
is a common foundation for many Health \& Fitness apps.

This workflow integrates the following APIs:

- [SensorManager](https://developer.android.com/guide/topics/sensors/sensors_motion) for retrieving steps data from a mobile device.
- [Room](https://developer.android.com/training/data-storage/room) for local data storage.
- [Health Connect](https://developer.android.com/health-and-fitness/guides/health-connect) for storing and sharing health and fitness data on device.

For additional support on data reading and the tools necessary, refer to [Use
Android Sensor Manager to track steps from a mobile device](https://developer.android.com/health-and-fitness/guides/basic-fitness-app/read-step-count-data).

If you haven't already set up your development environment for using
[Health Connect](https://developer.android.com/health-and-fitness/guides/health-connect), follow these [getting started](https://developer.android.com/health-and-fitness/guides/health-connect/develop/get-started) steps.

## Request permissions on handheld device

Before getting exercise data you must request and be granted the appropriate
permissions.

As a best practice, only request the permissions you need, and make sure to
[request each permission in context](https://developer.android.com/training/permissions/requesting#workflow_for_requesting_permissions), instead of requesting all
permissions at once when the user starts the app.

The [step counter sensor](https://developer.android.com/guide/topics/sensors/sensors_motion#sensors-motion-stepcounter), which many exercise apps rely on, uses the
`ACTIVITY_RECOGNITION` permission. Add this permission in your
AndroidManifest.xml file:  

    <?xml version="1.0" encoding="utf-8"?>
    <manifest xmlns:android="http://schemas.android.com/apk/res/android"
      xmlns:tools="http://schemas.android.com/tools">

      <uses-permission android:name="android.permission.ACTIVITY_RECOGNITION"/>

    </manifest>

To request the `ACTIVITY_RECOGNITION` permission at runtime refer to the
[permission request documentation](https://developer.android.com/training/permissions/requesting#request-permission).

You will also need to declare a `FOREGROUND_SERVICE` in the manifest. Since you
are requesting the `ACTIVITY_RECOGNITION` permission, declare
`FOREGROUND_SERVICE_TYPE_HEALTH`:  

    <uses-permission android:name="android.permission.FOREGROUND_SERVICE"/>
    <uses-permission android:name="android.permission.FOREGROUND_SERVICE_HEALTH"/>

Visit [Foreground services](https://developer.android.com/develop/background-work/services/fgs)
to learn more about foreground services and foreground service types.

## Manage UI state using a ViewModel

To properly manage the UI state, use a ViewModel.
[Jetpack Compose and ViewModels](https://developer.android.com/jetpack/compose/libraries#viewmodel) offers you a more in-depth look at this
workflow.

Also, use UI layering, which is a critical part for building UIs with Compose
and lets you follow architecture best practices, such as
[Unidirectional Data Flow](https://developer.android.com/jetpack/compose/architecture#udf). To learn more about UI layering, refer to the
[UI layer documentation](https://developer.android.com/topic/architecture/ui-layer).

In this example app, the UI has three basic states:

- **Loading:** Shows a spinning circle.
- **Content:** Shows information about your steps for today.
- **Error:** Shows a message when something goes wrong.

The `ViewModel` exposes these states as a Kotlin `Flow`. Use a sealed class to
contain the classes and objects that represent the possible states:  

    class TodayScreenViewModel(...) {

      val currentScreenState: MutableStateFlow<TodayScreenState> = MutableStateFlow(Loading)

      [...]

    }

    sealed class TodayScreenState {
        data object Loading : TodayScreenState()
        data class Content(val steps: Long, val dailyGoal: Long) : TodayScreenState()
        data object Error: TodayScreenState()
    }

Compose UI then collects this `Flow` as a Compose `State` and acts on it:  

    val state: TodayScreenState = todayScreenViewModel.currentScreenState.collectAsState().value