/sample-app-guide

name: sample-app-guide
description: Building a complete DAT app with session creation, camera streaming, and photo capture

Sample App Guide (Android)

Build an Android DAT app with registration, sessions, camera streaming, and photo capture.

Pair this with the [CameraAccess sample](https://github.com/facebook/meta-wearables-dat-android/tree/main/samples).

Project setup

1. Create an Android Studio app project. 2. Add the DAT Maven repository and dependencies. 3. Configure `AndroidManifest.xml` for registration callbacks plus `APPLICATION_ID` and `CLIENT_TOKEN`. 4. Initialize `Wearables` in your `Application`.

Suggested app structure

app/src/main/java/com/example/myapp/
├── MyApplication.kt
├── MainActivity.kt
├── session/
│   └── SessionViewModel.kt
└── ui/
    ├── RegistrationScreen.kt
    └── CameraScreen.kt

Registration and session creation

class MainActivity : ComponentActivity() {
    override fun onCreate(savedInstanceState: Bundle?) {
        super.onCreate(savedInstanceState)

        lifecycleScope.launch {
            Wearables.registrationState.collect { state ->
                // Update registration UI
            }
        }
    }

    fun register() {
        Wearables.startRegistration(this)
    }
}

`DeviceSession.start()` is fire-and-forget. Attach the camera from the session-state collector once the session reports `DeviceSessionState.STARTED`; adding a capability to an `IDLE` session fails with `DeviceSessionError.SESSION_IDLE`.

class SessionViewModel : ViewModel() {
    private var session: DeviceSession? = null
    private var camera: Camera? = null

    fun startCameraSession() {
        Wearables.createSession(AutoDeviceSelector()).fold(
            onSuccess = { createdSession ->
                session = createdSession

                viewModelScope.launch {
                    createdSession.errors.collect { error -> showError(error.description) }
                }
                viewModelScope.launch {
                    createdSession.state.collect { state ->
                        when (state) {
                            DeviceSessionState.STARTED -> attachCamera(createdSession)
                            DeviceSessionState.STOPPED -> clearSession(createdSession)
                            else -> Unit
                        }
                    }
                }

                createdSession.start()
            },
            onFailure = { error, _ -> showError(error.description) },
        )
    }

    private fun attachCamera(activeSession: DeviceSession) {
        if (camera != null) return
        activeSession.addCamera(
            StreamConfiguration(videoQuality = VideoQuality.MEDIUM, frameRate = 24),
        ).fold(
            onSuccess = { addedCamera ->
                camera = addedCamera
                addedCamera.stream.start().onFailure { error, _ ->
                    showError(error.description)
                }
            },
            onFailure = { error, _ -> showError(error.description) },
        )
    }

    private fun clearSession(stoppedSession: DeviceSession) {
        if (session !== stoppedSession) return
        camera = null
        session = null
    }
}

Observe frames and capture photos

viewModelScope.launch {
    camera?.stream?.videoStream?.collect { frame ->
        // Render preview
    }
}

fun capturePhoto() {
    viewModelScope.launch {
        camera?.stream?.capturePhoto()
            ?.onSuccess { photoData ->
                when (photoData) {
                    is PhotoData.Bitmap -> savePhoto(photoData.bitmap)
                    is PhotoData.HEIC -> saveHeic(photoData.data)
                }
            }
            ?.onFailure { error, _ ->
                showCaptureError(error.description)
            }
    }
}

Shutdown

fun stopCameraSession() {
    camera?.stop()
    session?.stop()
    camera = null
    session = null
}

Testing with MockDeviceKit

Use `MockDeviceKit` to simulate linking glasses, permission state, and camera media without physical hardware. See [MockDevice Testing](mockdevice-testing.md) for setup details.

Links

• [CameraAccess sample](https://github.com/facebook/meta-wearables-dat-android/tree/main/samples)
• [Android integration guide](https://wearables.developer.meta.com/docs/build-integration-android)
• [Developer documentation](https://wearables.developer.meta.com/docs/develop/)