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Setup and Maven Repository

Project requires Java 17. If necessary, adjust your Java version in your IDE, typically in IDE's File -> Project structure -> SDK Location. Update your project-level settings.gradle file and dependencyResolutionManagement section: 
dependencyResolutionManagement {
    repositoriesMode.set(RepositoriesMode.PREFER_PROJECT)
    repositories {
        // other repositories
        maven {
            name = 'truemetrics SDK'
            url = "https://github.com/TRUE-Metrics-io/truemetrics_android_SDK_p_maven/raw/main"
        }
    }
}

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Declare Dependency

Inside your build.gradle add the following dependency: 
implementation 'io.truemetrics:truemetricssdk:1.4.0'

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Initialize SDK

SDK behaves like a singleton object that manages its own internal state. Initialize it in your Application class: 
class MyApplication : Application() {
    override fun onCreate() {
        super.onCreate()

        val config = SdkConfiguration.Builder("YOUR_API_KEY").build()
        TruemetricsSdk.init(this, config)
    }
}

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Custom Foreground Notification

The SDK runs as a foreground service and shows a notification while recording. You can customize this notification using the SDK’s notification channel: 
class CustomNotificationFactory : ForegroundNotificationFactory {
    override fun createNotification(context: Context): Notification {
        // Use SDK's notification channel ID
        return NotificationCompat.Builder(context, "FOREGROUND_SERVICE")
            .setContentTitle("Truemetrics SDK Running")
            .setContentText("Collecting sensor data...")
            .setSmallIcon(R.drawable.ic_notification)
            .setOngoing(true)
            .build()
    }
}

val config = SdkConfiguration.Builder("YOUR_API_KEY")
    .foregroundNotificationFactory(CustomNotificationFactory())
    .build()
Make sure to ask user for notification permission if device runs Android 13 or later.

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Observing SDK Status

Use the observeSdkStatus() Flow to monitor SDK state changes: 
val sdk = TruemetricsSdk.getInstance()

sdk.observeSdkStatus().collect { status ->
    when (status) {
        is Status.Uninitialized -> {
            // SDK not yet initialized
        }
        is Status.Initialized -> {
            // SDK initialized, deviceId available
            val deviceId = status.deviceId
        }
        is Status.RecordingInProgress -> {
            // Recording is active
            val deviceId = status.deviceId
        }
        is Status.RecordingStopped -> {
            // Recording has stopped
        }
        is Status.DelayedStart -> {
            // Waiting for auto-start delay
            val deviceId = status.deviceId
            val delayMs = status.delayMs
        }
        is Status.TrafficLimitReached -> {
            // Traffic limit reached
        }
        is Status.ReadingsDatabaseFull -> {
            // Device storage full
        }
        is Status.Error -> {
            // SDK encountered an error
            val errorCode = status.errorCode
            val message = status.message
        }
        is Status.AskForPermissions -> {
            // SDK requesting permissions
            val permissions = status.permissions
        }
    }
}

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Error Codes

When Status.Error is received, the errorCode indicates what went wrong:
Error CodeDescription
AUTHENTICATION_ERRORAPI key is not valid, expired or revoked
UPLOAD_ERRORRecordings couldn’t be uploaded after exhausting all attempts
STORAGE_FULLDevice storage is full which prevents saving sensor readings
MISSING_NOTIFICATION_PERMISSIONNotification permission not granted, foreground service cannot start
CONFIG_ERRORConfiguration error
TRAFFIC_USED_UPAll allotted traffic has been used
SENSORS_NOT_WORKINGSome sensors are not working. Check if permissions are missing

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Start Recording

val sdk = TruemetricsSdk.getInstance()
sdk.startRecording()
Starting the recording also starts the Foreground service and shows the notification. Recording continues even when the app exits.

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Stop Recording

sdk.stopRecording()
Stopping recording also stops the Foreground service and removes the notification.

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Check Recording Status

val isRecording = sdk.isRecordingInProgress()
val isStopped = sdk.isRecordingStopped()
val startTime = sdk.getRecordingStartTime() // milliseconds since epoch

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Device ID

Get the unique device identifier (available after initialization): 
val deviceId = sdk.getDeviceId()

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Log Metadata

sdk.logMetadata(mapOf(
    "userId" to "user123",
    "sessionId" to "session_abc"
))
For advanced metadata management with templates and tags, see the metadata chapter.

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Statistics API

Monitor upload and sensor health: 
// Upload statistics
val uploadStats = sdk.getUploadStatistics()
uploadStats?.let {
    println("Successful uploads: ${it.successfulUploadsCount}")
    println("Last upload: ${it.lastSuccessfulUploadTimestamp}")
}

// Sensor statistics with quality assessment
val sensorStats = sdk.getSensorStatistics()
sensorStats?.forEach { stat ->
    println("Sensor: ${stat.sensorName}")
    println("Quality: ${stat.quality}") // EXCELLENT, GOOD, POOR, BAD, or UNKNOWN
}

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Deinitialize SDK

sdk.deinitialize()
De-initialization stops recording if in progress and tears down the SDK. Warning: After calling deinitialize(), the SDK instance becomes unusable. You must call init() again to use the SDK.