Android SDK - Phosra Developer Docs

The com.phosra.sdk Kotlin library provides on-device child safety enforcement for Android using UsageStatsManager, DevicePolicyManager, VpnService, and AccessibilityService.

Overview

The SDK has a two-layer architecture:

API Client — Communicates with the Phosra API to register devices, fetch compiled policies, submit enforcement reports, and acknowledge policy versions.
Enforcement Engine — Translates the compiled policy document into native Android API calls to enforce content filters, screen time limits, web filtering, purchase controls, and more.

API Client

Handles device registration, policy sync, and reporting via the Phosra REST API.

Enforcement Engine

Maps policy rules to UsageStatsManager, DevicePolicyManager, VpnService, and AccessibilityService.

Requirements

Requirement	Version
Android	8.0+ (API 26)
Kotlin	1.9+
Gradle	8+
compileSdk	35
targetSdk	35

Installation

The com.phosra:sdk Android library is in private preview — it is not published to Maven Central or Google’s Maven repo yet. Email developers@phosra.com for the AAR / private Maven URL and access credentials. Once you have access, add the private repository and the dependency to your Gradle build:

settings.gradle.kts

// Private preview: repo URL + credentials provided by Phosra
dependencyResolutionManagement {
    repositories {
        maven {
            url = uri("<private maven URL provided by Phosra>")
            credentials {
                username = providers.gradleProperty("phosraMavenUser").get()
                password = providers.gradleProperty("phosraMavenToken").get()
            }
        }
    }
}

Then add the dependency to your module-level build.gradle.kts:

dependencies {
    implementation("com.phosra:sdk:1.0.0")
}

dependencies {
    implementation 'com.phosra:sdk:1.0.0'
}

The SDK pulls in the following transitive dependencies:

kotlinx-coroutines-android — Async operations
kotlinx-serialization-json — JSON parsing
okhttp3 — HTTP networking
androidx.work:work-runtime-ktx — Background sync
androidx.security:security-crypto — Encrypted key storage

Quick Start

Device Registration

The registration flow requires parent authentication and produces a device-specific API key:

Parent App                    Phosra API                  Child Device
    |                             |                           |
    |-- POST /children/{id}/devices ------------------------> |
    |   (Authorization: Bearer parentJWT)                     |
    |                             |                           |
    |   <-- { device, api_key } --|                           |
    |                             |                           |
    |   -- Transfer api_key ------------------------------>   |
    |                             |                           | EncryptedSharedPrefs
    |                             |                           |

The RegisterDeviceRequest includes device metadata and capability declarations:

RegisterDeviceRequest(
    deviceName = "Emma's Pixel",
    deviceModel = "Pixel 8 Pro",
    osVersion = "14",
    appVersion = "1.0.0",
    capabilities = listOf(
        "UsageStats",        // UsageStatsManager access
        "DeviceAdmin",       // DevicePolicyManager enrollment
        "VPN",               // Local VPN for DNS filtering
        "Accessibility",     // Foreground app detection
        "NotificationListener" // Notification filtering
    )
)

Policy Sync

WorkManager-Based Sync

The SDK uses WorkManager for reliable background policy synchronization:

class PolicySyncWorker(
    context: Context,
    params: WorkerParameters
) : CoroutineWorker(context, params) {

    override suspend fun doWork(): Result {
        val deviceKey = KeystoreHelper.loadDeviceKey(applicationContext) ?: return Result.failure()
        val client = PhosraClient(PhosraConfiguration(deviceKey = deviceKey))

        return try {
            val currentVersion = PreferenceManager.getCurrentPolicyVersion(applicationContext)
            val policy = client.fetchPolicy(sinceVersion = currentVersion) ?: return Result.success()

            val engine = EnforcementEngine(applicationContext)
            val results = engine.apply(policy)

            client.submitReport(DeviceReport(
                reportType = ReportType.ENFORCEMENT_STATUS,
                payload = EnforcementStatusPayload(
                    policyVersion = policy.version,
                    results = results
                )
            ))
            client.ackPolicyVersion(policy.version)

            PreferenceManager.setCurrentPolicyVersion(applicationContext, policy.version)
            Result.success()
        } catch (e: Exception) {
            Result.retry()
        }
    }
}

Firebase Cloud Messaging (FCM)

For immediate policy refresh when a parent modifies rules, handle FCM data messages:

class PhosraMessagingService : FirebaseMessagingService() {

    override fun onMessageReceived(message: RemoteMessage) {
        val event = message.data["phosra_event"] ?: return
        val version = message.data["phosra_version"]?.toIntOrNull() ?: return

        if (event == "policy.updated") {
            val currentVersion = PreferenceManager.getCurrentPolicyVersion(this)
            if (version > currentVersion) {
                // Enqueue immediate one-time sync
                val syncRequest = OneTimeWorkRequestBuilder<PolicySyncWorker>()
                    .setExpedited(OutOfQuotaPolicy.RUN_AS_NON_EXPEDITED_WORK_REQUEST)
                    .build()
                WorkManager.getInstance(this).enqueue(syncRequest)
            }
        }
    }
}

Enforcement Engine

Each enforcer handles a specific policy section and maps it to the appropriate Android API.

Content Filter Enforcer

Monitors the foreground app using UsageStatsManager and AccessibilityService. Blocks restricted apps by displaying a full-screen overlay.

Policy Field	Android API	Mechanism
`contentFilter.blockedApps`	UsageStatsManager + Overlay	Detect foreground, show blocking overlay
`contentFilter.ageRating`	PackageManager	Check app age rating metadata
`contentFilter.allowlistMode`	UsageStatsManager + Overlay	Block all apps not in allowedApps

// Detect foreground app and block if restricted
val usageStatsManager = context.getSystemService(UsageStatsManager::class.java)
val events = usageStatsManager.queryEvents(startTime, System.currentTimeMillis())

val event = UsageEvents.Event()
while (events.hasNextEvent()) {
    events.getNextEvent(event)
    if (event.eventType == UsageEvents.Event.ACTIVITY_RESUMED) {
        if (event.packageName in policy.contentFilter.blockedApps) {
            showBlockingOverlay(event.packageName)
        }
    }
}

Screen Time Enforcer

Tracks cumulative daily usage and enforces time limits.

Policy Field	Android API	Mechanism
`screenTime.dailyLimitMinutes`	UsageStatsManager	Aggregate daily usage, lock when exceeded
`screenTime.perAppLimits`	UsageStatsManager	Track per-package usage
`screenTime.downtimeWindows`	AlarmManager	Schedule device lock during downtime
`screenTime.schedule`	AlarmManager	Enforce allowed-hours windows

Web Filter Enforcer

Runs a local VPN service that intercepts DNS queries and blocks restricted domains.

Policy Field	Android API	Mechanism
`webFilter.blockedDomains`	VpnService	DNS interception, return NXDOMAIN
`webFilter.safeSearch`	VpnService	Redirect search DNS to safe search IPs
`webFilter.blockedCategories`	VpnService	DNS-based category blocking
`webFilter.level`	VpnService	Preset domain blocklists

class PhosraVpnService : VpnService() {
    override fun onStartCommand(intent: Intent?, flags: Int, startId: Int): Int {
        val builder = Builder()
            .addAddress("10.0.0.2", 32)
            .addDnsServer("10.0.0.1")
            .setSession("Phosra Web Filter")

        val tunnel = builder.establish()
        // DNS query interception loop
        // Block domains matching policy.webFilter.blockedDomains
        return START_STICKY
    }
}

Purchase Enforcer

Policy Field	Android API	Mechanism
`purchases.requireApproval`	DevicePolicyManager	Restrict Play Store access
`purchases.blockIAP`	DevicePolicyManager	Disable in-app purchase flows
`purchases.spendingCapUSD`	None	Tracked in-app via Play Billing observer

Policy Field	Android API	Mechanism
`social.chatMode`	Overlay + UsageStats	Block messaging apps based on mode
`social.dmRestriction`	Overlay + UsageStats	Block DM-capable apps
`social.multiplayerMode`	Overlay + UsageStats	Block multiplayer gaming apps

Notification Enforcer

Policy Field	Android API	Mechanism
`notifications.curfewStart/End`	NotificationListenerService	Suppress notifications during curfew
`notifications.usageTimerMinutes`	AlarmManager	Fire reminder notification at interval

Permission Management

Android requires several special permissions. Each must be granted by the parent through system settings.

Required for screen time tracking and foreground app detection.

val intent = Intent(Settings.ACTION_USAGE_ACCESS_SETTINGS)
startActivity(intent)

Check: AppOpsManager.checkOpNoThrow(AppOpsManager.OPSTR_GET_USAGE_STATS, ...)

Required to display the blocking UI when a restricted app is opened.

if (!Settings.canDrawOverlays(context)) {
    val intent = Intent(
        Settings.ACTION_MANAGE_OVERLAY_PERMISSION,
        Uri.parse("package:${context.packageName}")
    )
    startActivity(intent)
}

Required for device-level restrictions (disabling app installs, factory reset protection).

val componentName = ComponentName(context, PhosraDeviceAdminReceiver::class.java)
val intent = Intent(DevicePolicyManager.ACTION_ADD_DEVICE_ADMIN).apply {
    putExtra(DevicePolicyManager.EXTRA_DEVICE_ADMIN, componentName)
    putExtra(DevicePolicyManager.EXTRA_ADD_EXPLANATION,
        "Required for enforcing child safety restrictions.")
}
startActivity(intent)

Required for DNS-based web content filtering.

val vpnIntent = VpnService.prepare(context)
if (vpnIntent != null) {
    startActivityForResult(vpnIntent, VPN_REQUEST_CODE)
}

Required for notification filtering during curfew hours.

val intent = Intent(Settings.ACTION_NOTIFICATION_LISTENER_SETTINGS)
startActivity(intent)

Required for accurate foreground app detection on some devices.

val intent = Intent(Settings.ACTION_ACCESSIBILITY_SETTINGS)
startActivity(intent)

Reporting

The SDK submits two types of reports to the Phosra API:

Enforcement Status Report

Sent after applying a policy, contains per-category results:

DeviceReport(
    reportType = ReportType.ENFORCEMENT_STATUS,
    payload = EnforcementStatusPayload(
        policyVersion = 3,
        results = listOf(
            CategoryEnforcementResult(
                category = "content_rating",
                status = "enforced",   // "enforced", "partial", "failed", "unsupported"
                framework = "UsageStatsManager"
            ),
            CategoryEnforcementResult(
                category = "web_filter_level",
                status = "enforced",
                framework = "VpnService"
            )
        )
    )
)

Screen Time Report

Aggregated daily usage data:

DeviceReport(
    reportType = ReportType.SCREEN_TIME,
    payload = ScreenTimePayload(
        byCategory = mapOf("social-media" to 45, "gaming" to 30, "education" to 60),
        topApps = mapOf("com.instagram.android" to 25, "com.google.android.youtube" to 20),
        totalMinutes = 135,
        date = "2026-02-23"
    )
)

CompiledPolicy Structure

The compiled policy is fetched from GET /device/policy and contains all enforcement rules organized by section:

{
  "version": 3,
  "child_id": "uuid",
  "child_age": 10,
  "age_group": "tween",
  "policy_id": "uuid",
  "status": "active",
  "generated_at": "2026-02-23T14:30:00Z",
  "content_filter": {
    "age_rating": "E10+",
    "max_ratings": { "esrb": "E10+", "mpaa": "PG" },
    "blocked_apps": ["com.instagram.android"],
    "allowed_apps": [],
    "allowlist_mode": false
  },
  "screen_time": {
    "daily_limit_minutes": 120,
    "per_app_limits": [
      { "bundle_id": "com.google.android.youtube", "daily_minutes": 30 }
    ],
    "downtime_windows": [
      { "days_of_week": ["monday","tuesday","wednesday","thursday","friday"],
        "start_time": "21:00", "end_time": "07:00" }
    ],
    "always_allowed_apps": ["com.android.dialer", "com.android.mms", "com.google.android.apps.maps"]
  },
  "purchases": {
    "require_approval": true,
    "block_iap": false,
    "spending_cap_usd": 10.00
  },
  "privacy": {
    "location_sharing_enabled": true,
    "profile_visibility": "private",
    "account_creation_approval": true,
    "data_sharing_restricted": true
  },
  "social": {
    "chat_mode": "friends_only",
    "dm_restriction": "contacts_only",
    "multiplayer_mode": "friends_only"
  },
  "notifications": {
    "curfew_start": "21:00",
    "curfew_end": "07:00",
    "usage_timer_minutes": 30
  },
  "web_filter": {
    "level": "moderate",
    "safe_search": true,
    "blocked_domains": ["reddit.com"],
    "allowed_domains": ["khanacademy.org"],
    "blocked_categories": ["gambling", "adult"]
  }
}

Supported Rule Categories

The 45 OCSS rule categories the Android SDK maps to native framework primitives (of the 123 categories in the OCSS rule registry; the remainder are policy-only or census-enforced and carry no client-side Android verb):

Content Rules

Category	Android API	Mechanism
`content_rating`	PackageManager	App age rating metadata check
`content_block_title`	UsageStatsManager + Overlay	Block by package name
`content_allow_title`	UsageStatsManager + Overlay	Allow only listed packages
`content_allowlist_mode`	UsageStatsManager + Overlay	Block all unlisted apps
`content_descriptor_block`	PackageManager	Content descriptor filtering

Time Rules

Category	Android API	Mechanism
`time_daily_limit`	UsageStatsManager	Aggregate usage, lock at limit
`time_scheduled_hours`	AlarmManager	Allow usage only during scheduled hours
`time_per_app_limit`	UsageStatsManager	Per-package usage tracking
`time_downtime`	AlarmManager	Lock device during downtime windows

Purchase Rules

Category	Android API	Mechanism
`purchase_approval`	DevicePolicyManager	Restrict Play Store access
`purchase_block_iap`	DevicePolicyManager	Block in-app purchase flows
`purchase_spending_cap`	None	Play Billing observer (in-app)

Category	Android API	Mechanism
`social_contacts`	ContactsContract	Restrict contact access
`social_chat_control`	UsageStatsManager + Overlay	Block messaging apps
`social_multiplayer`	UsageStatsManager + Overlay	Block multiplayer gaming apps

Web Rules

Category	Android API	Mechanism
`web_safesearch`	VpnService	DNS redirect to safe search
`web_category_block`	VpnService	DNS-based category blocking
`web_custom_allowlist`	VpnService	Allow only listed domains
`web_custom_blocklist`	VpnService	Block listed domains
`web_filter_level`	VpnService	Preset blocklist by level

Privacy Rules

Category	Android API	Mechanism
`privacy_location`	LocationManager	App-level location permission management
`privacy_profile_visibility`	None	App-level enforcement
`privacy_data_sharing`	None	App-level enforcement
`privacy_account_creation`	None	In-app parental gate

Monitoring Rules

Category	Android API	Mechanism
`monitoring_activity`	UsageStatsManager	Query and report usage data
`monitoring_alerts`	UsageStatsManager + AlarmManager	Threshold-based alerts

Engagement Rules

Category	Android API	Mechanism
`algo_feed_control`	UsageStatsManager + Overlay	Block/limit social apps
`addictive_design_control`	UsageStatsManager + Overlay	Block offending apps

Notification Rules

Category	Android API	Mechanism
`notification_curfew`	NotificationListenerService	Suppress during curfew
`usage_timer_notification`	AlarmManager	Periodic usage reminder

Legislation-Driven Rules

Category	Android API	Mechanism
`targeted_ad_block`	None	App-level (no system API)
`dm_restriction`	UsageStatsManager + Overlay	Block messaging apps
`age_gate`	None	In-app enforcement
`data_deletion_request`	None	App-level support flow
`geolocation_opt_in`	LocationManager	Per-app permission management

Compliance Rules

Category	Android API	Mechanism
`csam_reporting`	None	Server-side detection
`library_filter_compliance`	VpnService	DNS-based web filtering
`ai_minor_interaction`	UsageStatsManager + Overlay	Block AI apps
`social_media_min_age`	UsageStatsManager + Overlay	Block social apps for underage
`image_rights_minor`	None	App-level enforcement

Parental / Legislative Rules

Category	Android API	Mechanism
`parental_consent_gate`	None	In-app parental auth flow
`parental_event_notification`	AlarmManager + FCM	Push to parent on flagged events
`screen_time_report`	UsageStatsManager	Generate and submit usage summary
`commercial_data_ban`	None	App/server-level policy
`algorithmic_audit`	None	Platform transparency requirement

Google Play Compliance

Apps using UsageStatsManager, AccessibilityService, VpnService, and Device Admin require additional review by Google Play. Plan for a longer review cycle.

Required Declarations

Permissions Declaration Form: Submit in Play Console for QUERY_ALL_PACKAGES, PACKAGE_USAGE_STATS, and Accessibility Service usage.
Data Safety section: Declare all data collected from child devices. Phosra collects:
- App usage statistics (aggregated)
- Web activity (domain-level, via DNS)
- Device metadata (model, OS version)
VPN usage: Declare that the VPN is used exclusively for local DNS filtering, not for routing traffic through external servers.
Target audience: Set to “Parents” — the app is a parental control tool, not a child-facing app.
Families Policy: If your app appears in the Play Store’s Family section, ensure compliance with Google’s Families Policy.

Tips for Approval

Provide a detailed app description explaining the parental control use case
Include a demo video showing the parent setup flow and enforcement in action
Reference applicable child safety legislation (COPPA, KOSA, etc.)
Respond promptly to any review team questions about permission usage

​Overview

API Client

Enforcement Engine

​Requirements

​Installation

​Quick Start

​Device Registration

​Policy Sync

​WorkManager-Based Sync

​Firebase Cloud Messaging (FCM)

​Enforcement Engine

​Content Filter Enforcer

​Screen Time Enforcer

​Web Filter Enforcer

​Purchase Enforcer

​Social Enforcer

​Notification Enforcer

​Permission Management

​Reporting

​Enforcement Status Report

​Screen Time Report

​CompiledPolicy Structure

​Supported Rule Categories

​Content Rules

​Time Rules

​Purchase Rules

​Social Rules

​Web Rules

​Privacy Rules

​Monitoring Rules

​Engagement Rules

​Notification Rules

​Legislation-Driven Rules

​Compliance Rules

​Parental / Legislative Rules

​Google Play Compliance

​Required Declarations

​Tips for Approval

Overview

Requirements

Installation

Quick Start

Device Registration

Policy Sync

WorkManager-Based Sync

Firebase Cloud Messaging (FCM)

Enforcement Engine

Content Filter Enforcer

Screen Time Enforcer

Web Filter Enforcer

Purchase Enforcer

Social Enforcer

Notification Enforcer

Permission Management

Reporting

Enforcement Status Report

Screen Time Report

CompiledPolicy Structure

Supported Rule Categories

Content Rules

Time Rules

Purchase Rules

Social Rules

Web Rules

Privacy Rules

Monitoring Rules

Engagement Rules

Notification Rules

Legislation-Driven Rules

Compliance Rules

Parental / Legislative Rules

Google Play Compliance

Required Declarations

Tips for Approval