Native Module Android

How to Create a Native Module in Android

This detailed guide explains how to create a native module for the Android platform within a React Native application. The process follows the step-by-step instructions from the official documentation.

1. Open the Android Project in Android Studio

First, open the Android project of your React Native application in Android Studio. You can find the Android project in the folder: YourApp/android.

Using Android Studio helps in quickly identifying issues, such as syntax errors, and provides powerful tools for Android development.

2. Create the Native Module

Create a file named CafSmartAuthBridgeModule.kt in the directory android/app/src/main/java/com/your-app-name/. This file will contain the class that implements the native module.

Key Functions of the CafSmartAuthBridgeModule Class

• getName: This function returns the name of the native module, which will be used to access it in JavaScript within React Native. The name must be unique to avoid conflicts with other modules.

• build: The build function is responsible for configuring and instantiating the CafSmartAuth object using the provided parameters. This function applies various settings, such as defining stages and facial authentication, to prepare the SDK for use.

• emitEvent: Allows sending events from the native side to JavaScript. Events can include success, errors, or other relevant statuses.

• setupListener: Sets up a listener to monitor the status of verification operations, such as success, pending, error, cancellation, and others.

• requestPermission: Requests the necessary permissions, such as location permissions, for the proper functioning of the SDK.

• startSmartAuth: Exposed to JavaScript, this function starts the smart authentication process using the received parameters.

• requestLocationPermissions: Exposed to JavaScript, allows the application to request location permissions from the user.

Example Implementation of the CafSmartAuthBridgeModule.kt File

class CafSmartAuthBridgeModule(private val reactContext: ReactApplicationContext) :
    ReactContextBaseJavaModule(reactContext) {

    @Nonnull
    override fun getName(): String {
        return CAF_SMART_AUTH_BRIDGE_MODULE
    }

    private fun build(mfaToken: String, faceAuthToken: String, settings: String): CafSmartAuth {
        val faceAuthenticationSettings = CafSmartAuthBridgeSettings(settings = settings)

        return CafSmartAuth.CafBuilder(mfaToken, reactContext)
            .apply {
                setSdkPlatform(CafSdkPlatform.REACT_NATIVE)
                faceAuthenticationSettings.cafStage?.let { setStage(it) }
                setFaceAuthenticatorSettings(
                    CafFaceAuthenticatorSettings(
                        faceAuthToken,
                        faceAuthenticationSettings.faceAuthenticatorSettings?.loadingScreen,
                        faceAuthenticationSettings.faceAuthenticatorSettings?.enableScreenCapture,
                        faceAuthenticationSettings.faceAuthenticatorSettings?.filter
                    )
                )
            }
            .build()
    }

    private fun emitEvent(eventName: String, params: Any) {
        reactApplicationContext
            .getJSModule(DeviceEventManagerModule.RCTDeviceEventEmitter::class.java)
            .emit(eventName, params)
    }

    private fun setupListener() = object : CafVerifyPolicyListener {
        override fun onSuccess(
            isAuthorized: Boolean,
            attemptId: String?,
            attestation: String?
        ) {
            emitEvent(eventName = CAF_SMART_AUTH_SUCCESS_EVENT, params = WritableNativeMap().apply {
                putBoolean(CAF_WRITABLE_MAP_IS_AUTHORIZED, isAuthorized)
                putString(CAF_WRITABLE_MAP_ATTEMPT_ID, attemptId)
                putString(CAF_WRITABLE_MAP_ATTESTATION, attestation)
            })
        }

        override fun onPending(isAuthorized: Boolean, attestation: String) {
            emitEvent(eventName = CAF_SMART_AUTH_PENDING_EVENT, params = WritableNativeMap().apply {
                putBoolean(CAF_WRITABLE_MAP_IS_AUTHORIZED, isAuthorized)
                putString(CAF_WRITABLE_MAP_ATTESTATION, attestation)
            })
        }

        override fun onError(failure: CafFailure) {
            emitEvent(eventName = CAF_SMART_AUTH_ERROR_EVENT, params = WritableNativeMap().apply {
                putString(CAF_WRITABLE_MAP_ERROR_MESSAGE, failure.message)
            })
        }

        override fun onCancel() {
            emitEvent(eventName = CAF_SMART_AUTH_CANCEL_EVENT, params = true)
        }

        override fun onLoading() {
            emitEvent(eventName = CAF_SMART_AUTH_LOADING_EVENT, params = true)
        }

        override fun onLoaded() {
            emitEvent(eventName = CAF_SMART_AUTH_LOADED_EVENT, params = true)
        }
    }

    private fun requestPermission(permission: String, activity: Activity) {
        if (ContextCompat.checkSelfPermission(
                reactContext,
                permission
            ) != PackageManager.PERMISSION_GRANTED
        ) {
            ActivityCompat.requestPermissions(activity, arrayOf(permission), REQUEST_CODE)
        }
    }

    @ReactMethod
    fun startSmartAuth(
        mfaToken: String,
        faceAuthToken: String,
        personId: String,
        policyId: String,
        jsonString: String
    ) {
        Handler(Looper.getMainLooper()).post {
            val smartAuth =
                build(mfaToken = mfaToken, faceAuthToken = faceAuthToken, settings = jsonString)
            smartAuth.verifyPolicy(personId, policyId, setupListener())
        }
    }

    @ReactMethod
    fun requestLocationPermissions(promise: Promise) {
        val activity = currentActivity ?: return

        Handler(Looper.getMainLooper()).post {
            try {
                requestPermission(
                    permission = Manifest.permission.ACCESS_FINE_LOCATION,
                    activity = activity
                )
                requestPermission(
                    permission = Manifest.permission.ACCESS_COARSE_LOCATION,
                    activity = activity
                )
                promise.resolve(true)
            } catch (e: Exception) {
                promise.reject(
                    PERMISSION_ERROR,
                    "$PERMISSION_ERROR_DESCRIPTION ${e.message}"
                )
            }
        }
    }

    companion object {
        private const val REQUEST_CODE = 1234

        private const val CAF_SMART_AUTH_BRIDGE_MODULE = "CafSmartAuthBridgeModule"

        private const val CAF_SMART_AUTH_SUCCESS_EVENT = "CafSmartAuth_Success"
        private const val CAF_SMART_AUTH_PENDING_EVENT = "CafSmartAuth_Pending"
        private const val CAF_SMART_AUTH_ERROR_EVENT = "CafSmartAuth_Error"
        private const val CAF_SMART_AUTH_CANCEL_EVENT = "CafSmartAuth_Cancel"
        private const val CAF_SMART_AUTH_LOADING_EVENT = "CafSmartAuth_Loading"
        private const val CAF_SMART_AUTH_LOADED_EVENT = "CafSmartAuth_Loaded"

        private const val CAF_WRITABLE_MAP_IS_AUTHORIZED = "isAuthorized"
        private const val CAF_WRITABLE_MAP_ATTEMPT_ID = "attemptId"
        private const val CAF_WRITABLE_MAP_ATTESTATION = "attestation"

        private const val CAF_WRITABLE_MAP_ERROR_MESSAGE = "message"

        private const val PERMISSION_ERROR = "PERMISSION_ERROR"
        private const val PERMISSION_ERROR_DESCRIPTION = "Error checking location permissions:"
    }
}

3. Create the CafSmartAuthBridgeSettings.kt File

This file will handle the interpretation of data sent from React Native to the native module.

Example Implementation:

internal data class CafFaceAuthenticationSettingsModel(
    val loadingScreen: Boolean?,
    val enableScreenCapture: Boolean?,
    val filter: CafFilterStyle?
)

internal class CafSmartAuthBridgeSettings(settings: String) : Serializable {
    val cafStage: CafStage?
    val faceAuthenticatorSettings: CafFaceAuthenticationSettingsModel?

    init {
        val jsonObject = JSONObject(settings)

        cafStage = if (jsonObject.has(STAGE)) CafStage.values()[jsonObject.getInt(STAGE)]
        else null

        faceAuthenticatorSettings = if (jsonObject.has(FACE_AUTHENTICATION_SETTINGS)) {
            val faceAuthenticatorSettings = jsonObject.getJSONObject(FACE_AUTHENTICATION_SETTINGS)

            val filterStyle = if (faceAuthenticatorSettings.has(FILTER)) {
                CafFilterStyle.values()[faceAuthenticatorSettings.getInt(FILTER)]
            } else null

            CafFaceAuthenticationSettingsModel(
                faceAuthenticatorSettings.optBoolean(LOADING_SCREEN),
                faceAuthenticatorSettings.optBoolean(ENABLE_SCREEN_CAPTURE),
                filterStyle ?: CafFilterStyle.LINE_DRAWING
            )
        } else null
    }

    private companion object {
        const val STAGE = "stage"
        const val FACE_AUTHENTICATION_SETTINGS = "faceAuthenticationSettings"
        const val LOADING_SCREEN = "loadingScreen"
        const val ENABLE_SCREEN_CAPTURE = "enableScreenCapture"
        const val FILTER = "filter"
    }
}

4. Register the Native Module

To make the native module recognizable by React Native, create a file named CafPackage.kt in the same directory:

Example Implementation:

class CafPackage : ReactPackage {
    override fun createNativeModules(reactContext: ReactApplicationContext): List<NativeModule> {
        return listOf(CafSmartAuthBridgeModule(reactContext))
    }

    override fun createViewManagers(reactContext: ReactApplicationContext): List<ViewManager<*, *>> {
        return emptyList()
    }
}

In the MainApplication.kt file, add the CafPackage module inside the getPackages method:

Example Implementation:

override fun getPackages(): List<ReactPackage> =
    PackageList(this).packages.apply {
        add(CafPackage())
    }

With this, your native module is configured and ready to be used in React Native.