Very new to Android development ... actually trying to integrate an AR view in a Flutter app.

Been trying to set it up. Below is the ARActivity.kt and not sure why we keep getting this error

e: file:///Users/william/Documents/GitHub/game_native/android/app/src/main/kotlin/com/gps/app/ARActivity.kt:90:45 Unresolved reference: surfaceTexture

Maybe because the surfaceview is late and it's not declared when it's used?

private lateinit var surfaceView: SurfaceView

import android.content.Context
import android.app.Activity
import android.os.Bundle
import android.view.WindowManager
import androidx.appcompat.app.AppCompatActivity
import android.view.View
import android.view.SurfaceView
import android.view.SurfaceHolder
import com.google.ar.core.Config
import com.google.ar.core.Session
import com.google.ar.core.ArCoreApk
import com.google.ar.core.exceptions.CameraNotAvailableException

class ARActivity : AppCompatActivity() {

    private var arSession: Session? = null
    private lateinit var surfaceView: SurfaceView  

    override fun onCreate(savedInstanceState: Bundle?) {
        super.onCreate(savedInstanceState)
        
        window.addFlags(WindowManager.LayoutParams.FLAG_KEEP_SCREEN_ON)
        window.decorView.systemUiVisibility = (
                View.SYSTEM_UI_FLAG_LAYOUT_STABLE
                        or View.SYSTEM_UI_FLAG_LAYOUT_FULLSCREEN
                        or View.SYSTEM_UI_FLAG_FULLSCREEN
                        or View.SYSTEM_UI_FLAG_IMMERSIVE_STICKY)
    
        // First, check if ARCore is available and installed
        checkAndInstallARCore(this)
    
        // Then, initialize and set up the SurfaceView
        surfaceView = SurfaceView(this)
        setContentView(surfaceView)
    
        // Finally, set up the AR session
        setupARSession()
    }

    private fun checkAndInstallARCore(activity: Activity) {
        val availability = ArCoreApk.getInstance().checkAvailability(activity)
        when (availability) {
            ArCoreApk.Availability.SUPPORTED_INSTALLED -> {
                println("ARCore is installed and supported")
            }
            ArCoreApk.Availability.SUPPORTED_NOT_INSTALLED -> {
                println("ARCore is not installed but supported")
                ArCoreApk.getInstance().requestInstall(activity, true)
            }
            ArCoreApk.Availability.UNSUPPORTED_DEVICE_NOT_CAPABLE -> {
                println("This device does not support ARCore")
                finish() // or show a message and close the activity
            }
            else -> {
                println("ARCore availability check failed or unknown")
            }
        }
    }

    private fun setupARSession() {
        try {
            arSession = Session(this as Context)
            val config = Config(arSession)
            config.updateMode = Config.UpdateMode.LATEST_CAMERA_IMAGE
            config.planeFindingMode = Config.PlaneFindingMode.HORIZONTAL
            config.lightEstimationMode = Config.LightEstimationMode.ENVIRONMENTAL_HDR
            arSession?.configure(config)
        } catch (e: Exception) {
            println("Error setting up AR session: ${e.message}")
            finish()
            return
        }

        surfaceView.holder.addCallback(object : SurfaceHolder.Callback {
            override fun surfaceCreated(holder: SurfaceHolder) {
                try {
                    arSession?.resume()
                    checkAndSetTexture(holder)
                } catch (e: CameraNotAvailableException) {
                    println("Camera not available on surfaceCreated: ${e.message}")
                } catch (e: ClassCastException) {
                    println("Failed to cast holder to SurfaceHolder: ${e.message}")
                }
            }

            private fun checkAndSetTexture(holder: SurfaceHolder) {
                val surfaceTexture = holder.surfaceTexture
                if (surfaceTexture.isNotEmpty) {
                    arSession?.setCameraTextureName(surfaceTexture.getTextureId())
                    println("Texture ID set: ${surfaceTexture.getTextureId()}")
                } else {
                    println("SurfaceTexture not available, retrying in 100ms")
                    surfaceView.postDelayed({ checkAndSetTexture(holder) }, 100)
                }
            }

            override fun surfaceChanged(holder: SurfaceHolder, format: Int, width: Int, height: Int) {
                // This method can be used to adjust AR configuration if the surface size changes
            }
        
            override fun surfaceDestroyed(holder: SurfaceHolder) {
                arSession?.pause()
            }
        })
    }

    // ... rest of your lifecycle methods ...
    override fun onResume() {
        super.onResume()
        try {
            arSession?.resume()
        } catch (e: CameraNotAvailableException) {
            println("Camera not available during onResume: ${e.message}")
        }
    }

    override fun onPause() {
        super.onPause()
        arSession?.pause()
    }

    override fun onDestroy() {
        super.onDestroy()
        arSession?.close()
    }

}