Official Android samples following the Android Burrito Design Pattern https://github.com/jmfayard/camera-samples/blob/master/Camera2BasicKotlin/Application/src/main/java/com/example/android/camera2basic/Camera2BasicFragment.kt#L36-L136

android-camera-samples-fragment.kt

public inline fun needsRefactoring(): Nothing = throw NotImplementedError("""
    This does too much and needs to be refactored. 
    Don't put any kind of logic in the Activities and Fragments. 
""".trimIndent())


class Camera2BasicFragment : Fragment(), View.OnClickListener,
        ActivityCompat.OnRequestPermissionsResultCallback {
    private val surfaceTextureListener = object : TextureView.SurfaceTextureListener {
        override fun onSurfaceTextureAvailable(texture: SurfaceTexture, width: Int, height: Int) = needsRefactoring()
        override fun onSurfaceTextureSizeChanged(texture: SurfaceTexture, width: Int, height: Int) = needsRefactoring()
        override fun onSurfaceTextureDestroyed(texture: SurfaceTexture) = needsRefactoring()
        override fun onSurfaceTextureUpdated(texture: SurfaceTexture) = needsRefactoring()

    }
    private lateinit var cameraId: String
    private lateinit var textureView: AutoFitTextureView
    private var captureSession: CameraCaptureSession? = null
    private var cameraDevice: CameraDevice? = null
    private lateinit var previewSize: Size
    private val stateCallback = object : CameraDevice.StateCallback() {
        override fun onOpened(cameraDevice: CameraDevice) = needsRefactoring()
        override fun onDisconnected(cameraDevice: CameraDevice) = needsRefactoring()
        override fun onError(cameraDevice: CameraDevice, error: Int) = needsRefactoring()
    }
    private var backgroundThread: HandlerThread? = null
    private var backgroundHandler: Handler? = null
    private var imageReader: ImageReader? = null
    private lateinit var file: File
    private val onImageAvailableListener: ImageReader.OnImageAvailableListener = needsRefactoring()
    private lateinit var previewRequestBuilder: CaptureRequest.Builder
    private lateinit var previewRequest: CaptureRequest
    private var state = STATE_PREVIEW
    private val cameraOpenCloseLock = Semaphore(1)
    private var flashSupported = false
    private var sensorOrientation = 0
    private val captureCallback = object : CameraCaptureSession.CaptureCallback() {
        private fun process(result: CaptureResult): Unit = needsRefactoring()
        private fun capturePicture(result: CaptureResult): Unit = needsRefactoring()
        override fun onCaptureProgressed(session: CameraCaptureSession, request: CaptureRequest, partialResult: CaptureResult) = needsRefactoring()
        override fun onCaptureCompleted(session: CameraCaptureSession, request: CaptureRequest, result: TotalCaptureResult) = needsRefactoring()
    }

    override fun onCreateView(inflater: LayoutInflater, container: ViewGroup?, savedInstanceState: Bundle?): View? = needsRefactoring()
    override fun onViewCreated(view: View, savedInstanceState: Bundle?) = needsRefactoring()
    override fun onActivityCreated(savedInstanceState: Bundle?) {
        super.onActivityCreated(savedInstanceState)
        needsRefactoring()
    }

    override fun onResume() {
        super.onResume()
        needsRefactoring()
    }

    override fun onPause() {
        super.onPause()
        needsRefactoring()
    }

    private fun requestCameraPermission(): Unit = needsRefactoring()
    override fun onRequestPermissionsResult(requestCode: Int, permissions: Array<String>, grantResults: IntArray): Unit = needsRefactoring()
    private fun setUpCameraOutputs(width: Int, height: Int): Unit = needsRefactoring()
    private fun areDimensionsSwapped(displayRotation: Int): Boolean = needsRefactoring()
    private fun openCamera(width: Int, height: Int): Unit = needsRefactoring()
    private fun closeCamera(): Unit = needsRefactoring()
    private fun startBackgroundThread(): Unit = needsRefactoring()
    private fun stopBackgroundThread(): Unit = needsRefactoring()
    private fun createCameraPreviewSession(): Unit = needsRefactoring()
    private fun configureTransform(viewWidth: Int, viewHeight: Int): Unit = needsRefactoring()
    private fun lockFocus(): Unit = needsRefactoring()
    private fun runPrecaptureSequence(): Unit = needsRefactoring()
    private fun captureStillPicture(): Unit = needsRefactoring()
    private fun unlockFocus(): Unit = needsRefactoring()
    override fun onClick(view: View): Unit = needsRefactoring()
    private fun setAutoFlash(requestBuilder: CaptureRequest.Builder): Unit = needsRefactoring()

    companion object {
        init {
            needsRefactoring()
        }

        private val ORIENTATIONS = SparseIntArray()
        private val FRAGMENT_DIALOG = "dialog"
        private val TAG = "Camera2BasicFragment"
        private val STATE_PREVIEW = 0
        private val STATE_WAITING_LOCK = 1
        private val STATE_WAITING_PRECAPTURE = 2
        private val STATE_WAITING_NON_PRECAPTURE = 3
        private val STATE_PICTURE_TAKEN = 4
        private val MAX_PREVIEW_WIDTH = 1920
        private val MAX_PREVIEW_HEIGHT = 1080
        @JvmStatic
        private fun chooseOptimalSize(
                choices: Array<Size>, textureViewWidth: Int, textureViewHeight: Int,
                maxWidth: Int, maxHeight: Int, aspectRatio: Size): Size = needsRefactoring()

        @JvmStatic
        fun newInstance(): Camera2BasicFragment = needsRefactoring()
    }
}