onStart.kt

    override fun onCreate(savedInstanceState: Bundle?) {
        super.onCreate(savedInstanceState)
        setContentView(R.layout.activity_main)

        /*In the MainActivity class, initialize Fritz SDK.
        */
        Fritz.configure(this, API_KEY)

        /*Instead of calling `startCamera()` on the main thread, we use `viewFinder.post { ... }`
         to make sure that `viewFinder` has already been inflated into the view when `startCamera()` is called.
         */
        view_finder.post {
            startCamera()
        }
    }

    //Function that creates and displays the camera preview
    private fun startCamera() {

        //Specify the configuration for the preview
        val previewConfig = PreviewConfig.Builder()
            .apply {
                //Set the resolution of the captured image
                setTargetResolution(Size(1920, 1080))
            }
            .build()

        //Generate a preview
        val preview = Preview(previewConfig)

        //Add a listener to update preview automatically
        preview.setOnPreviewOutputUpdateListener {

            val parent = view_finder.parent as ViewGroup

            //Remove thr old preview
            parent.removeView(view_finder)

            //Add the new preview
            parent.addView(view_finder, 0)
            view_finder.surfaceTexture = it.surfaceTexture
        }

        val analyzerConfig = ImageAnalysisConfig.Builder().apply {
            // In our analysis, we care more about the latest image than
            // analyzing *every* image
            setImageReaderMode(
                ImageAnalysis.ImageReaderMode.ACQUIRE_LATEST_IMAGE
            )
        }.build()

        val imageAnalysis = ImageAnalysis(analyzerConfig).apply {
            setAnalyzer(executor, ImageProcessor())
        }

        /*  Bind use cases to lifecycle. If Android Studio complains about "this"
            being not a LifecycleOwner, try rebuilding the project or updating the appcompat dependency to
            version 1.1.0 or higher.
         */
        CameraX.bindToLifecycle(this, preview, imageAnalysis)
    }