CameraActivity.kt

private fun startCamera() {
        CameraX.unbindAll()

        val previewConfig = PreviewConfig.Builder().apply {
            setTargetResolution(Size(1920, 1080))
            setTargetRotation(viewFinder.display.rotation)
        }.build()

        // Build the viewFinder use case
        val preview = Preview(previewConfig)
        // Recompute layout every time viewFinder is updated
        preview.setOnPreviewOutputUpdateListener {
            val parent = viewFinder.parent as ViewGroup
            parent.removeView(viewFinder)
            parent.addView(viewFinder, 0)

            viewFinder.surfaceTexture = it.surfaceTexture
            updateTransform()

        }

        val analyzerConfig = ImageAnalysisConfig.Builder().apply {
            setImageReaderMode(
                ImageAnalysis.ImageReaderMode.ACQUIRE_LATEST_IMAGE
            )
        }.build()

        // perform image analysis
        val imageAnalysis = ImageAnalysis(analyzerConfig).apply {
            setAnalyzer(executor, Classify())
        }

        CameraX.bindToLifecycle(this, preview, imageAnalysis)
    }

    private fun updateTransform() {
        val matrix = Matrix()

        // calculate center of texture view
        val centerX = viewFinder.width / 2f
        val centerY = viewFinder.height / 2f

        // correct the preview output
        val rotationDegrees = when (viewFinder.display.rotation) {
            Surface.ROTATION_0 -> 0
            Surface.ROTATION_90 -> 90
            Surface.ROTATION_180 -> 180
            Surface.ROTATION_270 -> 270
            else -> return
        }

        // apply transformations
        matrix.postRotate(-rotationDegrees.toFloat(), centerX, centerY)
        viewFinder.setTransform(matrix)
    }