MainActivity.kt

class MainActivity: AppCompatActivity() {

    private var lensFacing = CameraX.LensFacing.BACK
    private val TAG = "MainActivity"

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

        view_finder.post { startCamera() }

        // Every time the provided texture view changes, recompute layout
        texture.addOnLayoutChangeListener { _, _, _, _, _, _, _, _, _ ->
            updateTransform()
        }
    }

    private fun startCamera() {
        val metrics = DisplayMetrics().also { texture.display.getRealMetrics(it) }
        val screenSize = Size(metrics.widthPixels, metrics.heightPixels)
        val screenAspectRatio = Rational(metrics.widthPixels, metrics.heightPixels)

        val previewConfig = PreviewConfig.Builder().apply {
            setLensFacing(lensFacing)
            setTargetResolution(screenSize)
            setTargetAspectRatio(screenAspectRatio)
            setTargetRotation(windowManager.defaultDisplay.rotation)
            setTargetRotation(texture.display.rotation)
        }.build()

        val preview = Preview(previewConfig)
        preview.setOnPreviewOutputUpdateListener {
            texture.surfaceTexture = it.surfaceTexture
            updateTransform()
        }


        // Create configuration object for the image capture use case
        val imageCaptureConfig = ImageCaptureConfig.Builder()
            .apply {
                setLensFacing(lensFacing)
                setTargetAspectRatio(screenAspectRatio)
                setTargetRotation(texture.display.rotation)
                setCaptureMode(ImageCapture.CaptureMode.MAX_QUALITY)
            }.build()

        // Build the image capture use case and attach button click listener
        val imageCapture = ImageCapture(imageCaptureConfig)
        btn_take_picture.setOnClickListener {

            val file = File(
                Environment.getExternalStorageDirectory().toString() +
                        "${MainActivity.folderPath}${System.currentTimeMillis()}.jpg"
            )

            imageCapture.takePicture(file,
                object : ImageCapture.OnImageSavedListener {
                    override fun onError(
                        error: ImageCapture.UseCaseError,
                        message: String, exc: Throwable?
                    ) {
                        val msg = "Photo capture failed: $message"
                        Toast.makeText(baseContext, msg, Toast.LENGTH_SHORT).show()
                     
                    }

                    override fun onImageSaved(file: File) {
                        val msg = "Photo capture successfully: ${file.absolutePath}"
                        Toast.makeText(baseContext, msg, Toast.LENGTH_SHORT).show()
                    }
                })

        }

        CameraX.bindToLifecycle(this, preview, imageCapture)
    }

    private fun updateTransform() {
        val matrix = Matrix()
        val centerX = texture.width / 2f
        val centerY = texture.height / 2f

        val rotationDegrees = when (texture.display.rotation) {
            Surface.ROTATION_0 -> 0
            Surface.ROTATION_90 -> 90
            Surface.ROTATION_180 -> 180
            Surface.ROTATION_270 -> 270
            else -> return
        }
        matrix.postRotate(-rotationDegrees.toFloat(), centerX, centerY)
        texture.setTransform(matrix)
    }
}