need help finishing activity in a Firebase QR code scanner in Kotlin

Question

I'm trying to create a QR code scanner for my company to scan QR codes on used parts during manufacturing. I currently have it where it will scan the code and update text views on the main activity, but after scanning, I have to manually hit the back button to get back to the main activity. also, the final version needs to add the scan results to a list, instead of a text view, so I need it to scan only one time. I'm trying to get the scanner to end the activity once it processes the code, but the finish() function isn't working for some reason.

class ScanActivity : AppCompatActivity() {

    lateinit var scanView: TextureView

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

        scanView = findViewById(R.id.scanView)
        scanView.addOnLayoutChangeListener { _, _, _, _, _, _, _, _, _ ->
            updateTransform()
        }
        if (allPermissionsGranted()) {
            scanView.post { startCamera() }

        } else {
            ActivityCompat.requestPermissions(
                    this, REQUIRED_PERMISSIONS, REQUEST_CODE_PERMISSIONS)
        }
    }

    private fun startCamera() {
        val previewConfig = PreviewConfig.Builder().apply {
            setTargetResolution(Size(800, 640))
        }.build()

        val preview = Preview(previewConfig)
        preview.setOnPreviewOutputUpdateListener {

            val parent = scanView.parent as ViewGroup
            parent.removeView(scanView)
            parent.addView(scanView, 0)
            scanView.surfaceTexture = it.surfaceTexture
            updateTransform()
        }

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

        val analyzerUseCase = ImageAnalysis(analyzerConfig).apply {
            setAnalyzer(executor,QRCodeAnalyzer())
        }

        CameraX.bindToLifecycle(this, preview,analyzerUseCase)
    }

    private fun updateTransform() {
        val matrix = Matrix()
        val centerX = scanView.width / 2f
        val centerY = scanView.height / 2f
        val rotationDegrees = when (scanView.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)
        scanView.setTransform(matrix)
    }

    private val executor = Executors.newSingleThreadExecutor()
    private fun allPermissionsGranted() = REQUIRED_PERMISSIONS.all {
        ContextCompat.checkSelfPermission(
                baseContext, it) == PackageManager.PERMISSION_GRANTED
    }

    override fun onRequestPermissionsResult(
            requestCode: Int, permissions: Array<String>, grantResults: IntArray) {
        if (requestCode == REQUEST_CODE_PERMISSIONS) {
            if (allPermissionsGranted()) {
                scanView.post { startCamera() }
            } else {
                Toast.makeText(this,
                        "Permissions not granted by the user.",
                        Toast.LENGTH_SHORT).show()
                finish()
            }
        }
    }

   private class QRCodeAnalyzer : ImageAnalysis.Analyzer {

        private fun degreesToFirebaseRotation(degrees: Int): Int = when (degrees) {
            0 -> FirebaseVisionImageMetadata.ROTATION_0
            90 -> FirebaseVisionImageMetadata.ROTATION_90
            180 -> FirebaseVisionImageMetadata.ROTATION_180
            270 -> FirebaseVisionImageMetadata.ROTATION_270
            else -> throw Exception("Rotation must be 0, 90, 180, or 270.")
        }

        @SuppressLint("SetTextI18n")
        override fun analyze(imageProxy: ImageProxy?, degrees: Int) {

            val mediaImage = imageProxy?.image
            val imageRotation = degreesToFirebaseRotation(degrees)
            if (mediaImage!=null) {
                val image = FirebaseVisionImage.fromMediaImage(mediaImage, imageRotation)
                val options = FirebaseVisionBarcodeDetectorOptions.Builder()
                        .setBarcodeFormats(FirebaseVisionBarcode.FORMAT_QR_CODE).build()
                val detector = FirebaseVision.getInstance().getVisionBarcodeDetector(options)
                val result = detector.detectInImage(image)
                        .addOnSuccessListener { barcodes ->
                            var code = ""
                            for (barcode in barcodes) {
                                code = barcode.rawValue.toString()
                            }
                            Log.i("STAGE ONE COMPLETE!!!", code)

                            //Start breaking down QR scan into Part Number and Lot Number

                            var partNumberText = ""
                            var partNumber: Pattern = Pattern.compile("MCU-(.*?) ")
                            var mPN: Matcher = partNumber.matcher(code)
                            while (mPN.find()) {
                                partNumberText = mPN.group(1)
                                MainActivity.partNumberTextView.text = "Part Number: $partNumberText"
                            }

                            if (code.length > 47) {
                                var lotNumberSubText = code.substring(0, 47)
                                var lotNumberText = ""
                                var lotNumber: Pattern = Pattern.compile("$lotNumberSubText(.*?) ")
                                var mLN: Matcher = lotNumber.matcher(code)
                                while (mLN.find()) {
                                    lotNumberText = mLN.group(1)
                                    MainActivity.lotNumberTextView.text = "Lot Number: $lotNumberText"
                                }
                            }
                            finish()
                        }
                        .addOnFailureListener {
                            Log.i("FAILURE", "Scan Failed")
                        }
            }
        }
    }
}

error screenshot

Answer 1

You can try this. Add constructor to QRCodeAnalyzer class:

private class QRCodeAnalyzer constructor(val activity: Activity) : ImageAnalysis.Analyzer 

You can call:

activity.finish()

and setAnalyzer:

setAnalyzer(executor,QRCodeAnalyzer(this))