Native Camera View in Flutter does not occupy the whole width and height

I am trying to integrate CameraX inside my flutter project. I am doing so via platform channels. I don’t want to integrate any third party lib.

Here is a screenshot of the camera only occupying one third of the height in Android

Below is my code

class ScanQr extends StatelessWidget {
  const ScanQr({super.key});

  @override
  Widget build(BuildContext context) {
    var width = MediaQuery.of(context).size.width;
    var height = MediaQuery.of(context).size.height;

    return Scaffold(
      backgroundColor: Colors.teal,
      body: SizedBox(
        height: height, 
        width: width,
        child: CealScanQrView(
          width: width,
          height: height,
        ),
      ),
    );
  }
}


class CealScanQrView extends StatelessWidget {
  const CealScanQrView({required this.width, required this.height, super.key});

  final double width;
  final double height;
 
  @override
  Widget build(BuildContext context) {
    final Map<String, dynamic> creationParams = <String, dynamic>{};

    creationParams["width"] = width;
    creationParams["height"] = height;

    return Platform.isAndroid
        ? AndroidView(
            viewType: cealScanQrView,
            layoutDirection: TextDirection.ltr,
            creationParams: creationParams,
            creationParamsCodec: const StandardMessageCodec(),
          )
        : UiKitView(
            viewType: cealScanQrView,
            layoutDirection: TextDirection.ltr,
            creationParams: creationParams,
            creationParamsCodec: const StandardMessageCodec(),
          );
  }
}

Here is my android code

In MainActivity's configureFlutterEngine method

flutterEngine
            .platformViewsController
            .registry
            .registerViewFactory("cealScanQrView", CealScanQrViewFactory(this))


class CealScanQrView(
    private val context: Context, id: Int, creationParams: Map<String?, Any?>?,
    private val activity: FlutterActivity
) : PlatformView {

    private var mCameraProvider: ProcessCameraProvider? = null
    private var linearLayout: LinearLayout = LinearLayout(context)

    private var preview: PreviewView = PreviewView(context)

    private lateinit var cameraExecutor: ExecutorService
    private lateinit var options: BarcodeScannerOptions
    private lateinit var scanner: BarcodeScanner

    private var analysisUseCase: ImageAnalysis = ImageAnalysis.Builder()
        .build()

    companion object {
        private val REQUEST_CODE_PERMISSIONS = 10
        private val REQUIRED_PERMISSIONS = mutableListOf(Manifest.permission.CAMERA).toTypedArray()
    }


    init {
        val linearLayoutParams = ViewGroup.LayoutParams(
            ViewGroup.LayoutParams.MATCH_PARENT,
            ViewGroup.LayoutParams.MATCH_PARENT
        )

        linearLayout.layoutParams = linearLayoutParams
        linearLayout.orientation = LinearLayout.VERTICAL

        preview.setBackgroundColor(Color.RED)
        preview.layoutParams = ViewGroup.LayoutParams(
            ViewGroup.LayoutParams.MATCH_PARENT,
            ViewGroup.LayoutParams.MATCH_PARENT
        )

        linearLayout.addView(preview)
        linearLayout.layoutParams.width = 400
        linearLayout.layoutParams.height = 400
        setUpCamera()

        preview.viewTreeObserver.addOnGlobalLayoutListener(object :
            ViewTreeObserver.OnGlobalLayoutListener {
            override fun onGlobalLayout() {
                preview.viewTreeObserver.removeOnGlobalLayoutListener(this)
                preview.layoutParams.height =
                    creationParams?.get("height").toString().toDouble().toInt()
                preview.requestLayout()
            }
        })
    }

    private fun setUpCamera() {
        if (allPermissionsGranted()) {
            startCamera()
        } else {
            ActivityCompat.requestPermissions(
                context as FlutterActivity, REQUIRED_PERMISSIONS, REQUEST_CODE_PERMISSIONS
            )
        }
        cameraExecutor = Executors.newSingleThreadExecutor()

        options = BarcodeScannerOptions.Builder()
            .setBarcodeFormats(
                Barcode.FORMAT_QR_CODE
            )
            .build()
        scanner = BarcodeScanning.getClient(options)
        analysisUseCase.setAnalyzer(
            // newSingleThreadExecutor() will let us perform analysis on a single worker thread
            Executors.newSingleThreadExecutor()
        ) { imageProxy ->
            processImageProxy(scanner, imageProxy)
        }
    }

    override fun getView(): View {
        return linearLayout
    }

    override fun dispose() {
        cameraExecutor.shutdown()
    }

    @SuppressLint("UnsafeOptInUsageError")
    private fun processImageProxy(
        barcodeScanner: BarcodeScanner,
        imageProxy: ImageProxy
    ) {
        imageProxy.image?.let { image ->
            val inputImage =
                InputImage.fromMediaImage(
                    image,
                    imageProxy.imageInfo.rotationDegrees
                )
            barcodeScanner.process(inputImage)
                .addOnSuccessListener { barcodeList ->
                    val barcode = barcodeList.getOrNull(0)
                    // `rawValue` is the decoded value of the barcode
                    barcode?.rawValue?.let { value ->
                        mCameraProvider?.unbindAll()
                        Toast.makeText(context, value, Toast.LENGTH_LONG).show()
                    }
                }
                .addOnFailureListener {
                    // This failure will happen if the barcode scanning model
                    // fails to download from Google Play Services
                }
                .addOnCompleteListener {
                    // When the image is from CameraX analysis use case, must
                    // call image.close() on received images when finished
                    // using them. Otherwise, new images may not be received
                    // or the camera may stall.
                    imageProxy.image?.close()
                    imageProxy.close()
                }
        }
    }

    private fun allPermissionsGranted() = REQUIRED_PERMISSIONS.all {
        ContextCompat.checkSelfPermission(context, it) == PackageManager.PERMISSION_GRANTED
    }

    private fun startCamera() {
        val cameraProviderFuture = ProcessCameraProvider.getInstance(context)
        cameraProviderFuture.addListener({
            // Used to bind the lifecycle of cameras to the lifecycle owner
            val cameraProvider: ProcessCameraProvider = cameraProviderFuture.get()
            mCameraProvider = cameraProvider
            // Preview
            val surfacePreview = Preview.Builder()
                .build()
                .also {
                    it.setSurfaceProvider(preview.surfaceProvider)
                }
            // Select back camera as a default
            val cameraSelector = CameraSelector.DEFAULT_BACK_CAMERA
            try {
                // Unbind use cases before rebinding
                cameraProvider.unbindAll()
                // Bind use cases to camera
                cameraProvider.bindToLifecycle(
                    activity,
                    cameraSelector,
                    surfacePreview,
                    analysisUseCase,
                )
            } catch (exc: Exception) {
                // Do nothing on exception
            }
        }, ContextCompat.getMainExecutor(context))
    }


}

In AndroidManifest.xml

<uses-permission android:name="android.permission.CAMERA" />

There are two problems which I am facing

Firstly I don’t see the camera permission when my screen opens even though I am asking the permission for it. I have to manually go to the settings screen to enable camera permission
And secondly the camera does not occupy entire screen

Even if I set linearLayout.layoutParams.height = 1000 still the height remains the same. I completely stopped the app and reran multiple times but no effect

Edit
I have created a gist where I have removed linear layout. Check here