Move method call impl to different class

+package dev.steenbakker.mobile_scanner
+
+import android.app.Activity
+import android.net.Uri
+import androidx.camera.core.CameraSelector
+import androidx.camera.core.ExperimentalGetImage
+import com.google.mlkit.vision.barcode.BarcodeScannerOptions
+import dev.steenbakker.mobile_scanner.objects.BarcodeFormats
+import dev.steenbakker.mobile_scanner.objects.DetectionSpeed
+import io.flutter.plugin.common.BinaryMessenger
+import io.flutter.plugin.common.MethodCall
+import io.flutter.plugin.common.MethodChannel
+import io.flutter.plugin.common.PluginRegistry.RequestPermissionsResultListener
+import io.flutter.embedding.engine.plugins.activity.ActivityPluginBinding
+import io.flutter.view.TextureRegistry
+import java.io.File
+
+class MethodCallHandlerImpl(
+    private val activity: Activity,
+    private val barcodeHandler: BarcodeHandler,
+    binaryMessenger: BinaryMessenger,
+    private val permissions: MobileScannerPermissions,
+    private val permissionsRegistry: MobileScannerPermissions.PermissionsRegistry,
+    textureRegistry: TextureRegistry): MethodChannel.MethodCallHandler {
+
+    private val analyzerCallback: AnalyzerCallback = { barcodes: List<Map<String, Any?>>?->
+        if (barcodes != null) {
+            barcodeHandler.publishEvent(mapOf(
+                "name" to "barcode",
+                "data" to barcodes
+            ))
+            analyzerResult?.success(true)
+        } else {
+            analyzerResult?.success(false)
+        }
+        analyzerResult = null
+    }
+
+    private var analyzerResult: MethodChannel.Result? = null
+
+    private val callback: MobileScannerCallback = { barcodes: List<Map<String, Any?>>, image: ByteArray? ->
+        if (image != null) {
+            barcodeHandler.publishEvent(mapOf(
+                "name" to "barcode",
+                "data" to barcodes,
+                "image" to image
+            ))
+        } else {
+            barcodeHandler.publishEvent(mapOf(
+                "name" to "barcode",
+                "data" to barcodes
+            ))
+        }
+    }
+
+    private val errorCallback: MobileScannerErrorCallback = {error: String ->
+        barcodeHandler.publishEvent(mapOf(
+            "name" to "error",
+            "data" to error,
+        ))
+    }
+
+    private var methodChannel: MethodChannel? = null
+
+    private var mobileScanner: MobileScanner? = null
+
+    private val torchStateCallback: TorchStateCallback = {state: Int ->
+        barcodeHandler.publishEvent(mapOf("name" to "torchState", "data" to state))
+    }
+
+    init {
+        methodChannel = MethodChannel(binaryMessenger,
+            "dev.steenbakker.mobile_scanner/scanner/method")
+        methodChannel!!.setMethodCallHandler(this)
+        mobileScanner = MobileScanner(activity, textureRegistry, callback, errorCallback)
+    }
+
+    fun dispose(activityPluginBinding: ActivityPluginBinding) {
+        methodChannel?.setMethodCallHandler(null)
+        methodChannel = null
+        mobileScanner = null
+
+        val listener: RequestPermissionsResultListener? = permissions.getPermissionListener()
+
+        if(listener != null) {
+            activityPluginBinding.removeRequestPermissionsResultListener(listener)
+        }
+
+    }
+
+    @ExperimentalGetImage
+    override fun onMethodCall(call: MethodCall, result: MethodChannel.Result) {
+        if (mobileScanner == null) {
+            result.error("MobileScanner", "Called ${call.method} before initializing.", null)
+            return
+        }
+        when (call.method) {
+            "state" -> result.success(permissions.hasCameraPermission(activity))
+            "request" -> permissions.requestPermission(
+                activity,
+                permissionsRegistry,
+                object: MobileScannerPermissions.ResultCallback {
+                    override fun onResult(errorCode: String?, errorDescription: String?) {
+                        if(errorCode == null) {
+                            result.success(true)
+                            return
+                        }
+
+                        result.error(errorCode, errorDescription, null)
+                    }
+                })
+            "start" -> start(call, result)
+            "torch" -> toggleTorch(call, result)
+            "stop" -> stop(result)
+            "analyzeImage" -> analyzeImage(call, result)
+            else -> result.notImplemented()
+        }
+    }
+
+    @ExperimentalGetImage
+    private fun start(call: MethodCall, result: MethodChannel.Result) {
+        val torch: Boolean = call.argument<Boolean>("torch") ?: false
+        val facing: Int = call.argument<Int>("facing") ?: 0
+        val formats: List<Int>? = call.argument<List<Int>>("formats")
+        val returnImage: Boolean = call.argument<Boolean>("returnImage") ?: false
+        val speed: Int = call.argument<Int>("speed") ?: 1
+        val timeout: Int = call.argument<Int>("timeout") ?: 250
+
+        var barcodeScannerOptions: BarcodeScannerOptions? = null
+        if (formats != null) {
+            val formatsList: MutableList<Int> = mutableListOf()
+            for (index in formats) {
+                formatsList.add(BarcodeFormats.values()[index].intValue)
+            }
+            barcodeScannerOptions = if (formatsList.size == 1) {
+                BarcodeScannerOptions.Builder().setBarcodeFormats(formatsList.first())
+                    .build()
+            } else {
+                BarcodeScannerOptions.Builder().setBarcodeFormats(
+                    formatsList.first(),
+                    *formatsList.subList(1, formatsList.size).toIntArray()
+                ).build()
+            }
+        }
+
+        val position =
+            if (facing == 0) CameraSelector.DEFAULT_FRONT_CAMERA else CameraSelector.DEFAULT_BACK_CAMERA
+
+        val detectionSpeed: DetectionSpeed = DetectionSpeed.values().first { it.intValue == speed}
+
+        try {
+            mobileScanner!!.start(barcodeScannerOptions, returnImage, position, torch, detectionSpeed, torchStateCallback, mobileScannerStartedCallback = {
+                result.success(mapOf(
+                    "textureId" to it.id,
+                    "size" to mapOf("width" to it.width, "height" to it.height),
+                    "torchable" to it.hasFlashUnit
+                ))
+            },
+                timeout.toLong())
+
+        } catch (e: AlreadyStarted) {
+            result.error(
+                "MobileScanner",
+                "Called start() while already started",
+                null
+            )
+        } catch (e: NoCamera) {
+            result.error(
+                "MobileScanner",
+                "No camera found or failed to open camera!",
+                null
+            )
+        } catch (e: TorchError) {
+            result.error(
+                "MobileScanner",
+                "Error occurred when setting torch!",
+                null
+            )
+        } catch (e: CameraError) {
+            result.error(
+                "MobileScanner",
+                "Error occurred when setting up camera!",
+                null
+            )
+        } catch (e: Exception) {
+            result.error(
+                "MobileScanner",
+                "Unknown error occurred..",
+                null
+            )
+        }
+    }
+
+    private fun stop(result: MethodChannel.Result) {
+        try {
+            mobileScanner!!.stop()
+            result.success(null)
+        } catch (e: AlreadyStopped) {
+            result.success(null)
+        }
+    }
+
+    private fun analyzeImage(call: MethodCall, result: MethodChannel.Result) {
+        analyzerResult = result
+        val uri = Uri.fromFile(File(call.arguments.toString()))
+        mobileScanner!!.analyzeImage(uri, analyzerCallback)
+    }
+
+    private fun toggleTorch(call: MethodCall, result: MethodChannel.Result) {
+        try {
+            mobileScanner!!.toggleTorch(call.arguments == 1)
+            result.success(null)
+        } catch (e: AlreadyStopped) {
+            result.error("MobileScanner", "Called toggleTorch() while stopped!", null)
+        }
+    }
+}