remove permission callback; move method call result to delegate

@@ -17,10 +17,9 @@ import com.google.mlkit.vision.barcode.BarcodeScanning
 import com.google.mlkit.vision.common.InputImage
 import dev.steenbakker.mobile_scanner.objects.DetectionSpeed
 import dev.steenbakker.mobile_scanner.objects.MobileScannerStartParameters
+import io.flutter.plugin.common.MethodChannel
 import io.flutter.plugin.common.PluginRegistry
 import io.flutter.view.TextureRegistry
-
-typealias PermissionCallback = (permissionGranted: Boolean) -> Unit
 typealias MobileScannerCallback = (barcodes: List<Map<String, Any?>>, image: ByteArray?) -> Unit
 typealias AnalyzerCallback = (barcodes: List<Map<String, Any?>>?) -> Unit
 typealias MobileScannerErrorCallback = (error: String) -> Unit
@@ -49,10 +48,9 @@ class MobileScanner(
         private const val REQUEST_CODE = 0x0786
     }
 
-    private var listener: PluginRegistry.RequestPermissionsResultListener? = null
-
     private var cameraProvider: ProcessCameraProvider? = null
     private var camera: Camera? = null
+    private var pendingPermissionResult: MethodChannel.Result? = null
     private var preview: Preview? = null
     private var textureEntry: TextureRegistry.SurfaceTextureEntry? = null
 
@@ -86,17 +84,7 @@ class MobileScanner(
     /**
      * Request camera permissions.
      */
-    fun requestPermission(permissionCallback: PermissionCallback) {
-        listener
-            ?: PluginRegistry.RequestPermissionsResultListener { requestCode, _, grantResults ->
-                if (requestCode != REQUEST_CODE) {
-                    false
-                } else {
-                    val authorized = grantResults[0] == PackageManager.PERMISSION_GRANTED
-                    permissionCallback(authorized)
-                    true
-                }
-            }
+    fun requestPermission(result: MethodChannel.Result) {
         val permissions = arrayOf(Manifest.permission.CAMERA)
         ActivityCompat.requestPermissions(activity, permissions, REQUEST_CODE)
     }
@@ -109,7 +97,14 @@ class MobileScanner(
         permissions: Array<out String>,
         grantResults: IntArray
     ): Boolean {
-        return listener?.onRequestPermissionsResult(requestCode, permissions, grantResults) ?: false
+        if (requestCode != REQUEST_CODE) {
+            return false
+        }
+
+        pendingPermissionResult?.success(grantResults[0] == PackageManager.PERMISSION_GRANTED)
+        pendingPermissionResult = null
+
+        return true
     }
 
     /**

@@ -23,14 +23,8 @@ class MobileScannerPlugin : FlutterPlugin, ActivityAware, MethodChannel.MethodCa
 
     private lateinit var barcodeHandler: BarcodeHandler
 
-    private var permissionResult: MethodChannel.Result? = null
     private var analyzerResult: MethodChannel.Result? = null
 
-    private val permissionCallback: PermissionCallback = {hasPermission: Boolean ->
-        permissionResult?.success(hasPermission)
-        permissionResult = null
-    }
-
     private val callback: MobileScannerCallback = { barcodes: List<Map<String, Any?>>, image: ByteArray? ->
         if (image != null) {
             barcodeHandler.publishEvent(mapOf(
@@ -78,7 +72,7 @@ class MobileScannerPlugin : FlutterPlugin, ActivityAware, MethodChannel.MethodCa
         }
         when (call.method) {
             "state" -> result.success(handler!!.hasCameraPermission())
-            "request" -> requestPermission(result)
+            "request" -> handler!!.requestPermission(result)
             "start" -> start(call, result)
             "torch" -> toggleTorch(call, result)
             "stop" -> stop(result)
@@ -124,11 +118,6 @@ class MobileScannerPlugin : FlutterPlugin, ActivityAware, MethodChannel.MethodCa
         onDetachedFromActivity()
     }
 
-    private fun requestPermission(result: MethodChannel.Result) {
-        permissionResult = result
-        handler!!.requestPermission(permissionCallback)
-    }
-
     @ExperimentalGetImage
     private fun start(call: MethodCall, result: MethodChannel.Result) {
         val torch: Boolean = call.argument<Boolean>("torch") ?: false