fix: Ignore additional calls to start() when the controller is starting

CHANGELOG.md

@@ -1,10 +1,18 @@
 ## NEXT
 
+Improvements:
 * [MacOS] Added the corners and size information to barcode results.
 * [MacOS] Added support for `analyzeImage`.
 * [MacOS] Added a Privacy Manifest.
 * [web] Added the size information to barcode results.
 * Added support for barcode formats to image analysis.
+* Updated the scanner to report any scanning errors that were encountered during processing.
+* Introduced a new getter `hasCameraPermission` for the `MobileScannerState`.
+* Fixed a bug in the lifecycle handling sample. Now instead of checking `isInitialized`,
+the sample recommends using `hasCameraPermission`, which also guards against camera permission errors.
+
+Bugs fixed:
+* Fixed a bug that would cause the scanner to emit an error when it was already started. Now it ignores any calls to start while it is starting.
 
 ## 5.2.3
 

README.md

@@ -127,7 +127,7 @@ class MyState extends State<MyStatefulWidget> with WidgetsBindingObserver {
   void didChangeAppLifecycleState(AppLifecycleState state) {
     // If the controller is not ready, do not try to start or stop it.
     // Permission dialogs can trigger lifecycle changes before the controller is ready.
-    if (!controller.value.isInitialized) {
+    if (!controller.value.hasCameraPermission) {
       return;
     }
 
@@ -192,4 +192,4 @@ Future<void> dispose() async {
 To display the camera preview, pass the controller to a `MobileScanner` widget.
 
 See the [examples](example/README.md) for runnable examples of various usages,
-such as the basic usage, applying a scan window, or retrieving images from the barcodes.
+such as the basic usage, applying a scan window, or retrieving images from the barcodes.

android/src/main/kotlin/dev/steenbakker/mobile_scanner/BarcodeHandler.kt

@@ -24,6 +24,12 @@ class BarcodeHandler(binaryMessenger: BinaryMessenger) : EventChannel.StreamHand
         }
     }
 
+    fun publishError(errorCode: String, errorMessage: String, errorDetails: Any?) {
+        Handler(Looper.getMainLooper()).post {
+            eventSink?.error(errorCode, errorMessage, errorDetails)
+        }
+    }
+
     override fun onListen(event: Any?, eventSink: EventChannel.EventSink?) {
         this.eventSink = eventSink
     }

android/src/main/kotlin/dev/steenbakker/mobile_scanner/MobileScannerHandler.kt

@@ -10,6 +10,7 @@ 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 dev.steenbakker.mobile_scanner.objects.MobileScannerErrorCodes
 import io.flutter.plugin.common.BinaryMessenger
 import io.flutter.plugin.common.MethodCall
 import io.flutter.plugin.common.MethodChannel
@@ -28,7 +29,7 @@ class MobileScannerHandler(
 
     private val analyzeImageErrorCallback: AnalyzerErrorCallback = {
         Handler(Looper.getMainLooper()).post {
-            analyzerResult?.error("MobileScanner", it, null)
+            analyzerResult?.error(MobileScannerErrorCodes.BARCODE_ERROR, it, null)
             analyzerResult = null
         }
     }
@@ -65,10 +66,7 @@ class MobileScannerHandler(
     }
 
     private val errorCallback: MobileScannerErrorCallback = {error: String ->
-        barcodeHandler.publishEvent(mapOf(
-            "name" to "error",
-            "data" to error,
-        ))
+        barcodeHandler.publishError(MobileScannerErrorCodes.BARCODE_ERROR, error, null)
     }
 
     private var methodChannel: MethodChannel? = null
@@ -106,21 +104,21 @@ class MobileScannerHandler(
 
     @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,
                 addPermissionListener,
                 object: MobileScannerPermissions.ResultCallback {
-                    override fun onResult(errorCode: String?, errorDescription: String?) {
+                    override fun onResult(errorCode: String?) {
                         when(errorCode) {
                             null -> result.success(true)
-                            MobileScannerPermissions.CAMERA_ACCESS_DENIED -> result.success(false)
-                            else -> result.error(errorCode, errorDescription, null)
+                            MobileScannerErrorCodes.CAMERA_ACCESS_DENIED -> result.success(false)
+                            MobileScannerErrorCodes.CAMERA_PERMISSIONS_REQUEST_ONGOING -> result.error(
+                                MobileScannerErrorCodes.CAMERA_PERMISSIONS_REQUEST_ONGOING,
+                                MobileScannerErrorCodes.CAMERA_PERMISSIONS_REQUEST_ONGOING_MESSAGE, null)
+                            else -> result.error(
+                                MobileScannerErrorCodes.GENERIC_ERROR, MobileScannerErrorCodes.GENERIC_ERROR_MESSAGE, null)
                         }
                     }
                 })
@@ -185,29 +183,29 @@ class MobileScannerHandler(
                     when (it) {
                         is AlreadyStarted -> {
                             result.error(
-                                "MobileScanner",
-                                "Called start() while already started",
+                                MobileScannerErrorCodes.ALREADY_STARTED_ERROR,
+                                MobileScannerErrorCodes.ALREADY_STARTED_ERROR_MESSAGE,
                                 null
                             )
                         }
                         is CameraError -> {
                             result.error(
-                                "MobileScanner",
-                                "Error occurred when setting up camera!",
+                                MobileScannerErrorCodes.CAMERA_ERROR,
+                                MobileScannerErrorCodes.CAMERA_ERROR_MESSAGE,
                                 null
                             )
                         }
                         is NoCamera -> {
                             result.error(
-                                "MobileScanner",
-                                "No camera found or failed to open camera!",
+                                MobileScannerErrorCodes.NO_CAMERA_ERROR,
+                                MobileScannerErrorCodes.NO_CAMERA_ERROR_MESSAGE,
                                 null
                             )
                         }
                         else -> {
                             result.error(
-                                "MobileScanner",
-                                "Unknown error occurred.",
+                                MobileScannerErrorCodes.GENERIC_ERROR,
+                                MobileScannerErrorCodes.GENERIC_ERROR_MESSAGE,
                                 null
                             )
                         }
@@ -252,9 +250,11 @@ class MobileScannerHandler(
             mobileScanner!!.setScale(call.arguments as Double)
             result.success(null)
         } catch (e: ZoomWhenStopped) {
-            result.error("MobileScanner", "Called setScale() while stopped!", null)
+            result.error(
+                MobileScannerErrorCodes.SET_SCALE_WHEN_STOPPED_ERROR, MobileScannerErrorCodes.SET_SCALE_WHEN_STOPPED_ERROR_MESSAGE, null)
         } catch (e: ZoomNotInRange) {
-            result.error("MobileScanner", "Scale should be within 0 and 1", null)
+            result.error(
+                MobileScannerErrorCodes.GENERIC_ERROR, MobileScannerErrorCodes.INVALID_ZOOM_SCALE_ERROR_MESSAGE, null)
         }
     }
 
@@ -263,7 +263,8 @@ class MobileScannerHandler(
             mobileScanner!!.resetScale()
             result.success(null)
         } catch (e: ZoomWhenStopped) {
-            result.error("MobileScanner", "Called resetScale() while stopped!", null)
+            result.error(
+                MobileScannerErrorCodes.SET_SCALE_WHEN_STOPPED_ERROR, MobileScannerErrorCodes.SET_SCALE_WHEN_STOPPED_ERROR_MESSAGE, null)
         }
     }
 

android/src/main/kotlin/dev/steenbakker/mobile_scanner/MobileScannerPermissions.kt

@@ -5,18 +5,14 @@ import android.app.Activity
 import android.content.pm.PackageManager
 import androidx.core.app.ActivityCompat
 import androidx.core.content.ContextCompat
+import dev.steenbakker.mobile_scanner.objects.MobileScannerErrorCodes
 import io.flutter.plugin.common.PluginRegistry.RequestPermissionsResultListener
 
 /**
  * This class handles the camera permissions for the Mobile Scanner.
  */
 class MobileScannerPermissions {
     companion object {
-        const val CAMERA_ACCESS_DENIED = "CameraAccessDenied"
-        const val CAMERA_ACCESS_DENIED_MESSAGE = "Camera access permission was denied."
-        const val CAMERA_PERMISSIONS_REQUEST_ONGOING = "CameraPermissionsRequestOngoing"
-        const val CAMERA_PERMISSIONS_REQUEST_ONGOING_MESSAGE = "Another request is ongoing and multiple requests cannot be handled at once."
-
         /**
          * When the application's activity is [androidx.fragment.app.FragmentActivity], requestCode can only use the lower 16 bits.
          * @see androidx.fragment.app.FragmentActivity.validateRequestPermissionsRequestCode
@@ -25,7 +21,7 @@ class MobileScannerPermissions {
     }
 
     interface ResultCallback {
-        fun onResult(errorCode: String?, errorDescription: String?)
+        fun onResult(errorCode: String?)
     }
 
     private var listener: RequestPermissionsResultListener? = null
@@ -53,25 +49,24 @@ class MobileScannerPermissions {
                           addPermissionListener: (RequestPermissionsResultListener) -> Unit,
                           callback: ResultCallback) {
         if (ongoing) {
-            callback.onResult(
-                CAMERA_PERMISSIONS_REQUEST_ONGOING, CAMERA_PERMISSIONS_REQUEST_ONGOING_MESSAGE)
+            callback.onResult(MobileScannerErrorCodes.CAMERA_PERMISSIONS_REQUEST_ONGOING)
             return
         }
 
         if(hasCameraPermission(activity) == 1) {
             // Permissions already exist. Call the callback with success.
-            callback.onResult(null, null)
+            callback.onResult(null)
             return
         }
 
         if(listener == null) {
             // Keep track of the listener, so that it can be unregistered later.
             listener = MobileScannerPermissionsListener(
                 object: ResultCallback {
-                    override fun onResult(errorCode: String?, errorDescription: String?) {
+                    override fun onResult(errorCode: String?) {
                         ongoing = false
                         listener = null
-                        callback.onResult(errorCode, errorDescription)
+                        callback.onResult(errorCode)
                     }
                 }
             )

android/src/main/kotlin/dev/steenbakker/mobile_scanner/MobileScannerPermissionsListener.kt

@@ -1,6 +1,7 @@
 package dev.steenbakker.mobile_scanner
 
 import android.content.pm.PackageManager
+import dev.steenbakker.mobile_scanner.objects.MobileScannerErrorCodes
 import io.flutter.plugin.common.PluginRegistry
 
 /**
@@ -29,11 +30,9 @@ internal class MobileScannerPermissionsListener(
         // grantResults could be empty if the permissions request with the user is interrupted
         // https://developer.android.com/reference/android/app/Activity#onRequestPermissionsResult(int,%20java.lang.String[],%20int[])
         if (grantResults.isEmpty() || grantResults[0] != PackageManager.PERMISSION_GRANTED) {
-            resultCallback.onResult(
-                MobileScannerPermissions.CAMERA_ACCESS_DENIED,
-                MobileScannerPermissions.CAMERA_ACCESS_DENIED_MESSAGE)
+            resultCallback.onResult(MobileScannerErrorCodes.CAMERA_ACCESS_DENIED)
         } else {
-            resultCallback.onResult(null, null)
+            resultCallback.onResult(null)
         }
 
         return true

ios/Classes/BarcodeHandler.swift

@@ -19,6 +19,12 @@ public class BarcodeHandler: NSObject, FlutterStreamHandler {
         eventChannel.setStreamHandler(self)
     }
 
+    func publishError(_ error: FlutterError) {
+        DispatchQueue.main.async {
+            self.eventSink?(error)
+        }
+    }
+
     func publishEvent(_ event: [String: Any?]) {
         DispatchQueue.main.async {
             self.eventSink?(event)

ios/Classes/MobileScannerErrorCodes.swift

@@ -20,7 +20,7 @@ struct MobileScannerErrorCodes {
     // because it uses the error message from the undelying error.
     static let BARCODE_ERROR = "MOBILE_SCANNER_BARCODE_ERROR"
     // The error code 'CAMERA_ERROR' does not have an error message,
-    // because it uses the error message from the underlying error.    
+    // because it uses the error message from the underlying error.
     static let CAMERA_ERROR = "MOBILE_SCANNER_CAMERA_ERROR"
     static let GENERIC_ERROR = "MOBILE_SCANNER_GENERIC_ERROR"
     static let GENERIC_ERROR_MESSAGE = "An unknown error occurred."

ios/Classes/MobileScannerPlugin.swift

@@ -42,7 +42,10 @@ public class MobileScannerPlugin: NSObject, FlutterPlugin {
     init(barcodeHandler: BarcodeHandler, registry: FlutterTextureRegistry) {
         self.mobileScanner = MobileScanner(registry: registry, mobileScannerCallback: { barcodes, error, image in
             if error != nil {
-                barcodeHandler.publishEvent(["name": "error", "data": error!.localizedDescription])
+                barcodeHandler.publishError(
+                    FlutterError(code: MobileScannerErrorCodes.BARCODE_ERROR,
+                                 message: error?.localizedDescription,
+                                 details: nil))
                 return
             }
 
@@ -150,20 +153,20 @@ public class MobileScannerPlugin: NSObject, FlutterPlugin {
                 }
             }
         } catch MobileScannerError.alreadyStarted {
-            result(FlutterError(code: "MobileScanner",
-                                message: "Called start() while already started!",
+            result(FlutterError(code: MobileScannerErrorCodes.ALREADY_STARTED_ERROR,
+                                message: MobileScannerErrorCodes.ALREADY_STARTED_ERROR_MESSAGE,
                                 details: nil))
         } catch MobileScannerError.noCamera {
-            result(FlutterError(code: "MobileScanner",
-                                message: "No camera found or failed to open camera!",
+            result(FlutterError(code: MobileScannerErrorCodes.NO_CAMERA_ERROR,
+                                message: MobileScannerErrorCodes.NO_CAMERA_ERROR_MESSAGE,
                                 details: nil))
         } catch MobileScannerError.cameraError(let error) {
-            result(FlutterError(code: "MobileScanner",
-                                message: "Error occured when setting up camera!",
-                                details: error))
+            result(FlutterError(code: MobileScannerErrorCodes.CAMERA_ERROR,
+                                message: error.localizedDescription,
+                                details: nil))
         } catch {
-            result(FlutterError(code: "MobileScanner",
-                                message: "Unknown error occured.",
+            result(FlutterError(code: MobileScannerErrorCodes.GENERIC_ERROR,
+                                message: MobileScannerErrorCodes.GENERIC_ERROR_MESSAGE,
                                 details: nil))
         }
     }
@@ -186,25 +189,25 @@ public class MobileScannerPlugin: NSObject, FlutterPlugin {
     private func setScale(_ call: FlutterMethodCall, _ result: @escaping FlutterResult) {
         let scale = call.arguments as? CGFloat
         if (scale == nil) {
-            result(FlutterError(code: "MobileScanner",
-                                message: "You must provide a scale when calling setScale!",
-                                details: nil))
+            result(FlutterError(code: MobileScannerErrorCodes.GENERIC_ERROR,
+                                message: MobileScannerErrorCodes.INVALID_ZOOM_SCALE_ERROR_MESSAGE,
+                                details: "The invalid zoom scale was nil."))
             return
         }
         do {
             try mobileScanner.setScale(scale!)
             result(nil)
         } catch MobileScannerError.zoomWhenStopped {
-            result(FlutterError(code: "MobileScanner",
-                                message: "Called setScale() while stopped!",
+            result(FlutterError(code: MobileScannerErrorCodes.SET_SCALE_WHEN_STOPPED_ERROR,
+                                message: MobileScannerErrorCodes.SET_SCALE_WHEN_STOPPED_ERROR_MESSAGE,
                                 details: nil))
         } catch MobileScannerError.zoomError(let error) {
-            result(FlutterError(code: "MobileScanner",
-                                message: "Error while zooming.",
-                                details: error))
+            result(FlutterError(code: MobileScannerErrorCodes.GENERIC_ERROR,
+                                message: error.localizedDescription,
+                                details: nil))
         } catch {
-            result(FlutterError(code: "MobileScanner",
-                                message: "Error while zooming.",
+            result(FlutterError(code: MobileScannerErrorCodes.GENERIC_ERROR,
+                                message: MobileScannerErrorCodes.GENERIC_ERROR_MESSAGE,
                                 details: nil))
         }
     }
@@ -215,16 +218,16 @@ public class MobileScannerPlugin: NSObject, FlutterPlugin {
             try mobileScanner.resetScale()
             result(nil)
         } catch MobileScannerError.zoomWhenStopped {
-            result(FlutterError(code: "MobileScanner",
-                                message: "Called resetScale() while stopped!",
+            result(FlutterError(code: MobileScannerErrorCodes.SET_SCALE_WHEN_STOPPED_ERROR,
+                                message: MobileScannerErrorCodes.SET_SCALE_WHEN_STOPPED_ERROR_MESSAGE,
                                 details: nil))
         } catch MobileScannerError.zoomError(let error) {
-            result(FlutterError(code: "MobileScanner",
-                                message: "Error while zooming.",
-                                details: error))
+            result(FlutterError(code: MobileScannerErrorCodes.GENERIC_ERROR,
+                                message: error.localizedDescription,
+                                details: nil))
         } catch {
-            result(FlutterError(code: "MobileScanner",
-                                message: "Error while zooming.",
+            result(FlutterError(code: MobileScannerErrorCodes.GENERIC_ERROR,
+                                message: MobileScannerErrorCodes.GENERIC_ERROR_MESSAGE,
                                 details: nil))
         }
     }
@@ -266,7 +269,7 @@ public class MobileScannerPlugin: NSObject, FlutterPlugin {
                                    barcodeScannerOptions: scannerOptions, callback: { barcodes, error in
             if error != nil {
                 DispatchQueue.main.async {
-                    result(FlutterError(code: "MobileScanner",
+                    result(FlutterError(code: MobileScannerErrorCodes.BARCODE_ERROR,
                                         message: error?.localizedDescription,
                                         details: nil))
                 }

lib/mobile_scanner.dart

@@ -11,8 +11,7 @@ export 'src/enums/phone_type.dart';
 export 'src/enums/torch_state.dart';
 export 'src/mobile_scanner.dart';
 export 'src/mobile_scanner_controller.dart';
-export 'src/mobile_scanner_exception.dart'
-    hide PermissionRequestPendingException;
+export 'src/mobile_scanner_exception.dart';
 export 'src/mobile_scanner_platform_interface.dart';
 export 'src/objects/address.dart';
 export 'src/objects/barcode.dart';