bug: fix start() and stop() crash when called multiple times on iOS and macOS. R…

…emove analyze mode on Android and iOS.

 include: package:flutter_lints/flutter.yaml
+
+linter:
+  rules:
+    unawaited_futures: true
\ No newline at end of file

@@ -38,8 +38,8 @@ class MobileScanner(private val activity: Activity, private val textureRegistry:
     private var camera: Camera? = null
     private var textureEntry: TextureRegistry.SurfaceTextureEntry? = null
 
-    @AnalyzeMode
-    private var analyzeMode: Int = AnalyzeMode.NONE
+//    @AnalyzeMode
+//    private var analyzeMode: Int = AnalyzeMode.NONE
 
     @ExperimentalGetImage
     override fun onMethodCall(@NonNull call: MethodCall, @NonNull result: MethodChannel.Result) {
@@ -47,8 +47,8 @@ class MobileScanner(private val activity: Activity, private val textureRegistry:
             "state" -> checkPermission(result)
             "request" -> requestPermission(result)
             "start" -> start(call, result)
-            "torch" -> switchTorch(call, result)
-            "analyze" -> switchAnalyzeMode(call, result)
+            "torch" -> toggleTorch(call, result)
+//            "analyze" -> switchAnalyzeMode(call, result)
             "stop" -> stop(result)
             else -> result.notImplemented()
         }
@@ -92,8 +92,8 @@ class MobileScanner(private val activity: Activity, private val textureRegistry:
 
     @ExperimentalGetImage
     val analyzer = ImageAnalysis.Analyzer { imageProxy -> // YUV_420_888 format
-        when (analyzeMode) {
-            AnalyzeMode.BARCODE -> {
+//        when (analyzeMode) {
+//            AnalyzeMode.BARCODE -> {
                 val mediaImage = imageProxy.image ?: return@Analyzer
                 val inputImage = InputImage.fromMediaImage(mediaImage, imageProxy.imageInfo.rotationDegrees)
 
@@ -106,9 +106,9 @@ class MobileScanner(private val activity: Activity, private val textureRegistry:
                         }
                         .addOnFailureListener { e -> Log.e(TAG, e.message, e) }
                         .addOnCompleteListener { imageProxy.close() }
-            }
-            else -> imageProxy.close()
-        }
+//            }
+//            else -> imageProxy.close()
+//        }
     }
 
 
@@ -116,6 +116,10 @@ class MobileScanner(private val activity: Activity, private val textureRegistry:
 
     @ExperimentalGetImage
     private fun start(call: MethodCall, result: MethodChannel.Result) {
+        if (camera != null) {
+            result.error(TAG, "Called start() while already started!", null)
+            return
+        }
 
         val facing: Int = call.argument<Int>("facing") ?: 0
         val ratio: Int? = call.argument<Int>("ratio")
@@ -186,24 +190,32 @@ class MobileScanner(private val activity: Activity, private val textureRegistry:
         }, executor)
     }
 
-    private fun switchTorch(call: MethodCall, result: MethodChannel.Result) {
-        val state = call.arguments == 1
-        camera!!.cameraControl.enableTorch(state)
-        result.success(null)
+    private fun toggleTorch(call: MethodCall, result: MethodChannel.Result) {
+        if (camera == null) {
+            result.error(TAG,"Called toggleTorch() while stopped!", null)
+            return
         }
-
-    private fun switchAnalyzeMode(call: MethodCall, result: MethodChannel.Result) {
-        analyzeMode = call.arguments as Int
+        camera!!.cameraControl.enableTorch(call.arguments == 1)
         result.success(null)
     }
 
+//    private fun switchAnalyzeMode(call: MethodCall, result: MethodChannel.Result) {
+//        analyzeMode = call.arguments as Int
+//        result.success(null)
+//    }
+
     private fun stop(result: MethodChannel.Result) {
+        if (camera == null) {
+            result.error(TAG,"Called stop() while already stopped!", null)
+            return
+        }
+
         val owner = activity as LifecycleOwner
         camera!!.cameraInfo.torchState.removeObservers(owner)
         cameraProvider!!.unbindAll()
         textureEntry!!.release()
 
-        analyzeMode = AnalyzeMode.NONE
+//        analyzeMode = AnalyzeMode.NONE
         camera = null
         textureEntry = null
         cameraProvider = null

@@ -23,7 +23,7 @@ public class SwiftMobileScannerPlugin: NSObject, FlutterPlugin, FlutterStreamHan
     var latestBuffer: CVImageBuffer!
     
     
-    var analyzeMode: Int = 0
+//    var analyzeMode: Int = 0
     var analyzing: Bool = false
     var position = AVCaptureDevice.Position.back
     
@@ -53,9 +53,9 @@ public class SwiftMobileScannerPlugin: NSObject, FlutterPlugin, FlutterStreamHan
         case "start":
             start(call, result)
         case "torch":
-            switchTorch(call, result)
-        case "analyze":
-            switchAnalyzeMode(call, result)
+            toggleTorch(call, result)
+//        case "analyze":
+//            switchAnalyzeMode(call, result)
         case "stop":
             stop(result)
         default:
@@ -89,10 +89,10 @@ public class SwiftMobileScannerPlugin: NSObject, FlutterPlugin, FlutterStreamHan
         latestBuffer = CMSampleBufferGetImageBuffer(sampleBuffer)
         registry.textureFrameAvailable(textureId)
 
-        switch analyzeMode {
-        case 1: // barcode
+//        switch analyzeMode {
+//        case 1: // barcode
             if analyzing {
-                break
+                return
             }
             analyzing = true
             let buffer = CMSampleBufferGetImageBuffer(sampleBuffer)
@@ -112,9 +112,9 @@ public class SwiftMobileScannerPlugin: NSObject, FlutterPlugin, FlutterStreamHan
                 }
                 analyzing = false
             }
-        default: // none
-            break
-        }
+//        default: // none
+//            break
+//        }
     }
     
     func imageOrientation(
@@ -154,6 +154,13 @@ public class SwiftMobileScannerPlugin: NSObject, FlutterPlugin, FlutterStreamHan
     }
 
     func start(_ call: FlutterMethodCall, _ result: @escaping FlutterResult) {
+        if (device != nil) {
+            result(FlutterError(code: "MobileScanner",
+                                    message: "Called start() while already started!",
+                                    details: nil))
+            return
+        }
+        
         textureId = registry.register(self)
         captureSession = AVCaptureSession()
         
@@ -219,7 +226,13 @@ public class SwiftMobileScannerPlugin: NSObject, FlutterPlugin, FlutterStreamHan
         result(answer)
     }
     
-    func switchTorch(_ call: FlutterMethodCall, _ result: @escaping FlutterResult) {
+    func toggleTorch(_ call: FlutterMethodCall, _ result: @escaping FlutterResult) {
+        if (device == nil) {
+            result(FlutterError(code: "MobileScanner",
+                                    message: "Called toggleTorch() while stopped!",
+                                    details: nil))
+            return
+        }
         do {
             try device.lockForConfiguration()
             device.torchMode = call.arguments as! Int == 1 ? .on : .off
@@ -230,12 +243,18 @@ public class SwiftMobileScannerPlugin: NSObject, FlutterPlugin, FlutterStreamHan
         }
     }
     
-    func switchAnalyzeMode(_ call: FlutterMethodCall, _ result: @escaping FlutterResult) {
-        analyzeMode = call.arguments as! Int
-        result(nil)
-    }
+//    func switchAnalyzeMode(_ call: FlutterMethodCall, _ result: @escaping FlutterResult) {
+//        analyzeMode = call.arguments as! Int
+//        result(nil)
+//    }
     
     func stop(_ result: FlutterResult) {
+        if (device == nil) {
+            result(FlutterError(code: "MobileScanner",
+                                    message: "Called stop() while already stopped!",
+                                    details: nil))
+            return
+        }
         captureSession.stopRunning()
         for input in captureSession.inputs {
             captureSession.removeInput(input)
@@ -246,7 +265,7 @@ public class SwiftMobileScannerPlugin: NSObject, FlutterPlugin, FlutterStreamHan
         device.removeObserver(self, forKeyPath: #keyPath(AVCaptureDevice.torchMode))
         registry.unregisterTexture(textureId)
         
-        analyzeMode = 0
+//        analyzeMode = 0
         latestBuffer = nil
         captureSession = nil
         device = nil

@@ -27,7 +27,7 @@ enum TorchState {
   on,
 }
 
-enum AnalyzeMode { none, barcode }
+// enum AnalyzeMode { none, barcode }
 
 class MobileScannerController {
   MethodChannel methodChannel =
@@ -62,8 +62,8 @@ class MobileScannerController {
 
     // Sets analyze mode and barcode stream
     barcodesController = StreamController.broadcast(
-      onListen: () => setAnalyzeMode(AnalyzeMode.barcode.index),
-      onCancel: () => setAnalyzeMode(AnalyzeMode.none.index),
+      // onListen: () => setAnalyzeMode(AnalyzeMode.barcode.index),
+      // onCancel: () => setAnalyzeMode(AnalyzeMode.none.index),
     );
 
     start();
@@ -94,20 +94,22 @@ class MobileScannerController {
     }
   }
 
-  void setAnalyzeMode(int mode) {
-    if (hashCode != _controllerHashcode) {
-      return;
-    }
-    methodChannel.invokeMethod('analyze', mode);
-  }
+  // TODO: Add more analyzers like text analyzer
+  // void setAnalyzeMode(int mode) {
+  //   if (hashCode != _controllerHashcode) {
+  //     return;
+  //   }
+  //   methodChannel.invokeMethod('analyze', mode);
+  // }
 
   // List<BarcodeFormats>? formats = _defaultBarcodeFormats,
   /// Start barcode scanning. This will first check if the required permissions
   /// are set.
   Future<void> start() async {
+
     ensure('startAsync');
 
-    setAnalyzeMode(AnalyzeMode.barcode.index);
+    // setAnalyzeMode(AnalyzeMode.barcode.index);
     // Check authorization status
     MobileScannerState state =
         MobileScannerState.values[await methodChannel.invokeMethod('state')];
@@ -132,8 +134,15 @@ class MobileScannerController {
     if (torchEnabled != null) arguments['torch'] = torchEnabled;
 
     // Start the camera with arguments
-    final Map<String, dynamic>? startResult = await methodChannel
+    Map<String, dynamic>? startResult = {};
+    try {
+      startResult = await methodChannel
           .invokeMapMethod<String, dynamic>('start', arguments);
+    } on PlatformException catch (error) {
+      debugPrint('${error.code}: ${error.message}');
+      // setAnalyzeMode(AnalyzeMode.none.index);
+      return;
+    }
 
     if (startResult == null) {
       throw PlatformException(code: 'INITIALIZATION ERROR');
@@ -146,17 +155,32 @@ class MobileScannerController {
         hasTorch: hasTorch);
   }
 
-  Future<void> stop() async => await methodChannel.invokeMethod('stop');
+  Future<void> stop() async {
+    try {
+      await methodChannel.invokeMethod('stop');
+    } on PlatformException catch (error) {
+      debugPrint('${error.code}: ${error.message}');
+    }
+  }
 
   /// Switches the torch on or off.
   ///
   /// Only works if torch is available.
-  void toggleTorch() {
+  Future<void> toggleTorch() async {
     ensure('toggleTorch');
-    if (!hasTorch) return;
+    if (!hasTorch) {
+      debugPrint('Device has no torch/flash.');
+      return;
+    }
+
     TorchState state =
         torchState.value == TorchState.off ? TorchState.on : TorchState.off;
-    methodChannel.invokeMethod('torch', state.index);
+
+    try {
+      await methodChannel.invokeMethod('torch', state.index);
+    } on PlatformException catch (error) {
+      debugPrint('${error.code}: ${error.message}');
+    }
   }
 
   /// Switches the torch on or off.
@@ -164,10 +188,15 @@ class MobileScannerController {
   /// Only works if torch is available.
   Future<void> switchCamera() async {
     ensure('switchCamera');
-    await stop();
+    try {
+      await methodChannel.invokeMethod('stop');
+    } on PlatformException catch (error) {
+      debugPrint('${error.code}: camera is stopped! Please start before switching camera.');
+      return;
+    }
     facing =
         facing == CameraFacing.back ? CameraFacing.front : CameraFacing.back;
-    start();
+    await start();
   }
 
   /// Disposes the controller and closes all listeners.

@@ -22,7 +22,7 @@ public class MobileScannerPlugin: NSObject, FlutterPlugin, FlutterStreamHandler,
     var latestBuffer: CVImageBuffer!
     
     
-    var analyzeMode: Int = 0
+//    var analyzeMode: Int = 0
     var analyzing: Bool = false
     var position = AVCaptureDevice.Position.back
     
@@ -52,9 +52,9 @@ public class MobileScannerPlugin: NSObject, FlutterPlugin, FlutterStreamHandler,
         case "start":
             start(call, result)
         case "torch":
-            switchTorch(call, result)
-        case "analyze":
-            switchAnalyzeMode(call, result)
+            toggleTorch(call, result)
+//        case "analyze":
+//            switchAnalyzeMode(call, result)
         case "stop":
             stop(result)
         default:
@@ -92,14 +92,14 @@ public class MobileScannerPlugin: NSObject, FlutterPlugin, FlutterStreamHandler,
         latestBuffer = CMSampleBufferGetImageBuffer(sampleBuffer)
         registry.textureFrameAvailable(textureId)
 
-        switch analyzeMode {
-        case 1: // barcode
+//        switch analyzeMode {
+//        case 1: // barcode
             
             // Limit the analyzer because the texture output will freeze otherwise
             if i / 10 == 1 {
                 i = 0
             } else {
-                break
+                return
             }
                 let imageRequestHandler = VNImageRequestHandler(
                     cvPixelBuffer: latestBuffer,
@@ -129,9 +129,9 @@ public class MobileScannerPlugin: NSObject, FlutterPlugin, FlutterStreamHandler,
               print(error)
             }
 
-        default: // none
-            break
-        }
+//        default: // none
+//            break
+//        }
     }
     
     func checkPermission(_ call: FlutterMethodCall, _ result: @escaping FlutterResult) {
@@ -159,6 +159,13 @@ public class MobileScannerPlugin: NSObject, FlutterPlugin, FlutterStreamHandler,
     }
 
     func start(_ call: FlutterMethodCall, _ result: @escaping FlutterResult) {
+        if (device != nil) {
+            result(FlutterError(code: "MobileScanner",
+                                    message: "Called start() while already started!",
+                                    details: nil))
+            return
+        }
+        
         textureId = registry.register(self)
         captureSession = AVCaptureSession()
         
@@ -222,7 +229,13 @@ public class MobileScannerPlugin: NSObject, FlutterPlugin, FlutterStreamHandler,
         result(answer)
     }
     
-    func switchTorch(_ call: FlutterMethodCall, _ result: @escaping FlutterResult) {
+    func toggleTorch(_ call: FlutterMethodCall, _ result: @escaping FlutterResult) {
+        if (device == nil) {
+            result(FlutterError(code: "MobileScanner",
+                                    message: "Called toggleTorch() while stopped!",
+                                    details: nil))
+            return
+        }
         do {
             try device.lockForConfiguration()
             device.torchMode = call.arguments as! Int == 1 ? .on : .off
@@ -233,12 +246,18 @@ public class MobileScannerPlugin: NSObject, FlutterPlugin, FlutterStreamHandler,
         }
     }
 
-    func switchAnalyzeMode(_ call: FlutterMethodCall, _ result: @escaping FlutterResult) {
-        analyzeMode = call.arguments as! Int
-        result(nil)
-    }
+//    func switchAnalyzeMode(_ call: FlutterMethodCall, _ result: @escaping FlutterResult) {
+//        analyzeMode = call.arguments as! Int
+//        result(nil)
+//    }
 
     func stop(_ result: FlutterResult) {
+        if (device == nil) {
+            result(FlutterError(code: "MobileScanner",
+                                    message: "Called stop() while already stopped!",
+                                    details: nil))
+            return
+        }
         captureSession.stopRunning()
         for input in captureSession.inputs {
             captureSession.removeInput(input)
@@ -249,7 +268,7 @@ public class MobileScannerPlugin: NSObject, FlutterPlugin, FlutterStreamHandler,
         device.removeObserver(self, forKeyPath: #keyPath(AVCaptureDevice.torchMode))
         registry.unregisterTexture(textureId)
         
-        analyzeMode = 0
+//        analyzeMode = 0
         latestBuffer = nil
         captureSession = nil
         device = nil

-